The effects of subcrestal and supracrestal implant placement on primary stability parameters

Immediate implant placement is a common procedure, with implant stability often assessed using insertion torque (N·cm) and resonance frequency analysis (RFA). This study aimed to compare insertion torque and RFA values in simulated immediate implants placed at crestal, subcrestal, and supracrestal levels to evaluate how vertical implant positioning influences primary stability. Ninety Dentsply Sirona PrimeTaper™ implants were divided into three groups: Group 1 (4.2 × 13 mm placed 2mm of implant exposed), Group 2 (4.2 × 11 mm placed flush with the bone surface), and Group 3 (4.2 × 11 mm placed 2 mm below the crest). Osteotomies were performed in rigid polyurethane foam blocks simulating D2/D3 bone quality at a 45-degree angle. Implants were positioned to achieve intraosseous depths of 5 mm (Groups 1 and 3) and 3 mm (Group 2). Insertion torque was measured with a Dentsply Sirona EV Torque Wrench, and RFA values were obtained using an Osstell device. Data were analyzed using two-way ANOVA with Bonferroni post hoc testing. Torque values differed significantly between Groups 1 vs. 2 and Groups 2 vs. 3 (p < 0.001), but not between Groups 1 and 3. RFA values showed significant differences across all groups (p < 0.001). Subcrestal depth influenced insertion torque, while RFA values were affected by both subcrestal and supracrestal placement. These findings suggest that deeper implant placement enhances mechanical stability and underscores the importance of considering implant dimensions in treatment planning