UCSF

PURPOSE: The purpose of this study is determine if there are differences in the permeability of untreated enamel, etched enamel, enamel that has been treated with self-etching primer, and enamel that has been treated with Pro Seal and then subjected to varying amounts of thermocycling. The specific aims were 1) to test the hypothesis that etched enamel is more permeable than untreated enamel, and enamel treated with Pro Seal is less permeable than untreated enamel; and 2) to test the hypothesis that enamel treated with Pro Seal followed by thermocycling is more permeable than sealed enamel that has not been thermocycled

METHODS: Sixty enamel samples were obtained from human molars in this in vitro study. Samples were divided into three experimental groups of twenty: etched, self-etching primer, and Pro Seal. Each sample had a control half and an experimental half. The samples were then placed in 50% aqueous silver nitrate solution, sectioned, mounted, and the amount of dye penetration measured using a light microscope to determine permeability. Twenty new Pro Seal samples were then divided into four experimental groups of five: 500, 1000, 2000, and 3000 thermocycles. Each sample had an untreated half and a Pro Seal half. Each sample was sectioned so that one section underwent thermocycling, and the other did not. Permeability was then determined in the same manner as the first part of the study.

RESULTS: Etched enamel was significantly the most permeable, enamel treated with Pro Seal was significantly the least permeable, and enamel treated with self-etching primer was significantly more permeable than untreated enamel but less permeable than etched enamel.

CONCLUSION: Etching the enamel or treating it with self-etching primer increases enamel permeability and thereby increases the susceptibility to white spot lesions immediately after orthodontic bonding. Pro Seal is an effective means of decreasing enamel permeability and thus white spot lesion susceptibility as long as it is able to stay on the tooth intraorally.