Shear bond strength of orthodontic attachments bonded to impacted teeth under in vivo and in vitro conditions

Objectives - To evaluate and compare the shear bond strength (SBS) of stainless steel and gold-plated attachments to impacted lower third molars in vivo and in vitro with a light-cured orthodontic resin. Setting and Sample Population - Sixteen patients with bilaterally full soft tissue impaction of lower third molars were recruited on a voluntary basis from an oral and maxillofacial surgery department. Materials and Methods - A split-arch technique was used. Following surgical exposure of the crown, the tooth was luxated but not extracted. Then, two attachments (one stainless steel button and one gold-plated eyelet) were bonded to the labial enamel surface of the loosened tooth. Five minutes later, the luxated tooth was removed from its socket. In each patient, the impacted tooth on the other side was extracted, and attachments were bonded in vitro. The SBSs of the attachments were evaluated. For comparison, analysis of variance and multiple range tests were used (alpha = 0.05). Results - Statistically significant differences were evident in attachment adhesion to the impacted tooth surfaces among the four groups (p < 0.001). Superior SBS values were obtained for stainless steel button groups bonded in vitro. The mean bond strengths of the groups bonded in vitro were better than those of the same groups bonded in vivo. Conclusions - Although the in vitro-bonded groups showed higher SBS values, adequate bond strength is possible with stainless steel buttons bonded in vivo.