THE EFFECT OF 2 INITIATOR STABILIZER CONCENTRATIONS IN A METAL PRIMERON BOND STRENGTHS OF A COMPOSITE TO A BASE-METAL ALLOY

This study examined the effect of three additives, amine, peroxide and stabilizer, in two concentrations in a metal primer on the adhesion b etween a cast metal alloy and a resin composite using a 23 factorial s tatistical design. The additives, benzoylperoxide (BPO) used at 1% or 2% w/w and N,N-dimethyl-p-toluidine (DMPT) at 0.5% or 1.8% w/w, are po lymerization initiators. The third additive, butylated hydroxytoluene (BHT) at 0.01 % or 0.03% w/w, is used as a stabilizer. BPO and BHT wer e dissolved in an acetone solution containing 20% of the adhesive resi n pyromellitic glyceroldimethacrylate (PMGDM). DMPT was in a separate acetone solution. Equal portions of each solution were mixed and appli ed to a sandpaper-abraded, air-blasted nickel-chrome alloy. Bonding re sin and composite were applied over the primer and stored overnight in water. Bond strengths were determined by shearing the composite from the metal at a cross head speed of 0.5 mm/min. Increasing the concentr ation of BPO caused a statistically significant increase in bond stren gth. A 3-way analysis of variance (ANOVA) at p < 0.05 showed that, of the interactions, only the one between DMPT and BPO was significant, w ith lower concentrations of DMPT being less sensitive to changes in BP O concentration.