Japanese Journal of Oral and Maxillofacial Surgery
Online ISSN : 2186-1579
Print ISSN : 0021-5163
ISSN-L : 0021-5163
Three-dimensional analysis of dental arches by lateral and frontal cephalograms
Katsuhiko HONMA
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JOURNAL FREE ACCESS

1991 Volume 37 Issue 2 Pages 314-326

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Abstract

A method for three-dimensional analysis of dental arches using cephalograms and dental casts was developed. One piece impression of the upper and lower dental arches at occlusion with a horseshoe-shaped resin skeleton containing steel wires of 0.4mm in diameter used as radiographic markers on the labial side of the dental arches was taken using silicon base impression material. Lateral and frontal cephalograms were then taken simultaneously with mouth impression. “After dental casts with impression” were made with piaster, three points were marked at the hase of each dental cast and three-dimensional coordinate values of three points at the rips of the steel wires and the six points of the dental casts were measured. Then, “final dental casts” were removed from the impression and three-dimensional coordinate values of measurement points on teeth and tne three points at the base of each “final dental cast” wen measured. All the values measured were input in a personal omputer. The lateral and frortal ephalograms were traced and five stmdard points and the three wire points were input using the digitizer and their three dimensional coordinate values were calculated and standardized by the method described by Kobayashi, et al 7). Finally, standardized three-dimensional coordinate values of the measurement points on teeth were calculated by coordinate transformation from “final dental cast” to “dental casts with impression” and to “cephalograms”.
To assess the reproducibility of this system, standardized three-dimensional coordinate values of three dental points of each dental arch on an incisor and two right and left molars were calculated twice in 10 subjects. The mean differences of coordinate values for the three axes and straight distances of the same dental points on the two measurements were in the ranges of 0.14mm to 0.43mm and 0.54mm to 0.60mm, respectively. Standard deviations of the coordinate values for the three ax s and for three-dimensional direction were between 0.13mm and 0.34mm, and 0.40mm and 0.45mm, respectively.
The results of the aralysis with this method in two cases in which mandibular protrusion with lateral deviation and open bite were corrected by a combination of sagittal split osteotomy and body ostectomy, and anterior alveular osteotomics of the maxilla or the mandible, respectively, indicated that it is quite useful in analysing the movement of dental arches during and after surgery in relation to the mandibular morphology because the standardized coordinate system is set in the cranium.

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© Japanese Society of Oral and Maxillofacial Surgeons
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