Surface topography and enamel-resin interface of pit and fissure sealants following visible light and argon laser polymerization: an in vitro study.
This in vitro study compared the effects of visible light and argon laser polymerization of pit and fissure sealants on surface topography and the enamel-sealant interface. Twenty caries-free human molars and premolars underwent soft tissue debridement and a fluoride-free prophylaxis. Fluoride-releasing sealant (UltraSeal XT Plus, South Jordan, UT 84095) was placed on the occlusal surfaces per the manufacturer's instructions, but underwent either visible-light polymerization for 30s (n = 10), or argon laser polymerization (0.231 J/cm2) for 10s (n = 10). The sealed teeth were thermocycled (500 cycles, 5 degrees to 50 degrees C) in artificial saliva. Surface morphology was evaluated by SEM. The teeth were sectioned for polarized light and SEM evaluation of the enamel-sealant interface, with two sections per tooth prepared for SEM. Phosphoric acid was used to unmask the enamel-sealant interface with one section; while the other section was not exposed to the phosphoric acid. Surface morphology of the sealant material was similar with both visible light and argon laser polymerization; however, there was a tendency for occasional areas of mild, focal cratering of the sealant surface with laser-curing. The junction between sealant and adjacent unsealed enamel was a relatively smooth transition without gaps, microspaces, crazing, exfoliative changes, or microfractures with both visible light and laser cured sealants. Acid treatment of the sections revealed resin tags which extended into the adjacent enamel for a considerable distance on SEM examination. The resin tas were similar in length and morphology with both visible light and argon laser curing. The enamel-sealant interface with visible light and laser curing showed intimate contact between the sealant and etched occlusal enamel with close apposition of the sealant. No microspaces were identified between the sealant and the occlusal enamel. An intact, interdigitating interface between a sealant and the adjacent etched enamel provides the first line of defense against a cariogenic challenge. Visible-light and argon laser curing allows for an intimate enamel-sealant interface without microspaces and protects sealed enamel from cariogenic challenges. The benefit of argon laser polymerization, fluoride release and mechanical protection of sealant material may provide improved caries resistance in sealed pits and fissures and adjacent nonsealed enamel surfaces.