Dimensional changes of demineralized dentin treated with HEMA primers

Objectives: The purpose of this study was to measure the dimensional changes of demineralized dentin before and after application of HEMA (2-hydroxyethyl methacrylate) by confocal laser scanning microscopy (CLSM). Methods: The middle portion of bovine dentin was ground, polished, and covered with a vinyl tape with a 4-mm hole punched through it. A strip of polysiloxane impression material was then placed across the center of the dentin surface to preserve a strip of the original unetched surface. Dentin surfaces were etched with 32% phosphoric acid for 60 s and rinsed with water. The impression material was then removed and the following sequential steps were performed: the dentin surface was mildly air-dried, then strongly air-dried, then treated with either 35 wt.% HEMA/water or 100 wt.% HEMA and mildly air-dried, and then strongly dried again. The shrinkage of the demineralized dentin surface from the original unetched level was measured by CLSM in each step and results analyzed by one-way ANOVA. Results: The dimensional changes of demineralized dentin after mild air drying were approximately −1 μm and, following strong air drying, resulted in −5 μm shrinkage. Following the application of 35 wt.% HEMA/water, the height of the demineralized dentin changed to a level of −3.3 μm, but then shrank to −4.8 μm after strong drying. ANOVA indicated that re-expansion of the shrunken etched dentin was significant (p<0.05); however, the treated surface collapsed when it was strongly dried again (p<0.05). 100% HEMA did not re-expand the shrunken demineralized dentin under any of the application on protocols (p>0.05). Significance: Thirty-five wt.% HEMA in water re-expanded the collapsed demineralized dentin matrix, however not to the original level. One hundred wt.% HEMA did not cause any re-expansion.