Date of Award

5-2008

Document Type

Thesis

Degree Name

Master of Dental Science (MDS)

Program

Orthodontics

Research Advisor

Edward Harris, Ph.D.

Committee

Cheryl DeWood, D.D.S., M.S. Quinton Robinson, D.D.S., M.S.

Keywords

Malocclusion, Tooth Size, Crowding, TSASD, Dental Cast, Mesiodistal, Buccolingual, Crown Index

Abstract

Malocclusion is an increasingly common, multifactorial problem in industrialized countries. Although the causes of dental malocclusion are obscure in most instances, one contributing factor may be tooth size. While several researchers have studied whether tooth size contributes to malocclusion, there still is no consensus. Some have found that the mesiodistal widths of the mandibular incisor teeth are significantly larger in subjects with anterior crowding, while others have been unable to support this conclusion. Study designs often have been confounded by combining the sexes, which confuses sexual dimorphism with the supposed effect of tooth size on crowding. The present study tested whether tooth crown dimensions (mesiodistal and buccolingual) differed in a sample of American white adult males with naturally-occurring good occlusions (n = 42) versus otherwise similar individuals who required orthodontic treatment to correct their malocclusions (n = 90). Crown dimensions were measured with digital sliding calipers. As assessed from our data, the sample means of 23 of the 24 tooth crown diameters tested were significantly larger in subjects with malocclusions versus those with naturally-occurring good occlusions. Multivariate analysis showed that mesiodistal diameter of the maxillary lateral incisor produced the most significant difference between the two samples, but this may reflect the American white composition of the sample, where this lateral incisor is notoriously small. Importantly, none of the individuals in either group had a significant Bolton discrepancy. Controlling for intercorrelations among crown dimensions, only mesiodistal crown diameters were predictive of crowding. Indeed, buccolingual crown diameters were only indirectly related to TSASD due to their high positive correlation with mesiodistal crown diameters. As such, the MD/BL crown ratio was not shown to be predictive of crowding.

DOI

10.21007/etd.cghs.2008.0005

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