Use of computerized microtomography, energy dispersive spectroscopy, scanning electron microscopy, and atomic force microscopy to monitor effects of adding calcium to bleaching gels.

Objectives: The aim of this study was to evaluate the loss of mineral content, expressed by calcium (Ca) and phosphate (P), in dental enamel exposed to bleaching agents using micro-computed tomography (micro-CT), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). Methods: Sixty bovine dental enamel specimens were randomly divided into three groups (n=20): HP35ca (bleached with 35% hydrogen peroxide with Ca); HP35wca (bleached with 35% hydrogen peroxide without Ca); and control (without bleaching). Five specimens from each group were used for SEM and EDS analyses, 10 specimens were used for AFM analysis, and the remaining five specimens were used for micro-CT analysis. The pH of the gels was measured using a pH meter. The EDS and micro-CT data were analyzed using one-way ANOVA and Pearson’s correlation test. The AFM data were analyzed using one-way ANOVA (α=0.05). Results: The weight percentages of Ca and P obtained using EDS were similar between the bleached and control groups. Small superficial changes were observed by SEM in the HP35wca group. The HP35ca group showed similar patterns to the control group. AFM results showed no significant changes in the enamel roughness in any of the tested groups. No significant difference in the volume or depth of structural enamel loss was found between gels with and without Ca. No mineral loss was observed in the dentin substrate. The EDS and micro-CT analysis data exhibited a high correlation (P < 0.001). Conclusion: The addition of Ca to the bleaching gel had no beneficial effect on the bleached tooth enamel in terms of composition, mineral loss, and surface roughness. Micro-CT results exhibited a high correlation with the EDS results.Trabalho de Conclusão de Curso (Graduação)O objetivo deste estudo foi avaliar a perda de conteúdo mineral, expressa por cálcio (Ca) e fosfato (P), no esmalte dental exposto a agentes clareadores por meio de microtomografia computadorizada (micro-CT), microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e microscopia de força atômica (AFM). Sessenta espécimes de esmalte dentário bovino foram divididos aleatoriamente em três grupos (n = 20): HP35ca (clareado com peróxido de hidrogênio a 35% com Ca); HP35wca (clareado com peróxido de hidrogênio 35% sem Ca); e controle (sem clareamento). Cinco amostras de cada grupo foram usadas para análises MEV e EDS, 10 amostras foram usadas para análise de AFM e as cinco amostras restantes foram usadas para análise de micro-CT. O pH dos géis foi medido usando um medidor de pH. Os dados de EDS e micro-CT foram analisados usando ANOVA de uma via e teste de correlação de Pearson. Os dados de AFM foram analisados usando ANOVA de uma via (α = 0,05). As porcentagens em peso de Ca e P obtidas por EDS foram semelhantes entre os grupos clareado e controle. Pequenas mudanças superficiais foram observadas por MEV no grupo HP35wca. O grupo HP35ca apresentou padrões semelhantes ao grupo controle. Os resultados de AFM não mostraram alterações significativas na rugosidade do esmalte em nenhum dos grupos testados. Nenhuma diferença significativa no volume ou profundidade da perda estrutural de esmalte foi encontrada entre os géis com e sem Ca. Nenhuma perda mineral foi observada no substrato dentinário. Os dados de análise de EDS e micro-CT exibiram uma alta correlação (P < 0,001). A adição de Ca ao gel clareador não teve efeito benéfico sobre o esmalte clareado do dente em termos de composição, perda mineral e rugosidade superficial. Os resultados de micro-CT exibiram uma alta correlação com os resultados de EDS

Biomechanical behaviour of bulk-fill resin composites in class II restorations

The aim of this study was to evaluate the biomechanical properties expressed by shrinkage stress, cuspal strain, fracture strength and failure mode in molars with large class II mesio-occlusal-distal restorations. Sixty-four human caries-free third molars were selected and distributed randomly into four groups: Z100 restorative material (Z100), Tetric N-Ceram Bulk-Fill (TNC), Filtek Bulk-Fill (FBF) and Aura Ultra Universal (ABF). The bulk-fill materials were inserted in one singular bulk increment and the conventional composite resin in three ones. Polymerisation shrinkage stress was evaluated by optical Fibre Bragg Gratings (FBG) sensors (n = 6). The cuspal deformation was measured using an extensometer during three moments: restorative procedure, axial compressive loading and at fracture (n = 10). The fracture strength was evaluated on a universal machine. The failure mode was analysed by Scanning Electron Microscopy (SEM). Data were analysed using one-way ANOVA tests with Tukey's posthoc test (α = 5%). Data of the failure mode were submitted to a likelihood ratio chi-square test. Z100 presented the highest mean value for the shrinkage stress (p  0.05). Bulk-fill composites promoted less polymerisation shrinkage stress than conventional microhybrid composite during and after the light curing process in class II posterior resin composite restorations98255261This study was supported by the Institute of Physics Gleb Wataghin (University of Campinas) and Dental Research Center Biomechanics, Biomaterials and Cell Biology (Dental School of Federal University of Uberlândia