INFLUÊNCIA DA TÉCNICA DO PREPARO CAVITÁRIO UTILIZANDO LASER DE Er:YAG ... - TEDE...
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CEPPE Centro de Pós-Graduação e Pesquisa Curso de Mestrado em Odontologia área de concentração em Dentística MARIO ALBERTO MARCONDES PERITO INFLUÊNCIA DA TÉCNICA DO PREPARO CAVITÁRIO UTILIZANDO LASER DE Er:YAG E DOS TIPOS DE MATERIAIS RESTAURADORES NA PREVENÇÃO DE CÁRIE Guarulhos 2009
Transcript of INFLUÊNCIA DA TÉCNICA DO PREPARO CAVITÁRIO UTILIZANDO LASER DE Er:YAG ... - TEDE...
CEPPE
Centro de Pós-Graduação e Pesquisa
Curso de Mestrado em Odontologia área de concentração em Dentística
MARIO ALBERTO MARCONDES PERITO
INFLUÊNCIA DA TÉCNICA DO PREPARO CAVITÁRIO
UTILIZANDO LASER DE Er:YAG E DOS TIPOS DE
MATERIAIS RESTAURADORES NA PREVENÇÃO DE
CÁRIE
Guarulhos
2009
MARIO ALBERTO MARCONDES PERITO
INFLUÊNCIA DA TÉCNICA DO PREPARO CAVITÁRIO
UTILIZANDO LASER DE Er:YAG E DOS TIPOS DE
MATERIAIS RESTAURADORES NA PREVENÇÃO DE
CÁRIE
Dissertação apresentada à Universidade Guarulhos para obtenção do título de Mestre em Odontologia. Área de Concentração em Dentística. Orientador Prof. Dr. José Augusto Rodrigues Co-orientadora Profa. Dra. Alessandra Cassoni Ferreira
Guarulhos
2009
Ficha catalográfica elaborada pela Coordenação Biblioteca Fernando Gay da Fonseca
Perito, Mario Alberto Marcondes
P446i Influência da técnica do preparo cavitário utilizando laser de ER: YAG e dos tipos de materiais restauradores na prevenção de cárie/ Mario Alberto Marcondes Perito. Guarulhos, SP, 2009.
77 f. ; 31 cm
Dissertação (Mestrado em Odontologia, área de concentração em Dentística) - Centro de Pós-Graduação e Pesquisa Universidade Guarulhos, 2009.
Orientador: Prof. Dr. José Augusto Rodrigues Co-orientadora: Profa. Dra. Alessandra Cassoni Ferreira Bibliografia: f. 71-72
1. Laser. 2. Cárie dental. 3. Cimentos de ionômero de vidro. 4. Laser de Er: YAG I. Título. II. Universidade Guarulhos.
CDD 22st
617.675
Dedico este trabalho à minha esposa Patrícia e
aos meus filhos Pedro e Giovana que me dão
força e coragem para prosseguir.
AGRADECIMENTOS
À Universidade Guarulhos, pela oportunidade dada na obtenção do título de Mestre.
Ao Prof. Dr. José Augusto Rodrigues pelo estímulo, amizade e paciência, cuja
dedicação o faz um exemplo de profissional.
À Profa. Dra. Patrícia Moreira de Freitas do Laboratório Experimental de Laser em
Odontologia (LELO) da Faculdade de Odontologia da Universidade de São Paulo por permitir
a utilização dos equipamentos para o desenvolvimento deste trabalho.
À Cirurgiã-Dentista Ana Carolina Tedesco Jorge pelo auxílio no desenvolvimento
deste trabalho.
A todos os professores do Curso de Mestrado em Odontologia da Universidade
Guarulhos, especialmente ao Prof. Dr. André Figueiredo Reis e à Profa. Dra. Cláudia Ota-
Tsuzuki pela compreensão e amizade.
À Profa. Tânia Rocha Cabral Ribas pela amizade, confiança e incentivo.
Aos funcionários do Curso de Odontologia da Universidade Guarulhos pela
dedicação e apoio.
Aos colegas de mestrado, Carlos Eduardo Pena, Luis Gustavo Barrotte Albino e
Ronaldo Viotti pelo companheirismo e amizade.
RESUMO Este estudo in vitro avaliou a influência do preparo cavitário com laser de Er:YAG e materiais
restauradores cariostáticos na prevenção de lesões de cáries secundárias. Em uma seqüência
lógica, o assunto foi abordado por intermédio do desenvolvimento de quatro trabalhos. No
primeiro foi realizada uma revisão bibliográfica sobre a utilização do laser na prevenção da
cárie dental. No segundo e no terceiro trabalho, blocos de esmalte dental humano foram
distribuídos em dois grupos para preparos cavitários (1,6 mm ∅), realizados com pontas
diamantadas ou com laser de Er:YAG (LA - 6Hz, 300mJ), ambos refrigerados. Cada grupo
foi dividido em 3 subgrupos e restaurados com ionômero de vidro (GI), ionômero de vidro
modificado por resina (RM) ou resina composta (CR). Os blocos foram termociclados (5º -
55ºC ± 2ºC, 1000 ciclos) e submetidos a ciclagem de pH. No segundo trabalho foi realizada a
análise visual da formação de lesões de cárie nas amostras, por três examinadores calibrados
(Kappa> 0,73) de acordo com escala ordinal com escores de 0-3. Os resultados foram
analisados pelo teste de Kruskal-Wallis e teste de Dunn (α=0,05). Não foi observado efeito
cariostático nas cavidades preparadas com pontas diamantadas e restauradas com compósitos.
Não foi observada nenhuma diferença no efeito cariostático nas cavidades restauradas com os
mesmos materiais e preparadas com pontas diamantadas ou laser de Er:YAG. Entretanto,
cavidades preparadas com laser mostraram menor formação de lesões cariosas que as
cavidades preparadas com pontas diamantadas. No terceiro trabalho foi realizada análise de
microdureza superficial (Knoop) das amostras a 100µm da margem das cavidades. A média
de 4 indentações foi utilizada para ANOVA seguida pelo teste de Tukey. O desenvolvimento
de lesões de cáries ao redor dos preparos por laser foi menor que nas cavidades preparadas
por pontas diamantadas, contudo, nenhum efeito cariostático sinérgico foi observado entre o
laser e o cimento de ionômero de vidro. No quarto trabalho foi avaliada a correlação de
Spearman entre o diagnóstico de lesões artificiais de cárie secundária em esmalte in vitro por
inspeção visual e por microdureza superficial (Knoop). Essa, foi estatisticamente significante
e demonstrou uma fraca correlação negativa entre as variáveis de resposta. Com base nos
trabalhos desenvolvidos, observou-se que o Laser de Er:YAG proporcionou efeito cariostático
ao redor dos preparos cavitários sendo mais evidente nas análises realizadas pelo teste de
microdureza. O GI apresentou maior efeito cariostático em relação à RM e não foi observado
efeito cariostático na CR independente do tipo de preparo.
Palavras-Chaves: Laser, cárie dental, compósitos resinosos, cimento de ionômero de vidro,
flúor, fluoretos, esmalte dental, microdureza.
ABSTRACT
The influence of the cavity preparation technique and the types of restorative materials
containing fluorides in the prevention of the secondary caries lesions was evaluated in this in
vitro study. In a logic sequence the subject was approach by four manuscripts. The first study
made a bibliographic revision about the laser employment in the prevention of the secondary
caries lesions. The second and the third manuscripts, human dental enamel blocks were
distributed into 2 groups for cavity preparations (1.6 mm ∅), performed with diamond burs or
Er:YAG laser (LA - 6Hz, 300mJ) both refrigerated. Each group was divided into 3 sub-groups
that were restored using a glass-ionomer cement (GI), a resin-modified glass-ionomer (RM),
or a composite resin (CR). The blocks were thermocycled (5º - 55ºC ± 2ºC, 1000 cicles) and
submitted to a pH challenge. In the second work the slabs were analyzed by visual
examination by 3 calibrated examiners (Kappa> 0.73) according to an ordinal scale ranked (0-
3). The results were analyzed by the Kruskal-Wallis test and the Dunn test (α=0.05). Non
cariostatic effect in the cavities performed with diamond burs and restored with composite
resin was observed. No differences in the cariostatic effect of the cavities restored with the
same material and prepared with diamond burs or Er:YAG laser was observed. However,
cavities prepared with Er:YAG laser showed less caries lesions formation than cavity
preparation with diamond burs. In the third study the blocks were analyzed by the
microhardness test (Knoop) in a distance of 100µm from the cavity walls. The average of 4
indentations was used in the ANOVA followed by Tukey’s test. The development of caries
lesion around lased cavity preparation were lesser than the cavities prepared with diamond
burs, however, no synergistic cariostatic effect was observed between Er:YAG laser and glass
ionomer cement. In the fourth study the correlation of in vitro artificial secondary caries
diagnosis on enamel between visual evaluation and superficial microhardness test (Knoop)
was verified by Spearman’s rho nonparametric correlation that showed a statistical significant
weak negative agreement between the response variables. Based in the manuscripts presented
it was observed that the Er:YAG laser provide cariostatic effect around the cavities
preparation, which was more evidenced with the microhardness analysis. The GI presented
more cariostatic effect than RM and no cariostatic effect was observed in CR despite the
cavity preparation technique.
Key words: Laser, dental caries, cariostatic agents, composite resin, glass-ionomer cement,
fluoride, dental enamel, microhardness.
SUMÁRIO
Página
1. INTRODUÇÃO............................................................................................................... 07
2. PROPOSIÇÃO................................................................................................................ 11
3. DESENVOLVIMENTO.................................................................................................. 12
3.1 Capítulo 1
Uso do laser na prevenção da cárie dental............................................................... 13
3.2 Capítulo 2
Effect of the cavity preparation with Er:YAG laser and fluoride releasing
materials in the prevention of caries lesions............................................................ 27
3.3 Capítulo 3
Cavity preparation and restorative materials influence on the prevention of
secondary caries....................................................................................................... 41
3.4 Capítulo 4
Correlation between visual and superficial microhardness evaluation
of artificial secondary caries.................................................................................... 57
4. CONCLUSÕES............................................................................................................... 70
REFERÊNCIAS ................................................................................................................. 71
ANEXOS............................................................................................................................. 73
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1. INTRODUÇÃO
Até o século passado a doença cárie era uma doença com alta incidência que
ocorria em quase todos os indivíduos. Atualmente, com os conhecimentos sobre a etiologia, e
desenvolvimento da doença, sabe-se que ela afeta indivíduos que possuem dentes,
microrganismos patogênicos e consomem uma dieta rica em carboidratos, levando a
freqüentes quedas de pH no meio bucal. Entretanto, seu desenvolvimento pode ser afetado por
outros fatores moduladores, como a quantidade e a qualidade da saliva, a classe social, renda
familiar, escolaridade, conhecimento e comportamento frente à doença (THYLSTRUP &
FEJERSKOV, 1994; MOI et al., 2005)
A presença de flúor na cavidade bucal também pode interferir nos fenômenos de
desmineralização e potencializar a remineralização. Os fluoretos estão disponíveis para a
maior parte da população na água de abastecimento, e na forma de dentifrícios, bochechos,
aplicações tópicas em géis ou vernizes ou ainda pode ser liberado de materiais restauradores
prevenindo as lesões secundárias (THYLSTRUP & FEJERSKOV, 1994; RODRIGUES et al.,
2005; MOI et al., 2005).
As lesões secundárias são lesões que se desenvolvem ao redor das restaurações,
sendo ocasionadas pelo mesmo agente da lesão primária, o ácido gerado no biofilme
bacteriano, promovendo um desequilíbrio entre a desmineralização e a remineralização,
favorecendo a desmineralização. Entretanto, estas lesões podem se desenvolver em duas
frentes: na superfície como a lesão primária e através da parede da cavidade quando há uma
falha no selamento marginal da restauração (TANTBIROJN et al., 1997).
Nesse contexto, o uso de materiais restauradores adesivos e que possuem a
vantagem de liberação de flúor com propósitos preventivos vem recebendo muita ênfase e é
amplamente discutido (TANTBIROJN et al., 1997; RODRIGUES et al., 2005; MOI et al.,
2005).
Essa técnica preventiva que emprega materiais que liberam flúor surgiu com os
cimentos de silicato que proporcionavam às paredes das cavidades um alto grau de resistência
à formação de lesões de cárie, causado pela alta liberação de fluoretos (HALS, 1975). Porém,
estes cimentos eram muito solúveis e foram substituídos pelos cimentos de ionômero de
vidro, que em relação aos cimentos de silicato, possuem menor solubilidade, mas mantém a
ação anticariogênica pela liberação de flúor, considerada de grande importância na prevenção
de cáries secundárias (HICKS et al., 1986; TANTBIROJN et al., 1997).
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Apesar de melhoras nas propriedades estéticas, mecânicas e biocompatibilidade,
os cimentos de ionômero de vidro ainda possuem algumas limitações podendo sofrer
desequilíbrios hídricos que podem comprometer seu desempenho clínico (ARAÚJO et al.,
2006).
Materiais híbridos de ionômero de vidro e resina composta foram desenvolvidos no
final da década de 80, apresentando como vantagens os resultados estéticos, a facilidade de
aplicação e a presa imediata pela luz, com maior resistência ao desgaste e efeito cariostático
semelhante aos ionômeros convencionais (DIJKMAN et al., 1993). Devido à necessidade
estética, fluoretos também foram adicionados à fórmula de algumas resinas compostas e
sistemas adesivos, mas o efeito cariostático destes materiais ainda é questionável pois para
que o flúor tenha ação deve se tornar ionizado e, para tanto, deve se desprender da matriz
resinosa a qual pode perder propriedades físicas. Poucos estudos demonstram a efetividade
destes materiais (KERBER & DONLY, 1993; PARK & KIM, 1997; FERRACANE et al.,
1998; LOBO et al., 2005; RODRIGUES et al., 2005).
Paralelamente ao desenvolvimento dos materiais restauradores com ação
cariostática, em 1965 estudos sugeriram a utilização do laser de alta potência, principalmente
o laser de Er:YAG, como ferramenta na prevenção da cárie dental por promover uma maior
ácido-resistência ao esmalte (YAMAMOTO & SATO, 1980).
