Objective: This study tested the hypothesis that fluoride release is mainly from the surface region, and can alter contact-angle of the surface. Methods: Forty-eight rectangular specimens were made of Fuji-II LC (F), Dyract-AP (D) and Ketac-Molar Aplicap (K), 16 each. Matrix-rich surface was removed by grinding. Half of the specimens were monitored for fluoride release in distilled water for 4w. The advancing and receding contact-angles (q_A& q_R) of each specimen were determined with a Dynamic Contact Angle Analyzer. The other half were monitored for 6d followed by surface grinding on both sides, weighing and then release for another 6d. The process was repeated three times. The fluoride concentration was measured with a fluoride ion selective electrode. Results: All materials exhibited high initial release followed by a gradual decrease. Subsequent surface grinding yielded different level of fluoride release bursts depending on the quantity of surface removed. The 4w data exhibited lower cumulative releases but similar release patterns to those of the ground specimens. The order of release by material was K>F>D (p<0.001). The materials showed no significant difference in q_A (mean±SD) before the release (F:77±6°, K:74±4°, D:71±2°; p=0.229), but were significantly different 4w of release (F:80±10°> K:71±8°>D:58±6°; p<0.001). There were significant difference in q_R (mean±SD) both before (F:48±7° & D:43±2°>K:32±4°; p<0.001) and after the release (D:39±7°, F:34±3°, K:32±4°; D>K while F is not different from either; p=0.027). Only D showed significant decreases in q_A& q_Rafter 4w (p=0.002). Conclusions: The release of fluoride is mainly from the surface layer, not uniformly from the bulk of the material, and that the release of fluoride does not result in the surface changes. The changes in the surface property are due to the chemical makeup of the matrix of each material and its interaction with water.

Supported by a UFCD student fellowship and 3M/ESPE Company.