Proposal for an Ultrasonic Tool to Monitor the Osseointegration of Dental Implants

Abstract

The longevity of dental implants depends on osseointegration, which providesload-bearing capacity without putting the prosthesis at risk from micromotions at theimplant-bone interface. This research involved an analysis of the viability of an ultrasonicevaluation tool to quantify osseointegration. Ultrasonic transmission is directly dependenton the difference between the acoustic impedance of materials in intimate contact witheach other. The closer their acoustic impedances the more intense their transmission.Therefore, an analysis of the ultrasonic echoes would presumably allow for a quantitativeevaluation of the bone tissue that has grown into the pores of the implant. In addition, theliterature reports that bone fracture healing can be accelerated by the application of acontrolled low-amplitude mechanical stimulus on the site of the lesion. In fact, acousticpressure waves of low-intensity pulsed ultrasound are reportedly a secure technique forpromoting mechanical stimulus without impairing the healing process. Many experimentaland clinical trials have confirmed that daily transcutaneous ultrasound applications on theinjured site are beneficial to the enhancement of fractured bone. This proposal aims tobring together the characteristics of ultrasound propagation and the positive effect ofultrasound on bone growth into a single tool that quantitatively monitors the evolution ofthe osseointegration process. The viability of a device with these features was investigatedthrough simulations and experimentally. The initial simulations were conducted to explorethe influence of waveguide shapes on the tool’s sensitivity to changes in the implantsupporting media. The waveguides were designed in two parts, one consisting of a screw-shaped part to attach to the implant and the other a conical or step-shaped part to which the ultrasonic source was fixed in the first simulations. The step-shaped waveguide proved to be the more sensitive; intermediate stages of the osseointegration process were simulated and experiments were conducted with the step-shaped aluminum waveguide attached to a cylindrical aluminum nut embedded at different depths, so that the results obtained were only due to lateral attachment of the parts. These devices indicated that the transmission of ultrasound through the lateral surface of the implant by dilatational waves could render this tool suitable for monitoring the osseointegration of dental implants.

Keywords

• Ultrasound. Waveguide. Dental implant. Osseointegration.