A grande parte dos estudos recentes está focada nos efeitos da irradiação laser
sobre o esmalte desmineralizado isolada ou em associação aos fluoretos tópicos. Estes
empregam ensaios de microradiografia, espectroscopia Raman, microscopia de luz polarizada,
microscopia eletrônica de varredura, ensaios de microdureza e avaliação clínica. Tais estudos
demonstram que os lasers que tem afinidade por hidroxiapatita e água como o de argônio,
CO2 ou os de Érbio podem reduzir a desmineralização do esmalte frente ao desafio
cariogênico em 30–50% (CEBALLOS et al., 2001; HARAZAK et al., 2001; KLEIN et al.,
2005; FREITAS et al., 2005; CECCHINI et al., 2005; KIM et al., 2006; LIU & HSU, 2007).
O mecanismo pelo qual ocorre o ganho de ácido-resistência ainda não está
totalmente claro, alguns autores atribuem ao efeito dos lasers de derretimento do esmalte
dental sem a ocorrência do fenômeno de ablação. A ablação é um efeito do aquecimento e
vaporização da água, resultando em altas pressões internas, com microexplosões resultando
na remoção do conteúdo orgânico e inorgânico, alterando a superfície do esmalte (HIBST &
KELLER, 1989).
Este mesmo efeito é esperado para estes lasers nos preparos cavitários, por
exemplo, o laser de Er:YAG causa uma efetiva ablação em tecido saudável, assim como em
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lesões cariosas, sem causar danos térmicos aos tecidos adjacentes, e é indicado para a
remoção de tecido dental no preparo de cavidades visto que possibilita o máximo de
conservação de estrutura dental e não ocasiona danos a polpa (MISERENDINO & PICK,
1995; CORDEIRO et al., 2005).
Ceballos et al. (2001), prepararam cavidades classe V e condicionaram com laser
de Er:YAG (300-250mJ2 - 2Hz) e restauraram com resina composta. Após um desafio
cariogênico observaram através de microscopia de luz polarizada uma redução de 56% na
profundidade de lesão. Concordando com Klein et al. (2005), que demonstraram que a
irradiação da margem cavo-superficial de restaurações de resina composta com laser de CO2
foi capaz de inibir a perda de minerais no esmalte humano e com Harazak et al. (2001); que
observaram através da avaliação por fotografias que o laser de Nd:YAG (40J/cm2 - 20Hz–5s)
é efetivo na prevenção da formação de manchas brancas in vitro, em pré-molares humanos,
imersos em ácido lático, bem como pode ser utilizado in vivo em associação com flúor na
reversão de lesões iniciais de mancha branca ao redor de braquetes ortodônticos.
No estudo in vitro, realizado por Freitas et al. (2005), observou-se que a
irradiação do laser de ER,Cr:YSGG inibe o processo de desmineralização do esmalte e
aumenta a sua ácido-resistência. Cecchini et al. (2005), avaliaram in vitro a eficácia do laser
de Er:YAG no aumento da ácido-resistência do esmalte, por meio de espectrometria de força
atômica verificando a quantidade de cálcio e fósforo do esmalte, e esta análise associada à
microscopia eletrônica de varredura demonstrou que a aplicação do laser de Er:YAG com
baixos níveis de energia oferece diminuição da solubilidade do esmalte sem causar alterações
na estrutura superficial. Observa-se ainda por difração de Rx e espectrofotômetro de emissão
de plasma atômico, que o esmalte bovino tratado com um pulso de laser de Er:YAG (33J/cm2
- 2Hz) apresentaram uma maior quantidade de Ca, sendo uma perda de 10% de Ca e 13% de
fosfato menor do que o esmalte bovino normal frente a um modelo de desafio cariogênico
(KIM et al., 2006). Ainda através de espectroscopia Raman, Liu & Hsu (2007) demonstraram
que dentes decíduos tornam-se mais resistentes à desafios cariogênicos após a aplicação do
laser de Er:YAG (5.1 J/cm2–2 Hz–5s).
Por outro lado Apel et al. (2003), compararam a resistência ao desafio cariogênico
de cavidades preparadas com lasers de Er:YAG e de Er,Cr:YSGG. Empregando microscopia
de luz polarizada, não encontraram diferenças estatísticas entre os lasers, e o grupo que
recebeu o preparo cavitário com pontas diamantadas apresentou profundidade de lesão
estatisticamente menor que os grupos preparados com os lasers. Assim, concluíram que o
preparo cavitário ou a aplicação de lasers não oferece resistência a cárie.
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Assim, pode-se notar a existência de poucos estudos que avaliam o efeito de
ácido-resistência sugerido ao laser durante o preparo cavitário e condicionamento da
superfície, bem como a ausência da associação desta técnica com materiais que apresentam
efeito cariostático, indicados para pacientes de alto risco de cárie. Dessa forma, não se sabe se
a associação do preparo cavitário com laser e o uso de materiais restauradores pode ter um
efeito sinérgico inibindo ainda mais o desenvolvimento de lesões cariosas secundárias.
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2. PROPOSIÇÃO
O propósito deste trabalho foi avaliar, in vitro, a influência da técnica do preparo
cavitário convencional com alta rotação e pontas diamantadas e com laser de Er:YAG
associadas a materiais restauradores cariostáticos na prevenção do desenvolvimento de cárie
secundária.
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3. DESENVOLVIMENTO
Em uma seqüência lógica o tema deste trabalho foi estudado por intermédio do
desenvolvimento de quatro estudos, aprovados no Comitê de Ética em Pesquisa da
Universidade Guarulhos (Anexos A, B e C), apresentados a seguir como capítulos:
Capítulo 1: Artigo de revisão de literatura: ¨Uso do laser na prevenção da cárie dental¨,
submetido à revista Dentística on line.
Capítulo 2: Artigo em fase de redação: ¨Effect of the cavity preparation with Er:YAG laser
and fluoride releasing materials in the prevention of caries lesions¨, a ser
submetido à revista Lasers in Medical Science.
Capítulo 3: Artigo aceito na revista Photomedicine and Laser Surgery: ¨Cavity preparation
and restorative materials influence on the prevention of secondary caries¨.
(Anexo D)
Capítulo 4: Artigo aceito na revista Saúde da Universidade Guarulhos: ¨Correlation between
visual and superficial microhardness evaluation of artificial secondary caries¨.
(Anexo E)
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3.1 Capítulo 1
Artigo submetido à revista Dentística on line
USO DO LASER NA PREVENÇÃO DA CÁRIE DENTAL
USE OF LASER IN DENTAL CARIES PREVENTION
Mario Alberto Marcondes Perito1
Ana Carolina Tedesco Jorge2
Alessandra Cassoni3
José Augusto Rodrigues4
ENDEREÇO PARA CORRESPONDÊNCIA: Prof. Dr. José Augusto Rodrigues Programa de Pós-Graduação em Odontologia Universidade Guarulhos - UnG Rua Dr. Nilo Peçanha, 81 Prédio U 6º Andar Centro Guarulhos - CEP 07011-040 Tel (+55 11) 64641769 Fax (+55 11) 64641758 [email protected] ou [email protected]
1 Prof. Assistente da Universidade Guarulhos (UnG) e Diretor do Curso de Odontologia da UnG 2 Cirurgiã-Dentista – Graduada na UnG. 3 Mestre e Doutora em Odontologia (Dentística) pela Faculdade de Odontologia da USP- SP, Profa. Adjunta da UnG. 4 Doutor e Mestre em Dentística pela Faculdade de Odontologia de Piracicaba (UNICAMP); Professor Adjunto da UnG
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Use of laser in dental caries prevention
Uso do laser na prevenção da cárie dental
Resumo
Desde o desenvolvimento dos primeiros lasers, pesquisas estão sendo realizadas com
a finalidade de aprimorar seu uso em diferentes áreas. Na Odontologia a luz laser pode ser
utilizada em diferentes especialidades, incluindo a prevenção de lesões cariosas primárias e
secundárias. Este trabalho tem como objetivo discutir o uso da luz laser na prevenção da cárie
dental. Os lasers mais utilizados na prevenção da cárie dental são os de Argônio, Érbio e
dióxido de carbono (CO2). Cada um destes trabalha com padrões diferentes mas com a mesma
finalidade, a modificação do tecido dental tornando-o mais ácido-resistente. Nota-se através
da revisão de literatura que os resultados observados em laboratório são muito promissores e
os lasers podem ser utilizados na prevenção da cárie dental.
Palavras-chave: Lasers, uso terapêutico, cárie dentária, desmineralização dental
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1- Introdução
A cárie dental é uma doença infecciosa que acarreta o desenvolvimento de lesões nos
tecidos dentais quando não controlada. As lesões cariosas são o resultado do metabolismo
bacteriano, na presença de carboidratos provenientes da dieta, com a produção de ácidos
orgânicos que causam a desmineralização do esmalte e da dentina1.
A prevenção da doença cárie é baseada no controle dos múltiplos fatores que podem
determinar ou moderar seu desenvolvimento, ou seja, é baseada na avaliação do risco de cárie
do paciente e instituição de medidas que possam diminuir este risco como aperfeiçoamento da
técnica de higiene bucal e aumento do uso de fluoretos pelos pacientes2.
Nos casos em que os pacientes necessitam de tratamento restaurador o objetivo
inicial deve ser a adequação do meio bucal e redução da atividade de cárie do paciente, para
que em seguida, sejam realizadas as restaurações definitivas e não haja reincidência de lesões,
ou seja, desenvolvimento de cárie secundária 2;3.
O desenvolvimento de lesões cariosas secundárias ainda é um dos principais motivos
para substituição de restaurações, e a possibilidade de evitar ou mesmo retardar este tipo de
lesão pode reduzir a necessidade de substituição de restaurações2;4. Para tanto, além da
instrução sobre higiene bucal na fase de adequação do paciente, pode-se utilizar materiais
cariostáticos restauradores, como os híbridos de ionômeros de vidro em pacientes de alto
risco5;6;7.
O potencial cariostático dos materiais ionoméricos convencionais e dos híbridos vem
sendo amplamente estudado desde a década de 19708 e o efeito cariostático dos materiais
ionoméricos na prevenção de lesões de cárie secundária já é bem descrito na literatura e estes
possuem grande aplicabilidade clínica5;6;7;8.
Paralelamente ao desenvolvimento destes materiais restauradores cariostáticos
ocorreu a descoberta do laser e iniciaram-se os primeiros experimentos em Odontologia9, nos
quais foi notada a capacidade da luz laser de modificar os tecidos dentais duros tornando-os
mais ácido-resistentes10;11;12.
Laser é o acrônimo de “Light Amplification by Stimulated Emission of Radiation”,
que significa “Ampliação de Luz por Meio da Emissão Estimulada de Radiação”, ou seja, o
laser nada mais é do que uma luz que quando emitida vai promover fenômenos físicos e
interagir com os tecidos como qualquer outro tipo de luz, a diferença é que é uma luz com
comprimento de onda específico emitida em um feixe monocromático, coerente e colimado
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que pode ser facilmente focado para aplicação no tecido desejado obtendo interação ou efeito
terapêutico12.
Entretanto, existem diferentes tipos de laser, que podem ser utilizados para o preparo
cavitário ou mesmo para modificar o esmalte e dentina visando a prevenção do
desenvolvimento de lesões cariosas e este trabalho tem como objetivo demonstrar os lasers
indicados para prevenção da cárie dental.
2- Uso do laser na prevenção de lesões cariosas
A luz laser quando incide sobre um material pode sofrer, em combinação ou não,
quatro fenômenos físicos: reflexão, quando a luz é refletida em outra direção; transmissão,
quando a luz atravessa diretamente o material e não causa nenhum efeito, difusão, quando a
luz penetra no material mas se difunde no mesmo; e absorção, quando a luz é absorvida.
Desses, a absorção é o fenômeno mais desejado sobre os tecidos dentais, pois é através deste
que a energia luminosa do laser se transforma em calor e promove alterações que podem
tornar os tecidos dentais mais ácido-resistentes13.
O primeiro laser desenvolvido foi o de rubi, e sua primeira tentativa de uso em
Odontologia, como substituto das pontas diamantadas, foi pouco explorada no início, pois a
quantidade de energia gerada era muito grande e somente 20% era absorvida e produzia uma
grande quantidade de calor que se difundia por todo o tecido14. A produção de calor em
excesso pelos lasers é um efeito co-lateral não desejado, pois pode acarretar em danos nos
tecidos pulpares e periodontais adjacentes. Assim, o laser ideal deve produzir a ação desejada
gerando pouco calor, o qual deve se restringir ao local desejado15.
Com o avanço da pesquisa científica novos lasers que possuem maior absorção pela
hidroxiapatita e pela água foram desenvolvidos e estes se destacaram para o uso em tecidos
dentais duros e na prevenção de lesões de cárie dental16;17. Esta prevenção é obtida pela
modificação da estrutura do esmalte tornando-o mais ácido-resistente16;18. A ácido-resistência
é obtida com a absorção do laser pela hidroxiapatita e sua subseqüente conversão em calor. O
calor gerado causa alterações microestruturais e químicas na hidroxiapatita, ocorre o
derretimento da mesma e re-cristalização que gera modificações da estrutura da hidroxiapatita
com o aumento da proporção de minerais e redução de carbonato e água que sofrem
evaporação14;16;18;19;20. Embora a presença de matéria orgânica seja pouca, sua eliminação
17
garante uma maior ácido-resistência e supõe-se que os micro-espaços formados são
rapidamente mineralizados e re-cristalizados10;21.
Outro efeito observado após a aplicação do laser é a redução da permeabilidade
dental, efeito que diminui a passagem dos ácidos gerados pelas bactérias através da estrutura
dental dificultando a desmineralização e retardando a progressão de lesões cariosas10.
Assim, o uso do laser nas superfícies dentais, ao redor das restaurações, bem como a
irradiação das paredes de preparos ou a total confecção dos mesmos com o laser pode ser
considerada uma medida profilática para o desenvolvimento de lesões cariosas secundárias4.
Diversos tipos de laser estão sendo estudados para o uso profilático da cárie dental,
entretanto, a inibição de lesões cariosas varia de acordo com o tipo de comprimento de onda,
modo operacional e densidade de energia utilizada, o que torna difícil uma comparação entre
eles4. Os lasers utilizados para este fim são os de Argônio, CO2, Nd:YAG, Er:YAG e
Er,Cr:YSGG.
