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Crown-root shape of the permanent maxillary central incisor
Grant T McIntyre1, Declan T Millett
1Orthodontic Department, Unit of Orthodontics, Glasgow Dental Hospital and Dental School, 378 Sauchiehall Street, Glasgow, UK. granttmcintyre@hotmail.com
The Angle Orthodontist
|January 15, 2004
Summary
The permanent maxillary central incisor crown-root shape differs significantly in Class II division 2 malocclusions. This unique shape, featuring axial bending, may contribute to deep overbites.
Area of Science:
- Orthodontics
- Dental Morphology
- Cephalometric Analysis
Background:
- Understanding variations in tooth morphology is crucial for diagnosing and treating malocclusions.
- The permanent maxillary central incisor's crown-root shape may be influenced by different malocclusion types.
Purpose of the Study:
- To investigate differences in the lateral cephalometric crown-root shape of permanent maxillary central incisors across various malocclusion classes (I, II div 1, II div 2, III).
- To characterize the specific nature of any observed shape variations.
Main Methods:
- Lateral cephalograms from 361 patients were analyzed.
- Ten landmarks of the maxillary central incisor crown-root were digitized and superimposed using Procrustes algorithms.
- Discriminant analysis of principal components identified shape differences between malocclusion groups.
Main Results:
- No significant crown-root shape differences were found among Class I, Class II division 1, and Class III malocclusions.
- A significant difference (P < .001) was observed in the crown-root shape of Class II division 2 incisors compared to other groups.
- Class II division 2 incisors exhibited axial bending, shorter roots, longer crowns, and reduced labiopalatal thickness.
Conclusions:
- The permanent maxillary central incisor crown-root shape is significantly distinct in Class II division 2 malocclusions.
- Observed shape characteristics in Class II division 2 may predispose individuals to deep overbites and influence orthodontic treatment outcomes, particularly palatal root torque.