Microhardness of Nd: YAG laser irradiated enamel surfaces

Several studies have been conducted in order to verify effects of laser irradiation on dental structures. However, different settings and methods employed have led to inconclusive results. The aim of this study was to evaluate the effects of several settings of Nd:YAG laser irradiation on enamel microhardness. Fifteen groups of 10 human third molars each were submitted to Vickers microhardness indentations prior to and after laser irradiation. The data were submitted to the t-test for dependent samples (P<0.05) for statistical evaluation. Lower total delivered energy (under 30 J) resulted in no statistically significant difference of microhardness between irradiated and non-irradiated samples, whereas higher energy settings decreased enamel surface microhardness significantly. This can be due to the significant temperature rise during irradiation. Thus, we conclude that laser irradiation, under the conditions of this study, is not suitable for improving enamel properties, because of decreased microhardness of irradiated samples.

Microleakage of resin-based composite restorations with ceramic inserts / Microinfiltração das restaurações de compósitos de resina com cerâmica

Purpose: To evaluate dye penetration of proximal vertical slot resin-based composite (RBC) restorations as a function of cavity size and restorative material employed (RBC, ceramic inserts with low-viscosity resin liner). Microleakage was measured using rank scoring and linear measurement of dye penetration and ANOVA and non-parametric tests were used to evaluate the statiscal significance of the results. Materials amd method: Ninety erupted crack- and caries-free mandibular third molars, extracted for orthodontic reasons, were used. Proximal vertical slots were prepared on the mesial surfaces of the teeth using diamond instruments at high speed under distilled water coolant. Teeth were placed randomly into nine groups. Three sizes of diamond burs of an ultrasonic cavity preparation system were used under low energy in order to standardize cavity size and shape, each tip size being used in 30 different teeth. The gingival margins were prepared 1 mm above the cemento-enamel junction. Specimens were etched, prepared with bonding agent, restored using three different materials, and immersed in a 50 per cent AgNOü solution for 8 hrs sectioned to evaluate the dye penetration. Results: Statiscal analysis revealed no statistically significant differences among the nine groups

Estudo morfológico de superfícies ósseas após secçäo por pontas diamantadas ou laser de érbio: YAG / Morphological evaluation of bone surfaces after sectioning with diamond points or erbium: YAG laser

O objetivo deste trabalho foi analisar morfologicamente as superfícies ósseas resultantes da secçäo por pontas diamantadas ou por laser de érbio: YAG. Cinco ratos (Rattus norvegicus albinus foram sacrificados por dose letal de fenobarbital. Após a execuçäo deste procedimento, os ossos predeterminados foram submetidos à secçäo por pontas diamantadas ou por laser de érbio: YAG em uma energia de 300 mJ por pulso e taxa de repetiçäo de 2 Hz. As amostras foram submetidas a análise em microscópio eletrônico de varredura, revelando a existência de um padräo para as secçöes obtidas com cada instrumento, sendo verificada uma superfície mais regular nas amostras seccionadas com o laser de érbio: YAG. Em aumentos da ordem de 3000 vezes, pode-se observar indícios de fusäo e seqüente solidificaçäo das superfícies seccionadas por meio do laser de érbio: YAG. Conclui-se que o laser de érbio: YAG foi eficaz na remoçäo de tecido ósseo, mas que, nos parâmetros utilizados neste estudo, foi responsável por alteraçöes morfológicas sugestivas de significativo aumento de temperatura, näo devendo ser indicado, nestas condiçöes, para a execuçäo de secçöes ósseas