In Vitro Evaluation of the Effect of Two Different Primers on the Peel Bond Strength Between Maxillofacial Silicone and Different Resin Substrates

Primary Objective To determine, within each of three resin substrates, whether surface treatment with A330G or A304 primer changes the 180° peel bond strength of M511 maxillofacial silicone compared with an untreated control. The substrates were autopolymerized polymethyl methacrylate (PMMA), heat-cured PMMA, and a light-cured hybrid-composite resin substrate. Materials and Methods This in vitro comparative experimental study included 108 specimens. Group I comprised autopolymerized acrylic resin, Group II heat-cured acrylic resin, and Group III a light-cured hybrid-composite resin substrate ( n = 36 each). Each group was subdivided into subgroup A (no primer), subgroup B (A330G), and subgroup C (A304), with 12 specimens per subgroup. M511 silicone was mixed in a 10:1 ratio and, following placement, was allowed to polymerize at room temperature for 24 h. Specimens were tested using a 180° peel test at a crosshead speed of 10 mm/min. Because all subgroup distributions were non-normal on Shapiro–Wilk testing, the Kruskal–Wallis test was used for omnibus comparisons, followed by Dunn pairwise comparisons with Bonferroni adjustment. Results Group I showed a significant overall difference ( H = 23.389, p = .00000834). Both A330G (IB) and A304 (IC) produced significantly greater peel bond strength than the untreated control (IA) (adjusted p = .000131 and 0.000056, respectively), while IB and IC did not differ significantly. Group II showed no significant overall difference ( H = 5.849, p = .053702). Group III showed a significant overall difference ( H = 7.554, p = .022891); the A304 subgroup (IIIC) had significantly lower peel bond strength than the untreated subgroup (IIIA) (adjusted p = .018896). Conclusion The primary objective was answered by a substrate-specific response to primer treatment. Compared with no primer, both A330G and A304 significantly increased peel bond strength for autopolymerized PMMA; neither primer produced a statistically significant change for heat-cured PMMA; and for the light-cured hybrid-composite substrate, A304 significantly reduced peel bond strength whereas A330G produced no significant change.