O laser de CO2, que possui meio ativo gasoso e como facilitadores os gases de He,
N2 e CO2, com comprimento de onda entre 9,3 e 10,6 µm no espectro infravermelho, foi um
dos primeiros aplicados na prevenção da cárie dental e se destacava por atuar com pequenas
densidades de energia, com 13 a 50 J/cm2 modificando o esmalte dental de uma forma similar
ao laser de rubi (trabalhando de 200 a 700J/cm2), diminuindo significativamente a produção
de calor e de fissuras na superfície dental22. Em uma revisão de literatura sobre laser de
dióxido de carbono em prevenção de cáries, Rodrigues et al.23 afirmam que irradiação do
esmalte dental pelo laser de CO2 altera os cristais de hidroxiapatita reduzindo a reatividade
ácida dos minerais.
Com o intuito de avaliar o efeito preventivo do laser de CO2 in vivo, Brugnera Junior
et al.24, em 1997, trataram 112 primeiros molares permanentes de pré-adolescente com selante
ou laser e observaram, após 4 anos, que a aplicação individual do laser não foi suficiente na
prevenção de lesões cariosas, porém, pode apresentar um efeito preventivo mais vantajoso se
associada à aplicação de selantes. Tsai et al.25 avaliaram a resistência ácida de dentes
humanos tratados com o laser de CO2 e laser de Nd:YAG ao processo de desmineralização
durante 24 e 72 hs e observaram que o grupo tratado com o laser de CO2 apresentou menor
concentração de cálcio dissolvida no tampão lactato do que o laser de Nd:YAG, e este não foi
diferente do grupo controle em 24 hs.
Mais focado na prevenção de lesões secundárias, Klein et al.4, em 2005, irradiaram
as paredes de preparos cavitários com o laser de CO2 com comprimento de onda de 10,6 µm e
18
observaram a fusão e derretimento das mesmas em microscopia eletrônica de varredura.
Quando os preparos restaurados foram submetidos ao desafio térmico e cariogênico
observaram uma redução na perda mineral, sendo que a maior redução foi obtida quando
utilizada densidade de energia de 16J/cm2 comparada a de 8J/cm2. Kantorowitz et al.19, em
um estudo in vitro também observaram que o aumento do número de pulsos do laser de CO2
levou a um aumento da inibição de lesões cariosas, e que existe um ponto limite, após o qual,
o aumento da densidade de energia não acarreta em uma maior ácido-resistência, sendo que o
laser de CO2 com comprimento de onda 10,6µm causou a fusão do esmalte dental e o de
9,6µm causou somente pequenos pontos de fusão, sendo o mais indicado.
Fried et al.17, em 2006, observaram que o laser de CO2 com comprimento de onda de
9,3 µm utilizado com refrigeração reduz a dissolução do esmalte dental, e que o uso sem a
refrigeração pode causar exposição excessiva ao calor e produzir cristais mais susceptíveis a
dissolução, proporcionou um efeito inverso. Segundo Tepper et al.26, em 2004, a associação
da irradiação com o laser de CO2 aos fluoretos pode promover um efeito sinérgico com maior
incorporação de flúor no esmalte dental e um menor desenvolvimento de trincas visto que o
flúor pode atuar refrigerando o esmalte durante a irradiação.
Assim, observa-se que o laser de CO2 possui efeito preventivo, sendo que o aumento
da densidade de energia pode aumentar a ácido-resistência do esmalte. Entretanto, é
extremamente necessário o uso de refrigeração para evitar a formação de trincas e poros, e a
associação de flúor pode ser o veículo de refrigeração e potencializar o efeito de ácido-
resistência26;27;28.
Outro laser muito utilizado em associação com a aplicação tópica de flúor é o de
Argônio que apresenta como meio ativo o gás Argônio e possui comprimentos de onda na
faixa do espectro eletromagnético visível 488nm (azul) e 514nm (verde)29;30;31. Este é
utilizado como co-adjuvante durante a aplicação tópica de flúor pois devido à baixa potência
empregada, embora seja classificado como laser de alta potência, causa mínimos efeitos aos
tecidos dentais duros e potencializa o efeito do flúor21.
Hicks et al.32 notaram mudanças topográficas na superfície adjacente às restaurações
de resinas compostas e cimento de ionômero de vidro modificado por resina ativados pelo
laser de Argônio. Acredita-se que as alterações na estrutura mineral e componentes orgânicos
produzem uma superfície menos susceptível à formação de cáries. Hicks et al.33 investigaram
o papel da radiação com laser de Argônio e sua combinação com aplicação tópica de flúor na
redução da formação de lesões de cárie in vivo. Somente a aplicação prévia de laser de
Argônio com baixa fluência (12J/cm2) reduziu em 44% a profundidade das lesões. Quando
19
associada à aplicação tópica de flúor houve uma redução das lesões de cárie na ordem de
62%. Em 1995, Flaitz et al.34 observaram uma redução de 26 a 32% das lesões no esmalte
dental após a irradiação com o laser de Argônio e de mais de 50% quando o laser foi
associado ao flúor. Da mesma forma, outros estudos tem demonstrado que o uso do laser de
Argônio promove um pequeno grau de ácido-resistência, mas quando aplicado juntamente
com o flúor pode-se aumentar significativamente a ácido-resistência do esmalte e
dentina29;30;35.
O laser mais estudado e utilizado na prevenção da formação de lesões cariosas é o de
Er:YAG, este apresenta como meio ativo sólido o cristal de ítrio-alumínio-granada dopado
com érbio (2,94µm), e atua diretamente na estrutura do esmalte e dentina assim como o de
CO2, vaporizando a água e outros componentes orgânicos para aumentar a ácido-
resistência18;27. Hossain et al.36, em 2003, demonstraram que após a irradiação com o laser de
Er:YAG observa-se um aumento na proporção de cálcio e Fósforo no tecido dental, sem
modificar a razão entre estes minerais e está de acordo com o estudo de Liu & Hsu21, em
2007, que relatam que a quantidade de minerais após a irradiação com este laser é a mesma, o
que ocorre é a diminuição do conteúdo orgânico, o que é associado ao aumento da ácido
resistência.
Este laser também pode ser utilizado para o preparo cavitário e seu uso associado à
irrigação dos tecidos o torna mais eficiente e efetivo sem causar danos térmicos, apresentando
como vantagem a modificação das paredes do preparo aumentando a cristalinidade e
diminuindo a perda mineral,37 ou seja, tornando-as mais ácido-resistentes, podendo resultar
em uma redução de 56% em profundidade na formação de lesões cariosas secundárias em
esmalte e 39% em superfície radicular 38. Liu et al.39, em 2005, relatam que uma energia de
200mJ para o Er:YAG (sem spray de água) atingiram redução do tamanho das lesões de cárie
em 32%.
Efeitos similares aos do laser de Er:YAG na prevenção de lesões cariosas primárias
ou secundárias tem sido observados com o laser de Er,Cr:YSGG (ítrio-scandiuum-gálio-
granada dopado com érbio e comprimento de onda de 2,79µm), mesmo em doses sub-
ablativas utilizadas somente como medida preventiva18. Yu et al.40 afirmam após análise em
microscopia atômica que o esmalte dental irradiado com Er,Cr:YSGG apresenta uma
diminuição dos íons cálcio, porém, a proporção entre cálcio e fósforo permaneceu a mesma
provavelmente devido a reorganização dos cristais de hidroxiapatita.
Além destes usos, é sugerido o seu uso para modificar o esmalte e dentina
promovendo uma melhor superfície para adesão, dispensando assim o condicionamento ácido,
20
visto que remove efetivamente toda a camada de esfregaço41. Entretanto, os parâmetros
testados ainda não permitem a formação de um padrão na superfície do esmalte que favorece
a adesão e em dentina o efeito térmico parece penetrar em camadas sub-superficiais
eliminando a água e desestruturando a dentina o que pode prejudicar a formação da camada
híbrida27;42.
Assim, ainda existem dúvidas sobre os parâmetros mais adequados para utilização
dos lasers de Érbio para obter uma boa adesão e evitar microinfiltração27;36;42;43.
Rolla et al.44 obtiveram bons resultados com o uso do laser de Nd:YAG para o
condicionamento e relatam ainda que este laser pode ser utilizado para prevenção da formação
de lesões cariosas. A irradiação dos tecidos dentais com o laser de Nd:YAG, que apresenta
como meio ativo sólido o cristal de ítrio-alumínio-granada dopado com neodímio e possui
comprimento de onda no infravermelho (1064nm), promove ácido-resistência pela
evaporação da água e conteúdo orgânico20;44;45. Kwon et al.46 afirma que o esmalte dental
irradiado com Nd:YAG apresenta um aumento da proporção entre cálcio e fósforo após
ablação devido a redistribuição dos minerais atuando de forma preventiva.
Apesar de poucos estudos comparativos sobre os efeitos do laser de Nd:YAG na
prevenção da cárie, ele parece ser tão eficiente quanto o laser de Er:YAG 47.
Assim, apesar de existirem diversos tipos de lasers que podem ser utilizados na
prevenção da cárie dental observa-se que todos promovem um aumento da ácido-resistência
do esmalte e da dentina. Dentre eles, os de Érbio são os mais promissores, pois apresentam
diversas indicações comprovadas quando comparados com outros lasers que possuem
indicações mais específicas, tornando o uso dos demais lasers mais oneroso aos clínicos pois
necessitariam adquirir diversos tipos de lasers. Porém, devido ao custo elevado para aquisição
dos lasers e seus efeitos colaterais, ainda discutidos, como alterações no processo adesivo
ainda são uma barreira para que os clínicos possam usufruir de seus benefícios, mas com o
avanço tecnológico e da pesquisa científica em um breve intervalo de tempo os lasers poderão
ter seu custo diminuído e os parâmetros de uso definidos para obter resultados ainda mais
efetivos e possivelmente se tornarão uma realidade clínica19.
21
3- Conclusão
Observa-se na literatura que a irradiação laser pode tornar os tecidos dentais mais
ácido-resistentes, o que pode evitar ou retardar o desenvolvimento de lesões cariosas
primárias ou secundárias.
22
Abstract
Since the development of the first lasers, research is being carried to improve its use
in different areas. In dentistry the laser light can be used in different specialties, including the
prevention of primary and secondary caries lesions. This literature review describes the laser
light use in the prevention dental caries. The lasers more used in the prevention dental caries
argon, erbium and CO2. Each one of these works with different standards but with the same
purpose, the modification of dental tissues and promoting it more acid resistance. Through the
present literature review it was observed in laboratory researches that lasers are a very
promising technology and they can be used in the prevention of dental caries development.
Key-words: Lasers, therapeutic use, Dental Caries, Tooth Demineralization
23
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24
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25
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26
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27
3.2 Capítulo 2
Artigo em fase de redação a ser submentido à revista
Lasers in Medical Science
Effect of the cavity preparation with Er:YAG laser and fluoride releasing
materials in the prevention of caries lesions
Ana Carolina Tedesco Jorge1, Mario Alberto Marcondes Perito1, Patricia Moreira de Freitas2,
Alessandra Cassoni3, Cristiane Mariote Amaral3, José Augusto Rodrigues3
1- DDS, Dental Research and Graduate Studies, Division Department of Restorative Dentistry, Guarulhos University, Guarulhos, SP, Brazil.
2- DDS, MS, PhD, Special Laboratory of Lasers in Dentistry, Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, Brazil.
3- DDS, MS, ScD, Dental Research and Graduate Studies, Division Department of Restorative Dentistry, Guarulhos University, Guarulhos, SP, Brazil.
Corresponding author: José Augusto Rodrigues
R. Dr. Nilo Peçanha, 67 - Prédio U - 6º Andar - Centro - Guarulhos -SP, CEP: 07023-070 Brazil. / Phone: ++ 55 11 64641769 - Fax: ++ 55 11 64641758
e-mail: [email protected] e-mail: [email protected] (e-mail to be published)
28
Effect of the cavity preparation with Er:YAG laser and fluoride releasing
materials in the prevention of caries lesions
Abstract
The influence of the cavity preparation technique and the restorative materials containing
fluoride in the prevention of the secondary caries were evaluated. Human teeth were sectioned
into 72 blocks and distributed into 2 groups. Cavities measuring 1.6mm were performed with
diamond burs or Er:YAG laser (6Hz, 300mJ, 47 J/cm2). Each group was divided into 3 sub-
groups restored with a glass-ionomer cement, a resin-modified glass-ionomer, or a composite
resin. The specimens were thermocycled and submitted to a pH cycling. Artificial caries were
scored using an ordinal scale by visual inspection. Kruskal-Wallis and Dunn test (α=0.05)
showed no differences in the cariostatic effect between the cavities restored with the same
material and prepared with diamond burs or Er:YAG laser.
Keywords: Erbium laser, dental caries, cariostatic agents, composite resins, glass ionomer cement, fluoride, dental enamel, secondary caries.
29
Introduction
The metabolic bacteria processes in the biofilm are a physiological phenomenon that
may lead to enamel mineral loss and subsequent cavity formation because of the imbalance in
the dynamic equilibrium between tooth mineral and plaque fluid determining caries lesion
development [1]. To avoid caries development, an individual preventive treatment based on
the patients’caries risk should be implemented [1]. Secondary caries is the lesion at the
margin of an existing restoration similar to the primary caries but also may show lines of
demineralized tissue on the cavity wall [2]. The presence of fluorides in the oral cavity may
inhibit the demineralization process caused by bacteria acid production in the biofilm.
Therefore the use of topical fluorides and restorative materials that release fluorides like glass
ionomer based materials are useful tools to prevent secondary caries and also in enamel
located at a considerable distance from the cavity margin [3-6].
However, some patients at high caries risk need additional care in preventive
treatments to avoid primary or secondary caries development [1,5]. Some studies have shown
the potential of laser irradiation on morphological and chemical changes in dental enamel by
organic matrix decomposition and carbonate content reduction resulting in a less acid-
permeable enamel with improved bacterial acid-resistance [6-8]. The most commonly used
lasers for preventive procedures are CO2 and Erbium lasers [6-8]. Although, they are
classified as high intensity lasers, the energy densities required for caries preventive treatment
are low and enamel ablation is avoided [7,9].
Ablation is a phenomenon that occurs when the laser energy is absorbed by water
molecules and hydrous organic components of biological tissues, and the water vapor
production induces an increase in internal pressure within the tooth tissue, resulting in
microexplosions which cause dental tissue removal [10]. This way, ablative parameters are
used to remove carious tissue and perform cavity preparations which shows as advantage,
compared to conventional bur preparations, a significantly reduced need for local anesthesia,
no vibratory or auditory irritation which is perceived by patients as more comfortable [11-12].
