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

Leixuri De Frutos-Valle,José Antonio Alarcón,Ricardo Ortega,Conchita Martín,Juan Carlos Palma-Fernández,Alejandro Iglesias-Linares

doi:10.3390/jcm9093048

Leixuri De Frutos-Valle, José Antonio Alarcón + Show 4 more

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https://doi.org/10.3390/jcm9093048

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Abstract

Current phenotypic characterizations of Class III malocclusion are influenced more by gender or ethnic origin than by raw linear skeletal measurements. The aim of the present research is to develop a Class III skeletal malocclusion sub-phenotype characterization based on proportional cranial measurements using principal component analysis and cluster analysis. Radiometric data from 212 adult subjects (115 women and 96 men) of southern European origin affected by Class III skeletal malocclusion were analyzed. A total of 120 measurements were made, 26 were proportional skeletal measurements, which were used to perform principal component analysis and subsequent cluster analysis. The remaining 94 supplementary measurements were used for a greater description of the identified clusters. Principal component analysis established eight principal components that explained 85.1% of the total variance. The first three principal components explained 51.4% of the variance and described mandibular proportions, anterior facial height proportions, and posterior–anterior cranial proportions. Cluster analysis established four phenotypic subgroups, representing 18.4% (C1), 20.75% (C2), 38.68% (C3), and 22.17% (C4) of the sample. A new sub-clustering of skeletal Class III malocclusions that avoids gender influence is provided. Our results improve clinicians’ resources for Class III malocclusion and could improve the diagnostic and treatment approaches for this malocclusion.

Highlights

Skeletal Class III malocclusions are among the most challenging malocclusions to treat, first because of the complexity of achieving an optimal treatment outcome [1,2,3] and second, because the clear genetic component determines the prognosis of this type of malocclusion [4,5,6,7,8,9]
Apart from absolute prevalence rates, clear indicators of the complexity and importance of this malocclusion are the fact that more than half the patients undergoing orthognathic surgery have skeletal Class III malocclusion and that it carries the highest need-for-correction score according to the index of the need for functional orthognathic treatment (IOFTN) [18,19,20,21,22]
The aim of the present research is to characterize Class III skeletal malocclusion sub-phenotypes on the basis of proportional cranial measurements using principal component analysis and cluster analysis

Summary

Introduction

Skeletal Class III malocclusions are among the most challenging malocclusions to treat, first because of the complexity of achieving an optimal treatment outcome [1,2,3] and second, because the clear genetic component determines the prognosis of this type of malocclusion [4,5,6,7,8,9]. 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]

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