The influence of insertion torque on the survival of immediately placed and restored single-tooth implants
Purpose: The purpose of this retrospective study was to evaluate the medium- to long-term clinical outcome of singletooth implants placed into fresh extraction sockets using a low-insertion-torque protocol and immediately restored with acrylic resin provisional crowns.
Materials and Methods: Sixty-one patients consecutively referred for the replacement of one or more failing teeth were planned for treatment by means of extraction and immediate implant placement and provisionalization using a low-insertion-torque protocol of ≤ 25 Ncm. Low rotational stability was not a contraindication to treatment unless there was a lack of axial stability. Implant survival and marginal bone levels were documented. A statistical analysis was performed to discover any correlations between insertion torque, age, gender, implant size and tooth position and marginal bone loss.
Results: Sixty-eight implants were placed. Three implants failed to osseointegrate; one was replaced and immediately restored and has been successful for more than 5 years. The overall survival rate for all implants was 95.5%, which have been in function for a period of 1.25 to 9.5 years. The mean marginal bone loss of the 54 implants followed for at least 24 months was 0.23 ± 0.60 mm mesially and 0.20 ± 0.72 mm distally. Overall, 78% of implants showed no marginal bone loss, 9% experienced 0.1 to 0.5 mm of bone loss, and 13% demonstrated > 0.5 mm of bone loss. There were no significant correlations between the various parameters analyzed and marginal bone loss.
Conclusion: A torque of only 25 Ncm would seem more than sufficient to yield a favorable clinical outcome, and there may be a misconception as to what actually represents adequate primary stability. Immediate provisionalization of single-tooth implants placed with a relatively low insertion torque can yield favorable survival rates and optimal maintenance of marginal bone levels compared to the generally accepted norm.