Abstract
Interaction changes of dental adhesive monomers with dentin during treating time are unknown. This study investigated the in situ interaction changes of dental self-etch adhesive with dentin during the treating time using both time-resolved FTIR-ATR and TEM measurements. Pure 4-acryloxyethyltrimellic acid (4-AET) and its calcium salts (4-AETCa) were synthesized. A 4-AET solution [4-AET/2-HEMA, 40/60 wt%] was placed on hydroxyapatite-exposing dentin, and time-resolved FTIR-ATR measurement was performed for 15 min. A 4-AET-containing, one-step adhesive was placed on cryofractured human dentin and left in the dark for 1/3, 5, 10 and 20 min before lightactivation. Ultrastrucural changes occurred at the resin-dentin interface were then observed using TEM. The FTIR-ATR subtraction spectra indicated that formation of 4-AETCa (1583, 1411 cm-1: assigned to ν C=O of Ca-carboxylate and identified by synthesized 4-AETCa) increased with contact time for 15 min. TEM study revealed the presence of an insoluble interaction layer on the dentin surface that increased in thickness (0-2500 nm thick) during the course of interaction. These findings support a hypothesis that formation of 4-AETCa increases with time of contact between the 4-AET acting as a ligand monomer and dentin apatite.
