Comparison of shear bond strength of metal orthodontic brackets bonded to a CAD/CAM prosthetic provisional material after the use of a self-adhesive resin cement versus a light adhesive paste and different surface conditioning protocols: An in vitro study

Background: Adult orthodontic treatment has been increasingly popular, and brackets may need to be bonded to provisional crowns, including CAD/CAM crowns. The use of self-adhesive resin cement or light adhesive paste have been suggested with different surface conditioning protocols to improve the adhesion to CAD/CAM PMMA provisional crowns. Objective To determine and compare the in vitro shear bond strength (SBS) of metal brackets bonded to a provisional prosthetic CAD/CAM material after the use of different adhesive cements and surface conditioning protocols. Materials and methods: One hundred twenty Telio® CAD specimens were manufactured in 12 groups (n = 10). Each specimen was bonded to a metal bracket and divided according to adhesive technique (3M™Transbond™ XT Light Cure Paste or 3M™RelyX™ U200) surface treatment (macroretentions) and the use of silane. Half of the specimens were thermocycled (5000 cycles, 5 °C/55 °C water baths). The SBS test was carried out using a shear bond strength tester, and the type of adhesive failure was determined by means of the adhesive remnant index. The data were analysed with the Mann–Whitney test (α = 0.05). Results: Statistically significant differences (P < 0.001) in SBS were found among the groups. The group with macroretentions, silane, and not thermocycled was the one that obtained the highest average value (17.31 ± 4.89 MPa). The lowest average value was the group without macroretentions, without silane, and thermocycled (3.4 ± 3.37 MPa). Conclusion: The shear bond strength of brackets to provisional prosthetic CAD/CAM materials depended on the type of adhesive, surface treatment, and aging by thermocycling.