Document Type

Thesis

Date of Degree

Spring 2015

Degree Name

MS (Master of Science)

Degree In

Orthodontics

First Advisor

Lina M. Moreno Uribe

Abstract

Objective: Variation in dental arch shape and arch relations from the primary to the permanent dentition were studied in an untreated longitudinal sample from the Iowa Fluoride Study and Growth Study data (55 females and 63 males). Methods: 3D coordinate data from 68 landmarks located on maxillary, mandibular, and occlusal dental cast scans from ages 5, 9, and 13 were submitted to a Procrustes fit prior to a Principal Component (PC) analysis to capture symmetric and asymmetric aspects of arch shape variation. Covariance pattern models were used to determine longitudinal arch shape changes from the primary to the permanent dentition and to correlate these changes with Angle class molar classification.

Results: The first 3 principal components capture 52-78% of the variation in arch shape. PC1 explains 30-44% of the variance and captures changes in overall dentoalveolar height. PC2 explains 14-22% and shows mainly variation in dentoalveolar height and width at the canines. Lastly, PC3 explains 8-12% and captures overall arch width and perimeter differences and changes in anteroposterior arch relations. Results on symmetric shape variation for the occlusal data set captured significant differences (p < 0.0001) in morphology for PC2 and PC3. For PC2, initial morphology in the deciduous dentition for an individual classified as Class II was significantly different than a Class I individual. Initial shape characteristics for the Class II features stepped down maxillary incisors and an increased curve of Spee with deep overbite. For PC3, the initial morphology for both the distocclusion and Class II individuals demonstrated characteristics such as stepped up maxillary incisors and increased overjet relative to their flush terminal plane and Class I counterparts. The rate of arch shape changes at which the distal step group transitions to the mixed dentition was also significantly different from the flush terminal plane sample.

Conclusions: Initial findings summarize the main aspects of arch shape variation throughout 3 dentition stages. The covariance pattern models estimated individual trajectories and dynamics of arch shape changes from the primary to the permanent dentition and correlated these changes with Angle molar classification. In the symmetric dataset, significant shape characteristic differences of both initial starting morphology and change in shape over time were discovered for two occlusal phenotypes highlighting differences primarily in the vertical and anteroposterior dimensions. The results found in the present study provide an excellent foundation for describing and identifying dental arch shape differences in the primary dentition that can aid in earlier detection, diagnosis, and treatment of malocclusion, or at a minimum warrant closer observation by the clinician.

Public Abstract

Misalignment or incorrect relation between the upper and lower teeth of the maxilla and mandible is caused by discrepancies in the size and shape of the various components of the maxilla-mandibular complex. The functional balance and adequate spatial alignment of the upper and lower dental arches is necessary for adequate chewing, swallowing, and speech. To aid in determining the underlying causes of dental misalignments and incorrect dental bites, a shape variation analysis was performed using a geometric morphometrics approach and principal components analysis. Variation in dental arch shape and arch relations as an individual transitions from their baby teeth to permanent teeth were studied in an untreated longitudinal sample from the Iowa Fluoride Study and Growth Study data (55 females and 63 males). Results illustrated significant dental arch shape differences (p < 0.0001) between individuals who started with abnormal bites (i.e. deep bite or increased overbite) in the primary (baby teeth) dentition compared to individuals who initially had normal bites. The findings summarize detail aspects of shape variation through time that may aid in earlier detection and treatment modalities for bite problems.

Keywords

publicabstract, geometric morphometrics, longitudinal, shape

Pages

xiii, 119 pages

Bibliography

Includes bibliographical references (pages 114-119).

Copyright

Copyright 2015 Taylor Varner

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