Three-dimensional Finite Element Analysis Of Obturator Retained With Anterior Attachment In Maxillectomy Patients

Bachground：Unilateral maxillary defect is a common type of maxillary defects,caused by tumor surgery, trauma, etc. If the prosthesis for unilateral maxillary defect isdesigned properly the abutments and residual ridge will be damaged because almostentirely retention and support provided by uninvolved pseudo side. How to optimizethe design of prosthesis for unilateral maxillary defect is focal point of the study. Somescholars use dental implants, such as zygoma implants, to improve retention of theprosthesis. But dental implant technique has economic, traumatic, doctor’s experienceproblems. Attachments have been used to improve retention of prosthesis. However,few relevant FEA reports on obturator retained with maxillary anterior attachment canbe found.Objeetive：To establish the FEA models of unilateral maxillary defect and obturatorretained with maxillary anterior attachment, which can be the foundation ofbiomechanical analysis of attachment retained prosthesis. To compare attachmentretained prosthesis with clasp retained traditional prosthesis after vertical and lateralloading to determine the sufficient number of associated porcelain crown. It canprovide theoretical basis for clinical design and manufacture of prosthesis.Methods：This study consists of four parts:Part1. Establish the3-D solid model of unilateral maxillary defect and obturatorbased on CT data. Use Mimics10.01software to read and reconstruct the image dataobtained by scanning a normal complete dentition volunteer by GE Light Speed32-slice spiral CT. Cut the left maxilla by the software in order to build unilateralmaxillary defect model. Reuse the cut-down part to shape the initial model ofobturator.Part2. Establish of the3-D FEA model of normal skull. Test validity of the model by observing stress distribution after vertical loading. Use ANSA software to modifythe initial model of obturator to establish clasp retained traditional obturator. Calculatestress value and distribution by ABAQUS software after vertical and lateral loading.Part3. Establish of the3-D FEA model of obturator retained with maxillaryanterior attachment. First, use CATIA V5software to establish3-D model of SG minislide-type attachment. Then, use ANSA software modify and assemble it to initialobturator to form the FEA model of attachment retained obturator. Cut the maxillarycentral incisor, lateral incisors, canine and first premolar of unilateral maxillary defectmodel to meet the requirement of porcelain crown abutment preparation. Eventuallyforming3-D FEA model of unilateral maxillary defect containing attachmentassociated porcelain crowns after adjusting by ANSA software.Part4.Compare stress value and distribution in FEA models of attachment retainedobturator with different number of associated porcelain crowns with FEA model ofclasp retained traditional obturator after vertical and lateral loading.Results：1. The establishment of3-D FEA model of unilateral maxillary defect, themodel has good biomechanical similarity to the real ones.2. The establishment of3-D FEA model of traditional obturator retained with claspsand obturator retained with maxillary anterior attachment, composed of92331,87957grid cells after meshing respectively.3. The models with attachment retained obturator has significantly reduced overallmaximum stress, even stress distribution of abutments, not significantly increasedstress of abutments except central incisor and lateral incisor which are connected withattachment. Considering tissue preservation, stress analysis of abutments and alveolarbone, the model with three abutments associated porcelain crowns works best.Conclusion：The modeling method using spiral CT scanning data combined withreverse engineering software Mimics10.01, ANSA and ABAQUS finite elementanalysis software can create unilateral maxillary defect model efficiently andaccurately.As the results of this study, obturators retained with anterior attachments have advantages in even stress distribution of abutments, avoiding excessive stresses andimproving retention and stability of denture comparing with traditional obturatorsretained with clasps.