Inibição da polimerização de resinas compostas por materiais usados como matrizes oclusais

Objective: To study the effect of the curing method, of the presence of oxygen and of the removal of the oxygen inhibited layer on the microhardness of the resin composite cured through oclusal matrix. Methods: Composite disks (GrandioSO, VOCO) were cured with a LED through oclusal [two polyvinylsyloxanes: Memosil 2 (Heraeus Kulzer) e Registrado Clear, (Voco) and one polyethylene: Bite-perf (Biteperf Dental Products)] (n = 10). Control groups without matrix and with a mylar strip matrix were also created. The study had three steps. On the first step, the curing method was evaluated (40. seconds through the matrix; 20. seconds through the matrix + 20. seconds without matrix). On the second step, specimens were prepared in different atmospheres (oxygen; nitrogen). On the third step, specimens prepared with polyvinylsyloxanes were polished with acetone or rubber cup. Knoop microhardness was tested 24. h after curing. Data were treated with Kruskal-Wallis e Mann-Whitney (p =0.05). Results: Only with the Bite-perf microhardness was similar (p > 0.05) to the mylar matrix group. In nitrogen, specimens from the groups with Memosil, Registrado and without matrix yielded significantly higher microhardness than the same groups in oxygen atmosphere (p < 0.05). After treatment of the superficial layer, microhardness was still lower than in the mylar matrix group (p < 0.05). Conclusions: Curing through the Bite-perf for 40. seconds the composite microhardness was similar to the one obtain after 20. seconds curing through the mylar matrix. Composite curing through the polyvinilsiloxanes lead to an inhibited oxygen layer that was not totally removed by the methods applied in this laboratory study.