In spite of the energy densities used for cavity preparation are higher than densities
used for caries prevention, heat is produced during ablation and transmitted through the cavity
margins and this not ablated surface may be fused or melted with enamel recristallization
resulting in a less permeable substrate to bacterial acid diffusion [13,14]. However it is not
30
known if the heat accumulation may be enough to thermally modify enamel chemical
structure and improve its acid resistance as occurs by direct laser irradiation with subablative
energy densities.
In this way, if such increase in the acid resistance of enamel cavities margins are
possible it may act synergistically with fluoride releasing restorative materials in the
prevention of caries lesion development. Therefore, the present study aimed to investigate, in
vitro by a visual evaluation, the effect of the cavity preparation with Er:YAG laser, on the
inhibition of secondary caries around cavities filled with fluoride releasing restorative
materials.
Examiners evaluated, by visual examination, the presence and severity of caries
lesions development around cavities prepared with burs or Er:YAG laser irradiation. Visual
inspection is frequently used to quantify opacities, fluorosis and white spots lesions resulting
from enamel demineralization in laboratorial and clinical studies [4,5,16-18]. Although this
method may be considered as subjective compared to other methods such as microradiograph,
polarized light microscopy or microhardness, visual inspection is simple, facilitates laboratory
investigation and allows the inspection of the total net area resulting in a general result. In
addition, it facilitates the conduction of studies faster and at lower costs and present
correlation to other sophisticated methods [4,16]. Also, the examiners performed the
diagnosis in a way similar to clinical diagnosis evaluating the absence or presence of white
spot lesions, and quantified their activity and severity, considering that the opacity of the
lesion increases as the mineral content decreases, by the use of a four-point ordinal scale [4,5]
with the advantage of the magnification and room standardized conditions [16].
31
Material and Methods
The Ethics Research Committee at the University Guarulhos approved the research
protocol. The effects of the 3 restorative materials and 2 cavity preparation techniques with
diamond burs or Er:YAG laser were evaluated by the use of human teeth. It resulted in 6
experimental groups (Table I).
Table I. Restorative systems and cavity preparation
Groups Cavity Preparation Restorative Systems
G 1 Diamond burs (#2292, KG Sorensen, Barueri, SP, Brazil)
Conventional glass ionomer cement (GI) (Ketac-Fil,3M/ ESPE, Seefeld, Germany)
G 2 Diamond burs Resin-modified glass ionomer (RM) (Vitremer, 3M/ESPE, St. Paul, MN, USA)
G 3 Diamond burs Composite resin (CR) (Z250, 3M/ESPE, St. Paul, MN, USA)
G 4 Laser Er:YAG (Kavo Key II; Kavo, Biberach, Germany)
Conventional glass ionomer cement
G 5 Laser Er:YAG Resin-modified glass ionomer
G 6 Laser Er:YAG Composite resin
For blocks preparation, unerupted third molars were selected and stored in a 0.1%
Thimol solution. The teeth were soft-tissue debrided and cleaned with water/pumice slurry
and rubber cups in a low-speed handpiece (Kavo do Brasil, Joinville, SC, Brazil). The crowns
were sectioned to obtain 72 dental enamel/dentin blocks (4x4x3mm3) from the middle of the
crows, using double-faced diamond discs #7020 (KG Sorensen, Barueri, SP, Brazil, 06454-
920). Then, the blocks were stored in 100% humidity until cavity preparation.
A total of 72 dental blocks (n=12/group) were restored in 12 steps. In each stage, 2
restoration of each restorative system in a cavity prepared with a diamond bur and in a cavity
prepared with Er:YAG laser were made according to a randomized complete block design
with 1 replication per block. The qualitative variable response “development of artificial
caries-like lesion” was evaluated blindly and independently by 3 calibrated examiners using
an ordinal scale based on visual examination.
The blocks were distributed in two halves, one half had cylindrical class V cavities
with approximately 1.6mm in diameter and 1.6mm depth prepared in high speedy with
diamond burs #2292 using constant water spray coolant.
The other half had the cavities prepared with Er:YAG laser working at 2,940 nm.
The output power and pulse rate ranged from 60–500 mJ and 1–15 Hz, respectively. Working
32
with a distance of 12 mm from the lased surface, a handpiece (# 2056) with a 0.63 spot size,
and energy of 300 mJ with a repetition rate of 6 Hz, with an approximately energy density of
47 J/cm2 was employed in a focused mode to prepare the cavities at continuous water spray (5
ml/min).
The prepared blocks were randomly assigned to the 3 restorative materials subgroups
(Table I). Restorations were done in 12 steps, in which one block per subgroup was filled.
The sequence of restoration was determined at random and the materials were inserted
according to the manufacturers’ instructions and photo-activated with an Optilux 501 device
(Demetrom/Kerr, USA) with a mean of 700 mW/cm2.
In cavities filled with Ketac-Fil (3M/ESPE), the Ketac conditioner was applied for 10
s, rinsed and dried for 10 s. Ketac-Fil was prepared within 20-25 s, inserted in the cavity with
a centrix injector, protected with a lead strip for 5 min, coated with Vitremer Finish Gloss
(3M/ESPE) and light-activated for 20 s to maintain the ionomer water stability. To Vitremer
(3M/ESPE) restoration, the Primer was applied for 30 s, dried for 5 s and light-activated for
20 s. Vitremer was prepared within 45 s, inserted in the cavity with a centrix injector, photo-
activated for 40 s, coated with Vitremer Finish Gloss and light-activated for 20 s. In cavities
filled with composite resin, the 3M Scotch Bond etchant was applied for 15 s, rinsed for 10 s
and air-dried. Two coats of Adper Single Bond 2 (3M/ESPE) were applied, air-dried for 5 s
and light-activated for 10 s. The Z250 (3M/ESPE) composite resin was inserted and light-
activated for 20 s.
All restored blocks were stored in 100% humidity for 24h and then polished using
the Sof-lex (3M ESPE) disks for 15s with each disk under water-cooling at a low speed.
The blocks were individually immersed in 1 mL of deionized distilled water to avoid
ionic changes among them and thermocycled together for 1000 cycles in water between 5 ±
2ºC and 55 ± 2ºC with a dwell time of 2 min for each bath and a 15 s transfer time between
baths [4].
A uniform area of exposed enamel surrounding the restorations was obtained by
covering the remaining dental block with red wax. To simulate high caries risk conditions, the
restored blocks were submitted to a demineralization/remineralization dynamic model, as
proposed by Featherstone et al. [4,5,15].
This model simultaneously measures the net result of the inhibition of
demineralization and the enhancement of remineralization. The demineralization stage uses an
acid buffer containing 2 mmol/L Ca, 2 mmol/L PO4, 0.075mol/L acetate at pH 4.3. The
33
remineralization solution contains calcium and phosphate at a know degree of saturation, to
mimic the remineralizing properties of saliva, and 50 mmol/L KCl, 1.5 mmol/L Ca, 0.9
mmol/L PO4, 20 mmol/L tri-hydroxymethylaminomathan buffered at pH 7.0 [5,15].
The blocks were immersed separately in 15 mL of demineralization solution for 6h,
washed with deionized distilled water, immersed in 15 mL of remineralization solution for 18
h, washed and immersed in demineralization solution, thereby initiating a new cycle. The pH
cycles were conducted during 14 days with 10 daily cycles. In the 6th, 7th, 13th, and 14th days
of the cycle, the blocks were kept only in the remineralization solution [4,5,15].
After the 14 days the wax was removed, the blocks were air-dried for 15 s and
standardized images were obtained from each slab with a Nikon D70 digital camera equipped
with a macro #105 lens. Three calibrated examiners evaluated independently and blindly the
images of all blocks projected in a dark room with approximately 100x magnification. The
examiners evaluated these specimens scoring the presence and severity of caries-like lesions
according to an ordinal scale ranked 0 to 3 based on visual examination, as described in
Figure I [4].
Figure I – Scores used to quantify artificial caries-like lesion development around restorative materials.
A median was obtained from scores given by the 3 examiners for each block.
Differences among the medians were analyzed by Kruskal-Wallis non-parametric test at a
95% confidence level and Dunn test. The calibration between examiners was verified by
Kappa test.
34
Results
The intra and inter-examiners kappa values are shown in Table II, and may be
considered with good or excellent agreement.
Table II- Kappa intra and inter-examiners values.
Examiners 1 2 3 1 0.797 - - 2 0.831 0.733 - 3 0.832 0.812 0.929
The exploratory values to estimate of effect (medium) and variation (amplitude) and
the results of Dunn test are shown in Table III. The greatest development of artificial caries
lesions was in G3, which was prepared with DB and restored with CR, which showed
statistical differences from G1, G2, G4, and G5. The G6 did not differ from G3 or from the
other groups. The lowest incidence of artificial caries was observed in G4.
Table III- Exploratory results of medium scores, median post, range from minimum to maximum scores (min-max), and Dunn test results per group. Glass-ionomer cement (GI), resin-modified glass-
ionomer (RM), composite resin (CR), diamond bur (DB), Er:YAG laser (LA) Restorative material GI RM CR Cavity preparation DB LA DB LA DB LA Group G1 G4 G2 G5 G3 G6 Median 1 1 1 1 3 3 Median post 27.6 24.5 29.3 32.5 58.8 46.0 Min - Max 0-3 0-2 0-3 0-3 2-3 0-3 Dunn test A A A A B AB
35
Discussion
In the present study, the Er:YAG laser used for cavity preparation was not able to
change enamel surface and guarantee a significantly higher acid-resistance than bur
preparation against the acid challenge. The pH cycling model used to create the acid challenge
and promote artificial caries like lesion is similar to the acid challenge found in a patient at
high caries risk and shows a correlation with the onset and progression of caries lesions
[15,19]. This method simulates the demineralization and remineralization phenomena
occurring in oral environment and has often been recommended to investigate the effects of
different substances in dental caries prevention aiming to correctly predict clinical outcomes
[15,19].
There is an agreement that the fluoride released from restorative materials may
inhibit secondary caries development [1-5,20-22]. Among the groups which cavities were
prepared with burs, the group G1 restored with the glass ionomer cement showed the least
artificial caries development. This result is in agreement with some previous studies that
described the potential to prevent secondary caries by glass ionomer cements [4,5,22].
Also, some studies demonstrated that the resin-modified glass ionomer materials,
which are hybrid materials, exhibit intermediate properties between their precursors glass
ionomer cements and light-curing composite resin [4,5,23]. This result was observed in the
present study, as G2 and G1 showed a similar anticariogenic effect, such effect was also
observed among the lased preparations.
Neither the composite resin nor the adhesive system used in the present study
contains fluorides in their formulations, so it was observed that all blocks prepared with burs
and restored with the composite resin showed artificial caries development, which scores
ranged form 2 to 3. This result is in agreement with other studies that demonstrated that Z-250
did not present any cariostatic effect [4,5,16,20,25].
Chimello et al. reveal that after in situ caries development the Er:YAG laser did not
differ from conventional cavity preparation with regard to enamel microhardness when
restored with a composite resin [25]. Also a Polarized Light Microscopic analysis showed no
differences irrespective of the Er:YAG laser parameters in comparison with the conventional
bur cavity preparation [16]. However, after visual inspection of the specimens by image
presentation in a dark room Chimello et al. observed that inhibition zone scores showed
36
significant difference among groups, which was ascribed to the control group which cavities
were prepared with diamond burs and suggest a lower degree of demineralization at the
restoration margin of the irradiated samples [16]. Although no statistical significant
differences were found between the groups restored with composite resin (G3 and G6), all
blocks in Group G3 presented caries development (scores 2-3) and the blocks prepared with
Er:YAG laser (G6) ranged from 0 to 3. The presence of blocks without caries development in
this group suggests some acid-resistance gained by enamel due to laser preparation that
prevented the artificial caries development. This theory may be strongly reinforced by the
absence of differences between the group prepared by Er:YAG laser and restored with
composite resin (G6) and the group prepared with burs and restored with glass ionomer
cement (G1). Also, from the comparison of scores range of groups G1 and G4 restored with
glass ionomer cement, it can be observed that G1 present scores form 0 to 3 and G4 showed
no advanced active caries like lesions (score 3) that also may suggest that some acid-
resistance may be promoted by laser preparation.
Additionally, some studies showed that erbium lasers used with low energy densities
may improve enamel acid-resistance [7,24], and a clinical trial showed that cavities prepared
with Er,Cr:YSGG, after six months presented no secondary caries at the margins of the
preparation sites [12].
In a previous study Perito et al. found less development of caries lesion around
Er:YAG laser-prepared cavities than around the cavities prepared with diamond burs.
However, no synergistic cariostatic effect was observed between the Er:YAG laser and glass-
ionomer cement [26].
Despite of some evidence of acid-resistance gain was suggested, under the
experimental conditions a synergic effect with glass ionomers materials or a simple
improvement in the enamel acid-resistance after Er:YAG cavity preparation were not
statistically confirmed.
Conclusion
In the present study, the Er:YAG laser used for cavity preparation did not show the
ability to change enamel surface and guarantee significantly more acid-resistance than bur
preparation against the acid challenge.
37
ACKNOWLEDGEMENTS
We would like to thank the Special Laboratory of Lasers in Dentistry of the School
of Dentistry of the University of São Paulo (LELO) for making their facilities available for us
and for their friendly help during research. We also thank FAPESP (Grant n. 97/10823-0).
DISCLOSURE STATEMENT
The authors disclose any commercial or other associations that might pose a conflict
of interest in connection with submitted material.
38
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4. Rodrigues JA, Marchi GM, Serra MC, Hara AT (2005) Visual evaluation of in vitro
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9. Kantorowitz Z, Featherstone JD, Fried D (1998) Caries prevention by CO2 laser treatment:
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10. Aoki A, Sasaki KM, Watanabe H, Ishikawa I. 2000 Lasers in nonsurgical periodontal
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11. Keller U, Hibst R, Geurtsen W, Schilke R, Heidemann D, Klaiber B, Raab WH (1998)
Erbium:YAG laser application in caries therapy. Evaluation of patient perception and
acceptance. J Dent 26(8):649-56.
12. Hadley J, Young DA, Eversole LR, Gornbein JA (2000) A laser-powered hydrokinetic
system for caries removal and cavity preparation. J Am Dent Assoc 131(6):777-85.
