REVERSE-TORQUE FAILURE OF SCREW-SHAPED IMPLANTS IN BABOONS AFTER 6 MONTHS OF HEALING

Mechanical testing of the implant-tissue interface has been the focus of numerous investigations concerning the anchorage capacity of implan ts. The purpose of this study was to measure reverse-torque failure af ter 6 months of healing for three different biomaterials in the poster ior jaws of four adult female baboons. The animals had all of their po sterior teeth surgically extracted and, following 10 weeks of healing, 7 implants were placed in each quadrant. The biomaterials included ti tanium plasma-sprayed surfaces, titanium-aluminum-vanadium surfaces (b oth 3.8 mm x 10 mm), and a commercially pure titanium surface (3.75 mm x 10 mm). After 6 months, torque data were collected using a counterc lockwise computerized torque driver and were analyzed by repeated meas ures analysis of variance for differences related to biomaterial, jaw and biomaterial/jaw. Post-hoc Tukey Kramer analysis was also performed for within-group differences (alpha = .05 level). The biomaterial com parison revealed a significant difference between the titanium plasma- sprayed and the combined commercially pure titanium/titanium-aluminum- vanadium groups (analysis of variance, Tukey Kramer, P < .05). The jaw comparison showed no significant difference, although the data sugges t that higher forces may be required for mandibular torsional failure. The biomaterial/jaw comparison revealed that jaw differences for the mean values of commercially pure titanium and titanium-aluminum-vanadi um implants were greater than jaw differences for mean values of titan ium plasma-sprayed implants, although these differences were not stati stically significant. Because of the lack of correlation between singl e-cycle biomechanical tests and clinical performance, it is necessary to be selective in assigning usefulness to data of this type.