QUANTITATIVE BONE TISSUE-RESPONSE TO COMMERCIALLY PURE TITANIUM IMPLANTS

Commercially pure titanium implants were inserted in rabbit tibia for 3, 6 and 12 weeks. Each rabbit had two implants inserted, one for remo val torque measurements and the other for histomorphometrical analysis . Light microscopic observations revealed that there was a continuing bone remodelling, with new bone formation in the periosteal region aft er 3 and 6 weeks, which diminished with time, i.e. up to 12 weeks of f ollow-up. A higher removal torque was observed with increasing time of implant insertion. The removal torque values for the 12 week samples were converted to three different shear forces depending on three diff erent theoretically calculated implant to bone attachment levels. The mean shear forces related to the entire length of the implant surface was 0.6 N mm-2. If considering the length of the implant inside the co rtical bone only, the mean shear force was 1.9 N mm-2, and if the bone -metal contact length as related to an estimate of the bone-implant co ntact a mean shear force of 14.8 N mm-2 was calculated. Histomorphomet rical measurements revealed more bone-metal contact as well as a large r bone area in the threads with increasing time of insertion. Statisti cally significant differences were observed between all measurements o f the 3 and 6 week samples and between the 3 and 12 week samples. For the 6 and 12 week sections a statistically significant difference coul d be demonstrated only when comparing bone areas in the three best con secutive threads located in the cortical region.