Background. Detachment of acrylic teeth from denture base material is a common complication in dentistry which accounts for 26–30% of repair cases. This study aimed to evaluate the effect of alumina-blasting, silane coupling agent, and thermal cycling on the shear bond strength of repaired teeth to denture base. Materials and Methods. Specimens (140) of repaired teeth to denture bases were fabricated and divided into 14 groups: 7 groups before thermal cycling and 7 groups after thermal cycling (n = 10). The groups were divided according to surface treatment into no treatment (control), treatment of the base (B), the tooth (T), or both (BT). Each group was further subdivided according to the surface treatment method into alumina-blasting or alumina-blasting and silane coupling agent. After treatment, acrylic discs and teeth were fixed in a jig, and the repair procedure was done. Half the specimens were thermally cycled. Shear bond strength was measured using a universal testing machine. ANOVA and Tukey HSD tests were performed at α = 0.05. Results. Surface treatment significantly improved the bond strength compared to the control group P < 0.001 . Comparing surface treatments, alumina-blasting with silane coupling agent treatment resulted in significantly higher strength compared to alumina-blasting alone P < 0.001 . The BT group treated with alumina-blasting and silane coupling agent showed the highest significant shear bond strength (23.91 ± 0.96 MPa) P < 0.001 . Significant drop in strength value was observed in all groups after thermal cycling P < 0.004 except the BT group treated with alumina-blasting P = 0.096 . Conclusion. Surface treatment using alumina-blasting with silane coupling agent for denture base and tooth increased repair strength.

Background. The number of patients seeking orthodontic treatment has been consistently increasing. During orthodontic treatment, it is recommended to place the provisional restoration and to delay the final restoration until completion of orthodontic treatment. Recurrent bracket debonding necessitates orthodontists to prepare the bonding area with special measures. Objective. This study aimed to evaluate the effect of different grit sizes of diamond burs and sandblasting surface treatment on the shear bond strength of orthodontic brackets to provisional crowns. Materials and Methods. A total of 75 discs were fabricated from a bisacrylic composite and divided into 5 groups (n = 15) according to surface treatment by black, blue, and green diamond burs and sandblasting in addition to a control group. Metal orthodontic brackets were bonded to discs in a standardized conventional manner. All specimens were subjected to thermocycling with 5000 cycles of alternating 5°C and 55°C waterbaths. The shear bond strength test was performed using a universal testing machine. A scanning electron microscope (SEM) was used to analyze the surface treatment effect and features of debonded surfaces. The amount of composite resin left on the specimen surfaces was analyzed and classified with the adhesive remnant index. One-way ANOVA was performed at α = 0.05. Results. The shear bond strength of specimens treated with sandblasting was significantly higher than that of the control group under thermal aging conditions ( p = 0.022 ), as well as blue burs ( p = 0.001 ), while no significant differences were found between different grit diamond burs and the controls ( p > 0.05 ). Conclusion. Under thermocycling conditions, sandblasting of provisional crowns increases the bond strength of orthodontic brackets.