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Orthod Craniofac Res. 2019 May;22(2):99-104. doi: 10.1111/ocr.12288. Epub 2019 Feb 8.

Ethnic differences in the root to crown ratios of the permanent dentition.

Author information

1
Department of Orthodontics, University of Alabama at Birmingham School of Dentistry, Birmingham, Alabama.
2
School of Nursing, University of Alabama at Birmingham, Birmingham, Alabama.
3
Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada.

Abstract

OBJECTIVE:

Root resorption due to orthodontic tooth movement may adversely affect the root-crown (R/C) ratios of permanent teeth, especially in patients with Short Root Anomaly (SRA), a poorly understood disorder affecting root development. Evaluation of SRA R/C ratios to normal dentition would facilitate diagnosis and orthodontic treatment planning. However, reference values are not available for all ethnicities. Our goal was to determine R/C ratios of permanent teeth and their relationship to gender and ethnicity.

SETTING/SAMPLE:

A retrospective study of 333 patients (109 Caucasians, 112 African Americans and 112 Hispanics) from the University of Alabama at Birmingham School of Dentistry.

MATERIALS/METHODS:

Root lengths and crown heights were measured from panoramic radiographs of 6241 teeth using modified Lind's method. A linear mixed model was used to compare the R/C ratios of teeth among subgroups (gender, ethnicity).

RESULTS:

The mean R/C ratios varied from 1.80 to 2.21 for the maxillary teeth and 1.83-2.49 for the mandibular teeth. Gender differences in R/C ratios were found to be significant only for the lower central incisors (P < 0.05). Hispanics showed significantly lower ratios for most teeth compared to the other two groups (P < 0.05). There were significant differences in R/C ratios between African Americans and Caucasians in the upper lateral incisors, lower central incisors and lower first premolars (P < 0.05).

CONCLUSION:

Our results suggest that ethnicity is an important factor in determining the R/C ratios of permanent teeth. Therefore, when diagnosing developmental conditions such as SRA, ethnic group-specific reference values should be considered.

KEYWORDS:

ethnic differences; permanent dentition; radiographic evaluation; root-crown ratios; short root anomaly

PMID:
30650237
PMCID:
PMC6449179
[Available on 2020-05-01]
DOI:
10.1111/ocr.12288

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