The anchorage of Branemark and ITI implants of different lengths. I. An experimental study in the canine mandible

The anchorage of machined Branemark and ITI TPS-coated implants of various lengths was investigated in an animal model. Branemark fixtures 7 and 10mm long and ITI implants 6 and 10mm long were inserted in the mandible of dogs and were reverse-torqued after 3 months of healing. The failing mode was different for the two implant systems. For the ITI implants, loosening coincided with the peak reverse-torque values. For the Branemark fixtures, two reverse-torque values were identified and recorded, a 'start to rotate' and a peak value. The 'start to rotate' values for the 7 and 10mm Branemark fixtures were 36.67 and 38.57 Ncm, respectively, the peak values were 61.88 and 69.13 Ncm. The increase in implant length from 7 to 10 mm did not significantly improve the anchorage. The mean reverse-torque values for the 6- and 10-mm ITI implants were 104.66 and 192.25 Ncm, respectively; the difference was statistically significant. The mean removal torque of the 6-mm ITI implant was higher than the 7- and 10-mm Branemark implants. It is suggested that the distinct anchorage magnitude and the distinct loosening patterns registered for both implant systems might be related to the various surface states. The latter might account for the different failure tendencies mentioned in the literature for short Branemark and ITI implants.