Articulation simulation for an Intelligent Dental Care System Tosiyasu L Kunii, Jens Herder, Karol Myszkowski, Oleg Okunev, Galina G Okuneva and Masumi Ibusuki* CAD/CAM techniques are used increasingly in dentistry for design and fabrication of teeth restorations. An important issue is preserving occlusal contacts of teeth after restoration. Traditional techniques based on the use of casts with mechanical articulators require manual adjustment of the occlusal surface, which becomes impractical when hard restoration materials like porcelain are used; they are also time- and labour-consuming. Most existing computer systems ignore completely such an articulation check, or perform the check at the level of a tooth and its immediate neighbours. We present a new mathematical model and a related user interface for global articulation simulation, developed for the Intelligent Dental Care System project. The aim of the simulation is elimination of the use of mechanical articulators and manual adjustment in the process of designing dental restorations and articulation diagnostics. The mathematical model is based upon differential topological modelling of the jaws considered as a mech- anical system. The user interface exploits metaphors that are familiar to dentists from everyday practice. A new input device designed specifically for use with articulation simulation is proposed. Keywords: articulation, occlusion, dental systems The Intelligent Dental Care System (IDCS) is an ongoing research project focused on computer-aided production of ceramic dental restorations, diagnosis for occlusal therapy and treatment and protocoling with the use of a database. An important feature of the system is use of articulation simulation for check of restoration design. The restorations created by the system should fit as well as possible the existing articulation of the patient; in usual dental practice this is achieved by manual adjustment of the restoration. Most tooth restoration work in dental clinics is done by The University of Aizu, Tsuruga, Ikki-machi, Aizu-Wakamatsu City, Fukushima 965-80 Japan *Sannon Clinic; 8-5-35 Akasaka, Minato-ku, Tokyo 107, Japan Paper received: 2 May 1994; revised: 13 June 1994 dentists and technicians using traditional methods. In the case of high-quality and long-life restoration materials such as porcelain or metal, the process of production of an inlay, onlay or crown (all of which we will refer to as restorations) requires significant resources, both in terms of time and human energy. Usually a mould of the tooth is taken and used by a technician to prepare a cast restoration, which in most cases must be adjusted by the dentist to have proper occlusal contacts with opposing teeth 1. The cast is used with an adjustable mechanical articulator for manual simulation of the articulation. At least two visits by the patient to the clinic are required to prepare even a simple restoration using this technology. However, manual adjust- ment is quite difficult in the case of the use of hard materials (such as porcelain) for dental restoration. A computer articulation simulation checks the designed preparation before manufacturing a physical example of it, following fast automatic adjustment of the preparation. Another goal is articulation problem diagnosis, even if no particular tooth is under treatment. The idea is to detect articulation problems in more detail than is possible using traditional approaches, such as use of mechanical articulators. The computer articulation simulation is also used for planning treatment, evaluating automatically the results of various versions of virtual treatment. Thus, our objectives are speedup of restoration design and manufacturing (ideally a single visit to the clinic should be sufficient to complete treatment of a single tooth) and reduction of human labour (possibly eliminating the dental technician completely). These goals are achieved by: • automation of manufacturing of restorations, including occlusal surface design, following gnathological rules (related to teeth and temporomandibular joint); • simplification of articulation simulation by avoiding creation of mechanical models; • elimination of manual adjustment of the inlay/onlay/ crown after its manufacture; 0141-9382/9410310181-08 © 1994 Butterworth-Heinemann Ltd Displays Volume 15 Number 3 1994 181