<abstract xmlns="http://www.w3.org/1999/xhtml">

<p>The rotation of the maxillary molars is considered important in the orthodontic treatment of malocclusions. In this study, a computer analysis program was developed to examine the rotations of maxillary molars, mandibular molars, and maxillary first premolars in casts of permanent dentitions with acceptable occlusions. Ninety-three sets of untreated ‘acceptable occlusion’ models from the collection of the Foundation for Orthodontic Research (FOR) were scanned on a flat bed scanner. The images were analysed using eustom software. Measurements were made by relating maxillary first permanent molars to the midline, archform, opposite canine, and mandibular first permanent molars. The mandibular first molars and maxillary first premolars were also analysed and their rotations measured. The mean rotations of the maxillary first molars, measured as the angle between a line joining the tips of the buccal cusps and a line tangent to the appropriate archwire form (from Ricketts’ Pentanmorphic Arches) at the first molars, were 0.59 and −0.72 degrees (positive values represent mesio-lingual rotations) for the right and left, respectively. For the mandibular molars, these means were 6.34 and 8.40 degrees, respectively. The mean differences in rotation betweeu buccal cusp tips of maxillary and mandibular first molars in occlusion were 5. 75 and 9.12 degrees for the right and left, respectively, with the mandibular being more mesio-lingually rotated. The differences between left and right were significant for all measurements. The present study brings into question the suitability of onr present “straight wire” prescriptions in producing similar occlusions. It also suggests that scanning models for computer analysis may be a practical and precise way to measure similar rotations in untreated normal and treated occlnsious.</p>
</abstract>

The rotation of the maxillary molars is considered important in the orthodontic treatment of malocclusions. In this study, a computer analysis program was developed to examine the rotations of maxillary molars, mandibular molars, and maxillary first premolars in casts of permanent dentitions with acceptable occlusions. Ninety-three sets of untreated ‘acceptable occlusion’ models from the collection of the Foundation for Orthodontic Research (FOR) were scanned on a flat bed scanner. The images were analysed using eustom software. Measurements were made by relating maxillary first permanent molars to the midline, archform, opposite canine, and mandibular first permanent molars. The mandibular first molars and maxillary first premolars were also analysed and their rotations measured. The mean rotations of the maxillary first molars, measured as the angle between a line joining the tips of the buccal cusps and a line tangent to the appropriate archwire form (from Ricketts’ Pentanmorphic Arches) at the first molars, were 0.59 and −0.72 degrees (positive values represent mesio-lingual rotations) for the right and left, respectively. For the mandibular molars, these means were 6.34 and 8.40 degrees, respectively. The mean differences in rotation betweeu buccal cusp tips of maxillary and mandibular first molars in occlusion were 5. 75 and 9.12 degrees for the right and left, respectively, with the mandibular being more mesio-lingually rotated. The differences between left and right were significant for all measurements. The present study brings into question the suitability of onr present “straight wire” prescriptions in producing similar occlusions. It also suggests that scanning models for computer analysis may be a practical and precise way to measure similar rotations in untreated normal and treated occlnsious.

The Rotation of Maxillary First Molars, Mandibular First Molars, and Maxillary First Premolars in Acceptable Occlusions

Associate Professor of Orthodontics at Loma Linda University

Assistant Professor of Orthodontics at Loma Linda University

Professor of Orthodontics at Loma Linda University

Australasian Orthodontic Journal

This work is licensed under the Creative Commons Attribution 4.0 International License.

The rotation of the maxillary molars is considered important in the orthodontic treatment of malocclusions. In this study, a computer analysis program was...

The Rotation of Maxillary First Molars, Mandibular First Molars, and Maxillary First Premolars in Acceptable Occlusions

Published Online: Jan 16, 2024

Page range: 242 - 246

Received: Nov 01, 1995

Accepted: Aug 01, 1996

DOI: https://doi.org/10.2478/aoj-1997-0005

© 1997 G. Kristian Hansen et al., published by Sciendo

This work is licensed under the Creative Commons Attribution 4.0 International License.