Comparison of Debonding Force Between Ceramic and Metal Brackets

Ceramic brackets often fracture during debonding, it is unclear whether creating occlusal and gingival grooves around the bracket can effectively aid in the removal of brackets. OBJECTIVES: To compare the in vitro debond shear strength and the bracket failure interface of metal orthodontic brackets and ceramic brackets with and without occlusal and gingival channels. METHODS: Thirty-nine extracted, non-carious human third molars were divided into 3 groups (n=13). Gp I: Ceramic brackets debonded without the channels; Gp II: Ceramic brackets (Mystique) debonded by first creating an occlusal and gingival channel with a Mystique Adhesive Bur; and Gp III: Metal brackets debonded without channels which acted as the control. Orthodontic brackets were bonded on tooth surface using light-cured adhesives (Light Bond) and after 24 hrs storage, shear bond strengths were determined using an Instron testing machine with a crosshead speed of 1mm/min. Bracket failure interface was evaluated using a modified Adhesive Remnant Index (ARI). Data were analyzed using ANOVA and t test (p=0.05). RESULTS: Significant differences in debond strengths were found between Gp I [non-grooved ceramic bracket](10.49± 2.72 MPa) and Gp III [metal bracket](13.13 ± 2.34 MPa)(p<0.01). No significant differences were found between Gp I and Gp II [grooved ceramic bracket] (11.44 ± 3.57 MPa). Significant differences in ARI were found between Gp I (3.5 ± 1.3) and Gp III (4.5 ± 0.5) (p<0.01). No differences were found between Gp I and Gp II (4.2 ± 1.2). CONCLUSION: These results suggest that less force is necessary to debond ceramic brackets compared to metal brackets, but there is no difference in debond shear strength for brackets with or without occlusal and gingival channels. Less remnant resins on the tooth surface when debonding grooved ceramic brackets makes clean up easier.