Rethinking Implant Length: A Density‐Dependent Analysis of Primary Stability—An In Vitro Evaluation Using Resonance Frequency Analysis and Insertion Torque

Purpose Accurate assessment of the primary stability of dental implants is essential for predicting osseointegration and determining loading protocols. This in vitro study aimed to evaluate the primary stability of dental implants of varying lengths across simulated bone densities using the insertion torque value (ITV) and resonance frequency analysis (RFA). Materials and Methods Morse‐taper implants (5.0 mm diameter) were divided into four groups based on length: 5, 6, 7, and 8 mm. Implants were placed into polyurethane foam blocks of varying densities: PCF 40, PCF 30 (with 2 and 1 mm cortical layers), and PCF 20 (with a 1 mm cortical layer). Primary stability was measured via ITV and RFA, yielding an implant stability quotient (ISQ). Results In high‐density foam (PCF 40), both ITV and ISQ increased proportionally with implant length, with the 8 mm implant demonstrating the highest stability (ITV = 109.26 ± 4.79 Ncm and ISQ = 73.5 ± 2.32). Conversely, in low‐density foam (PCF 20/1 mm), a direct relationship was observed, where the shortest implant (5 mm) exhibited the lowest stability (ITV = 36.8 ± 3.27 Ncm and ISQ = 45.8 ± 2.66), whereas the highest stability was presented by the 8 mm implant (ITV = 61.36 ± 2.00 Ncm and ISQ = 56.3 ± 2.67). Conclusion Implant length significantly influences primary stability, but its effect is highly dependent on bone density. While shorter implants provide sufficient primary stability and may reduce surgical risks in highly dense bone, increased implant length is crucial for achieving superior primary stability in poor‐quality bone with thin cortical plates.