Analysis of bone stress and primary stability of a dental implant using strain and torque measurements

Introduction: The consensus among researchers is that early failure of dental implants is due to the lack of primary stability and compressive stress on the peri-implant bone that exceeds the physiological tolerance. Objective: The objective of this work is to propose a new methodology to quantify bone stress during dental implant insertion and to correlate it with primary stability. Materials and Methods: Titanium dental implants with a diameter of 3.75 mm were inserted in a 3.35 mm hole of a synthetic bone of polyurethane (PU) foam with a density of 20 PCF (0.32 g/cm3). During insertion, the insertion torque was measured with a digital torque meter and the bone strain was measured with strain gages located at 2, 4, 6, 8, and 10 mm from the coronal region. Results: The tests showed that the compressive strain is maximum in the third coronal region and decreases in the apical direction. The data also showed that there is a relationship between strain, insertion torque, and the primary stability of dental implants. Conclusion: The stress and strain on the bone progressively decreased from the coronal to the apical third. The maximum compressive stress (0.42 MPa) during insertion of the implant did not exceed bone strength. Insertion of 3.75 mm implants in type D2 bone with a 3.35 mm hole provides adequate primary stability without excessive compression of the bone. Clinical Significance: For the implant-bone combination used in the present study, the compressive stress generated during implant insertion did not exceed the physiological limit of cortical and medullary bone to the point of impairing osseointegration.