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13. Hossain M, Nakamura Y, Kimura Y, Yamada Y, Ito M, Matsumoto K 2000 Caries-
preventive effect of Er:YAG laser irradiation with or without water mist. J Clin Laser Med
Surg 18:61–65. 14. Ying D, Chuah GK, Hsu CS. Effect of Er:YAG laser and organic matrix
on porosity changes in human enamel. J Dent 2004;32:41–46.
15. Featherstone JDB, O’Really MM, Shariati M, Brugler S. Enhancement of remineralization
in vitro and in vivo. In: Factors Relating to Demineralization and Remineralization of the
Teeth. Leach SA (Editor). Oxford: IRL, 1986. p. 23-34.
16. Chimello DT, Serra MC, Rodrigues AL Jr, Pécora JD, Corona SA (2008) Influence of
cavity preparation with Er:YAG Laser on enamel adjacent to restorations submitted to
cariogenic challenge in situ: a polarized light microscopic analysis. Lasers Surg Med
40(9):634-43. DOI: 10.1002/lsm.20684
17. Gorelick L, Geiger AM, Gwinnet AJ (1982) Incidence of white spot formation after
bonding and banding. Am J Orthod 81:93-98.
18. Noel L, Rebellato J, Sheats RD (2003) The effect of argon laser irradiation on
demineralization resistance of human enamel adjacent to orthodontic brackets: an in vitro
study. Angle Orthod 73(3):249-58.
19. Featherstone JD (1996) Modeling the caries-inhibitory effects of dental materials. Dent
Mater 12(3):194-7.
20. Pin ML, Abdo RC, Machado MA, da Silva SM, Pavarini A, Marta SN (2005) In vitro
evaluation of the cariostatic action of esthetic restorative materials in bovine teeth under
severe cariogenic challenge. Oper Dent May-Jun;30(3):368-75.
21. Gonzalez Ede H, Yap AU, Hsu SC (2004) Demineralization inhibition of direct tooth-
colored restorative materials. Oper Dent 29(5):578-85.
22. Cenci MS, Tenuta LM, Pereira-Cenci T, Del Bel Cury AA, ten Cate JM, Cury JA (2008)
Effect of microleakage and fluoride on enamel-dentine demineralization around restorations.
Caries Res 42(5):369-79. DOI: 10.1159/000151663
23. Sidhu SK, Watson TF (1995). Resin-modified glass ionomer materials. A status report for
the American Journal of Dentistry. Am J Dent 8(1):59-67.
24. Liu Y, Hsu CY (2007) Laser-induced compositional changes on enamel: a FT-Raman
study. J Dent 35(3):226-30. DOI:10.1016/j.jdent.2006.08.006
25. Chimello DT, Serra MC, Rodrigues-Júnior AL, Pécora JD, Corona SA (2008) Influence
of Er:YAG laser on microhardness of enamel adjacent to restorations submitted to cariogenic
challenge in situ. Photomed Laser Surg 26(4):379-85. DOI:10.1089/pho.2008.2193.
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26. Perito MAM, Jorge ACT, Freitas PM, Cassoni A, Rodrigues JA (in press) Cavity
preparation and restorative materials influence on the prevention of secondary caries.
Photomed Laser Surg.
41
3.3 Capítulo 3
Artigo aceito na revista Photomedicine and Laser Surgery
Cavity preparation and restorative materials influence on the prevention of secondary caries
Running Title: cavity preparation and secondary caries prevention
Mario Alberto Marcondes Perito1, Ana Carolina Tedesco Jorge2, Patrícia Moreira de Freitas3, Alessandra Cassoni4, José Augusto Rodrigues5
1- DDS, Dental Research and Graduate Studies, Division Department of Restorative Dentistry, Guarulhos University, Guarulhos, SP, Brazil. Phone: +55 11 24641769 Fax: +55 11 24641668 e-mail:[email protected]
2- DDS, Dental Research and Graduate Studies, Division Department of Restorative Dentistry, Guarulhos University, Guarulhos, SP, Brazil. Phone: +55 11 24641769 Fax: +55 11 24641758 e-mail: [email protected]
3- DDS, MS, PhD, Special Laboratory of Lasers in Dentistry, Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, Brazil. Phone: +55 11 30917645 Fax: +55 11 30856907 e-mail: [email protected]
4- DDS, MS, ScD, Dental Research and Graduate Studies, Division Department of Restorative Dentistry, Guarulhos University, Guarulhos, SP, Brazil. Phone: +55 11 24641769 Fax: +55 11 24641758 e-mail:[email protected]
5- DDS, MS, ScD, Dental Research and Graduate Studies, Division Department of Restorative Dentistry, Guarulhos University, Guarulhos, SP, Brazil. Phone: +55 11 24641769 Fax: +55 11 24641758 e-mail:[email protected]
*Corresponding Author: Dr. José A. Rodrigues Department of Operative Dentistry, Guarulhos University Rua Dr. Nilo Peçanha 81, Predio U, 6o. Andar Guarulhos, SP, Brazil, 07011-040 Phone: +55 11 6464-1769 Fax: +55 11 6464-1758 Email: [email protected] or [email protected]
42
ABSTRACT
Objective: This study evaluated in vitro the influence of cavity preparation using the Er:YAG
laser and restorative materials containing fluoride on preventing caries lesions. Background: It
has been suggested that cavity preparation using the Er:YAG laser has a potential for
improving resistance to secondary caries on enamel. Methods: Forty unerupted human third
molars teeth were used to obtain was sectioned into 72 blocks of dental enamel and
distributed into 2 groups to prepare cavities measuring (1.6mmØ) with diamond burs (DB) or
Er:YAG laser (LA - 6 Hz, 300 mJ, 47 J/cm2). After that, each group was divided into 3 sub-
groups and restored with a glass-ionomer cement (GI), a resin-modified glass-ionomer (RM),
or a composite resin (CR). Blocks were thermalcycled and submitted to a pH challenge to
develop artificial caries-like lesions. Lesions were evaluated by Knoop microhardness test.
An average of 4 indentations was used. Statistical analyses were performed by ANOVA
followed by Tukey’s test. Results: The results (in KHN) for diamond bur cavity preparation
(DB) were (GI) 235.5 (±75.5); (RM) 137.1 (±64.1); (CR) 39.3 (±26.5); and for Er:YAG laser
cavity preparation (LA) were (GI) 410.0 (±129.7); (RM) 310.3 (±119.5); (CR) 96.4 (±57.4).
Conclusions: There was less development of caries lesion around laser-prepared cavities than
around the cavities prepared with diamond burs, however, no synergistic cariostatic effect was
observed between the Er:YAG laser and glass ionomer cement.
Keywords: Erbium laser, dental caries, cariostatic agents, composite resins, glass ionomer
cement, fluorides, dental enamel, hardness.
43
INTRODUCTION
A few decades ago dental caries was considered a common and unavoidable disease1.
Nowadays knowledge of the etiology and development of caries disease has allowed a
reduction in caries risk and activity, by preventing and arresting caries lesions. Thus, the
diagnoses of caries risk and individual treatment based on the reduction of their determinant
and modulating factors are very important because there is a need for patient revert to a
disease-free status by restoring the balance so that the forces tending to prevent the diseases
outweigh the forces contributing to their progression.1
One of the factors capable of moderating caries development is the presence of
fluorides in the oral environment. Fluorides acts by reducing the critical pH for enamel
dissolution from 5.5 to 4.5, thus enamel is able to resist a higher acid challenge2. Fluorides
may be found in the drinking water, toothpastes, mouthwash solutions, varnishes, and are also
released from restorative materials. Fluoride releasing restorative materials are indicated to
prevent secondary caries development in high-risk patients.3,4,5
The potential cariostatic effect of restorative materials is described for researches that
have shown high cariostatic effect of conventional glass ionomer cements, moderate
cariostatic effect of glass ionomer and composite resin hybrid materials, and no cariostatic
effect of composite resin materials.3,4,6,7
On the other hand, few studies have suggested the use of lasers to modify dental
enamel structure and improve its acid-resistance. The first lasers recommended for caries
prevention were CO2 laser, followed by Nd:YAG, Er:YSGG, and Er:YAG lasers.8 Because of
coincident band absorption by water and hydroxyapatite, CO2 and erbium lasers efficiently
heat the enamel surface to temperatures sufficient to inhibit acid dissolution and can prevent
up to 80% of enamel dissolution in the face of an acid challenge with energy densities below
the enamel ablation threshold.9,10
Ablation is a phenomenon that occurs during laser irradiation when the laser energy
is absorbed selectively by water molecules and hydrous organic components of biological
tissues, causing evaporation of water and organic components and resulting in thermal effects
due to the heat generated by this process, and the production of water vapor induces an
increase in internal pressure within the tooth tissue, resulting in microexplosions that cause
dental tissue removal.11
44
Ablative parameters are used to perform cavity preparations, and although the more
clinical time expensed, patients have perceived laser as more comfortable, without vibratory
and auditory irritation, with a significantly reduced need for local anesthesia compared to
mechanical means.12 Among high intensity lasers, Fried et al. (1997)9 suggested that an
advantage of the Er:YAG lasers is the enamel ablation mechanism, which is primarily based
on the principal absorber not in hard tissue. They reported that primary absorption in water
results in water-mediated ablation, and primary absorption in the bulk of enamel rods results
in melting and vaporization.9 The absorption of the Er:YAG lasers by inorganic components
(hydroxyapatite) is much lower than that of other lasers, such as CO2 laser.13 Thus, the
absorption in water and hydrous organic components occurs rapidly before heat accumulation
caused by absorption in inorganic components takes place, resulting in thermo-mechanical,
explosive ablation.13
Although the energy densities used for cavity preparation are higher than densities
used for caries prevention, some heat is generated at the cavity margins during ablation, but it
is not known if this heat accumulation would be enough to thermally modify the enamel and
improve its acid resistance. This theory can be speculated from the results of studies that
showed a tendency towards increased caries resistance after sub-ablative erbium laser
irradiation14; and that low energy densities of Er:YAG laser can decrease enamel solubility; as
well as a clinical trial that showed that after six months, cavities prepared with Er,Cr:YSGG
presented no secondary caries at the margins of the preparation sites.15
Many studies showed the caries preventive potential of Er:YAG laser but the articles
are focused on the use of sub-ablative parameters, and it is not known whether the heat
accumulation during cavity preparation could provide enamel surface around cavity margins
with some acid-resistance, and also whether this possible improvement in acid-resistance
could act synergistically with restorative materials that release fluorides for the prevention of
caries lesion development. Therefore, the aim of the present study was to investigate the
effect in vitro, of cavity preparation with Er:YAG laser, on inhibiting enamel
demineralization around fluoride releasing adhesive restorations.
45
METHODS AND MATERIALS
Since this study was performed using human third molars, the research protocol was
submitted to the Research Ethics Committee of the Guarulhos University and was approved in
accordance with the resolution CNS# 196/96 of the National Health Committee/Health
Department (Brazil).
EXPERIMENTAL DESIGN
The experimental units consisted of 72 dental blocks (n=12 per group) obtained from
40 unerupted human third molars. The factors under study were ‘Method of Cavity
Preparation’ (at two levels) and ‘Restorative Material’ (at three levels) in a factorial design
(Table 1). The response variable was surface microhardness in Knoop Hardness Number
(KHN).
Table 1- Experimental groups.
Group Method of cavity preparation Restorative material
DBGI Diamond bur (#2292, KG Sorensen, Barueri, SP, Brazil)
Glass ionomer cement (Ketac-Fil,3M/ ESPE, Seefeld, Germany)
DBRM Diamond bur Resin modified glass ionomer (Vitremer, 3M/ESPE, St. Paul, MN, USA)
DBRC Diamond bur Resin composite (Z250, 3M/ESPE, St. Paul, MN, USA)
LAGI Er:YAG laser (Kavo Key II; Kavo, Biberach, Germany)
Glass ionomer cement
LARM Er:YAG laser Resin modified glass ionomer
LARC Er:YAG laser Resin composite
PREPARATION OF DENTAL BLOCKS
Following extractions, teeth were stored in a 0.1% Timol solution (pH 7.0) for no
more than 30 days.16 Soft-tissues were removed using periodontal curettes (HU-FRIEDY do
Brasil, Rio de Janeiro- Brazil) and cleaning was performed using a slurry of pumice in a
46
webbed rubber cup applied with a slow-speed handpiece (Kavo do Brasil, Joinville- Brazil).
The roots were removed, and the crowns were longitudinally and transversally sectioned to
obtain 72 dental blocks measuring 4x4x3 mm3 using double-faced diamond discs (#7020, KG
Sorensen, São Paulo- Brazil).
CAVITY PREPARATION AND RESTORATION
Standardized circular cavities were prepared in the enamel blocks. Half of the
samples were prepared with diamond burs. Cavities of approximately 1.6 mm in diameter and
1.6 mm deep were prepared at high speed with diamond burs No. 2292 (KG Sorensen,
Barueri, SP, Brazil, 06454-920) under a constant water spray coolant.
The other half of the samples were irradiated using the Er:YAG laser (KaVo Key II;
KaVo, Biberach, Germany) working at 2940 nm. The output power and pulse rate ranged
from 60–500 mJ and 1–15 Hz, respectively. Working at a distance of 12 mm from the tooth
surface (focused mode), a handpiece (# 2056) with a 0.63 mm spot size, and energy of 300 mJ
with a repetition rate of 6 Hz was used to prepare the cavities under continuous water spray (5
mL/min). The energy density was approximately 47 J/cm2 and cavities were standardizing by
visual and contact comparisons to diamond burs No. 2292 used to mechanical preparation.
After the cavity preparations, the blocks were randomized among the restorative
material subgroups (Table 1) and the cavities in 12 blocks were restored, with one sample of
each group, in one increment, according to the manufacturer’s instructions.
In cavities filled with Ketac-Fil, the Ketac conditioner was applied for 10 s, rinsed
and dried for 10 s. Ketac-Fil was prepared within 20-25 s, inserted in the cavity with a Centrix
injector, protected with a mylar strip (Dentart, Polidental, São Paulo, Brazil; dimension
10x120x0.05mm3) for 5 min, coated with Vitremer Finish Gloss and light-activated for 20 s
by an Optilux 501 light unit (Demetron/Kerr, Danbury, CT, USA). The power density was
measured by placing the light tip at the radiometer of the light unit. The light curing unit had a
light tip diameter of 11 mm with an irradiance of 700 mW/cm2.
