Date of Degree
MS (Master of Science)
Steven F. Miller
First Committee Member
Lina M Moreno Uribe
Second Committee Member
Nathan E Holton
Third Committee Member
Thomas E Southard
Introduction: In order to properly diagnose and treatment plan, an orthodontist needs to be knowledgeable about the changes that occur to the maxillary and mandibular dental arches throughout growth. The purpose of this study is to provide an analysis of morphological shape differences seen in the maxillary and mandibular dental arches individually, as well as together, from birth to 3 years of age.
Methods: Dental casts from the Iowa Infant Growth study ranging from 2 months to age 4 were photographed in the occlusal plane. The images were landmarked with 3 standard landmarks and 10 sliding semi-landmarks along the curvature of the maxillary and mandibular arches. TpsRelW was used to slide the semi-landmarks and superimpose the date to facilitate shape analysis. MorphoJ was used to determine the degree to which size influences dental arch shape. Once the effects of allometry had been removed, a principal component analysis was run on the residuals to display major features of shape variation in the dataset. Finally, a two block partial least squares analysis was run to determine the degree to which the maxillary and mandibular arches were integrated throughout early growth.
Results: Allometry accounts for 9.63% of symmetric shape variation in the maxilla, while it accounts for 56% of symmetric shape variation in the mandible. Asymmetric shape variation is independent of allometry as it only affects 0.34% of the maxillary and 1.46% of the mandibular shape variation. Principal component one accounts for over 60% of all shape variation seen in maxillary and mandibular residuals. Principal component one of symmetric residuals results in a longer, wider dental arch or a shorter, narrower one. Principal component one of asymmetric residuals results in a dental arch with one posterior side being longer and wider while the contralateral side is shorter and narrower. The first three time points (2 months- 1 year) do not display significant integration between the maxillary and mandibular arches. Integration increases with age, displaying significant integration at the last three time points, with the most integration being displayed at 2.5 years.
Conclusions: Allometry affects some of the symmetric shape variation in the maxilla, but over half of the symmetric shape variation in the mandible. The asymmetric components are independent of allometry. Integration of the maxillary and mandibular arches increase with age from 2 months to 3 years, peaking at a time point of 2.5 years.
An orthodontist needs to know what occurs to the maxillary and mandibular arches as a person grows in order to properly diagnose problems and determine an adequate treatment plan. The purpose of this study was to evaluate those changes in each arch separately and together from birth to 3 years of age. This was done using dental casts of children in the Iowa Infant Growth study from 2 months to 4 years of age. The casts were photographed and landmarked. The data were then analyzed in MorphoJ to see the effect that size has on shape variation. These size effects were then removed and further analyses were run to determine the principal components of shape variation in each arch as well as the similarities in growth of both arches together, or integration, as the individual got older. Results indicate that size affects the shape variation of the symmetric component for the maxilla and mandible, but does not affect the shape variation of the asymmetric components. It was also found that as the arches are growing from 2 months to 3 years, the integration, or the amount that arch shapes covary, increases with age.
Dental Arch Shape
viii, 47 pages
Includes bibliographical references (pages 45-47).
Copyright © 2017 Gisela Lilian Borget
Borget, Gisela Lilian. "Variation in arch shape and dynamics of shape change from infancy to early childhood." MS (Master of Science) thesis, University of Iowa, 2017.