Bonding the Titanium Attachment Matrix Housing to Acrylic Overdentures Using Different Primers, Adhesives, and Resin Materials: An In Vitro Study

<b>Background and objectives:</b> Dislodgement of attachment matrix housing (AMH) from acrylic resin base is considered a major problem in overdentures. It is necessary to achieve a strong and durable bond between AMH and the acrylic part. The application of primers, adhesives, and resin materials containing multifunctional monomers may improve their adhesion. The purpose of this in vitro study was to evaluate, the effects of bonding protocols on shear bond strength (SBS) of resin materials to Ti and denture acrylic base. <b>Methods:</b> Sixty poly methyl methacrylate (PMMA) blocks (15 × 15 × 15 mm) and 60 AMH were prepared and divided into six groups (<i>n</i> = 10). The acrylic resin specimens were bonded using one of the following adhesive strategies: (P) flowable resin composite, (A-SR-P) air abrasion + SR Connect primer + flowable resin composite, (A-SR-Q) air abrasion + SR connect primer + Quick up, (A-SR-MHA) air abrasion + SR Connect primer + autopolymerizing luting composite, (Q) Quick up and (T) autopolymerizing acrylic resin. The surfaces of the Ti housing were bonded using one of these protocols: (GP-P): G-Premio BOND + light-cured resin composite, (AP-GP-P) ALLOY PRIMER + G-Premio BOND + resin composite, (Q) Quick Up, (AP-Q) ALLOY PRIMER + Quick Up, (MP-MHA) Monobond Plus primer + Multilink Hybrid Abutment, and (T) autopolymerizing acrylic resin. After thermal cycling (5000 cycles), the SBS was evaluated and the failure modes were recorded. Data (MPa) were analyzed using Shapiro-Wilk, one-way ANOVA, the post hoc Tukey HSD, and Games-Howell tests (<i>α</i> = 0.05). <b>Results:</b> In the acrylic resin groups, the greatest SBS values were reported in Q (11.97 ± 2.65 MPa), T (15.11 ± 5.36 MPa), and A-SR-P (8.32 ± 4.51 MPa) groups with no significant differences among them (<i>p</i> > 0.05). The SBS of A-SR-MHA and P groups was significantly lower than other study groups. In AMH, the SBS of GP-P (9.36 ± 1.57 MPa), AP-GP-P (7.66 ± 3.35 MPa), and MP-MHA (6.37 ± 2.39 MPa) were noticeably higher than other groups. There was no significant difference in adhesion to Ti between GP-P and AP-GP-P (<i>p</i>=0.63), as well as Q and AP-Q (<i>p</i>=0.65). <b>Conclusions:</b> For improving the adhesion of AMH to acrylic resin of overdentures, the application of G-Premio BOND with or without ALLOY PRIMER in Ti substrate and Quick Up and autopolymerizing acrylic resin to the acrylic resin of denture base produced the best adhesion. ALLOY PRIMER could not increase the adhesion to Ti substrate.