A Study of Three-Dimensional Accuracy in Dental Prosthesis

尽管预计牙科修复体将很快用CAD/CAM技术制造，但使用该技术建造牙科修复体的三维精度尚不清楚。我要求5名牙科技术人员每人在以下三种情况下制作3颗模型牙：目测原始牙齿；用卡尺测量原始牙齿；在没有原始牙齿的情况下，从现有的对牙和相邻牙齿外推测量牙齿。用激光测位仪对再生牙进行测量，并与原牙进行比较，发现目测再生牙的距离误差约为500微米。使用卡尺进行测量时，距离误差并未减小。一般来说，牙科技术人员制作的复制牙都是畸形的。当技术人员试图重建拔除的牙齿时，复制误差增加到1000微米左右。

Even though it is projected that the dental prosthesis will soon be manufactured with CAD/CAM technology, the three-dimensional accuracy of dental prosthesis construction using this technology is not known. I requested each of 5 dental technicians to produce 3 model teeth under each of the following three conditions : the original tooth measurement by visual inspection ; the original tooth measurement with calipers ; and in the absence of the original tooth, tooth measurement by extrapolation from the existing opposite and adjacent teeth. The reproduced teeth were measured with a laser displacement meter, and the results compared with the orginal tooth.It was found that the reproduced teeth constructed based on the visual inspection had error of distance of about 500mum. The error of distance was not reduced when the measurement was made using calipers. In general, reproduced teeth made by the dental technicians were deformed. When the technicians attempted to reconstructar eliminated tooth, the error of reproduction increased to about 1000mum.