Abstract: Objective To evaluate the influence of penetration time on the microleakage, penetration ability and atomic force microscope (AFM) of pit and fissure sealants in vitro. Methods Fifty extracted third molars of human mandibular were randomly divided into five groups with ten in each group. Occlusal surfaces of the teeth in all groups were prepared using enameloplasty, etched, rinsed and dried. In group 1-5, the fissure sealant was applied onto the surface and allowed to penetrate for 0 s, 15 s, 30 s, 45 s and 60 s respectively. Each tooth was subjected to dye immersion (1% methylene blue). Microleakage and penetration ability were examined after sectioning. The quality of tag formation was examined using an AFM. Results The penetration time of 30 s, 45 s and 60 s resulted in significantly more (P<0.05) penetration depths compared to 0 s and 15 s. AFM showed that 0 s group and 30 s group had obvious, dense and regular resin tags. Conclusion The findings reveal that it should permit a penetration time around 30 s before lightcure in clinical treatment.

Key words: pit and fissure sealant, penetration time, penetration ability, microleakage, atomic force microscope