Effect of Bonding and Re-Bonding on the Shear Bond Strength of Two-Piece Implant Restorations.

Purpose To evaluate the rebonding strength of ceramics to titanium alloy after disassembling by heat treatment. Materials and Methods A total of 40 titanium alloy (titanium-6 aluminum-4 vanadium) disks (4.0 x 6.6 mm) and 20 zirconia (Lava Plus) disks were manufactured using computer-aided design and computer-aided manufacturing (CAD/CAM) technology. Twenty heat-pressed lithium disilicate glass-ceramic (IPS e.max Press LT) disks were fabricated and used as controls. Bonding protocol for each specimen surface was performed according to manufacturer's instructions. Specimens (n = 10) of zirconia/titanium alloy (ZR) and lithium disilicate/titanium alloy (LD) were bonded using adhesive resin cement (RelyX Ultimate) and then subjected to a heat treatment (HT, 320 degrees C, 2 minutes) to disassemble the bonding complex, cleaned with aluminum oxide airborne-particle abrasion, and rebonded following the initial protocol, group ZRHT and group LDHT, respectively. After 5000 cycles of thermal cycling, a shear bond test was conducted. A universal testing machine was used at a 5 mm/min crosshead speed. Failed specimens were examined with stereomicroscopy at 10x magnification to identify the mode of failure. One-way ANOVA and Tukey HSD tests were applied for statistical analysis of the shear bond strength data, with statistical significance at alpha = 0.05. Results The mean +/- SD bond strength values ranged from 28.3 +/- 7.2 to 45.9 +/- 9.7 MPa. Statistically significant lower shear bond strength values were obtained from the LD group (p = 0.002, F = 5.89), while no statistically significant differences in bond strength were observed between the ZR and ZRHT groups (p > 0.05). Failure mode was predominantly mixed-type failure pattern for all specimens. Conclusions Heat and abrasion surface treatment increased the bond strength of lithium disilicate glass-ceramics cemented to titanium alloy, but no effect was observed on zirconia/titanium alloy bonding.