As increasing number of adult patients, the esthetic orthodontic appliances are needed. They are tooth-colored or translucent ceramic and resin brackets. Although ceramic and resin bracket have good esthetics, there are some disadvantage such as frictions. Recently, metal-reinforced resin bracket(MRRB) were introduced. The purpose of this study is to find frictional force of MRRB, ceramic bracket and resin brackets. There is few study in frictional force about metal reinforced resin bracket(MRRB). This study used 4 orthodontic wire(.016S-S, .016TMA^?, .017X.025 TMA^?)and 5 brackets(one metal bracket, one ceramic bracket, one resin bracket, two MRRB). the following result is obtained using metal bracket(Ormco.Co., U.S.A), ceramic brackets(Crystalline^?, resin bracket(Clear Medium Siamase^?). Following conclusions are obtained. 1. Ceramic and resin bracket have significantly more frictional forces than metal reinforced resin bracket and metal bracket. 2. There is no significant difference in frictional force according to the slot types of metal-reinforced resin brackets. 3. There is no significant difference in frictional force between metal reinforced resin bracket and metal bracket. 4. Frictional force is decreased in S-S wire than TMA wire.

Keywords: friction , esthetic , ceramic , composite , bracket , wire