Young Kyung Kim1, Hyo-Sang Park2, Kyo-Han Kim3, Tae-Yub Kwon4. 1. Departments of *Conservative Dentistry. 2. Orthodontics, and. 3. Dental Biomaterials, School of Dentistry, Kyungpook National University, Daegu, Korea. 4. Dental Biomaterials, School of Dentistry, Kyungpook National University, Daegu, Korea tykwon@knu.ac.kr.
Abstract
OBJECTIVE: 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. MATERIALS AND METHODS: 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. RESULTS: 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). LIMITATIONS: The results were drawn only from ex vivo experiments. CONCLUSIONS: The hypothesis is rejected. This study suggests that a more flexible MMA resin is favourable for avoiding enamel fracture during metal bracket debonding.
OBJECTIVE: 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. MATERIALS AND METHODS: 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. RESULTS: 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). LIMITATIONS: The results were drawn only from ex vivo experiments. CONCLUSIONS: The hypothesis is rejected. This study suggests that a more flexible MMAresin is favourable for avoiding enamel fracture during metal bracket debonding.
Authors: Fernanda de Souza Henkin; Érika de Oliveira Dias de Macêdo; Karoline da Silva Santos; Marília Schwarzbach; Susana Maria Werner Samuel; Karina Santos Mundstock Journal: Dental Press J Orthod Date: 2016 Nov-Dec