The Three-dimensional Finite Element Analysis Of Two Sliding Mechanics Methods In Space Closing

Objective:To construct a three-dimensional finite element model, comparing the en-masse retraction and two-step retraction of sliding space closure in roots control of anterior teeth, provides the basic choices for clinical operation.Methods:By cone-beam CT scanning can we obtain the digital imaging and communications in medicine(DICOM) image data including the maxillary and teeth, and by importing Mimics software, separating maxillary, teeth and periodontium, can we get the three-dimensional models of four anterior teeth and six anterior teeth respectively. Having models instantiated by PROE software and using Abaqus finite element analysis software to simulate the sliding method by loading 1.47 N force on traction hooks whose heights were 2,4,6,8,10,12 and 14 mm respectively in order to compare the initial displacement between six maxillary anterior teeth and four maxillary anterior teeth.Results:When moving anterior teeth in roots control, initial gap displacement of central incisors in en-masse retraction of sliding space closure was 31.01×10-6 mm, that in two-step retraction was 15.74×10-6 mm; Initial gap displacement of lateral incisors in en-masse retraction of sliding space closure was 46.34×10-6 mm, while that in two-step retraction was 23.18×10-6 mm. Under the same condition of loading the light force, the initial displacement of anterior teeth in two-step retraction of sliding space closure was as twice as that in en-masse retraction of sliding space closure. Canine teeth of en-masse retraction couldn’t realize the roots control movement. In direction of crown to apical,the initial gap displacement of central incisors in en-masse retraction was -218.55×10-6 mm, that two-step retraction was -216.55×10-6 mm; Initial gap displacement of lateral incisors in en-masse retraction was -185.12×10-6 mm, while that in two-step retraction was -45.33 ×10-6 mm.Conclusions:When using in en-masse retraction of sliding space closure on traction hooks whose heights were about 8.5mm, anterior teeth moving in roots control and intruding. The canine teeth is inclined to move in en-masse retraction. When using two-step retraction of sliding space closure on traction hooks whose heights were about 9.0mm, anterior teeth moving in roots control and intruding. During the process of root control of teeth, two-step retraction of sliding space closure can produce more initial displacement than en-masse retraction of sliding space closure. Therefore, two-step retraction of sliding space closure is better to realize the roots control movement of anterior teeth.