Abstract
This in vitro study compares a self-etch primer (SEP) to an etch-and-rinse (EaR) for bonding sapphire brackets by evaluation of the enamel etch-pattern, shear bond strength, amount of remnant adhesive and enamel surface damage following thermal and fatigue cyclic loading. Ceramic (sapphire) brackets were bonded to 80 extracted human premolars using two enamel etching protocols: conventional EaR using 37% phosphoric acid (PA) gel (control), and a SEP (Transbond Plus). Each group was subdivided into two subgroups (n=20 teeth) according to the time of bracket debonding: after 24 h water storage or following 5000 thermo-cycles plus 5000 cycles fatigue loading, to determine the shear bond strength (SBS), adhesive remnant index (ARI score), with scanning electron microscopy (SEM) evaluation of enamel condition. The control subgroups consistently exhibited significantly higher (p<0.05) SBS mean values (23.4-29.8 MPa) than the SEP subgroups (15.1-22.4 MPa) at both bracket debonding time points. However, the SEP subgroups yielded milder etch-patterns and attained SBS values above the minimum requirement range for clinical performance. In addition, the higher SBS of control subgroups was accompanied with higher ARI scores and enamel damage grades than SEP subgroups as confirmed by SEM. Thermocycling and fatigue significantly reduced the SBS of all subgroups, with a non-significant drop in the amount of adhesive residue or enamel damage. The use of SEP can be a suitable alternative to the conventional PA gel for sapphire bracket bonding as it maintains suitable bond strength and has the potential to produce both less remnant adhesive and enamel damage. Key words:Enamel etching, ceramic brackets, orthodontic bonding, adhesive remnants, enamel damage.
Highlights
Correction of mal-aligned teeth and/or jaw discrepancies using fixed orthodontic appliances can improve the facial aesthetics and oral function, resulting in a profound effect on both the psychological well-being of the person and dental health
The debonded teeth were examined with a stereomicroscope (MEIJI, EMZ-TR, Japan) under x10 magnification for the amount of remnant adhesive left, and scored according to the adhesive remnant index (ARI) scoring system [16]: Score 0: No adhesive left on the tooth, Score 1: Less than half of the adhesive left on the tooth, Score 2: More than half of the adhesive left on the tooth, Score 3: All adhesive left on the tooth, with a distinct impression of the bracket mesh
Adhesive remnant index (ARI) scores: (0): No adhesive left on the tooth, [1]: Less than half of the adhesive left on the tooth, [2]: More than half of the adhesive left on the tooth, [3]: All adhesive left on the tooth with a distinct impression of the bracket mesh
Summary
Correction of mal-aligned teeth and/or jaw discrepancies using fixed orthodontic appliances can improve the facial aesthetics and oral function, resulting in a profound effect on both the psychological well-being of the person and dental health. This study aims to determine the SBS, amount of remnant adhesive, enamel etch-patterns, and evaluate the enamel damage of highly aesthetic ceramic brackets (monocrystalline sapphire) bonded with a SEP following exposure to rigorous thermocycling and fatigue tests in comparison with the standard EaR technique. The tested hypothesis was whether sapphire bracket bonding with a SEP could eliminate the remnant adhesive and enamel damage after debonding, without compromising the bond strength This in vitro study compares a self-etch primer (SEP) to an etch-and-rinse (EaR) for bonding sapphire brackets by evaluation of the enamel etch-pattern, shear bond strength, amount of remnant adhesive and enamel surface damage following thermal and fatigue cyclic loading. Each group was subdivided into two subgroups (n=20 teeth) according to the time of bracket debonding: after 24 h water storage or following 5000 thermo-cycles plus 5000 cycles fatigue loading, to determine the shear bond strength (SBS), adhesive remnant index (ARI score), with scanning electron microscopy (SEM) evaluation of enamel condition. Conclusions: The use of SEP can be a suitable alternative to the conventional PA gel for sapphire bracket bonding as it maintains suitable bond strength and has the potential to produce both less remnant adhesive and enamel damage
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