Influence of self-etchant application time on bracket shear bond strength

Area of Science:

• Dental Materials Science
• Orthodontic Adhesion
• Biomaterials Engineering

Background:

• Orthodontic bracket debonding is influenced by adhesive bond strength.
• Self-etching primers (SEPs) are used to enhance adhesion between brackets and enamel.
• Optimizing SEP application time is crucial for predictable bond strength.

Purpose of the Study:

• To investigate the effect of extended self-etching primer (SEP) application time on the shear bond strength (SBS) of orthodontic brackets.
• To compare the failure modes (Adhesive Remnant Index - ARI) associated with different SEP application durations.

Main Methods:

• Forty human molars were divided into two groups, receiving SEP application for either 3-5 seconds (control) or 15 seconds.
• Standard orthodontic brackets and adhesive systems were used for all teeth.
• Shear bond strength (SBS) and Adhesive Remnant Index (ARI) were measured after debonding using a universal testing machine.

Main Results:

• The mean SBS for the 3-5 second SEP group was 8.0±4.6 MPa, while the 15-second group showed a mean SBS of 8.9±3.4 MPa.
• No statistically significant difference in SBS was found between the two SEP application time groups (P=.494).
• Adhesive Remnant Index (ARI) scores were comparable between groups (P=.340), with most failures occurring at the bracket-adhesive interface.

Conclusions:

• Extending SEP application time from 3-5 seconds to 15 seconds does not significantly enhance the shear bond strength of orthodontic brackets.
• The duration of SEP application within the tested range does not appear to influence bracket bond failure modes.