Load Transfer Characteristics of Craniofacial Implant Systems

Load Transfer Characteristics of Craniofacial Implant Systems
27 June 2003
T. OGANESYAN, A.A. CAPUTO, and R. NISHIMURA, UCLA School of Dentistry, Los Angeles, CA, USA
IADR
Objectives: The success of osseointegrated craniofacial implants is dependent upon the establishment and maintenance of an adequate bone-implant interface capable of withstanding functional stresses and upon the health of the peri-implant soft tissues. The bone-implant interface is influenced by the transfer and distribution of stress from the implant to the surrounding bone. The purpose of this investigation was to photoelastically determine the force transfer characteristics of three craniofacial implant designs. Methods: Rectangular models of dimensions 49 x11 x 7 mm were fabricated of a photoelastic bone simulant to represent a segment of the temporal bone. Single implants of the following systems were embedded in the models representing complete integration: Nobel Biocare, 3.75 mm dia, BUD, 3.1 mm dia, ITI, 3.2 mm dia. Three flange contact conditions with the simulated bone were considered: flange engagement, no flange engagement, and flange submerged. Axial and inclined forces were applied to the implants and the stresses developed in the bone simulant were observed and recorded photographically in a circular polariscope. Results: For all designs and flange conditions, inclined forces generated higher, more concentrated stresses in the supporting structures. Engagement of the coronal flange with the bone simulant produced lower concentrations of stress compared with the flange being above and below the surface. The Nobel Biocare implant, with tapered apex and larger diameter, tended to generate the lowest stresses. The ITI implant, with flat apex and shallow threads, was most stressful. Widely spaced, u-shaped implant threads of the BUD implant resulted in intermediate stress levels. Conclusions: Inclined loading of all implants tested resulted in higher stress concentration regardless of implant design. Further, lower stresses occurred with flange engagement with the supporting structure. The most equitable stress distribution occurred with the Nobel Biocare implant, the least equitable with the ITI, with the BUD being intermediate.