Dentine bond strength of a composite resin polymerized with conventional light and argon laser Resistência de união à dentina de resina composta polimerizada com luz halógena e laser de argônio

The use of argon laser (488 nm) has been suggested as a new alternative for polymerizing adhesive materials. This study aimed to evaluate the tensile bond strength of a microfilled composite (A110, 3M) inserted by incremental technique (3 increments of 1 mm) and by single increment (3 mm) polymerized by argon laser for 10, 20 and 30 seconds and halogen light for 40 seconds. Eighty (8 groups of 10 teeth) freshly extracted bovine teeth were stored in a freezer in distilled water for one week. The crowns were cross-sectioned from the roots. Pulpectomy was performed and the pulp chambers were sealed with wax. The buccal surfaces of the teeth were ground with wet sandpaper (grains: 120, 400, and 600) to expose the surface dentin, and the teeth were then included in acrylic resin. A metal device was used to fix each sample and a black propylene matrix25 (3 mm high with an internal millimetric delimitation) was used to insert the material according to the groups studied. The polymerization intervals were of 10, 20 and 30 seconds for the laser polymerization and 40 seconds for the conventional polymerization. Tensile tests were performed by a Universal Testing Machine 4442 (Instron) at a speed of 0.5 mm/min and 500 N load. According to the methodology used, the incremental technique increased bond strength values. There was no difference between the studied polymerization techniques when resin was filled in 3 increments.<br>O uso do laser de argônio (488 nm) tem sido sugerido como uma nova alternativa para polimerização de materiais adesivos. Este estudo tem o objetivo de avaliar a resistência adesiva de uma resina composta microparticulada (A110, 3M) inserida pela técnica incremental (3 incrementos de 1 mm) e de incremento único (3 mm) polimerizada com laser de argônio por 10, 20 e 30 segundos e com luz halógena por 40 segundos. Oitenta (8 grupos com 10 dentes) dentes bovinos recém-extraídos foram armazenados em geladeira, em água destilada, por uma semana. As coroas foram separadas das raízes. Foi realizada a pulpectomia, e as coroas foram seladas com cera. As faces vestibulares foram desgastadas com seqüência de lixas (120, 400 e 600) para expor a dentina superficial, e os dentes foram incluídos em resina acrílica. Foi utilizada uma mesa metálica para fixar cada espécime com a matriz de polipropileno preta (3 mm de altura com delimitação interna milimetrada) e inserir a resina de acordo com os grupos estudados. Os tempos de polimerização foram de 10, 20 e 30 segundos para a polimerização com laser e de 40 segundos para a polimerização convencional. Os testes de resistência adesiva foram realizados com a máquina universal de ensaios 4442 (Instron) com velocidade de 0,5 mm/min e carga de 500 N. De acordo com a metodologia usada, a técnica incremental aumentou os valores de resistência adesiva. Não houve diferença entre as técnicas de polimerização usadas quando a resina foi inserida em 3 incrementos

Microleakage in conservative cavities varying the preparation method and surface treatment

OBJECTIVE: To assess microleakage in conservative class V cavities prepared with aluminum-oxide air abrasion or turbine and restored with self-etching or etch-and-rinse adhesive systems. Materials and Methods: Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV - self-priming etchant (Tyrian-SPE). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey's test (&#945;=0.05). RESULTS: Marginal seal provided by air abrasion was similar to high-speed handpiece, except for group I. There was SIGNIFICANT difference between enamel and dentin/cementum margins for to group I and II: air abrasion. The etch-and-rinse adhesive system promoted a better marginal seal. At enamel and dentin/cementum margins, the highest microleakage values were found in cavities treated with the self-etching adhesive system. At dentin/cementum margins, high-speed handpiece preparations associated with etch-and-rinse system provided the least dye penetration. CONCLUSION: Marginal seal of cavities prepared with aluminum-oxide air abrasion was different from that of conventionally prepared cavities, and the etch-and-rinse system promoted higher marginal seal at both enamel and dentin margins