[Comparison of friction force between Lock-loose bracket and traditional bracket].

OBJECTIVE: Frictions of Lock-loose brackets with ligated main wings or all six wings were measured as they slid along archwires in dry and artificial saliva environments. The Lock-loose brackets were then compared with traditional brackets and self-ligating brackets. METHODS: The surface states of the stainless steel archwires were observed with atomic force microscopy before and after mechanical traction. The Lock-loose brackets, traditional brackets, and self-ligating brackets used in this study were composed of 0.406 4 and 0.457 2 mm stainless steel round archwires and 0.457 2 mm x 0.634 9 mm and 0.482 6 mm x 0.634 9 mm stainless steel rectangular archwires. Two different ligating methods were applied to the Lock-loose brackets, i.e., main wings ligated and all six wings ligated. Frictions were measured by using an electronic universal testing machine. RESULTS: No significant differences were found between the roughness of different archwires before and after mechanical traction in different brackets (P > 0.05). When the main wings of the Lock-loose brackets were ligated, the frictions of the four different stainless steel archwires were close to zero, and the difference with frictions of traditional brackets was significant (P < 0.05). When using 0.457 2 mm x 0.634 9 mm rectangular archwires, maximum friction (P < 0.05; significantly different from those of other brackets) was reached when all six wings of the Lock-loose brackets were ligated. Frictions in the dry state were higher than those in the wet state (P < 0.05). CONCLUSION: The Lock-loose brackets can adjust the friction efficiently with different ligating methods, thus solving the problem of low friction and strengthening anchorage.