RESUMEN
Objective To study the effects of resin micro-leakage of different angles of cavity margins with composite resin filling.Methods Thirty extracted human molar with occlusal surfaces preparing hole into 3mm × 3mm × 3mm.Specimens were randomly divided into 3 groups,1 mm slopes of cavity margins were designed respectively,and three kinds of angles of cavity margins(45°,70°,90°)were filled on the ocelusive surfaces,then using Prime&Bond NT and Composite resin(ChrismaA2)to repair the holes directly.After 500 thermal cycling,all specimens were immersed in Indian ink for one week and the penetration depth was examined under stereo microscope.Results Cavity margin angles of 70°was better than those of 90° and 45°,the results was statistically significant(t=3.530,4.179,all P＜0.05).Conclusion To reduce the occurrence of the resin micro-leakage,cavity margin angles should be designed as short slant with an angle of 70°or so.