Skeletal class Ⅲ ; Craniofacial growth ; Classification
Abstract
Skeletal class Ⅲ had been classified by the position of the maxilla, the mandible, the maxillary alveolus,
the mandibular alveolus and vertical development. This morphologic approach is simple and useful for clinical
use, but it is insufficient to permit understanding of the pathophysiology of dysmorphoses.
The author hypothesizes that there are different patterns of mutual relation of the skeletal components
which have contributed pathologic equilibrium of skeletal class Ⅲ. The purpose of this study are threefold:
1) to classify skeletal class Ⅲ in subgroups, which can show the architectural characteristics of the deformity,
2) to analyse the craniofacial architecture of each subgroup on etio-pathogenic basis, and 3) to characterize
and visualize the pattern as a prototype.
Materials used in this study were lateral cephalograms of 106 skeletal class Ⅲ adults, which were
analysed with modified Delaire’s architectural and structural analysis. Linear and angular measurements
of the individual subject were obtained and cluster analysis was used for the subgrouping. Data were evaluated
for verification of the statistical significances. The following results were obtained.
1. By the modified Delaire’s architectural and structural analysis and cluster analysis, skeletal class Ⅲ
adults were classified into 7 clusters and presented as prototypes, which could show the pathophysiology
of the skeletal architecture
2. There was significant relationship in measurement variables of each cluster, which could reflect characteristics
of the skeletal pattern of growth.
3. The flexure of cranial base had a close relationship to the anterior rotational growth of the maxilla
and contributes to understand the etio-pathology of skeletal class Ⅲ.
4. The proportion of craniospinal area in cranial depth, craniocervical angle and vertical position of point
Om had a close relationship to rotational growth of the mandible and direction of condylar growth.
They contribute to understand the etio-pathology of skeletal class Ⅲ.
In summary, the cranium and the craniocervical area must be considered in diagnosis and treatment
planning of dentofacial deformity. And the occlusal plane can be considered as a representative which
shows the mutual relationships of the skeletal components.