Experimental study of the primary stability of dental implants using different osteotomy protocols

Objective. To evaluate the influence of an undersized drilling protocol on primary stability of «A2» dental implants in low-density D3-D4 bone using a comprehensive diagnostic approach. Materials and Methods. An in vitro study was performed on two porcine vertebral bone macro-specimens and «Sawbones» polyurethane blocks of four densities. Density was assessed by shadow and echo-pulsed ultrasonographic densitometry. Two experimental models were created; in each, six implants of the A2 system were placed with dimensions of 3.5×6.6 mm (A6.6) and 3.5×11 mm (A11). In all cases, an undersized drilling protocol with subcrestal placement (1—2 mm) was applied. The osteotomy bed was prepared with a 2 mm pilot drill and a three-fluted bur, followed by a conical reamer. Implant placement was performed using the «W&H Implantmed Plus» physiodispenser with torque curve registration. Primary stability was assessed by resonance frequency analysis (ISQ) using the «Osstell Beacon»; implant position was verified by CBCT (Axeos, Dentsply Sirona). Statistics included mean, standard deviation (SD), 95% confidence intervals (CI) and coefficient of variation (CV). Results. In polyurethane blocks: shadow densitometry 952—1344 m/s; echo-pulsed ultrasonographic densitometry 1870—2674 m/s. In porcine bone, trabecular bone was 1408—1500 m/s and cortical up to 2303 m/s; the model corresponded to D3-D4 density. In group «A11», torque at placement was 31.67±4.80 N·cm, ISQ=81.92±1.12, torque at removal 37.00±4.43 N·cm; in «A6.6» -23.33±3.61; 71.83±7.22 and 22.33±6.19, respectively. Differences were statistically significant Conclusion. The undersized drilling protocol provides high primary stability in low-density D3-D4 bone. Ultrasonic densitometry may serve as an additional objective method for assessing bone quality and selecting an appropriate drilling protocol to predict primary stability. A comprehensive diagnostic approach supports optimization of the surgical protocol and reduces the risk of early postoperative complications.