Tooth Inclination in Elderly with Many Remaining Teeth Observed by 3-D Imaging

Abstract

Tooth inclination has been discussed many times in terms of esthetics and functionality, but reports related to aging are extremely rare. The purpose of this study was to evaluate tooth inclination in the elderly from the orthodontic point of view. The dental casts of twenty elderly persons with many remaining teeth were digitized with a 3-D laser scanner (VMS-100F,UNISN INC., Osaka, Japan) for reconstruction into 3-D images. Inclination of each tooth was then measured with an analytical software (SURFLACER, UNISN INC. and IMAGEWARE 12, UGS PLM Solutions, MO, USA). The occlusal plane formed by the incisal edge of the central incisor and distal buccal cusp tip of the first molar on either side was used as a reference plane to measure tooth inclination, and the complementary angle as tooth inclination was measured. The average tooth inclinations (degrees) of the maxillary teeth were 8.08 for central incisors, 8.10 for lateral incisors, 4.85 for canines, ‫86.6מ‬ for first premolars, ‫85.5מ‬ for second premolars, ‫51.5מ‬ for first molars, and ‫14.5מ‬ for second molars. The corresponding values for the mandibular teeth were 6.78 for central incisors, 4.87 for lateral incisors, ‫37.5מ‬ for canines, ‫47.31מ‬ for first premolars, ‫12.91מ‬ for second premolars, ‫67.32מ‬ for first molars, and ‫36.82מ‬ for second molars. There was no statistical difference between men and women, except for in the maxillary lateral incisors (pϽ0.05). Tooth inclination showed a progressive decrease from anterior to posterior. The decrease in the mandibular teeth was more regular than that of the maxillary teeth.

Comparison of linear and angular changes assessed in digital dental models and cone‐beam computed tomography

“…Assessment of mesiodistal and buccolingual angulation, needed to guide orthodontic biomechanics and treatment objectives, as proposed by Andrews, 1,2 continues to contribute to the literature until the present days. [3][4][5][6][7][8][9][10][11] Tooth displacement is ruled by the crown and root positions. A correct and accurate understanding of these changes can be extremely helpful in clinical practice, since the ideal treatment goal is to correctly position the whole tooth and not only the clinical crown.…”

“…[12][13][14] Different methodologies have since then been proposed to assess the mesiodistal and buccolingual angulation in stone casts and, more recently, in digital dental models (DDMs). [6][7][8]12,13 The challenge is to develop an adequate and reproducible method to measure mesiodistal and buccolingual angulation, considering that the buccal crown contour is not a uniform curve and DDMs do not show the tooth root. [12][13][14][15][16][17][18] Conventional radiographs have also been used to assess the changes in mesiodistal and buccolingual angulation.…”

Change in Anterior Crowding over 20 Years from Third Decade of Life in Untreated Angle Class I Crowding

“…The 3-dimensional (3-D) shape of the parallel dental casts was inputted using a noncontact shape measuring system (VMS-100F, UNISN, Osaka, Japan). It was measured using a 3-D point processing software package (Imageware 13, Siemens PLM Software, Inc., Plano, TX, USA) 7,8,19,26) .…”

“…3) Inclination (Fig. 4) The angle formed by a tangential line on the LA point (labial clinical crown midpoint) and a line orthogonal to the occlusal plane was calculated 7) . Labial inclination of the crown with respect to the occlusal plane is indicated as positive (+) and lingual inclination as negative (−).…”

Effect of Different Bracket Prescriptions on Orthodontic Treatment Outcomes Measured by Three-dimensional Scanning

“…(2) Inclination (buccolingual axial inclination of the teeth) (Figs. 2,3) Inclination was determined based on the method of Fukagawa et al 5) . First, the orientation of the sagittal plane of the tooth axis was established by creating a coordinate axis at the intersection of the aforementioned offset copied crown width line and the tooth axis perpendicular line.…”