Experimental and numerical predictions of Biomet(®) alloplastic implant in a cadaveric mandibular ramus

The purpose of this study was to evaluate experimentally the behaviors of an intact and an implanted cadaveric ramus, to compare and analyze load mechanism transfers between two validated finite element models. The intact, clean cadaveric ramus was instrumented with four rosettes and loaded with the temporal reaction load. Next, the Biomet microfixation implant was fixed to the same cadaveric mandibular ramus after resection. The mandibular ramus was reconstructed from computed tomographic images, and two finite element models were developed. The experimental results for the mandibular ramus present a linear behavior of up to 300 N load in the condyle, with the Biomet implant influencing strain distribution; the maximum influence was near the implant (rosette #4) and approximately 59%. The experimental and numerical results present a good correlation, with the best correlation in the intact ramus condition, where R(2) reaches 0.935 and the slope of the regression line is 1.045. The numerical results show that screw #1 is the most critical, with maximum principal strains in the bone around 21,000 με, indicating possible bone fatigue and fracture. The experimental results show that the Biomet temporomandibular joint mandibular ramus implant changes the load transfer in the ramus, compared to the intact ramus, with its strain-shielding effect. The numerical results demonstrate that only three screws are important for the Biomet TMJ fixation. These results indicate that including two proximal screws should reduce stresses in the first screws and strains in the bone.