In cavities filled with Vitremer, the Primer was applied for 30 s, dried for 5 s and
light-activated for 20 s. Vitremer was prepared within 45 s, inserted in the cavity with a
Centrix injector, light-activated for 40 s, coated with Vitremer Finish Gloss and light-
activated for 20 s.
47
In cavities filled with Z-250, the 3M Scotch Bond etchant was applied for 15 s,
rinsed for 10 s and air-dried. Two coats of 3M Single Bond were applied, air-dried for 5 s and
light-activated for 10 s. The composite resin was inserted and light-activated for 20 s.
All restored blocks were stored in 100% humidity for 24 h and then polished using
the Sof-lex (3M ESPE) disks system for 15 s with each disk.
THERMAL AND ACID CHALLENGE
The blocks were placed into separate bags with 1 mL of deionized water and
thermalcycled together for 1000 cycles in water between 5±2ºC and 55±2ºC with a dwell time
of 2 min in each bath and a 15 s transfer time between baths3. All external surfaces of each
slab were coated with wax, leaving a 1.5 mm-wide margin around the restoration free of wax.
The test scheme for acid challenge was designed to model a daily demineralization
challenge of a 6 h and a 18 h repair (remineralization) by saliva as described by Featherstone
et al. (1986)17 and Serra & Cury (1992)18, with the aim of simulating a high in vitro caries risk
and producing artificial caries like-lesions around the restorations2,7,19,20.
The demineralization stage used an acid buffer containing 2 mmol/L Ca, 2 mmol/L
PO4, 0.075 mol/L acetate at pH 4.3. The remineralization solution contained calcium and
phosphate at a known degree of saturation (1.5 mmol/L Ca, 0.9 mmol/L PO4), to mimic the
remineralizing properties of saliva, and 50 mmol/L KCl, 20 mmol/L tri-
hydroxymethylaminomathan buffer at pH 7.0.17;18 The blocks were immersed separately in 15
mL of demineralization solution for 6 h, immersed in 15 mL of remineralization solution for
18 h, washed and immersed in demineralization solution, thereby initiating a new cycle. The
pH cycles were conducted for 14 days with 10 daily cycles. In the 6th, 7th, 13th, and 14th days
of the cycle, the blocks were kept only in the remineralization solution.
At the end of the pH cycles, the wax was eliminated and the blocks were stored at
100% humidity until the microhardness test.
MICROHARDNESS TEST
The demineralization of the restored enamel blocks was assessed with a
microhardness tester (PanTec, Panambra Ind. e Técnica SA, São Paulo- Brazil) and a Knoop
indenter. The indentations were made keeping the long axis of the diamond instrument parallel to
48
the outer-leveled enamel surface, using a 25 g load applied for 5 s, and the value in micrometers of
the higher diagonal was measured and automatically changed to KHN by the microhardness tester.
Four measurements were made in each 100 µm around the restoration margins in the upper, left,
right, and bottom sides (Figure 1).
Figure 1- Location scheme for microhardness test.
RESULTS
The mean microhardness values and standard deviations per restorative material in
each cavity preparation are presented in Table 2. Data were changed to √x to obtain a normal
distribution and were submitted to ANOVA considering the factorial 3X2 model to observe
the factors and their interactions. There were statistical differences in the factors Restorative
Materials and Method of Cavity Preparation (p<0.00001); there was no interaction between
the factors Restorative Materials and Method of Cavity preparation (p=0.3181).
49
Table 2- Means (standard deviation) of surface microhardness (KHN) for factors Method of Cavity Preparation
(vertical), for Restorative Material (Horizontal) and for experimental subgroups. Means followed by the same
lower case letters in the row indicate no statistical difference (Tukey’s test, p<0.05) and different upper case
letters indicate mean values that are statistically different in the column (Analysis of Variance, p<0.05)
GI- Ketac Fil
309.1a RM- Vitremer
207.3b CR- Z-250
59.0c LA- Er:YAG laser
242.8 A 410.0
(129.7) 310.3
(119.5) 96.4
(57.4) DB- Diamond Bur
117.9 B 235.5 (75.5)
137.1 (64.1)
39.3 (26.5)
The microhardness of enamel around cavities filled with GI showed the highest
microhardness values, differing significantly from the cavities restored with RM, which
showed intermediate values. The cavities filled with CR showed the lowest value (Table 2).
The cavities prepared with LA showed significantly higher microhardness values than the DB
cavities.
50
DISCUSSION
Lasers with wavelengths that interact with water and hydroxyapatite allow the
conservative removal of caries lesions and cavity preparation, and can also change the
solubility of enamel, improving its acid resistance.9,10,14,15 This study evaluated the
development of artificial caries lesion on enamel around cavities prepared with diamond burs
and Er:YAG laser, and filled with restorative materials with or without fluoride releasing
properties, using a dynamic cyclic model of demineralization and remineralization, whose
acid challenge was correlated to patients with high caries risk.17
The highest development of artificial caries lesions in this study was observed in
groups restored with composite resin, which had been expected because the composite resin
or adhesive system used did not contain fluorides in their compositions.3 This is consistent
with reports from other studies, in which only composite resins and adhesive systems
containing fluorides or antibacterial monomers are capable of showing an anticariogenic
effect, which is lower than that of glass ionomers.5,19
During acid challenges glass ionomer cements mobilize and release increased
amounts of fluoride into the environment. The presence of fluorides continuously released by
these restorative materials is an important feature for facilitating the re-precipitation of
minerals, improving remineralization or inhibiting demineralization.2 This is the reason for
less artificial caries lesion development around cavities restored with conventional glass
ionomer cement.18,20,21 Therefore, the protection rendered by the glass ionomer cement is
extended for some distance from the restoration and it is greatest in the cavity preparation
area.6
To a lesser extent than in conventional glass ionomers, the smaller concentrations of
fluoride released from resin modified glass ionomer caused moderate development of
artificial caries lesion, but in comparison with glass ionomer cement, it resulted in less
inhibition.4
The statistical analysis of the factor Cavity Preparation showed more artificial caries
development in cavities prepared with diamond burs than in the cavities prepared with the
Er:YAG laser. Numerous in vitro studies using a variety of laser wavelengths within sub-
ablative parameters have been conducted to investigate caries prevention and showed this
effect.14,22 They have shown the potential of some wavelengths to be absorbed by
hydroxyapatite and water in enamel and dentin, and the conversion of the irradiated energy
51
into heat. This heat increase is considered to be the cause of the micro-structural and chemical
changes occurring in lased enamel and dentin22,23 and explains the increased acid resistance
due to the reduction in permeability by the evaporation of organic matrix.
However, the potential of the Er:YAG laser irradiation in an ablative parameter to
improve the acid resistance of enamel around the cavity preparation was not totally clear, and
although Chimello et al.25 revealed that the Er:YAG laser did not differ from conventional
cavity preparation, in the present study the enamel adjacent to cavities prepared with the
Er:YAG laser showed less development of artificial caries lesion.26 The mechanisms by
which lasers can improve the tooth acid resistance may be due to the absorption of heat and
penetration into the non-ablated enamel layers adjacent to cavity wall whose enamel was
ablated during cavity preparation.26
Thus, it can be supposed that the penetration of heat into the adjacent layers around
the cavity walls may act in the same way as in the outer enamel with a reduction in organic
matrix and enamel vitrification.26 However, the present study was conducted with water
cooling and it is recommended and indeed indispensable in order to avoid temperature
damage to the dental pulp.25 It is also important to point out that the present study selected
safe parameters as regards temperature increase in the intrapulpal region. According to
Geraldo-Martins et al.27 the samples irradiated with the Er:YAG laser using the same
parameters as the present study achieved an intrapulpal temperature increase of 1.45
(+0.64)oC. It can be also speculated that heat caused by laser is restricted to the superficial
layers of the irradiated walls, which can be a limiting factor for obtaining high acid-resistance
at some extended distance from the restoration margins.
Although the G1 Group (GI/LA) followed by G2 Group (RM/LA) showed the
highest numerical means, the interaction of factors Cavity Preparation and Restorative
Materials expected to have a synergistic effect between fluoride release and the increase in the
enamel acid resistance by the Er:YAG laser was not found in this study.
As observed in the in vitro results, the use of Er:YAG laser in cavity preparations
may be a suitable option for patients at high caries risk, by the increase in the enamel acid-
resistance and other advantages such as its microbial reduction potential and smear layer
removal.28 Although cavity sterilization and conditioning are obtained by Er:YAG laser
irradiation,29 some researchers showed the presence of a laser-modified layer that may
adversely affect enamel and dentin bonding. This layer may obliterate enamel micropores,
thus blocking the intra and interprismatic spaces, restricting resin interdiffusion into the
enamel surface.30,32 Moreover, the more acid-resistant lased surface might reduce the
52
effectiveness of acid etching and hybridization may be compromised.32 In dentin
hybridization, subsurface damage initiated by Er:YAG ablation may alter the subsurface
under the hybrid zone and remnant denatured collagen fibrils may not resist to the forces from
the polymerization shrinkage and fractures may occur, leading to microleakage.30,31
A negative influence on marginal sealing of composite resin restorations with a total
etch adhesive system after Er:YAG laser use has also been showed in microleakage
studies.30,31 However, results are poor and contradictories, other researches found no
differences in the microleakage of composite resin, glass ionomer cement or resin modified
glass ionomer restorations etched or prepared with Er:YAG laser.34,35,36 Only Hadley et al.
(2000)12, in in vivo research, observed the performance of composite resin restorations in 66
cavities prepared with Er,Cr:YSGG (68,1 J/cm2), in comparison with 66 cavities prepared
with diamond burs. After 6 months all restorations were retained and no secondary caries was
observed.
In order to avoid secondary caries, not only the improvement of dental acid
resistance is necessary4 but further studies are needed as regards Er:YAG laser parameters to
achieve the ideal association with adhesive systems, to produce an adequate hybrid layer to
avoid the microleakage phenomena and improve dental acid-resistance. However, the use of
Er:YAG laser in cavity preparation may thus be useful and effective in the prophylaxis and
management of patients at high risk for dental caries, the present study showed less caries
development around cavities prepared with Er:YAG laser than bur preparation but in vivo
studies are necessary to confirm these in vitro results and verify the performance of the
restorative materials inserted in these cavities.
CONCLUSIONS
The cavity preparation with Er:YAG laser may lead to an increase in the acid-
resistance in the enamel layers surrounding cavity walls, irrespective of the presence of
fluorides in the restorative material. The high cariostatic effect was observed to conventional
glass ionomer followed by the resin modified glass ionomer with a moderated cariostatic
effect. The composite resin showed no cariostatic effect. No synergistic effect between glass
ionomer cement and laser was observed.
53
DISCLOSURE
The authors have no interest in any of the companies or products mentioned in this
article.
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15. Cecchini, R.C., Zezell, D.M., de Oliveira, E., de Freitas, P.M., and Eduardo, C. de P.
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16. Soares, L.E., Martin, A.A., Pinheiro, A.L., and Pacheco, M.T. (2004). Effects of treatment
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24. Chimello, D.T., Serra, M.C., Rodrigues-Júnior, A.L., Pécora, J.D., Corona, S.A. (2008).
Influence of Er:YAG laser on microhardness of enamel adjacent to restorations submitted to
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25. Apel, C., Schafer, C., and Gutknecht, N. (2003). Demineralization of Er:YAG and
Er,Cr:YSGG laser-prepared enamel cavities in vitro. Caries Res. 37, 34-7.
26. Beviláqua, F.M., Zezzell, D.M., Magnani, R., Ana, P.A., and Eduardo, C.P. (2008).
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for cavity preparation: an SEM evaluation. Microsc. Res. Tech. 70, 803-08.
29. Délme, K.I.M., De Moor, R.J.G. (2007). Scanning electron microscopic evaluation of
enamel and dentin surfaces after Er:YAG laser preparation and laser conditioning. Photomed.
Laser Surg. 25, 393-401.
30. De Moor, R.J.G., Délme, K.I.M. (2006). Erbium lasers and adhesion to tooth structure. J.
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31. Chimello-Sousa, D.T., de Souza, A.E., Chinelatti, M.A., Pecora, J.D., Palma-Dibb, R.G.,
and Milori-Corona, S.A. (2006). Influence of Er:YAG laser irradiation distance on the bond
strength of a restorative system to enamel. J. Dent. 34, 245-51.
32. Ceballos, L., Toledano, M., Osorio, R., Garcia-Godoy, F., Flaitz, C., and Hicks, J. (2001).
ER-YAG laser pretreatment effect on in vitro secondary caries formation around composite
restorations. Am. J. Dent. 14, 46-9.
33. Corona, S.A., Borsatto, M.C., Pecora, J.D., De S.A. Rocha, R.A., Ramos, T.S., and
Palma-Dibb, R.G. (2003). Assessing microleakage of different class V restorations after
Er:YAG laser and bur preparation. J. Oral Rehabil. 30, 1008-14.
34. Niu, W., Eto, J.N., Kimura, Y., Takeda, F.H., and Matsumoto, K. (1998). A study on
microleakage after resin filling of Class V cavities prepared by Er:YAG laser. J. Clin. Laser
Med. Surg. 16, 227-31.
35. Delme, K.I., Deman, P.J., Nammour, S., and De Moor, R.J. (2006). Microleakage of class
V glass ionomer restorations after conventional and Er:YAG laser preparation. Photomed.
Laser Surg. 24, 715-22.
