Does the time interval after bleaching influence the adhesion of orthodontic brackets?

Area of Science:

• Dental Materials Science
• Orthodontic Materials Research
• Biomaterials Engineering

Background:

• Dental bleaching agents can affect the mechanical properties of tooth enamel.
• The impact of bleaching on the bond strength of orthodontic brackets is a critical clinical consideration.
• Understanding the timing of bracket bonding after bleaching is essential for successful treatment outcomes.

Purpose of the Study:

• To evaluate and compare the effects of at-home and in-office dental bleaching on the shear bond strength (SBS) of orthodontic brackets.
• To determine the optimal time interval for bracket bonding after dental bleaching procedures.
• To test the null hypothesis of no difference in SBS between bleaching methods and time intervals.

Main Methods:

• Ninety extracted human premolars were divided into groups based on bleaching method (at-home, in-office) and bonding time (30 min, 1 day, 2 weeks, 3 weeks).
• A control group was stored in artificial saliva for 7 days without bleaching.
• Brackets were bonded using the Transbond XT system, followed by SBS testing and Adhesive Remnant Index (ARI) assessment. Statistical analysis included ANOVA and Tukey tests (p < 0.05).

Main Results:

• The shear bond strength (SBS) of the unbleached control group was significantly higher than most bleached groups (p < 0.05).
• A notable exception was the group bonded 30 minutes after at-home bleaching, which showed comparable SBS to the control.
• SBS values generally returned to levels near those of unbleached enamel by 3 weeks post-bleaching.

Conclusions:

• The null hypothesis was not entirely rejected, as bleaching generally decreased bracket bond strength.
• Bonding brackets 30 minutes after at-home bleaching did not significantly reduce SBS.
• A waiting period of up to 3 weeks allows SBS to recover to levels similar to unbleached enamel.