A comparison of bond strength between direct- and indirect-bonding methods.

The purpose of this study was to evaluate and compare the shear bond strength and the sites of bond failure for brackets bonded to teeth, using two indirect-bonding material protocols and a direct-bonding technique. Sixty extracted human premolars were collected and randomly divided into three groups. The direct-bonded group (group 1) used a light-cured adhesive and primer (Transbond XT). One indirect-bonded group (group 2) consisted of a chemical-cured primer (Sondhi Rapid Set) and light-cured adhesive (Transbond XT), whereas the other group (group 3) used a light-cured primer (Orthosolo) and adhesive (Enlight LV). Forty hours after bonding, the samples were debonded. Mean shear bond strengths were 16.27, 13.83, and 14.76 MPa for groups 1, 2, and 3, respectively. A one-way analysis of variance showed no significant difference in mean bond strength between groups (P = .21). Furthermore, a Weibull analysis showed all three groups tested provided over a 90% survival rate at normal masticatory and orthodontic force levels. For each tooth, an Adhesive Remnant Index (ARI) score was determined. Group 2 was found to have a significantly lower ARI score (P < .05) compared with groups 1 and 3. In addition, Pearson correlation coefficients indicated no strong correlation between bond strength and ARI score within or across all groups.