Effect of 4-acryloxyethyltrimellitic acid in a self-etching primer on bonding to ground dentin

To develop a self-etching primer for ground dentin, 4-acryloxyethyltrimellitic acid (4-AET) was newly synthesized, and the effect of concentrations varying from 0 (control) to 56.5 wt% 4-AET in the water/ HEMA primer on bonding to the dentin was investigated. Bond strength to the dentin was significantly affected by the inclusion of 4-AET in the primer which also contained N,N-di(hydroxyethyl)-p-toluidine (DEPT) when compared with the control (0% 4-AET) (p < 0.01). The optimum 4-AET-concentration and the mean bond strength (SD) were found to be 6.5 wt%: 24.2 (3.6 MPa, 37.4 wt%: 25.3 (4.4) MPa, 47.2 wt%: 26.9 (11.6) MPa and 54.4 wt%: 29.7 (12.9) MPa. The role of DEPT in the 4-AET/HEMA primer was assessed, and the optimum DEPT-concentration was found to be 0.154 and 0.307 mol%. Regarding the hypothetical bonding mechanism to dentin, it was thought that the ionized 4-AET in water/HEMA would penetrate into dentin substrates, and DEPT as an accelerator in situ would facilitate photo-polymerization at the dentin-resin interface, and result in increased bond strength to ground dentin.