The Relationship Between Recorded Bone Quality and Primary Implant Stability Measured by Insertion Torque: A Retrospective Study

Background and objective Primary implant stability is a key determinant of successful osseointegration and long-term survival. Bone density and bone quality influence the biomechanical interaction between dental implants and the surrounding bone and may affect both insertion torque and implant stability. Evaluating these parameters is important for treatment planning and predicting implant outcomes. This study aimed to investigate the relationship between cone beam (CBCT)-derived bone density and primary implant stability in patients undergoing dental implant placement. Materials and methods This retrospective observational study included 62 dental implants placed in 25 patients between January 2018 and December 2023. Preoperative CBCT scans were used to assess bone density at the implant sites, and bone quality was categorized into Type I, Type II, Type III, or Type IV. Primary implant stability was evaluated using insertion torque and resonance frequency analysis (RFA) and expressed as the implant stability quotient (ISQ). Statistical analyses included descriptive statistics, the Kruskal-Wallis test, the Mann-Whitney U test, and Spearman correlation analysis, with statistical significance set at p < 0.05. Results The mean bone density across all implant sites was 493.5 ± 274.6 HU, while the mean insertion torque and ISQ values were 30.7 ± 8.9 Ncm and 68.3 ± 7.4, respectively. Bone density differed significantly among the bone quality categories (p < 0.001), with Type I bone demonstrating the highest density values and Type IV bone the lowest. A strong positive correlation was observed between insertion torque and ISQ (ρ = 0.78, p < 0.001). Mandibular implants exhibited significantly higher ISQ values than maxillary implants (p < 0.001), whereas anterior implant sites demonstrated greater stability than posterior sites (p = 0.023). Conclusions Higher bone density was associated with improved primary stability and greater implant stability. A strong positive relationship was observed between insertion torque and ISQ, indicating that both measures reflect related aspects of primary implant stability. Preoperative assessment of bone density may assist clinicians in predicting implant stability and optimizing treatment planning.