Microhardness of composite resins at different depths varying the post-irradiation time

OBJECTIVE: The purpose of this study was to assess the microhardness of posterior composite resins at different depths varying the post-irradiation time. MATERIALS AND METHODS: For each composite resin [Solitaire 2 (SO) - Heraus Kulzer, P60 (P) - 3M, Prodigy Condesable (PC) - Kerr, Surefil (S) - Dentsply and Alert (A) - Pentron], 6 specimens (3 mm in diameter; 4mm high) were prepared using a black polyurethane cylindrical matrix. The resins were inserted in a bulk increment and light cured for 40 seconds. Microhardness was analyzed at different depths (top, 0.4 mm, 1.0 mm, 2.0mm, 3.0 mm and 4.0 mm) and at two moments (20 minutes and 24 hours after light-curing). Data were analyzed by ANOVA and Tukey's test (

Influence of light-curing unit systems on shear bond strength and marginal microleakage of composite resin restorations

The aim of the present study was to evaluate the influence of different photopolymerization (halogen, halogen soft-start and LED) systems on shear bond strength (SBS) and marginal microleakage of composite resin restorations. Forty Class V cavities (enamel and dentin margins) were prepared for microleakage assessment, and 160 enamel and dentin fragments were prepared for the SBS test, and divided into 4 groups. Kruskal-Wallis and Wilcoxon tests showed statistically significant difference in microleakage between the margins (p < 0.01) with incisal margins presenting the lowest values. Among the groups, it was observed that, only at the cervical margin, halogen soft-start photo polymerization presented statistically significant higher microleakage values. For SBS test, ANOVA showed no statistical difference (p > 0.05) neither between substrates nor among groups. It was concluded that Soft-Start technique with high intensity end-light influenced negatively the cervical marginal sealing, but the light-curing systems did not influence adhesion.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)FAPES

Influence of sterilization methods on physical properties of dental substrate

O objetivo do presente estudo foi avaliar a influência de métodos de esterilização do substrato dental sobre a microdureza de dentes extraídos (esmalte e dentina radicular) submetidos a ciclos de pH, e ainda verificar a influência destes métodos sobre a resistência adesiva do esmalte, dentina coronária e radicular. Para os testes de microdureza, dez terceiros molares extraídos foram seccionados em 40 fragmentos de esmalte e 40 de dentina radicular, sendo divididos aleatoriamente em 4 grupos (para ambos os substratos): Controle - não esterilizado, Óxido de Etileno 7h ciclo de OE/48h aeração, Autoclave 30 à 121oC e Formalina 10% - por 7 dias. Após a esterilização, as amostras foram lavadas, reumidificadas e submetidas a ciclos de pH. Os testes de microdureza em profundidade (30, 60, 90, 120 e 300&micro;m) foram realizados no substrato hígido e desmineralizado. Para os teste de resistência adesiva, 30 terceiros molares extraídos foram seccionados em 60 fragmentos de esmalte, 60 fragmentos de dentina coronária e 60 fragmentos de dentina radicular, sendo divididos aleatoriamente em 4 grupos (para todos os substratos): Controle, Óxido de Etileno, Autoclave e Formalina 10%. Em seguida, os sítios de adesão foram demarcados e cilindros de resina composta foram confeccionados em 3 incrementos. Após 24 horas, os espécimes foram submetidos a testes de cisalhamento. Os dados obtidos para ambas as avaliações foram submetidos à ANOVA e teste de Fisher (&alpha; =0,05). Para microdureza em esmalte hígido pode-se verificar que o controle apresentou maior valor de dureza e estatisticamente diferente dos outros grupos, sendo que os métodos promoveram alteração da dureza, diminuindo-a (controle>óxido de etileno>autoclave>formalina). Contudo, para as profundidades não houve diferença estatística. Para o esmalte desmineralizado, o grupo controle apresentou maiores valores de dureza diferente estatisticamente da formalina e óxido de etileno e semelhante a autoclave (controle &asymp; autoclave > Formalina &asymp; óxido de etileno). Para as profundidades, observou-se que 30&micro;m formalin &asymp; ethylene oxide). Comparing depths, it was observed that 30&micro;m < 60&micro;m &asymp; 90&micro;m &asymp; 120&micro;m < 300&micro;m. For sound root dentin, control group was similar to formalin and ethylene oxide and higher than steam autoclave, being formalin similar to ethylene oxide and different from steam autoclave. It was not verified statistical difference for depths in this substrate. For desmineralized root dentin, ANOVA showed no statistical difference among the methods. For depths, 30&micro;m was similar to 90&micro;m and different from 300 and 120&micro;m. 300&micro;m provided the highest values. For bond strength in root dentin, it was observed statistically significant difference among sterilization methods, presenting formalin the highest values. However, when enamel and dentin were evaluated, ANOVA showed no statistical difference among sterilization methods. It can be concluded that, the sterilization methods employed in this study affect the microhardness of sound and demineralized enamel and sound dentin. On the other hand, the sterilization methods did not affect the microhardness of demineralized root dentin. Shear bond strength was affected by the sterilization methods only in root dentin

Clinical comparison between the bleaching efficacy of 37% peroxide carbamide gel mixed with sodium perborate with established intracoronal bleaching agent

Objective. The aim was to evaluate the bleaching efficacy of sodium perborate/37% carbamide peroxide paste and traditional sodium perborate/distilled water for intracoronal bleaching. Study design. Thirty patients with dark anterior teeth were divided into 2 groups (n = 15): group A: sodium perborate/ distilled water; and group B: sodium perborate/37% carbamide peroxide paste. The bleaching treatment limited each patient to the maximum of 4 changes of the bleaching agent. Initial and final color shades were measured using the Vita Lumin shade guide. Results. Data was analyzed with Wilcoxon test for initial and final comparison according to the bleaching agent, demonstrating efficacy of the bleaching treatment with both agents. Mann-Whitney test was used for comparison of the efficacy of the bleaching agents, showing that there was no significant difference between them. Conclusion. The sodium perborate/37% carbamide peroxide association for intracoronal bleaching has proven to be as effective as sodium perborate/distilled water. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: e43-e47

Influence of different light-curing units on the surface roughness of restorative materials: in situ study

The aim of this study was to evaluate the influence of different light sources (LED and Halogen lamp) on the roughness (superficial) of composite resin (Filtek Z250, Filtek P60, Charisma and Durafill) varying post-irradiation times, in an in situ experiment. For this purpose, 80 specimens were made in polyurethane moulds. Ten volunteers without medicament use and good oral condition were selected and from them study moulds were obtained. A palatal intra-oral acrylic resin appliance was made for each of the subjects of the experiment. In each appliance, two specimens of each material were fixed (LED/Halogen lamp - control group). Roughness tests were performed immediately and 30 days after initial light-curing. Statistical analysis was performed using ANOVA. Statistically significant difference was observed only between post-irradiation times, where the 30th day showed the highest roughness values. It be concluded that roughness was influenced only by post-irradiation times, presenting the 30- days period inferior behavior