Effect on enamel shear bond strength of adding microsilver and nanosilver particles to the primer of an orthodontic adhesive

Abstract

Background: The objective of this study was to determine whether the addition of microsilver or nanosilver particles to an orthodontic primer affects shear bond strength (SBS) and bracket/adhesive failure. Methods: Bovine incisors were randomly divided into six groups with 16 specimens in each: In group 1 (control), brackets were bonded with Transbond™ XT primer. In the experimental groups, microsilver (groups 2 and 3) and nanosilver (groups 4-6) particles of different sizes were added to Transbond XT primer and light cured for 15seconds [group 2: 0.1% (w/w) microsilver particle size 3.5-18μm; group 3: 0.3% (w/w) microsilver particle size 3.5-18μm; group 4: 0.11% (w/w) nanosilver particle size 12.6-18.5nm; group 5: 0.18% (w/w) nanosilver particle size 12.6-18.5nm; group 6: 0.33% (w/w) nanosilver particle size 12.6-18.5nm]. Thereafter, brackets were bonded by light curing the adhesive for 20seconds. After 24hours of storage in distilled water at 37°C, SBS was measured with a Zwicki 1120 testing machine. The adhesive remnant index and the prevalence of silver spots on the specimen surface were determined under 10× magnification. Statistical two-way analysis of variance was performed to compare SBS, and a chi-square test was used to compare ARI scores and the prevalence of silver spots. Results: No significant differences in SBS (control: 16.59±6.82MPa; group 2: 20.6±4.19MPa; group 3: 16.98±4.84MPa; group 4: 17.15±5.92MPa; group 5: 20.09±3.35MPa; group 6: 16.44±4.51MPa; p>0.665) and ARI scores (p=0.901) were found between the control group and any experimental group. Only experimental groups with nanosilver particles revealed statistically more silver spots on the remaining adhesive. Conclusions: Addition of small concentrations of microsilver or nanosilver particles affects neither SBS nor ARI scores. Addition of nanosilver particles results in silver spots in the remaining primer visible under 10× magnification. Further studies are needed to investigate the anti-caries potential and clinical performance of conventional orthodontic primer with incorporated nanosilver or microsilver particles.