Measurement of bone deformation and insertion torque during dental implant installation.

Abstract

Aim: Insertion of dental implants causes bone deformation and induces residual bone compression stress, which can lead to implant failure if the bone loss threshold is exceeded. The current literature about bone stress is restricted to computer simulations and implant primary stability measurements after installation. This work measures the torque and deformation during implant insertion testing.

Purpose: The aim of this work was to analyze the influence surface treatment, thread profile, body shape and the presence of microthreads in the neck on the primary stability, bone deformation and residual stress during dental implants insertion. The insertion torque and resonance frequency analysis (RFA) are the main technique used to measure the primary stability of dental implants.

Material and methods: Five models of dental implants with different surface treatments (machined and acid etching), thread profiles (triangular and trapezoidal) and body shapes (cylindrical and conical) were inserted in synthetic bone blocks (polyurethane) with a density of 30 PCF (0.48 g/cm³) compatible with the D2 bone. The insertion torque was quantified by a digital torque driver. Strain gauge extensometry technique was used to measure bone deformation during implant insertion.

Results: The bone deformation and torque increase as the number of implants turns insertion increases. Dental implant with trapezoidal thread profile needs higher insertion torque than triangular threads. Implants with a conical shape require higher insertion torque than cylindrical ones. The bone stress induced by machined implant insertion exceeded the bone's mechanical resistance, causing cracks. Conical implants showed better performance than cylindrical ones. The implants with a trapezoidal thread and those with a conical body induce greater insertion torque.

Conclusion: Comparing the mechanical behavior, it was found that the machined implants had the worst performance in terms of stress distribution in the synthetic bone, resulting in cracks in the specimen during insertion. Implants with trapezoidal threads and those with a conical body induce insertion torque and bone compression stresses that do not harm osseointegration.

Clinical relevance: Excessive deformations in the peri-implant bone led to bone necrosis and implant failure. Thus, the surgeons must analyze the influence of surface treatment, thread profile, and body shape on the osseointegration process.