The influence of bracket material, ligation force and wear on frictional resistance of orthodontic brackets.

Planar static frictional phenomena were investigated for two types of ceramic and one type of stainless steel orthodontic bracket against rectangular stainless steel archwire. The brackets studied were 'Starfire' (single crystal aluminium oxide), 'Allure III' (polycrystalline aluminium oxide), and 'Dentaurum' (stainless steel). The investigative parameters were: bracket material, force of ligation and whether the brackets were new or 'worn'. Without exception, both types of ceramic bracket produced greater frictional resistance than the stainless steel brackets throughout testing. At a ligation force of 500 g, the Starfire bracket gave the greatest frictional resistance. At ligation forces of 200 and 50 g, the greatest frictional resistance was seen with Allure III. After a period of simulated wear, frictional resistance of Starfire tended to increase at the greatest ligation load while that of both ceramics decreased slightly at the two lower ligation loads. The ceramic brackets caused abrasive wear of the archwire surfaces and the consequent wear debris may have contributed to the changes in frictional resistance seen with Starfire and Allure III. Dentaurum brackets produced minimal frictional resistance in any test and negligible change with wear.