ABSTRACT
Objective @#To analyze the effect of different cavosurface angles on the stress distribution of ClassⅠ cavity composite resin filling of molars through the three-dimensional finite element method and to provide references for the preparation of ClassⅠ cavities.@*Methods@#Three-dimensional finite element models of ClassⅠ composite resin filling of mandibular first molars with three different cavosurface angles (group A: 90°, group B: 120°, group C: 135°) were established. Polymerization shrinkage of composites was simulated with a thermal expansion approach. The mechanical behavior of the restored models in terms of stress and displacement distributions under the combined effects of polymerization shrinkage and occlusal load (600 N) was analyzed.@*Results@# For ClassⅠ cavities with the same cavity size, the total stress of the restoration model and the maximum stress of the enamel in group A were less than those in groups B and C after cavity composite resin restoration with three cavity cavosurface angles (in which the width of the enamel bevel was 1 mm in groups B and C). The maximum stress of the dentin and adhesive was similar in the three groups, the maximum stress of the composite in group C was the largest, and the maximum stress of the composite in group B was the smallest. In terms of stress distribution, the maximum stress in each restoration model was mainly concentrated in the enamel at the cavosurface, near the enamel-dentin interface and at the edge of the restoration material.@*Conclusion@#From the point of reducing the stress of residual tooth tissue, the preparation of 90° angle without enamel bevel is an ideal method for cavity preparation when composite resin is used to fill ClassⅠ cavities of molars.
ABSTRACT
Objectives: This study evaluated the infl uence of mechanical and thermal cycling on the nanoleakageof Class V composite resin restorations with and without enamel beveling. Material and method:Using 60 Class V cavities prepared on the buccal surfaces of human molars, specimens were dividedinto two groups (n = 30) based on the confi gurations of the enamel cavosurface margins. (beveled andnon-beveled) After restoring the cavity preparations with a fl owable composite, half of the specimenswere mechanically load-cycled. The specimens were sealed leaving a 1 mm window around the cervicaland enamel margins. Specimens were placed in a 50% (W/V) silver nitrate solution then immersedin photodeveloping solution and exposed to fl uorescent light for 8h. The teeth were buccolinguallysectioned, gold sputter coated and examined with a SEM to evaluate the nanoleakage values. The datawere analyzed using two-way ANOVA (α = 0.05). Results: Enamel margin confi guration had no significant effect on nanoleakage (p > 0.05). However, the nanoleakage value was signifi cantly higher inthe load-cycled group than in the group not load-cycled (p < 0.05). Conclusion: Since enamel margin confi guration does not affect nanoleakage, there is no need to bevel enamel margins of Class V cavitypreparations for composite restorations.
Objetivos: O presente estudo avaliou a infl uência dos ciclos de carga mecânico e térmico na nanoinfi ltração derestaurações Classe V em resinas compostas, com e sem biselamento do esmalte. Material e método: Os espécimes(60 cavidades Classe V preparadas na superfície vestibular de molares humanos) foram divididos em dois grupos(n = 30) baseados nas confi gurações das margens cavosuperfi ciais do esmalte (biseladas e não biseladas). Após restauraçãodos preparos cavitários com um compósito tipo fl ow, metade dos espécimes foi carregada mecanicamente.Os espécimes foram selados mantendo janela de 1 mm em torno das margens cervical e de esmalte. Os espécimesforam colocados em solução de nitrato de prata (50%), imersos na sequência em solução processadora fotográfi cae expostos à luz fl uorescente por oito horas. Os dentes foram cortados em sentido vestíbulo-lingual, revestidos emouro e observados em microscopia eletrônica para avaliar os valores de nanoinfi ltração. Os dados foram analisadospelo ANOVA (α = 0,05). Resultados: A confi guração das margens do esmalte não teve efeito signifi cante nananoinfi ltração (p > 0,05). Entretanto, os valores da nanoinfi ltração foram signifi cativamente mais altos no grupode carga que no grupo sem carga (p > 0,05). Conclusão: Uma vez que a confi guração da margem do esmalte nãoafeta a nanoinfi ltração, não há necessidade de biselar as margens do esmalte nos preparos de cavidades Classe V emrestaurações de compósitos.