Effect of rinse time on microleakage between composite and etched enamel

This study compared microleakage of composite bonded to etched flattened enamel in seven groups of five extracted maxillary molars. The facial enamel of the molars was ground flat and etched for 20 seconds with 37% phosphoric acid gel. In one group, etching gel was not rinsed but dried only. In four groups, gel was rinsed with an air/water spray for varying amounts of time. In the other two groups, gel was rinsed with water only for two different amounts of time. Etched surfaces were dried, and a liquid resin was applied and polymerized; a button of composite resin was polymerized to the flattened surface. Specimens were thermocycled, stained, then sectioned longitudinally. Microleakage was measured at the occlusal and gingival enamel margins and expressed as a percentage of the total length of interface. A mean (SD) percentage microleakage was determined at the occlusal and at the gingival margins for each group as follows: no rinse--89.60 (14.34); one second--water 0 (0), air/water 0 (0); three seconds--water 0.98 (1.34), air/water 0 (0); five seconds--air/water 0 (0); 20 seconds--air/water 0 (0). Because of abnormal distribution, data were analyzed using Wilcoxon two-sample tests. The no-rinse group had significantly more microleakage than any of the other groups (P = 0.0067), which were not significantly different from each other (P = 0.18). A one-second rinse with either water or air/water spray was as effective as a 20-second rinse with air/water spray in preventing microleakage at the resin-enamel interface.