Effect of torque customization with composite resin bases on the shear bond strength and adhesive remnant patterns of lingual brackets : An in vitro evaluation

• Published in: Journal of orofacial orthopedics 2024-12
• Main Authors: Kumar, Sekar Santhosh, Ramteke, Shivangi, Nivethitha, Bhaskar, Madhan, Balasubramanian
• Format: Article
• Language: English
• ISSN: 1615-6714; 1615-6714
• DOI: 10.1007/s00056-024-00559-6

This study evaluated the effect of torque customization of lingual brackets with resin-modified bases on their shear bond strength (SBS), adhesive remnant index (ARI), and bond failure patterns (BFP). The sample comprised 200 lingual lower incisor brackets (DTC® ORG, DTC Medical Apparatus, Hangzhou, China); 40 brackets were tested as-received and 4 groups with 40 brackets each were customized for -10, -20, +10 and +20° torque respectively with light-cured composite resin (Transbond XT™, 3M Unitek, Monrovia, CA, USA) bases. All brackets were bonded to bovine mandibular incisors. Their SBS were estimated in a universal testing machine (INSTRON®, Norwood, MA, USA) with a gingivally directed force applied at the incisal bracket-adhesive interface with 1 mm/min crosshead speed. Their ARI and BFP were evaluated under 20× magnification. The SBS was 19.9 ± 7.6 MPa for noncustomized brackets, 20.1 ± 9.0 and 18.7 ± 8.2 MPa for brackets with 10 and 20° of negative torque, and 16.6 ± 5.68 and 19.45 ± 5.84 MPa for brackets with 10 and 20° of positive torque, respectively. The differences were not statistically significant (p = 0.097). Teeth with the -20° brackets exhibited higher median ARI scores than noncustomized brackets (1.5 vs 2, p = 0.018). Adhesive-cohesive bond failure with nearly axial split was more frequent in noncustomized brackets than customized ones, the reverse being true for adhesive-cohesive failure with nearly vertical split (p