The Effect of Digitizing Conditions on the Accuracy of Ceramic Crowns Fabricated by Using the Second Version of the Experimentally Developed Dental CAD/CAM Machine

Abstract

We have been developing a dental CAD/CAM system for fabricating crowns automatically. We have already developed a compact machine containing both a digitizing apparatus and a machining apparatus. Previous studies using a simple model for digitizing should that the adjacent tooth influenced the accuracy on the axial wall and the margin area on the abutment. In this study, a stone model of the standard abutment with a clinical taper and shoulder margin was digitized on the second version of the CAD/CAM machine with different digitizing conditions. Ceramic crowns were fabricated from a block by machining with a CAM procedure followed by their being cemented to abutments. Cement thickness measured on different spots appeared should that the accuracy on the transitional part on the shoulder to the axis of the wall increased when the digitizing model was separated from the adjacent teeth. Furthermore, the accuracy of the crown increased with the decrease of the digitizing pitch. Accurate crowns with a cement thickness designed on the CAD process were available when the digitizing pitch was 180μm. Therefore we can fabricate ceramic crowns with clinically acceptable accuracy by using a second version of the developed CAD/CAM machine.