Evaluation of friction during sliding tooth movement in various bracket-arch wire combinations

Frictional forces during simulated sliding tooth movement were measured wit h a model that was representative of the clinical condition. The model allo wed tipping of the tooth until contact was established between the arch wir e and diagonally opposite corners of the bracket wings; it also allowed rot ation until the wire contacted opposite corners of the ligature tie, or the buccal shield with self-ligating brackets, and the base of the slot, Conve ntional and self-ligating stainless steel brackets as well as conventional ceramic brackets, and ceramic brackets with a stainless steel slot, all wit h 0.022 inch bracket slot, were tested with 0.019 x 0.025 inch arch wires o f stainless steel, nickel titanium, and beta titanium. Each of the 12 brack et-arch wire combinations was tested 10 times. No significant interaction w as detected between brackets and arch wires (P = .89), but the bracket and arch wire effects were significant (P < .001). The pairwise differences bet ween conventional and self-ligating stainless steel brackets and ceramic br ackets with stainless steel slot were not significant. However, the convent ional ceramic brackets generated significantly higher friction than the oth er brackets tested. Beta titanium arch wires produced higher frictional for ces than nickel titanium arch wires, but no significant differences were fo und between each of the two and stainless steel arch wires. Attempts to ide ntify differences in surface scratches of the arch wires produced by the di fferent brackets were unsuccessful.