Time-dependent effects after enamel fluoride application on an acid etching system in orthodontic bracket bonding

Area of Science:

• Dental Materials Science
• Orthodontic Adhesion
• Fluoride Research

Background:

• Acidulated phosphate fluoride (APF) gel is commonly used for caries prevention.
• Fluoride application can potentially affect the enamel surface properties and adhesion of orthodontic brackets.
• Understanding the timing of orthodontic bracket bonding after fluoride treatment is crucial for successful treatment outcomes.

Purpose of the Study:

• To investigate the impact of varying time intervals after 1.23% APF gel application on enamel surface hardness and shear bond strength (SBS) of orthodontic brackets.
• To evaluate the effectiveness of acid etching on APF-treated enamel over time.
• To determine the optimal timing for orthodontic bracket bonding after APF gel application.

Main Methods:

• Bovine teeth were treated with 1.23% APF gel and immersed in distilled water for 1, 7, 14, 21, and 28 days.
• Control group received no fluoride pretreatment.
• Enamel surface hardness, scanning electron microscopy (SEM) analysis, and shear bond strength (SBS) tests were performed after 35% phosphoric acid etching.

Main Results:

• Enamel surface hardness decreased with longer immersion periods post-APF treatment.
• SEM analysis revealed etched patterns similar to the control group as immersion time increased.
• SBS generally increased with longer immersion periods, with no significant difference from the control at 21 days.
• Higher adhesive remnant index scores were observed with increased ageing periods.

Conclusions:

• Fluoride pretreatment, specifically APF gel, interferes with acid etching, potentially reducing bond strength for orthodontic brackets.
• An interval of 21 days between APF gel application and acid etching is recommended for optimal bond strength in orthodontic bonding.
• Clinicians should consider the timing of fluoride treatments when planning orthodontic bracket placement.