A Study on the Tooth-axis about Upper Central Incisors Determination of Quantitative Tooth-axis

• Published in: Nihon Hotetsu Shika Gakkai Zasshi Vol. 48; no. 1; pp. 74 - 83
• Main Authors: Iijima, Shingo, Kasahara, Shin, Kimura, Kohei, Kikuchi, Masayoshi, Muramoto, Mutsushi
• Format: Journal Article
• Language: English; Japanese
• Published: Japan Prosthodontic Society 10.02.2004
• Subjects: non-contact high-speed device to measure 3-dimensional form; principal component analysis; quantitative tooth-axis
• ISSN: 0389-5386; 1883-177X
• DOI: 10.2186/jjps.48.74

Purpose: The long axis of a tooth was analytically determined from 3-dimensional and measured data of the dental surface, using a non-contact high-speed device to measure the 3-dimensional form. Its validity as the long axis of the tooth was evaluated by comparing it with that determined by the conventional method. Methods: Five upper central incisors chosen at random from 50 that were considered to be the average form in the left-hand side were measured by using the non-contact high-speed device to measure the 3-dimensional form. Applying principal component analysis and using software to analyze the 3-dimensional form, the long axis of the tooth was obtained. Furthermore, as conventional methods to determine the tooth axis reported until now, Tamazawa's method was selected. About five natural teeth, the angle that the long axis of the tooth and tooth-axes make, and the positional relation made by the long axis of the tooth and tooth-axes in level 5 sections, with the long axis of the tooth as the starting point, were compared. Results: In the long axis of the tooth and tooth-axis, the difference of the angle that the two axes make was very small. In five data, the position of tooth-axes was approximated to the starting point, i.e., the long axis of the tooth in each section. Conclusions: The long axis of the tooth computed from the 3-dimensional image data of the surface of the tooth used by this research may be valid as the tooth-axis. It was quantitatively to the utmost limit obtained by applying for the principal component analysis.