Evaluation of Stress Distribution on Two Craniofacial Implants in Implant-Retained Auricular Prosthesis Using Hader bar Attachment Design and Different Removal Angulation: a finite Element Method

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Evaluation of Stress Distribution on Two Craniofacial Implants in Implant-Retained Auricular Prosthesis Using Hader bar Attachment Design and Different Removal Angulation: A Finite Element Method.

Ahmed Abbas11, Peerapong Santiwong22, Teeranoot Chanthasopeephan 33, Amornrat Wonglamsam 44, M.L. Theerathavaj Srithavaj55.
1 Master degree student, combined diploma/master degree, international program of oral and maxillofacial Prosthetic, faculty of dentistry, Mahidol University, Thailand.

2 Ph.D., Lecturer at orthodontic department, faculty of dentistry, Mahidol University, Thailand.

3 Assistant professor, Ph.D., faculty of mechanical engineering, King Mongkut’s University of Technology Thonburi, Thailand.

4 Ph.D., Lecturer at prosthodontics department, faculty of dentistry, Mahidol University, Thailand.

5 Assistant professor, M.S., maxillofacial prosthetic service, faculty of dentistry, Mahidol University, Thailand.

E-Mail: drahmed_77@yahoo.com, Peerapong.san@mahidol.ac.th, teeranoot.cha@kmutt.ac.th, dttst@mahidol.ac.th,


Removal angulation of auricular prosthesis is one of the critical consideration in patients with auricular defect. The prosthodontist usually instruct patients to pull the prosthesis out at the direction perpendicular to attachment plane. The aim of this study was to investigate the magnitude of stress distribution on the auricular implants at both 90 and 45 degrees using Hader bar attachment.

The Hader bar assembly fabricated using two craniofacial implants (Nobel Biocare Goteborg, Sweden), the measurements of each components this assembly recorded using digital caliper. The measurements corrected using micro CT of each components. Soildworks 2012 (Premium 2012 x64 Edition, Dassault Systems SolidWorks Corporation, Massachusetts, USA) used to draw a 3D model of the assembly, then model applied to Ansys version 13.0 (Ansys Inc., USA) using mechanical parameters of the assembly and defining the boundary conditions. The results showed that the angular pull of the prosthesis exerts higher stress on the implants mainly in red clips (253.1 MPa). In addition, the angular removal of the prosthesis can give high stress concentration around that area of the implant coincide with extension bar which is opposite to the direction of removal. Stress around the implant, hence contacted bone, at 45o was 2.6 and 3.1 times more that of 90o in case of red clips and yellow clips respectively.

In conclusion, the prosthodontist must emphasize on the perpendicular pull of the prosthesis by the patient avoiding angular removal. However, in case of absence of patient’s compliance, a lower retention mean (yellow clips) must be considered.
Key words: craniofacial implants, Hader bar, removal angulation,

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