Classification and characterization of class III malocclusion in Chinese individuals

Abstract

BackgroundClass III malocclusion is a maxillofacial disorder that is characterised by a concave profile and can be attributed to both genetic inheritance and environmental factors. It is a clinical challenge due to our limited understanding of its aetiology. Revealing its prototypical diversity will contribute to our sequential exploration of the underlying aetiological information. The objective of this study was to characterize phenotypic variations of Class III malocclusion via a lateral cephalometric analysis in a community of Chinese individuals.MethodOne-hundred-and-forty-four individuals (58 males ≥18 and 86 females ≥16) with Class III malocclusion ranging from mild to severe were enrolled in this study. Principal component analysis and cluster analysis were performed using 61 lateral cephalometric measurements.ResultsSix principal components were discovered in the examined population and were responsible for 73.7 % of the variability. Four subtypes were revealed by cluster analysis. Subtype 1 included subjects with mild mandibular prognathism with a steep mandibular plane. Subjects in subtype 2 showed a combination of prognathic mandibular and retrusive maxillary with a flat or normal mandibular plane. Subtype 3 included individuals with purely severe mandibular prognathism and a normal mandibular plane. Individuals in subtype 4 had a mild maxillary deficiency and severe mandibular prognathism with the lowest mandibular plane angle.ConclusionThe six principal components extracted among the 61 variables improve our knowledge of lateral cephalometric analysis for diagnoses. We successfully identified four Class III malocclusion subtypes, indicating that cluster analysis could supplement the classification of Class III malocclusion among a Chinese population and may assist in our on-going genetic study.Electronic supplementary materialThe online version of this article (doi:10.1186/s13005-016-0127-8) contains supplementary material, which is available to authorized users.

Sub-clustering in skeletal class III malocclusion phenotypes via principal component analysis in a southern European population

“…As described in previously published studies 5,8,17 , the first three axes represented more than half [58.5%] of the total variation found in the sample, essentially referring to the description of sagittal and vertical parameters, while others 5,8,17 also represented the position of the lower incisor in the first half of the variation derived from the involvement of dental variables in the formation of PCs. Most of the parameters that represent sagittal and vertical measurements in our PC1 (26.6% of variation), PC2 (19.6% of variation), and PC3 (12.3% of variation) are equivalent to the parameters of PC1 (23.7% and 20.6%) and PC2 (17.3% and 19.34%) in other studies 5,8 , while PC1 in another study 17 is more like PC4 (9.3%) and PC5 (6.5%) (ANB, facial angle, and Pg-N perp) in the present research, despite the fact that the same sagittal and vertical parameters were included in these aforementioned components. The observed differences might be at least partially explained by the type of class III patients included and their distribution, essentially based on distinct ethnic origin and growing stage of the included subjects.…”

“…Class III malocclusion has been commonly described as having a retruded or hypoplastic upper maxilla, a prognathic or hyperplastic mandible, or a combination of both 1 . These shared characteristics in skeletal class III malocclusion vaguely define the different sub-phenotypes clearly identified in recent studies [2][3][4][5][6][7][8] .…”

Novel Sub-Clustering of Class III Skeletal Malocclusion Phenotypes in a Southern European Population Based on Proportional Measurements

“…Few studies indicate the total number of each gender in the different subgroups identified. Nevertheless, differences in gender within clusters can be observed in other studies; for instance, in Li et al [ 34 ], two of the four characterized clusters were disproportionately made up of females (67.4% and 75%).…”

“…Cluster analysis for the phenotypic classification of skeletal Class III malocclusion is being increasingly used to establish specific sub-phenotypes within the large variations of this malocclusion [ 23 , 24 , 25 , 26 , 27 , 34 , 40 , 41 ]. The establishment of appropriate, specific, distinguishable, and easy-to-use clinical sub-phenotypes would facilitate future studies focused on treatment outcomes, relapse prognosis, or even diagnostic characterization of this particular malocclusion, which may ultimately lead to more appropriate therapeutic protocols for each sub-phenotype.…”

“…Cranial measurements by gender indicate that raw linear measurements are higher in males than in females, whereas the raw values of these measurements are frequently of lower magnitude in males [ 29 , 30 , 31 ]. Due to these differences in total linear size, gender-related sub-phenotypic differences have been found in cases of skeletal Class III malocclusion in the same population [ 28 , 33 , 34 ].…”