A probability distribution of shape for the dental maxillary arch using digital images

Abstract

Selected landmarks from each of 47 maxillary dental casts were used to define a Cartesian-coordinate system from which the positions of selected teeth were determined on standardized digital images. The position of the i-th tooth was defined by a line of length (l(i)) joining the tooth to the origin, and the angle (θ(i)) of this line to the horizontal Cartesian axis. Four teeth, the central incisor, lateral incisor, canine and first molar were selected and their position were collectively used to represent the shape of the dental arch. A pilot study using clustering and principal component analysis strongly suggest the existence of 3 groups of arch shape. In this study, the homogeneity of the 3 groups was further investigated and confirmed by the Dunn and Davies-Bouldein validity indices. This is followed by an investigation of the probability distribution of these 3 groups. The main result of this study suggests 3 groups of multivariate (MV) normal distribution. The MV normal probability distribution of these groups may be used in further studies to investigate the issues of variation of arch shape, which is fundamental to the practice of prosthodontics and orthodontics.

Comparative study of the dental arch shape in young Brazilians with normal occlusion

“…The traditional dental casts were scanned and the measurements obtained through 3D images in specific software, as previously tested by Sousa et al 24 and reasoned by Fleming et al 25 In the literature the authors use different ways to obtain the measurements, directly over the dental casts using a caliper, [26][27][28] with photographic techniques, 29,30 photocopies or digitalized images, 6,10,19,21,31 and 3D digital casts. 20,23,[32][33][34] In order to determine the dental arches dimensions and shapes, some authors have chosen either one of the arches, the maxillary 19 or the mandibular, 14 and sometimes both of them. 28,30 In addition, several landmarks have been used such as clinical bracket points, 10,14-17 facial axis points, 20,33 center on the occlusal surface.…”

“…Some authors 10,19 found more than one type of arches. This information will help orthodontists about the variation of arch shape which is useful for diagnosis and treatment plan, also permit the fabrication of preformed archwires with the most common dental arch forms or templates to help in the manual contouring of archwires, eliminating the use of dental casts during orthodontic treatment and thus reducing the possibility of breaking them.…”