The depth of cure of clear versus opaque sealants as influenced by curing regimens

Background. The authors conducted a study to test the hypothesis that hght-curing regimens affect depth of cure of clear versus opaque sealants. Methods. The authors light-cured samples of one clear and two opaque sealants at 20 seconds, 0 millimeters; 40 seconds, 0 mm; and 40 seconds, 2.2 mm (n = 5 each). They assessed the depth of cure with Knoop hardness at 0.5-mm increments five minutes and one hour after curing. The authors used analysis of variance. Results. Curing regimens and sealant types affected the depth of cure. The clear sealant maintained a greater hardness than did the opaque sealants through a depth of 3 mm (P < .001). A 20-second duration reduced the depth of cure for all sealants (P < .001). The distance from the light source did not affect the cure depth of the clear sealant (P = .34), but it reduced the cure depth of the opaque sealants (P < .05). Sealant hardness increased significantly one hour after light curing (P < .001). Conclusions. A clear sealant cured deeper than did opaque sealants. Curing duration is crucial to achieve an adequate depth of cure. A 20-second duration may not suffice. Light source distance affected the depth of cure for the opaque sealants, but not for the clear sealant with sufficient curing duration. Clinical Implications. The authors advocate a curing duration of longer than 20 seconds to ensure thorough polymerization at the interface between the sealant and tooth. Insufficient curing could contribute to failure of the sealants, especially the opaque sealants, under clinical conditions that restrict the light tip position.