Bond Strength of Orthodontic Brackets to Temporary Crowns: In Vitro Effects of Surface Treatment

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.