Smartphone Jaw Tracking to Quantitatively Model Tooth Contact

Abstract

Surgical design and simulation uses Computer Aided Design (CAD)/Computer Aided Manufacturing (CAM) software to virtually plan for jaw reconstructive surgery. One part of the process includes the design of a dental prosthesis with the use of an articulator. The articulator is limited in its ability to recreate patient specific jaw motion. This thesis presents a smartphone application to track jaw motion photo-metrically. The jaw motion was used to virtually recreate a bench-top model of a patient’s occlusal kinematics and dynamics with biomechanical simulation. The jaw tracking system uses a 3D printed tracking harness that interfaces with the surface of the maxillary and mandibular teeth. Each tracking harness has a dodecahedron attached to it with 12 binary fiducial markers mounted to its faces. A 3D model of each dodecahedron tracking harness was made to calculate the position of each binary fiducial marker’s centre and corner points. The smartphone application detects the visible centre and corner points to solve a Perspective-n-Point (PnP) problem that estimates the mandible’s pose relative to the maxilla. The experimental results showed that the smartphone application was capable of achieving static position and orientation accuracy of < 1mm and 5°. The smartphone application repeatably tracked jaw motion along an arced path with a dynamic accuracy < 1mm up to 20mm of jaw opening. Past 20mm of opening, the reported dynamic accuracy was < 2mm. The smartphone application was also capable of tracking a left, right, and protrusive excursion. The occlusal contact between the teeth was successfully recreated with biomechanical simulation kinematically (no occlusal forces) and dynamically (occlusal forces).