A Model Building For Testing The Resistance To Sliding Of Self-ligating Bracket And The Correlation Study

一,Objective.1. There was few researchers who mentioned pericementum which has some effect of resistance to sliding(RS) when they studyed the friction of archwire-bracket. So a new model will be built which including tooth, pericementum and alveolar bone for friction tests.2. On the new model, the RS of conventional brackets, active self-ligating brackets and passive self-ligating brackets were tested when they combined with 4 types of Ni-Ti archwires and 6 types of stainless steel archwires.二,Material and method1. Building a new testing model. Take the advantage of epoxide resin's property, a model was made, in which the Youth module proportion of tooth, pericementum and alveolar bone was in accordance with the somatic data.2. On this model, 3 types of brackets were bonded to the tooth. And the resistances to sliding were tested when they combined with 4 types of Ni-Ti archwire and 6 types of stainless steel archwire.三,Result.1. Comparing the testing model and control model, the variation of bracket-archwire's RS is different, and that of testing model close to the condition of clinic.2. Combine with a same size of archwire and a same degreed of malocclusion, the passive self-ligating bracket makes the least RS.3. Multistrand Ni-Ti archwire makes less RS when it combined with self-ligating bracket than a single-stranded one. But when it combined with conventional brackets, the result was converse4. When the level of malocclusion increase, the RS of all brackets increase at the same time.5. When there was no difference in the material of archwire, the resistance will increase as the cross-sectional area increased. But in this study, the RS of the 0.019×0.025 inch rectangular archwire was the least one.四,Conclusion.1. When a patient care more about his irregular tooth alignment , a active self-ligating bracket may be a good choice for him, because it reduces the RS, and it can get good control of the tooth.2. A stiffer archwire and a wider bracket will both increase the stiffness of archwire. And making an angle between the hook and the archwire will decrease the force which may incurve the archwire. These two ways will both decrease the RS.3. When a patient care more about his protrusion( gangtooth, snaggletooth),a passive self-ligating bracket may be a good choice for him. And combined with the 0.019×0.025 inch rectangular archwire, the RS of bracket-archwire will decrease to a satisfactory level.