The Biomechanical Research Of Dental Tissue With Composite Archwire(CoAW)

To accelerate orthodontic tooth movement and reduce the orthodontictreatment period are the main exploring subjects of clinical orthodontic research .There are two research aspects in this field, one is focusing on how to acceleratebone remodeling induced by orthodontic force,and the other is focusing on how todevelop the advanced and efficient orthodontic appliance, that is also called theresearch about the orthodontic materials .The orthodontic archwire play the key role of developing the orthodonticmaterials. Up to now, the TiNi shape-memory alloy archwire(TiNiSMA) andStainless Steel archwire (SS) materials are employed in clinical orthodontics notonly in china but also in abroad. The superiority of TiNiSMA archwire is itswell-elasticity which could produce the physio-logical orthodontic force to movethe tooth toward the right way when it was placed in the slots. But the rigidity ofTiNiSMA archwire is too small which could result in the anchorage loss and getthe undesirable tooth movement in some circumstances. On the contrary, therigidity of SS is too high, which could produce enough anchorage for posteriorteeth ,but it is hard to place the SS in the slots in the iTiNiSMAal stage oforthodontic treatment because of its low elasticity, therefore sequence of archwireapplication should be from the thinner to the thicker and from the softer and theharder . It is generally accepted in orthodontic clinic that we must use TiNiSMAfirstly ,then use SS secondly, thus the treatment duration is prolonged. In mostorthodontic cases, we need the less rigidity archwire match to anterior teeth for itsaccessibility for being placed in the slots and need the more rigid archwire matchto posterior teeth for its strengthing anchorage. Because the rigidityof two kinds ofarchwires are different, they play distinct roles in orthodontic treatment and shouldbe used respectively in different stages. Because of different rigidity, the two kindsof archwires bring about not only orthodontic effect but also certain unfavourableeffect in some treatment stages. Therefore,both two kinds of archwires have someadvantages and disadvantages. If archwires of diverse rigidity are applied inorthodontic process according to diverse regions, which contributes to optimaltooth movement and less orthodontic duration.TiNiSMA and SS are welded into CoAW(compound archwire) so that softerTiNiSMA has direct action to malposed teeth and contributes to teeth movement,while SS of higher rigidity enhances stabilization of anchorage teeth and avoidsthe negative movement of anchorage teeth.Application of CoAW can cost less orthodontic duration than mereapplication of TiNiSMA.In addition, application of CoAW can save orthodonticmaterial.So once CoAW with advantages of TiNiSMA and SS is applied toorthodontic treatment,it will be of vital significance. In 1997, TiNiSMA andSS(φ=1.0mm)were connected together and used to expansing arch orthodontictreatment by Japanese scholars.In 2001, TiNiSMA and SS were connectedtogether with riveting technology and adopted in orthodontic practice byGerman researchers .There are currently a few domestic researchers who are studying anddeveloping CoAW and are limited in Stomatology School and Material Institute ofJilin University. Through cooperation of the two organization, Xianchun Zhu andXinhua Sun et al. have undertook preliminary study and acquired a series ofachievements on material structure, mechanical property and clinical applicationof CoAW. The objectives of this experiment: 1.To do further numericalcalculation of mechanical property of CoAW by the method of three-dimensionalfinite element on the basis of previous researches. 2. To optimize the structure ofCoAW in order to improve orthodontic result. 3.To investigate the changedregularity of stress force exerted on malocclusion teeth and anchorage teeth bydifferent types of CoAWs when crowded anterior teeth and tooth extracted casesare treated . 4. To analyze mechanism of action of CoAW. 5. To provide analyticalmethods and data basis for the design and manufacture of CoAW. 6. To offertheoretical guidance and lectotype standard to clinical application of CoAW.The experimental model derived from mandible specimen of a young male.The mandible specimen characterizes complete dentition (except for bilateralmandibular third molars), crowding and anterior process of anterior teeth androughly regular middle and posterior teeth alignment. CoAW is suitable for thiskind of case. This experiment employed helico-CT to scan the mandible specimenby 1mm-thickness layer,finished assembly with SolidWorks technology andattained modularization of serial dentition models by finite element analysis.Thus,we can construct all kinds of malformation of dentition according todifferent malocclusion.The conclusion of this experiment :(1). CoAW has greater application range of orthodontic treatment than SS .CoAW can form suitable orthodontic force, contribute to movement of malposedteeth effectually and maintain the stabilization of anchorage teeth.(2). THE orthodontic force effect on malocclusion teeth produced by CoAWis greater than TiNiSMA but smaller than SS, we can obtain more gentle forceapproximate to that produced by TiNiSMA if theTiNi segment of CoAW waselongaged .(3)it was investigated that CoAW can exert less side force on posterior teeththan TiNiSMA and SS,so CoAW have more superiority on protecting anchorage.(4). There are important social and economic profits for applying CoAW inorthodontic treatment.(5). The scan of screw ct and the 3d remodeling should be a reliablemethod for the research of clinical orthodontics.