Effect of an acidic sodium salt on the polymerization behavior of self-adhesive resin cements formulated with different adhesive monomers.

OBJECTIVE

To determine the influence of benzenesulfinic acid sodium salt 98% (BAS) and the activation mode on the polymerization behavior of experimental self-adhesive resin cements (SARCs) formulated with distinct self-etch methacrylates.

MATERIALS AND METHODS

Three catalyst-pastes using different self-etch methacrylates (2MP - bis 2-(methacryloyloxy) ethyl phosphate; 4META - 4-methacryloxyethyl trimellitic acid anhydride; and GDMAP - 1,3-glycerol dimethacrylate phosphate) and four base-pastes were formulated from the incorporation of different amounts of BAS associated to N-N-dihydroxyethyl-p-toluidine (DHPT). BAS/DHPT ratios were blended respectively based on the following final weight (wt%): control (0.0;2.0%), BP1 (0.5;1.5%), BP2 (0.8;1.2%) and BP3 (1.0;1.0%). Real-time polymerization kinetics (KP) was assessed for 10min by FTIR spectroscopy. Maximum rate of polymerization (Rp) was obtained from the first derivative of the curve conversion versus time. Degree of conversion (DC) was determined over 10min and after 24h. SARCs were tested in self and dual activation modes. Data of Rp and DC 24h were respectively analyzed by two-way ANOVA followed by Tukey's method (α=0.05).

RESULTS

All factors and their interactions were statistically significant (p<0.01). BAS caused an increase in DC in the first minutes of the KP analysis, especially in self-activated groups. After 24h, all groups showed higher DC than those observed in the first 10min. In general, the addition of BAS increased the Rp. The GDMAP-based materials group showed the highest Rp values when exposed to light but self-activated formulations with GDMAP or 2MP showed the lowest Rp.

SIGNIFICANCE

The addition of BAS increased the degree of conversion of SARCs in the first minutes and 24h after the polymerization reaction. This finding showed the importance of adding this type of salt during resin cement production to achieve better polymerization in the first minutes of the luting procedure specially when light exposure is not possible.