Comparative Research On The Friction Force Of Different Fixed Appliance At Front Teeth Inittal Leveling Stage And Influences On Three-Dimensional Variation Trend

Dentognathic deformity was considered to be one of the three dental diseases by the World Health Organization. Orthodontic treatment is the only means to deal with dentognathic deformity. "force" is the only weapon of the orthodontics and light force correction/orthotherapy is the generally accepted principle.In 1975, Nikolai defined the optimal force as a kind of force which can generate maximum ideal biological response and minimum tissue damage, and then cause teeth fastest movement while with no or little discomfort. The suitable orthodontic force is the guarantee for the high efficient and safe orthodontic movement.Different orthodontic force design is important to the high efficient and safe orthodontic movement. Therefore, this thesis will analyse the influences to the friction force and three-dimensional variation trend because of the various designs by friction force testing at the front teeth aligning stage and the three-dimensional displacement result scanning of steel orthodontic brackets commonly used in clinical.1.Comparative research on the Friction force of fixed-appliances at front teeth inittal leveling stage .Choose 40 maxillary standard occlusal Typodont, make two types of 3mm experimental models at vertical displaced of canines and level displaced of lateral incrsors, randomly divide into five groups-MBT, self -ligating, Tip-Edge and MDD, and each group has five samples. 0.012 niti bending mechanical properties of round wire serve as alignment experimental archwire. Make friction force test of the experimental models before and after water bath by universal material test prototype at the speed of 10mm/min, set the displacement as 3mm, the computer reads the maximum static friction and sliding friction every 10 milisecond, every sample will repeat 3 times. The result is: before water bath the sliding and static friction order is MBT>Tip-Edge>MDD>self-ligating, no matter canines displaced experiment and lateral incisor displaced experiment, and there have statistical significance between the differences of the two groups. (P<0.05).The lower rate of sliding and static friction after water bath: Tip-Edge and MBT there was no statistical significance(P>0.05).The self-ligating appliance showed the highest friction reduce rate, The MDD appliance showed the lowest friction reduce rate, there all statistical significance(P<0.05), This experimental think the self-ligating appliance have lowest friction at the front teeth inittal leveling stage; Friction reducing rates reflect the leveling situation, MDD appliance have light force; MDD friction and friction reducing rate reflect theθc more bigger more conducive to reducing friction and archwrie rigid.2. Comparative research on the teeth three-dimensional change trend of fixed-appliances at front teeth inittal leveling stage .This experiment and friction test interaction, also use 40 Typodont modeling model and groups. Record the initial model 3d images from used ATOS scanning the experiment model, Then put 45°constant temperature water-bath 30min out immediately after box water-bath water cooling, again by ATOS scanner, supporting software will water-bath obtained before and after the experiment model overlap each point displacement value teeth. Results: the canines'Z axis cusps and tongue axon protruding point change trend are: MBT>self-ligating>Tip-Edge>MDD. the difference was statistically significant(P<0.05).lateral incrsors ,Z axis trend of the three dots are not statistically significant (P>0.05); X axis, MDD group in the three points are less than the change trend of the other three groups, the difference was statistically significant(P<0.05). MBT group with self-locking group in the nearly edge crest point difference was statistically significant (P>0.05). Tip-Edge group and self-ligating group in the near, far edge of crest point, no statistically significant (P>0.05). The Y axis MDD group in the three points are less than the change trend of the other three groups, the difference was statistically significant (P<0.05). MBT group with self-ligating group both in the near and far edge of crest point, have no statistically significant (P>0.05). Tip-Edge group with self-ligating group in the near edge crest point was no statistically significant (P>0.05). This experiment think the MDD appliance have least change trend and most light force at front teeth inittal leveling stage. Vertical displaced of canines experiment proves fixed-appliance the more smallerθc and larger width, the archwire rigidity will bigger. level displaced of lateral incrsors experiment proves fixed-appliance more narrower and the archwire rigid more lower and also the worse teeth control.In summary, at the inittal leveling stage both friction test or teeth three-dimensional change trend, common confirmed the different design of the appliance can produce different treatments force system. This study, namely for MBT appliance, self-ligating appliance, Tip-Edge appliance and MDD appliance provides a certain reference data, and benefit guide clinical application ,while provides the reference for appliance's design at front teeth inittal leveling stage .