The specific aim of the activities described in this proposal is to create a CAD/CAM system capable of automating the currently practiced restoration fabrication techniques from impression through final restoration. Methodology required for system development capitalizes on recent technologic advances in robotics, three-dimensional vision systems, stereophotogrammetry, computer graphics, and computer integrated engineering. The restorations produced by this technique will be of equivalent or enhanced quality compared with those produced by traditional impression - lost-wax techniques. The first priority is to create a single metal crown. The quality of crowns produced by the automated CAD/CAM systems will be determined using both analytic and clinical criteria. The analytic criteria include measurement of marginal, interproximal, and occlusal fit; measurement of surface finish with stylus profilometers; and evaluation of product integrity through both scanning electron and dispersive x-ray analysis. The clinical tests are based on criteria routinely used at the University of Minnesota School of Dentistry and include evaluation in (1) a preclinical setting on Bureau of Standard dies and green teeth and (2) actual clinical evaluation with annual followup for at least the duration of the grant funding period to establish long-term stability and tissue response. Complementing these activities, are two additional aims: (1) investigations into materials and (2) system enhancement. Materials investigations includes (a) identification of the availability and feasibility of using tooth-colored materials, (b) identification of alternative materials that can be milled but historically have not been used for dental restorations because they could not be cast, and (c) alternative preparation designs that capitalize on material properties identified in step (b) above. System enhancement includes (a) adding the capability of producing partial coverage crowns, inlays, and bridges; (b) developing a clinically usable high-precision customized machining system; and (c) optimizing data acquisition and image processing. A CAD/CAM system for dental restorations offers a number of potential advantages including opening the possibility of new, stronger materials and the opportunity of creating the equivalent of cast restorations in a single appointment, eliminating the potential of tissue involvement caused by temporary crowns.
