Kim Young Kyung, Park Hyo-Sang, Kim Kyo-Han, Kwon Tae-Yub
Departments of *Conservative Dentistry.
Orthodontics, and.
Eur J Orthod. 2015 Oct;37(5):550-5. doi: 10.1093/ejo/cju086. Epub 2014 Dec 29.
To test the null hypothesis that neither the flexural properties of orthodontic adhesive resins nor the enamel pre-treatment methods would affect metal bracket debonding behaviours, including enamel fracture.
A dimethacrylate-based resin (Transbond XT, TX) and two methyl methacrylate (MMA)-based resins (Super-Bond C&B, SB; an experimental light-cured resin, EXP) were tested. Flexural strength and flexural modulus for each resin were measured by a three-point-bending test. Metal brackets were bonded to human enamel pretreated with total-etch (TE) or self-etch adhesive using one of the three resins (a total of six groups, n = 15). After 24 hours of storage in water at 37°C, a shear bond strength (SBS) test was performed using the wire loop method. After debonding, remaining resin on the enamel surfaces and occurrence of enamel fracture were assessed. Statistical significance was set at P < 0.05.
The two MMA resins exhibited substantially lower flexural strength and modulus values than the TX resin. The mean SBS values of all groups (10.15-11.09MPa) were statistically equivalent to one another (P > 0.05), except for the TE-TX group (13.51MPa, P < 0.05). The two EXP groups showed less resin remnant. Only in the two TX groups were enamel fractures observed (three cases for each group).
The results were drawn only from ex vivo experiments.
The hypothesis is rejected. This study suggests that a more flexible MMA resin is favourable for avoiding enamel fracture during metal bracket debonding.
检验零假设，即正畸粘结树脂的弯曲性能和牙釉质预处理方法均不会影响金属托槽的脱粘行为，包括牙釉质骨折。
测试了一种基于二甲基丙烯酸酯的树脂（Transbond XT，TX）和两种基于甲基丙烯酸甲酯（MMA）的树脂（Super-Bond C&B，SB；一种实验性光固化树脂，EXP）。通过三点弯曲试验测量每种树脂的弯曲强度和弯曲模量。使用三种树脂之一将金属托槽粘结到用全蚀刻（TE）或自蚀刻粘结剂预处理的人牙釉质上（共六组，n = 15）。在37°C水中储存24小时后，使用钢丝圈法进行剪切粘结强度（SBS）测试。脱粘后，评估牙釉质表面残留的树脂和牙釉质骨折的发生情况。统计学显著性设定为P < 0.05。
两种MMA树脂的弯曲强度和模量值明显低于TX树脂。除TE-TX组（13.51MPa，P < 0.05）外，所有组的平均SBS值（10.15 - 11.09MPa）在统计学上彼此等效（P > 0.05）。两个EXP组的树脂残留较少。仅在两个TX组中观察到牙釉质骨折（每组三例）。
结果仅来自体外实验。
零假设被拒绝。本研究表明，一种更具柔韧性的MMA树脂有利于在金属托槽脱粘过程中避免牙釉质骨折。
