Shear bond strength of three composite resins for orthodontic bracket bonding on enamel and ceramic surfaces: an in vitro study after accelerated aging.

Abstract

Objective: To evaluate and compare the shear bond strength (SBS) of three composite resins, Z250 (3M), Transbond XT (3M), and Brace Paste (AO), used for orthodontic bracket bonding on human enamel and ceramic surfaces, after undergoing accelerated aging.

Materials and methods: An in vitro experimental design was conducted using 30 enamel specimens (human premolars) and 30 ceramic specimens (Brava Block, FGM), divided into three subgroups per substrate (n = 10 each). All specimens were etched (37% phosphoric acid for enamel, 9.6% hydrofluoric acid for ceramic), treated with silane (ceramics), and bonded using the designated composite resins. Specimens were subjected to an autoclave aging protocol. SBS was measured using a universal testing machine, and statistical analysis included Analysis of Variance (ANOVA), t tests, and chi-square tests (α = 0.05).

Results: Transbond XT exhibited the highest mean SBS on ceramic surfaces (10.4 ± 5.2 MPa), while Brace Paste showed the highest SBS on enamel (7.3 ± 2.4 MPa). However, no statistically significant differences were observed among the composite resins in either substrate (p > 0.05). All materials demonstrated SBS values within or close to the clinically acceptable range for orthodontic bonding (approximately 6-8 MPa).

Conclusion: Although numerical differences were found, all three composite resins demonstrated comparable performance. When appropriate surface conditioning protocols are applied, any of the tested materials can be considered reliable for bracket bonding to both enamel and ceramic substrates. Further in vivo studies are recommended to validate long-term durability.