Abstract
In order to design functional occlusal surfaces, dental CAD systems have to simulate tooth articulation during excursions. In commercial dental CAD systems, however, a method for the simulation of patient's tooth excursions has not yet been established. We have developed a tooth excursion simulator for dental CAD by numerical simulating a dental articulator. Tooth excursion paths in the simulator are decided on adjustable components such as sagittal inclination of the condylar housing denoted as Cs; and sagittal inclination of the incisal table, denoted as Is. Our previous tooth excursion simulator, however, was not easily customizable to be applied to specific patients. The purpose of this study is to develop an easily adjustable function of the virtual articulator in accordance with patient's tooth excursions.
In order to optimize the adjustable parameters of the simulator in accordance with patient's tooth excursions, we employed the following procedure: 1) we took a functional occlusal impression formed by a tooth excursion, 2) we computed the value of parameters Cs and Is to make a simulated virtual impression agree with the actual occlusal impression, and 3) we adjusted the virtual articulator. Then, we defined an evaluation parameter represented as the “agreement,” and proposed an advanced 3D-registration-based method to automatically adjust the articulator in accordance with patient's functional occlusal impression.
Experiments were carried out, as follows: 1) we created a functional occlusal impression using a real articulator, 2) we adjusted the virtual articulator from the impression by means of the proposed method, and 3) we evaluated the values of the articulator parameters. To optimize articulator parameters Cs and Is for patient's impression, the simulated annealing method was employed with an evaluation parameter. Empirical results are summarized as follows: 1) the evaluation value was converged into the maximum value by the SA, 2) the estimated value included error components, ΔIs = 0.9° and = ΔCs = 0.6°, and 3) a local maximum was observed near the optimum solution. From these results, the proposed method was verified to be able to adjust the simulator with the accuracy required for its clinical application.
