Finite Element Analysis of Ultrasound Propagation through Dog Mandible

Objectives:  

The aim of this study was to understand the magnitude of the mechanical stresses induced by the low intensity pulsed ultrasound (LIPUS) while it propagates through the dentoalveolar structures of a dog mandible.

Methods:  

A two-dimensional finite element model (FEM) of the dentoalveolar structure of beagle dog mandible was reconstructed using Micro computed tomography image.  The finite element analysis was performed using the software package ABAQUS to model the LIPUS propagation through dentoalveolar structures of a dog mandible. The FEM contained 64,000 triangular plain strain elements. The LIPUS was modeled as the average uniform pressure load exerted on the gingival surface by the ultrasonic transducer. LIPUS output power was set as 30mW/cm² of the transducer surface area (2.5 cm²). The FEM output was validated using a power sensor in live beagle dogs while applying LIPUS treatment to prevent orthodontically induced root resorption.

Results:  

 The magnitudes of stresses decreased while LIPUS was propagated through dentoalveolar structures due to dynamic attenuation (scattering and material damping). Also the stress magnitudes (maximum principle) were calculated on different locations around the third premolar root area. The FEM predicted a 90% decrease of the principal LIPUS power as it passed through the dentoalveolar structure and reached the lingual side of the gingiva. This was in agreement with the power sensor measurement.

 Conclusions:

This study showed that the FEM analysis can predict the LIPUS power attenuation as it propagates through the dentoalveolar structure. This in turn can reveal any power-dependent correlation between LIPUS and its biological effects on the dentoalveolar structures. Future work will focus on 3-D FEM and correlating its stresses distribution results with the biological response observed from in-vivo experiments.