Inner Surface Working Accuracy of Titanium Crowns Milled with CAD/CAM.

The titanium crown is rapidly replacing other metallic crowns today. However, it has a crucial problem; the crown worked in a conventional way is less adaptable. To solve that problem, a new technique employing CAD/CAM with a laser measuring system has been developed to produce an accurate and desirable inner surface of the titanium crown. Then a coordinate measuring machine was set to measure and contrast two of the candidates:1. The inner surface of the titanium crown worked in the conventional way:Laser beams were applied to the titanium crown at 90°to the long axis of the tooth and the inner surface was finished with the ball-end-mill of a 2.0-mm diameter.2. The inner surface of the titanium crown worked in the new technique:The model abutment was set at a 10°angle to apply the laser beams effectively to the cervical part of the titanium crown for measuring the accuracy. The same ball-end-mill was used to rough-finish it, and then the 1.0-mm diameter one was used to elaborate it.The result showed remarkable contrasts to reveal the superiority of the new technique: the conventional way produced a significant tolerance from the occlusal area to the cervical; the new technique produced a fine marginal form and a high adaptability in the working accuracy.