RCT Trial of Insertion Torque relative to ISQ Implant Stability

Implant prognosis may be related to bone quality, insertion torque and bone density. Objectives: This randomized clinical trial evaluated loading though 16 weeks. Methods: Subjects needing single tooth implants (4mm diameter x 11mm; Astra Tech AB) in the maxillary or mandibular premolar region (N=31) were recruited with IRB approved criteria. Based on implant insertion torque values (ITV, Elcomed, W&H) subjects were randomized to one of three loading periods (Immediate, 6 or 12 weeks). Implants placed with >20Ncm (High ITV) were randomized to all three loading periods, those with 10-20Ncm (Intermediate ITV) were randomized to 6 or 12 week loading and those with < 10Ncm (Low ITV) were allowed to heal for 12 wks prior to loading. Outcomes measured every 2 though 16 weeks included Implant Stability Quotient (ISQ, SmartPeg), clinical mobility and bone loss. Associations among ordinal and quantitative outcomes were measured using Spearman Rank Correlation or Kendall's tau-b. Kruskal-Wallis tests compared subgroups. Results: 16 implants (49%) had high initial torque values, 11 (33%) intermediate and 6 (18%) low torque values. ITV values averaged 26.6±17 (4-70). At placement, ITV was significantly correlated with Lekhom & Zarb bone quality scale (r=-0.50, p=0.0042,n=31). At 16 weeks there was no correlation between loading class defined by ITV and loading time for the 24 individuals completing follow-up. In the high ITV group there was no correlation to buccal ISQ (p=0.52) or mesial ISQ (p=0.70). Low baseline ISQ measures had a greater change than subjects with high initial baseline values (Spearman r=-0.94 P<0.0001). There was no evidence ISQ at 16 weeks was related to either initial ISQ or ITV. Conclusions: This interim analysis provides no evidence that placement ITV correlates with ISQ after 4 months of healing regardless of when the implant is loaded. Support: Astra Tech AB, Mölndal Sweden and NIH NCRR CTSA UL1RR024979.