56
36. Chinelatti, M.A., Ramos, R.P., Chimelo, D.T., Corona, S.A., Pecora, J.D., and Dibb, R.G.
(2006). Influence of Er:YAG laser on cavity preparation and surface treatment in
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57
3.4 Capítulo 4
Artigo aceito na revista Saúde da Universidade Guarulhos
Correlation between visual and superficial microhardness evaluation of
artificial secondary caries
Mario Alberto Marcondes Perito1, José Augusto Rodrigues2
1- DDS, Dental Research and Graduate Studies, Division Department of Restorative
Dentistry, Guarulhos University, Guarulhos, SP, Brazil. Phone: +55 11 24641769 Fax: +55
11 24641668 e-mail:[email protected]
2- DDS, MS, ScD, Dental Research and Graduate Studies, Division Department of
Restorative Dentistry, Guarulhos University, Guarulhos, SP, Brazil. Phone: +55 11 24641769
Fax: +55 11 24641758 e-mail:[email protected]
*Corresponding Author:
Dr. José A. Rodrigues
Department of Operative Dentistry, Guarulhos University
Rua Dr. Nilo Peçanha 81, Predio U, 6o. Andar
Guarulhos, SP, Brazil, 07011-040
Phone: +55 11 6464-1769 Fax: +55 11 6464-1758
Email: [email protected] or [email protected]
58
Correlation between visual and superficial microhardness evaluation of
artificial secondary caries
Correlação entre avaliação visual e de microdureza superficial de cáries
secundárias em esmalte
Abstract
This in vitro study evaluated the correlation of artificial secondary caries diagnosis on enamel
between visual evaluation and superficial microhardness test. Cavities with standardized
diamond burs (1.6mmØ) were prepared on thirty-six enamel blocks obtained from unerupted
human third molars and were assigned into 3 groups. Each group was restored with glass-
ionomer cement (GI), resin-modified glass-ionomer (RM), or composite resin (CR). Blocks
were thermocycled and submitted to a pH challenge to develop artificial caries-like lesions.
Lesions were analyzed by visual evaluation using scores and the results were submitted to
Kruskal Wallis and Dunn Test. The hardness of the enamel surface surrounding the restored
cavity was evaluated using Knoop microhardness test and results were submitted to ANOVA
followed by Tukey’s post-hoc test. Afterwards, the correlation between visual and
microhardness analyses was verified by Spearman’s rho nonparametric correlation test.
Regarding visual analysis, no significant difference was observed between GI and RM
groups, which showed less caries development than CR group. The microhardness evaluation
showed significant differences among all groups with the least caries development in GI
group, followed by RM and CR, respectively. The Spearman’s rho coefficient of correlation
demonstrated a significant weak negative correlation between the response variables. The
superficial microhardness test was more sensitive to detect artificial secondary caries than
visual evaluation.
Key-words: dental caries, composite resin, glass ionomer cement, dental enamel, hardness,
visual evaluation.
59
Resumo
Este estudo in vitro avaliou a correlação entre a inspeção visual e a microdureza superficial no
diagnóstico de lesões artificiais de cárie secundária em esmalte. Trinta e seis blocos de
esmalte obtidos de terceiros molares humanos inclusos foram utilizados para a confecção de
cavidades circulares padronizadas (1,6 mmØ) e distribuídas em 3 sub-grupos. Cada sub-grupo
foi restaurado com cimento de ionômero de vidro (GI), ionômero de vidro modificado por
resina (RM), ou resina composta (CR). Os fragmentos foram termociclados e submetidos ao
desenvolvimento de lesões artificiais de cárie por ciclagem de pH. As lesões foram avaliadas
por inspeção visual empregando-se escores e foram avaliadas estatisticamente pelos testes de
Kruskal Wallis e Dunn; e por ensaio de microdureza Knoop, que foi avaliado por ANOVA e
teste de Tukey. Em seguida, a correlação entre inspeção visual e o teste de microdureza foi
avaliada pelo teste não paramétrico de correlação de Spearman. Os resultados da inspeção
visual não apresentaram diferença significante entre os grupos GI e RM, os quais
apresentaram menor desenvolvimento de cárie do que o grupo CR. A avaliação de
microdureza demonstrou diferenças significantes entre todos os grupos, sendo o menor
desenvolvimento de lesão no GI seguido por RM e CR, respectivamente. O coeficiente de
correlação de Spearman foi significante e demonstrou uma fraca correlação negativa entre as
variáveis de resposta. O ensaio de microdureza superficial foi mais sensível para o
diagnóstico da cárie secundária do que a inspeção visual.
Palavras-Chave: cárie dental, resina composta, cimento de ionômero de vidro, esmalte
dental, dureza, inspeção visual.
60
Introduction
The knowledge of the etiology and development of caries disease has allowed a
reduction in caries risk and activity by preventing and arresting primary and secondary caries
lesions. Secondary caries should be firstly prevented by the reduction in their determinant and
modulating factors to revert the patient condition from high to low risk disease status by
hygiene procedures such as brushing and flossing.1
However, the fluorides released from restorative materials may be a viable
alternative to prevent secondary caries development in high-risk patients.2,3,4 The potential
cariostatic effect of restorative materials is described in researches showing high cariostatic
effect of conventional glass ionomer cements, moderate cariostatic effect of glass ionomer
and composite resin hybrid materials, and no cariostatic effect of composite resin materials by
different analysis.2,3,5,6
These analyses may involve less complex and cheaper methods such as visual
evaluation and superficial and sub-superficial microhardness, or more difficult evaluation
techniques involving expensive equipments, such as microradiography and polarized light
microscopy. Since all these analyses are based on different parameters of evaluation, there is a
need to verify the correlation among methods. The main objective of the present study was to
evaluate the agreement between visual evaluation and superficial microhardness analysis used
for the diagnosis of artificial secondary caries development.
61
Methods and Materials
This study was performed using 20 unerupted human third molars. The research
protocol was approved in accordance with the resolution CNS# 196/96 of the National Health
Committee/Health Departments by the Research Ethics Committee of the Guarulhos
University (Brazil). Following extractions, teeth were stored in 0.1% Timol solution (pH 7.0)
for no longer than 30 days. Soft-tissues were removed using periodontal curettes (HU-
FRIEDY do Brasil, Rio de Janeiro- Brazil) and teeth were cleaned using pumice slurry in a
webbed rubber cup applied with a slow-speed handpiece (Kavo do Brasil, Joinville- Brazil).
The crowns were longitudinally and transversally sectioned to obtain 36 dental blocks
measuring 4x4x3 mm3 using double-faced diamond discs (#7020, KG Sorensen, São Paulo-
Brazil).
Cavity preparation and restoration
The 36 enamel blocks (n=12 per group) were assigned into three subgroups
according to the restorative material described in Table 3. The response variables were visual
evaluation and surface microhardness expressed in Knoop Hardness Number (KHN).
Table 3- Experimental groups, manufactures and composition.
Group Restorative material Ingredients
GI Glass ionomer cement (Ketac-Fil,3M/ ESPE, Seefeld, Germany)
Powder: glass powder 100% Liquid: water 60-65%, polyethylene, polycarbonic acid 30-40%, tartaric acid 5-10%
RM Resin modified glass ionomer (Vitremer, 3M/ESPE, St. Paul, MN, USA)
Primer: 2-hydroxyethyl methacrylate 45-55%, ethyl alcohol 35-45%, copolymer of itaconic and acrylic acids 10-15%. Powder: silane treated glass 90–100%, potassium persulfate < 1% Liquid: copolymer of acrylic and itaconic acids 45-50%, water 25-30%, 2-hydroxyethyl methacrylate 15 – 20%. Finish gloss: triethylene glycol dimethacrylate 40-60%, bisphenol a diglycidyl ether dimethacrylate (bisgma) 40 – 60%.
RC Resin composite (Z250, 3M/ESPE, St. Paul, MN, USA)
Silane treated ceramic 75-85%, bisphenol a polyethylene glycol diether dimethacrylate (bisema6) 5-10%, diurethane dimethacrylate 5-10%, bisphenol a diglycidyl ether dimethacrylate (bisgma) 1-10%, triethylene glycol dimethacrylate (tegdma) <5%, water <2%.
62
Standardized circular cavities with 1.6 mm in diameter and 1.6 mm deep were
prepared in the enamel blocks with diamond burs No. 2292 (KG Sorensen, Barueri, SP,
Brazil, 06454-920) at high speed under a constant water spray coolant. Afterwards, the blocks
were randomly distributed to the subgroups, and were restored in one increment with each
restorative material according to the manufacturers’ instructions.
In cavities filled with Ketac-Fil, the Ketac conditioner was applied for 10 s, rinsed
off and dried for 10 s. Ketac-Fil was prepared within 20-25 s, inserted into the cavity with a
Centrix injector, protected with a Mylar strip (Dentart, Polidental, São Paulo, Brazil) for 5
min, coated with Vitremer Finish Gloss and light-activated for 20 s with an Optilux 501 light
curing unit (light tip diameter: 11 mm; irradiance: 700 mW/cm2; Demetron/Kerr, Danbury,
CT, USA). The power density was constantly measured by placing the light tip on the
radiometer attached to the light curing unit.
In cavities filled with Vitremer, the Primer was applied for 30 s, dried for 5 s and
light-activated for 20 s. Vitremer was prepared within 45 s, inserted into the cavity with a
Centrix injector, light-activated for 40 s, coated with Vitremer Finish Gloss and light-
activated for 20 s.
In cavities filled with Z-250, the 35% phosphoric acid (Scotch Bond Etchant; 3M
ESPE) was applied for 15 s, rinsed off for 10 s and the cavity was air-dried. Two coats of
Adper Single Bond 2 (3M ESPE) were applied, air-dried for 5 s and light-activated for 10 s.
The composite resin was inserted and light-activated for 20 s.
All restored blocks were stored in 100% humidity for 24 h and were then polished
using the Sof-lex (3M ESPE, St. Paul, MN, USA) disks system for 15 s with each disk.
Thermal and acid challenge
The restored blocks were placed into separate bags with 1 mL of deionized water and
were thermocycled for 1000 cycles in water with temperature ranging from 5±2ºC to 55±2ºC
with a dwell time of 2 min in each bath and 15 s-transfer time between baths.2 The external
enamel surfaces of blocks were covered with wax, leaving a 1.5 mm-wide margin around the
restoration free of wax.
The acid challenge was designed to simulate a daily demineralization challenge of 6
h and 18 h repair (remineralization) by saliva as described by Featherstone et al. (1986)6 and
63
Serra & Cury (1992)7, to simulate a high in vitro caries risk and to produce artificial caries
like-lesions around the restorations2,7.
The demineralization stage was based on the use of an acid buffer containing 2
mmol/L Ca, 2 mmol/L PO4, 0.075 mol/L acetate at pH 4.3. The remineralization solution
contained calcium and phosphate at a previously established degree of saturation (1.5 mmol/L
Ca, 0.9 mmol/L PO4), to mimic the remineralizing properties of saliva, and 50 mmol/L KCl,
20 mmol/L tri-hydroxymethylaminomathan buffer at pH 7.0.6,7 The blocks were immersed
separately in 15 mL of demineralization solution for 6 h, were immersed in 15 mL of
remineralization solution for 18 h, washed and immersed in demineralization solution,
thereby initiating a new cycle. The pH cycles were conducted for 14 days with 10 daily
cycles. In the 6th, 7th, 13th, and 14th days of the cycle, the blocks were kept only in the
remineralization solution.
At the end of the pH cycles, the wax was eliminated and the blocks were stored at
100% humidity until the moment of visual evaluation and microhardness test.
Visual evaluation
The blocks were air-dried for 15s and standardized images were obtained from each
block with a Nikon D70 digital camera with lens #105. Three calibrated examiners
(Kappa>0.73) independently and blindly evaluated the images of all images projected in a
dark room with approximately 100x magnification. The examiners evaluated the specimens
scoring the presence and severity of caries-like lesions according to an ordinal scale ranked
from 0 to 3 based on visual examination, as described in previous studies (Figure 1).2,8 A
median score was obtained from scores given by the 3 examiners for each specimen.
Differences among medians were analyzed by Kruskal-Wallis and Dunn non-parametric tests.
Figure 1- Scores used to visual evaluation
64
Microhardness test
The demineralization of the restored enamel blocks was assessed with a
microhardness tester (PanTec, Panambra Ind. e Técnica SA, São Paulo- Brazil) and a Knoop
indenter. The indentations were made keeping the long axis of the diamond instrument parallel to
the outer-leveled enamel surface, using a 25 g load applied for 5 s, and the highest diagonal length
was measured in micrometers and was automatically changed to KHN. Four measurements were
made on the enamel surface 100 µm far from the restoration margins in the upper, left, right, and
bottom sides (Figure 2). The means of the four indentations represented the block microhardness
value. The mean values of each block were analyzed by ANOVA and Tukey’s post-hoc test at a
pre-set alpha of 0.05.
Figure 2 – Location of indentation in the microhardness test.
Correlation between visual evaluation and microhardness test
The correlation between non-parametric visual evaluation and parametric evaluation of
microhardness test was evaluated by the Spearman’s rho coefficient of correlation, which ranges
in value from r=+1.0 for a perfect positive correlation to r=-1.0 for a perfect negative
correlation. The midpoint of its range (r=0.0) corresponds to a complete lack of correlation.
Values falling between r=0.0 and r=+1.0 represent a range in degrees of positive correlation,
while those falling between r=0.0 and r=-1.0 represent a range in degrees of negative
correlation.9
65
Results
The medians, minimum, and maximum scores of visual evaluation and the means of
microhardness values and standard deviations per restorative material are presented in Table
1. The statistical analysis of visual data showed no differences between GI and RM groups,
which in turn showed significantly less caries development than CR group (p<0.01). The
microhardness data showed significant differences among groups with less caries in GI than
in RM and CR, which in turn showed the highest incidence of caries (p<0.05).
Table 1- Medians, minimum, and maximum of visual evaluation and the means of
microhardness values and standard deviations per restorative material; Tukey’s and Dunn test
results.
GI- Ketac Fil RM- Vitremer CR- Z-250
Visual
Evaluation
1
(0-3) A
1
(0-3) A
3
(2-3) B
Microhardness
test
235.5
(75.5) a
137.1
(64.1) b
39.3
(26.5) c
Different upper case letters indicate statistical difference (Dunn test, p<0.01); Different lower case letters indicate statistical difference (Tukey’s test, p<0.05).
The Spearman’s rho coefficient of correlation between the response variables was
statistically significant (p<0.01) but the negative correlation was considered weak (r=-0.51).
