Are flowable resin-based composites a reliable material for metal orthodontic bracket bonding?

Area of Science:

• Dental Materials Science
• Orthodontic Adhesion
• Biomaterials Engineering

Background:

• Orthodontic bracket bonding relies on effective adhesive materials.
• Flowable resin-based composites offer handling advantages but require evaluation for bond strength.
• Assessing tensile bond strength (TBS) and adhesive remnant index (ARI) is crucial for clinical success.

Purpose of the Study:

• To compare the tensile bond strength (TBS) and adhesive remnant index (ARI) of three flowable resin-based composites against three conventional orthodontic adhesive systems.
• To determine the suitability of flowable composites for metal bracket bonding in orthodontics.

Main Methods:

• Sixty bovine incisors were bonded with metal brackets using three flowable composites (FL, TF, WA) or three orthodontic adhesives (TX, CO, FM) after acid etching.
• Specimens underwent thermal cycling before TBS testing using a universal testing machine.
• ARI scores were evaluated post-failure, with data analyzed using ANOVA, Tukey, and Kruskal-Wallis tests.

Main Results:

• Orthodontic adhesive TX exhibited the highest TBS (6.4 ± 2.1 MPa), while flowable composite WA showed the lowest (2.4 ± 0.6 MPa).
• ARI scores varied, with CO showing the lowest (0.9 ± 1.2) and WA the highest (3.0 ± 0.01), indicating minimal differences among most materials.
• Flowable composites generally demonstrated lower TBS compared to conventional orthodontic adhesives.

Conclusions:

• Flowable resin-based composites (FL, TF, WA) yielded low mean TBS values for bonding metal orthodontic brackets to bovine enamel.
• While ARI scores were acceptable, the low TBS suggests flowable composites may not be ideal for high-stress orthodontic scenarios.
• Consideration of occlusal forces is recommended when evaluating the clinical applicability of flowable composites for bracket bonding.