[A study on application of multiple jointed contact-type measuring apparatus for dental use].

The measurement of oral maxillofacial region, including dentition and teeth, is important information for diagnosis and assessment of treatment in clinical dentistry. There are two kinds of the measuring systems, i.e., contact-type system and non-contact-type system. The latter mainly has been investigated in dentistry, because of its simplicity and quickness for measurement. However, since the objects in dentistry have complex shapes with curved surfaces and many dead angles, accuracy of values obtained by this system is insufficient for clinical use. Even though divided measurement is employed to overcome the problems, the increase of measuring element results in deterioration of the accuracy. In the present study, the accuracy of a contact-type measuring apparatus with 5 pivoting joints was investigated. For the cavity model, the depth and the width were measured. For the standardized dental cast which consists of three spheres, the diameter of three spheres and the distance of each sphere were measured. The values obtained by this apparatus were compared with those obtained by the precise 3D-measurement apparatus. The differences were insignificant in the cavity model. Significant difference was found in the standardized dental cast. However, the difference was very small, and so it is negligible in clinical use. By using this apparatus, the form of undercut and teeth was reconstructed completely. The results suggested that the multiple jointed contact-type measuring apparatus could be applied to the measurement in clinical dentistry.