Comparative Evaluation of the Shear Bond Strength of Metallic and Ceramic Brackets Bonded Using Seventh- and Eighth-Generation Bonding Agents: An In Vitro Study

Objective This in vitro study aims to compare the shear bond strength (SBS) of metal and ceramic orthodontic brackets bonded using seventh- and eighth-generation bonding agents. Materials and methods Eighty extracted premolars were cleaned with pumice, rinsed with distilled water, air-dried, and embedded in acrylic resin. The samples were divided into four groups (n = 20). Group A consisted of 3M Unitek™ metal brackets (3M Company, Monrovia, CA, USA) bonded with 3M ESPE Single Bond Universal (seventh generation). Group B included 3M Unitek ceramic brackets bonded with 3M ESPE Single Bond Universal. Group C comprised 3M Unitek metal brackets bonded with GC G-Premio BOND (eighth generation, GC Corporation, Tokyo, Japan), and Group D included 3M Unitek ceramic brackets bonded with GC G-Premio Bond. Brackets were bonded with 3M ESPE composite under dry conditions at room temperature. The bonded samples were stored in artificial saliva at 37 °C for 24 hours, and SBS was measured using an Instron universal testing machine. Results The SBS for metal brackets bonded with 3M ESPE Single Bond Universal was 11.54 ± 0.91 MPa, while ceramic brackets with the same adhesive showed 13.42 ± 0.80 MPa. For metal brackets bonded with GC G-Premio Bond, the SBS was 13.09 ± 0.79 MPa, and for ceramic brackets, it was 15.17 ± 0.98 MPa. One-way ANOVA revealed statistically significant differences among the groups (p = 0.0001). Conclusions The findings indicate that both adhesive type and bracket material significantly influence bond strength. Eighth-generation adhesives outperformed seventh-generation adhesives, and ceramic brackets demonstrated higher bond strength than metal brackets. All SBS values exceeded Reynolds' clinical threshold, confirming the adequacy of both adhesives. The superior performance and simplified application of the eighth-generation adhesive support its effectiveness in contemporary orthodontic practice.