IADR Abstract Archives
Shear bond strength of orthodontic bracket to enamel at various time intervals after tooth bleaching
Objectives: Currently, some of young patients may receive the tooth bleaching before starting orthodontic treatment. Previous works reported the changes both in microstructure and hardness property of bleached enamel. Therefore, this may affect the bond strength between bleached enamel and orthodontic bracket. What is the proper time interval after bleaching for orthodontic bonding? The aim of this study is to find out the optimal time interval after tooth bleaching.
Methods: 60 extracted human premolars were root cut and embedded in acrylic block. Then, all specimens were divided into 4 groups according to different time intervals after bleaching as: G1, control (No bleaching); G2, immediate bonding after bleaching; G3, 14 days after bleaching; G4, 30 days after bleaching. Each specimen was bleached with bleaching gel (Opalescence®, Ultradent, USA) according to manufacturer's recommendation, and then orthodontic bracket was fixed on each enamel surface with light-cured composite resin adhesive (Transbond™XT, 3M ESPE, USA). Shear bond strength (SBS) was evaluated by using a universal testing machine (EZ-S, Shimadzu, Japan) with cross-head speed of 0.5 mm/min. Statistical analysis of SBS was determined by using 1-way ANOVA with Tukey test. The quality of bonding appearance was investigated under stereomicroscope (Meiji EMZ-5TR, Meiji, Japan) and the percentage of different debonding failure was calculated.
Results: Mean SBS of G1, G2, G3 and G4 were 14.57(4.95), 8.37 (6.36), 11.08(5.39), 11.56(4.75) MPa, respectively. Statistic analyses indicated significant differences in SBS between control and experimental group. The highest percentage of adhesive failure occurred in G2 while G3 showed the highest percentage of both partially cohesive and cohesive failure.
Conclusions: Based on the result of this study, it is recommended for orthodontic bonding after tooth whitening at least 14 days. The SBS increases at 30 days delayed-bonding.
Methods: 60 extracted human premolars were root cut and embedded in acrylic block. Then, all specimens were divided into 4 groups according to different time intervals after bleaching as: G1, control (No bleaching); G2, immediate bonding after bleaching; G3, 14 days after bleaching; G4, 30 days after bleaching. Each specimen was bleached with bleaching gel (Opalescence®, Ultradent, USA) according to manufacturer's recommendation, and then orthodontic bracket was fixed on each enamel surface with light-cured composite resin adhesive (Transbond™XT, 3M ESPE, USA). Shear bond strength (SBS) was evaluated by using a universal testing machine (EZ-S, Shimadzu, Japan) with cross-head speed of 0.5 mm/min. Statistical analysis of SBS was determined by using 1-way ANOVA with Tukey test. The quality of bonding appearance was investigated under stereomicroscope (Meiji EMZ-5TR, Meiji, Japan) and the percentage of different debonding failure was calculated.
Results: Mean SBS of G1, G2, G3 and G4 were 14.57(4.95), 8.37 (6.36), 11.08(5.39), 11.56(4.75) MPa, respectively. Statistic analyses indicated significant differences in SBS between control and experimental group. The highest percentage of adhesive failure occurred in G2 while G3 showed the highest percentage of both partially cohesive and cohesive failure.
Conclusions: Based on the result of this study, it is recommended for orthodontic bonding after tooth whitening at least 14 days. The SBS increases at 30 days delayed-bonding.