Kumar Sekar Santhosh, Ramteke Shivangi, Nivethitha Bhaskar, Madhan Balasubramanian
Division of Orthodontics and Dentofacial Orthopedics, Department of Dentistry, Jawaharlal Institute of Postgraduate Medical Education and Research, 605006, Puducherry, India.
J Orofac Orthop. 2024 Dec 6. 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 < 0.05). Truly cohesive bond failures were seen only in brackets with positive torque.
Torque customization with a resin base is an acceptable strategy for metal orthodontic brackets as it does not affect their SBS. However, their BFP differed from noncustomized brackets, depending on the type of torque introduced.
本研究评估了采用树脂改良基底对舌侧托槽进行扭矩定制对其剪切粘结强度（SBS）、粘结剂残留指数（ARI）和粘结失败模式（BFP）的影响。
样本包括200个下颌切牙舌侧托槽（DTC® ORG，中国杭州DTC医疗器械公司）；40个托槽按收到时的状态进行测试，另外4组每组40个托槽分别用光固化复合树脂（Transbond XT™，美国3M Unitek公司，加利福尼亚州蒙罗维亚）基底定制为-10°、-20°、+10°和+20°扭矩。所有托槽均粘结到牛下颌切牙上。在万能材料试验机（INSTRON®，美国马萨诸塞州诺伍德）上以1毫米/分钟的十字头速度在托槽-粘结剂界面的切端施加龈向力来估计其SBS。在20倍放大倍数下评估其ARI和BFP。
未定制的托槽SBS为19.9±7.6兆帕，负扭矩为10°和20°的托槽SBS分别为20.1±9.0和18.7±8.2兆帕，正扭矩为10°和20°的托槽SBS分别为16.6±5.68和19.45±5.84兆帕。差异无统计学意义（p = 0.097）。使用-20°托槽的牙齿的ARI中位数得分高于未定制的托槽（1.5对2，p = 0.018）。未定制的托槽中，带有近乎轴向裂开的粘结-内聚性粘结失败比定制的托槽更常见，而带有近乎垂直裂开的粘结-内聚性失败则相反（p < 0.05）。真正的内聚性粘结失败仅在正扭矩托槽中出现。
用树脂基底进行扭矩定制对于金属正畸托槽是一种可接受的策略，因为它不影响其SBS。然而，根据引入的扭矩类型，其BFP与未定制的托槽不同。
