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Mandibular morphology in subjects with Class III malocclusions: Finite-element morphometry
G D Singh1, J A McNamara, S Lozanoff
1Dept. of Dental Surgery and Periodontology, Dundee Dental Hospital & School, University of Dundee, Scotland, UK. g.d.singh@dundee.ac.uk
The Angle Orthodontist
|October 14, 1998
Summary
Mandibular prognathism, a condition causing an underbite, may result from a lack of physical restraint during growth. This study found specific size and shape differences in the mandibles of children with this condition.
Area of Science:
- Orthodontics
- Craniofacial Biology
- Developmental Biology
Background:
- Mandibular prognathism is a common malocclusion.
- The etiology of mandibular prognathism is multifactorial, with genetic and environmental factors playing a role.
- The role of physical restraint in mandibular development is not fully understood.
Purpose of the Study:
- To investigate the association between the absence of physical restraint and mandibular allometry in prepubertal children with Class III malocclusions.
- To compare mandibular morphology in children with Class III malocclusions to a control group with Class I malocclusions.
Main Methods:
- Cephalometric analysis of 73 prepubertal children with untreated Class III malocclusions.
- Digitization of eight mandibular landmarks and normalization of geometries.
- Procrustes analysis and color-coded finite-element (FEM) analysis to compare mean Class III and Class I mandibular configurations.
Main Results:
- Statistically significant differences (p < 0.05) were found between mean Class III and Class I mandibular configurations.
- FEM analysis revealed positive allometry (15% size increase) in the mandibular corpus and around the supramentale in Class III subjects.
- Reductions (30%) in size were observed between the incisor alveolus and menton, with anisotropic anterior regions in Class III subjects.
Conclusions:
- The absence of physical restraint is associated with mandibular allometry contributing to mandibular prognathism.
- Observed incremental growth differences support the hypothesis that lack of physical restraint influences mandibular development.
- Findings suggest that environmental factors, such as physical restraint, play a significant role in the development of Class III malocclusions.