Significance of Primary Stability in Non-Immediate Loaded Dental Implants: A Systematic Review & Meta-Analysis

Primary stability is considered critical for osseointegration of immediately-loaded implants. However, evidence does not conclude whether this is equally critical for early or delayed-loaded protocols. This systematic review aims to determine the significance of primary stability, as measured by insertion torque (IT) and/or implant stability quotient (ISQ), in achieving osseointegration of non-immediate loaded implants. Three electronic databases were searched. Studies were included if they measured IT and/or ISQ at time of placement and reported survival for up to 1 year. For studies where at least one implant failed, a random effects meta-analysis was carried out for the odds of survival. 3431 publications were screened; 79 were accepted for analysis. These comprised of 28 RCTs, 12 CCTs, 10 cohort studies, and 29 case series. Twenty-one studies provided individual implant data for a total of 1413 implants. Seven studies were included for metaanalysis. 264 implants were placed with ISQ <60, and 249 with IT <35. Survival of implants placed with ISQ <60 and IT <35 were 97.7% and 95.2% respectively. Meta-analysis found no evidence that an ISQ≥60 was less likely to fail compared with ISQ<60 (OR 0.54, 95%CI 0.17-1.75, P=0.31), or that an IT≥35 resulted in higher odds of failure compared to IT<35 (OR 0.82, 95%CI 0.13-5.40, P=0.84). This study found no evidence to support an IT≥35 or ISQ≥60 for non-immediately loaded implants results in higher survival than those below these values.