Discussion
This study evaluated the development of artificial caries lesion on enamel around
cavities filled with restorative materials with or without fluoride release. A dynamic cyclic
model of demineralization and remineralization was applied to simulate acid challenge in
patients with high caries risk.6 The highest development of artificial caries lesions in this
study was observed in cavities restored with composite resin. As expected, the composite
resin associated to an adhesive system deprived of fluoride in their compositions do not
inhibit caries progression.2 This is consistent with reports from other studies, in which only
bioactive composite resins and adhesive systems containing fluorides or antibacterial
monomers were capable of showing few cariostatic effect, which was lower than that
promoted by glass ionomer cements.4,10
66
In agreement with dental literature, the ionomer-based materials showed some
cariostatic effect, as they mobilize and release increased amounts of fluoride into the
environment during acid challenges, so enamel demineralization is prevented. Then, the
presence of fluorides continuously released from ionomers is an important feature for
improving enamel remineralization or inhibiting demineralization.11 This is the reason for less
artificial caries lesion development around cavities restored with conventional glass ionomer
cement and moderated inhibition of resin modified glass ionomer evaluated by microhardness
test. Most studies showed that the smaller fluoride concentration released from resin modified
glass ionomer in comparison to that released by conventional glass ionomer cement causes
moderate development of artificial caries lesion, which is generally considered less than that
observed when glass ionomer cement is used.2,3,7,11 Therefore, the visual evaluation was not
able to detect the difference in caries inhibition between the group using conventional glass
ionomer and that using resin modified glass ionomer. It can be supposed that the protection
rendered by the glass ionomer cement is extended to some distance from the restoration and is
the greatest one in the cavity preparation area.5 Based on such assumption and on the distance
of 100 µm from cavity margins stipulated for the microhardness test, the caries inhibition area
provided by conventional glass ionomer could be higher than that created by the resin
modified glass ionomer. Therefore, microhardness test may be considered more specific, as
the visual evaluation allowed the examiners to check all enamel area free of wax around the
restoration. This area was exposed to fluoride released from the glass ionomer material to the
solution resulting in a general caries inhibition which was clinically similar to the resin
modified glass ionomer.
Thus, it can be considered that for a specific evaluation site, superficial
microhardness may be required while a general evaluation of wider surrounding area may be
performed by visual evaluation. This difference explains the weak agreement between visual
and microhardness evaluation observed in Spearman’s correlation test. The Spearman’s rho
correlation measures how well two variables are connected without making any assumption
about the frequency distribution of the variables. The negative coefficient value observed in
the present study indicates that the two evaluations are systematically inverselly related, as
caries lesions visually increases while the superficial microhardness tends to decrease.
However, a coefficient value closer to -1.00 could have showed a perfect negative association.
Another aspect that should be considered is that visual evaluation is subjective and
this exam depends on the examiner expertise and calibration. The examiners in the present
study were calibrated and Kappa qualified the agreement from excellent to good. In a similar
67
methodology, Serra induced artificial secondary caries lesion and found a good agreement
between visual evaluation and sub-superficial analysis (r=-0.78; p<0.01).
Visual evaluation has been associated with scores in clinical12, epidemiological13
studies to quantify opacities, fluorosis and white spots resulting from enamel
demineralization. Also in in vitro 2,8,14, and in situ studies15 are well accepted. When
compared to other methodologies, this evaluation has some advantages, such as low cost and
the possibility of the identification of differences in the cariostatic potential of restorative
materials under conditions similar to clinical diagnosis conditions.2,8 As showed in the current
study, visual evaluation is simple to perform, which facilitates laboratory investigation and
allows the conduction of studies in less time and at lower costs.2,8 In addition, reproducible
results have been shown between visual evaluation and microradiography and polarized light
microscopy.15
However, the use of visual evaluation needs to be cautiously inferred by the bias of
the macro vision of the secondary artificial caries development by the examiner and the
cariostatic effect of restorative materials close to cavity margins could not be totally observed.
Then, when specific analysis of a site is required, microhardness profiles are recommended
and may be used in association with visual evaluation to provide a micro and a micro
response of caries development.
Conclusions
The superficial microhardness test was more sensitive regarding the diagnosis of
artificial secondary caries development than visual evaluation, and specific analysis
microhardness profiles may be recommended when a micro-site analysis is required.
68
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2. Rodrigues JA, Marchi GM, Serra MC, Hara AT. Visual evaluation of in vitro cariostatic
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4. Mukai Y, Tomiyama K, Shiiya T, Kamijo K, Fujino F, Teranaka T. Formation of inhibition
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5. Tantbirojn D, Douglas WH, Versluis A. Inhibitive effect of a resin-modified glass ionomer
cement on remote enamel artificial caries. Caries Res. 1997;31(4):275-80.
6. Featherstone, J.D.B, O’Really, M.M., Shariati, M., and Brugler, S. (1986). Enhancement of
remineralization in vitro and in vivo, in: Factors Relating to demineralization and
remineralization of the teeth. Leach SA (ed.). Oxford IRL: pp. 23-34.
7. Serra MC, Cury JA. The in vitro effect of glass-ionomer cement restoration on enamel
subjected to a demineralization and remineralization model. Quintessence Int. 1992
Feb;23(2):143-7.
8. Serra MC. Análises sensorial e quantitativa do potencial cariostático de materiais
restauradores contento flúor. Piracicaba, 1999. [Tese (Livre Docência) - Faculdade de
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9. Lowry, R. Concepts and Applications of Inferential Statistics. Chapter 3. Introduction to
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10. Okuyama K, Nakata T, Pereira PN, Kawamoto C, Komatsu H, Sano H. Prevention of
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11. Mount GJ. Glass-ionomer cements: past, present and future. Oper Dent. 1994 May-
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12. Gorelick L, Geiger AM, Gwinnet AJ. Incidence of white spot formation after bonding and
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14. Edgar WM, Rugg-Gunn AJ, Jenkins GN, Geddes DA. Photographic and direct visual
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70
4. CONCLUSÕES
Com base nos trabalhos desenvolvidos, apresentados em forma de artigos, pode-se
concluir que:
- Na análise visual o Laser de Er:YAG não mostrou capacidade de aumentar a
resitência do esmalte à cárie, apesar da observação de um número menor de lesões cariosas
quando utilizado para o preparo cavitário;
- Na análise de microdureza superficial o laser de Er:YAG apresentou efeito
cariostático a despeito da presença de materiais restauradores contendo flúor;
- O teste de microdureza superficial é mais preciso no diagnóstico do
desenvolvimento de lesões de cárie secundária que a avaliação visual;
Conclui-se que o Laser de Er:YAG proporcionou efeito cariostático ao redor dos
preparos cavitários sendo mais evidente nas análises realizadas pelo teste de microdureza.
71
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Apel C, Schafer C, Gutknecht N. Demineralization of Er:YAG and Er,Cr:YSGG laser-prepared enamel cavities in vitro. Caries Res. 2003;37(1):34-7.
Araujo JM; Dionísio R; Reis JIF; Santos LM. Estudo comparativo do efeitos de diferentes
materiais restauradores estétuticos fluoretados no desenvolvimento de cárie dentes decíduos. Pesqui. bras. odontopediatria clín. integr. 2006;6(2):131-136.
Ceballos L, Toledano M, Osorio R, Garcia-Godoy F, Flaitz C, Hicks J.ER-YAG laser
pretreatment effect on in vitro secondary caries formation around composite restorations. Am J Dent. 2001;14(1):46-9.
Cecchini RC, Zezell DM, de Oliveira E, de Freitas PM, Eduardo C de P. Effect of Er:YAG
laser on enamel acid resistance: morphological and atomic spectrometry analysis. Lasers Surg Med. 2005;37(5):366-72.
Cordeiro RCL, da Silva VL, Josgriber EB. Avaliação da forma de preparos cavitários
realizados com laser, abrasão a ar e ponta diamantada. Cienc odontol. Bras 2005;8 (3) 29-36.
Dijkman GE, de Vries J, Lodding A, Arends J. Long-term fluoride release of visible light-
activated composites in vitro: a correlation with in situ demineralisation data. Caries Res. 1993;27(2):117-23.
Ferracane JL, Mitchem JC, Adey JD. Fluoride penetration into the hybrid layer from a dentin
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processo de desmineralização do esmalte dental. USP São Paulo ;2005. 102p. Tese de Doutorado.
Hals, E. Histology of natural secondary caries associated with silicate cement restorations in
human teeth. Arch. Oral Biol., 1975; 20: 291-296. Harazaki M, Hayakawa K, Fukui T, Isshiki Y, Powell LG. The Nd-YAG laser is useful in
prevention of dental caries during orthodontic treatment. Bull Tokyo Dent Coll. 2001;42(2):79-86.
Hibst R, Keller V. Experimental studies of the application of the Er:YAG laser on dental hard
substance: I. Measurement of the ablation rate. Laser Surg Med. Cap 9, pag 338-344; 1989). Hicks MJ, Flaitz CM, Silverstone LM. Secondary caries formation in vitro around glass
ionomer restorations. Quintessence Int. 1986;17(9):527-32.
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Kerber LJ, Donly KJ. Caries inhibition by fluoride-releasing primers. Am J Dent. 1993 Oct;6(5):216-8.
Kim JH, Kwon OW, Kim HI, Kwon YH. Acid resistance of erbium-doped yttrium aluminum
garnet laser-treated and phosphoric acid-etched enamels. Angle Orthod. 2006;76(6):1052-6. Klein AL, Rodrigues LK, Eduardo CP, Nobre dos Santos M, Cury JA. Caries inhibition
around composite restorations by pulsed carbon dioxide laser application. Eur J Oral Sci. 2005 Jun;113(3):239-44.
Liu Y, Hsu CY. Laser-induced compositional changes on enamel: a FT-Raman study. J Dent.
2007;35(3):226-30. Lobo MM, Gonçalves RB, Pimenta LA, Bedran-Russo AK, Pereira PN. In vitro evaluation of
caries inhibition promoted by self-etching adhesive systems containing antibacterial agents. J Biomed Mater Res B Appl Biomater. 2005 Oct;75(1):122-7.
Miserendino LJ & Pick RM. Laser in desntistry. Cap.11; pág 161-172, Ed Quintessence P.
Co, Inc., 1995. Moi GP, Araujo FB; Barata J. Abordagem contemporânea das lesões cariosas adjacentes às
restaurações na clínica odontopediátrica. Rev. Fac. Odontol. Porto Alegre 2005;46(2):5-8. Park SH, Kim KY. The anticariogenic effect of fluoride in primer, bonding agent, and
composite resin in the cavosurface enamel area. Oper Dent. 1997 May-Jun;22(3):115-20. Rodrigues JA, Marchi GM, Serra MC, Hara AT. Visual evaluation of in vitro cariostatic
effect of restorative materials associated with dentifrices. Braz Dent J. 2005;16(2):112-8. Tantbirojn D, Douglas WH, Versluis A. Inhibitive effect of a resin-modified glass ionomer
cement on remote enamel artificial caries. Caries Res. 1997;31(4):275-80. Thylstrup A. & Fejerskov O. Cariologia Clínica. 2ª ed. Ed. Santos. 1994. Yamamoto HY, Sato K. Prevention of dental caries by Nd:YAG laser irradiation. J Dent Res.
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73
ANEXOS
ANEXO A - Certificado de Aprovação do Comitê de Ética
74
ANEXO B – Termo de Consentimento Livre e Esclarecido
Termo de Consentimento Livre e Esclarecido
A influência da técnica do preparo cavitário e dos tipos de materiais restauradores na prevenção de cárie secundária
A cárie secundária, lesão cariosa que se forma ao redor das restaurações, pode ser prevenida pelo uso de materiais restauradores que liberem flúor, sabe-se ainda que a aplicação de laser pode tornar o esmalte dental, mais resistente a cárie. Entretanto, o que não se sabe é se em restaurações com materiais que liberam flúor aonde a remoção da cárie foi realizada com laser o esmalte será mais resistente a cárie secundária. O objetivo deste trabalho será avaliar, in vitro, a influência da técnica do preparo cavitário e dos tipos de materiais restauradores na prevenção do desenvolvimento da ocorrência de cárie secundária. . Portanto, contamos com sua participação como doador, devido ao fato de utilizarmos 3º molares inclusos como indicação de exodontia para a realização da pesquisa. As informações contidas neste termo foram fornecidas pelo Prof. Dr. José Augusto Rodrigues (Orientador) e pela aluna Ana Carolina Tedesco Jorge, tel: (11) 6464-1769, R. Dr. Nilo Peçanha 67, prédio U, 6º andar, para firmar o seu consentimento livre e esclarecido, através do qual você, sujeito da pesquisa, autoriza a sua participação. Esta pesquisa consistirá em comparar, in vitro, a influência da técnica do preparo cavitário e dos tipos de materiais restauradores na prevenção de cárie secundára. Como o estudo será realizado “in vitro” o doador não terá nenhum desconforto ou risco, pois doará somente o dente. Assim, não está prevista nenhuma forma de ressarcimento ou garantia de tratamento Odontológico na UnG. O doador tem a liberdade de retirar seu consentimento ou se recusar a doar dentes para o estudo, a qualquer momento, conforme determinação da Resolução 196/96 do CNS do Ministério da saúde, sem qualquer tipo de prejuízo ou penalização. Os pesquisadores comprometem-se em resguardar todas as informações individuais acerca da pesquisa de forma sigilosa, não revelando a identidade do sujeito que doou os dentes. Conforme definido pela resolução 196/96 do conselho nacional de saúde, esta pesquisa foi submetida á comissão de Ética e pesquisa da UnG, e aprovada pela mesma. Por este instrumento particular declaro, para efeitos éticos e legais, que eu_____________________________________________________, CPF:___________________, concordo com absoluta consciência dos procedimentos a que vou me submeter para a realização da pesquisa “A influência da técnica do preparo cavitário e dos tipos de materiais restauradores na prevenção de cárie secundária”. Guarulhos,____de______________________de 2007. _____________________________ Assinatura do doador _____________________________ Prof.Dr. José Augusto Rodrigues
75
ANEXO C – Termo de Doação
CURSO DE ODONTOLOGIA
Banco de Dentes Humanos
TERMO DE DOAÇÃO
Eu, _________________________________________________________________,
RG nº______________________________, residente à __________________________________
__________________________________________________bairro _______________________,
cidade ____________________________, UF______________________CEP________________
dôo ___________ dentes para o Banco de Dentes Humanos – estes dentes foram extraídos por
indicação terapêutica, cujos históricos fazem parte dos prontuários dos pacientes de quem se
originam. Estou ciente de que estes dentes serão utilizados para a realização de pesquisas
previamente aprovadas por Comitê de Ética em Pesquisa ou em atividades didáticas no processo
de ensino-aprendizagem da Odontologia.
Guarulhos, _______ de _______________ de 20_____.
______________________________ Assinatura do doador
_______________________________________________________________________________
76
ANEXO D – Carta de aceite do artigo 3
77
ANEXO E - Carta de aceite do artigo 4
