QUANTITATIVE AND QUALITATIVE INVESTIGATIONS OF SURFACE ENLARGED TITANIUM AND TITANIUM-ALLOY IMPLANTS

Screw shaped implants of commercially pure (c.p.) titanium and titaniu m-6aluminum-4vanadium (Ti6Al4V) were blasted with particles of TiO2 of mean sizes of 25 mu m (Group I) and 75 mu m (Group II) and inserted i n rabbit bone for 3 months. The surface roughness of the implants was examined and quantified with an optical scanning 3-dimensional instrum ent (TopScan 3D system), revealing the two alloy surfaces in each grou p had similar surface roughness. Biomechanical (removal torque) tests showed the c.p. titanium implants to be significantly more stable in t he bone bed than those of Ti6Al4V. In Group I, the c.p titanium implan ts demonstrated a mean removal torque of 38 N cm while the Ti6Al4V dem onstrated a mean removal torque of 27 N cm (P=0.004). Group II implant s revealed a mean removal torque of 70 N cm for the c.p. ti and 50 N c m for the alloy samples (P=0.003). The removal torque values were conv erted to shear forces/strengths by three calculation methods, based on (a) the entire length of the implant surface in the cortical region, (b) the thickness of the cortical bone measured in close vicinity to t he thread peaks and (c) the bone-metal contact length measured on the non-unscrewed neighbouring implants. Group I: (a) the c.p. ti implants revealed a mean shear force of 4 vs a mean of 3 N/mm(2) for the alloy samples. Shear strengths based on (b); were 8 for c.p. ti vs 6 N/mm(2 ) for the alloy. The mean shear strength/force if calculated according to (c) revealed 23 for c.p. ti vs 18 N/mm(2) for the alloy. Correspon ding numbers for Group II; (a) c.p. ti 8 compared to 6 N/mm(2) for the alloy, (b) c.p. ti demonstrated a mean value of 17 vs 11 N/mm(2) for the alloy. According to method (c); c.p. ti had a mean shear strength of 26 vs 22 N/mm(2) for the alloy samples. Histomorphometrical compari sons were performed on 10 mu m thick undecalcified ground sections in the light microscope. In both Group I and Group II, the calculations o f the mean bone-to-metal contact demonstrated more bone in contact to the c.p. titanium implants than to the Ti6Al4V ones. Whereas compariso ns of the bone volume inside the threads demonstrated slightly higher bone volumes around the alloy samples, no statistically significant di fference was obtained between the two materials histomorphometrically.