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, References
1. Del V, Faulkner G, Wolfaardt J, Rangert B, Tan HK. Mechanical evaluation of craniofacial osseointegration retention systems. Int J Oral Maxillofac Implants 1995;10:491-498.
2. Tjellstrom A, Portmann D. (Osseointegrated implants in facial prosthesis and hearing aids). Rev Laryngol Otol Rhinol. 1992;113:439-445.
3. Nishimura RD, Roumanas E, Sugai T, Moy PK. Auricular prostheses and osseointegrated implants: UCLA experience. J Prosthet Dent 1995;73:553-558.
4. Parel SM, Branemark PI, Tjellstrom A, Gion G. Osseointegration in maxillofacial prosthetics. Part II: Extraoral applications. J Prosthet Dent 1986;55:600-606.
5. Parel SM, Holt GR, Branemark PI, Tjellstrom A. Osseointegration and facial prosthetics. Int J Oral Maxillofac Implants 1986;1:27-29.
6. Tjellstrom A, Rosenhall U, Lindstrom J, Hallen O, Albrektsson T, Branemark PI. Five-year experience with skin-penetrating bone-anchored implants in the temporal bone. Acta Otolaryngol 1983;95:568-575.
7. Watson RM, Coward TJ, Forman GH, Moss JP. Considerations in treatment planning for implant-supported auricular prostheses. Int J Oral Maxillofac Implants 1993;8:688-694.
8. Rubenstein JE. Attachments used for implant-supported facial prostheses: a survey of United States, Canadian, and Swedish centers. J Prosthet Dent 1995;73:262-266.
9. de Sousa AA, Mattos BS. Magnetic retention and bar-clip attachment for implant-retained auricular prostheses: a comparative analysis. Int J Prosthodont 2008;21:233-236.
10. Williams BH, Ochiai KT, Baba T, Caputo AA. Retention and load transfer characteristics of implant-retained auricular prostheses. Int J Oral Maxillofac Implants 2007;22:366-372.
11. Srithavaj T, Wijitworawong A, Kharel A, Sanohkann S, Santawisuk W. Attachment use in designing a stable facial prosthesis: A new clinical and technical report. Mahidol Dent J 2006;26:337-343.
12. Chung RW, Siu AS, Chu FC, Chow TW. Magnet-retained auricular prosthesis with an implant-supported composite bar: a clinical report. J Prosthet Dent 2003;89:446-449.
13. Hashaw SJ, Brunski JB, Cochran CVB. Mechanical loading of Braonemark implants affecting interfacial bone modeling and remodeling. Int J Oral Maxillofac Implants 1994;9:345-360.
14. Clelland NL, Ismail YH, Zaki HS, Pipko D. Three dimensional finite elemnet stress analysis in and around the Screw-Vent implant. Int J Maxillofac Implants 1991;4:391-398.
15. Meroueh KA, Watanabe F, Mentag PJ. Finite element analysis of partially edentulous mandible rehabilitated with an osseointegrated cylindrical implant. J Oral Implantol 1987;2:215-237.