Classification and characterization of class III malocclusion in Chinese individuals

Is Incisor Compensation Related to Skeletal Discrepancies in Skeletal Class III? A Retrospective Cephalometric Study

This study investigated compensation in skeletal Class III subjects to compare various severities of abnormal jaws. A retrospective analysis of 137 skeletal Class III cephalograms (63 males and 74 females) was conducted, with cephalometric assessments determining skeletal and dental values. The results were compared with Class I cephalograms. Incisor compensation was examined by pairing normal jaws with varied abnormal jaws, classified by severity using one standard deviation (SD). Statistical analyses included Kruskal-Wallis tests, Bonferroni tests, Spearman's correlations, and multiple linear regression. Four skeletal Class III groups were identified: OMx+PMd, RMx+OMd, OMx+OMd, and PMx+PMd (P = prognathic; O = orthognathic; R = retrognathic; Mx = maxilla; Md = mandible.). The upper central incisor (U1) showed proclination, and the lower central incisor (L1) showed retroclination across all groups except for U1 in PMx+PMd and L1 in OMx+OMd, which exhibited normal inclination. U1 exhibited limited compensation even with progressive maxillary retrognathism, while L1 showed limited compensation after one SD of mandibular prognathism. Maxilla (SNA) and jaw discrepancy (ANB) were inversely related to the U1 degree, whereas only jaw discrepancy (ANB) was positively related to the L1 degree. U1 in PMx+PMd and L1 in OMx+OMd showed no incisor compensation. U1 had limited compensation even with progressive maxillary retrognathism while L1 showed limited compensation after one SD mandibular prognathism.

Effects of eruption guidance appliance in the early treatment of Class III malocclusion

OBJECTIVES

To evaluate the dentoskeletal effects and effectiveness of the eruption guidance appliance in Class III patients in the mixed dentition.

MATERIALS AND METHODS

The experimental group comprised 22 patients with Class III malocclusion and anterior cross-bite (12 males, 10 females, mean age 7.63 ± 0.96 years) treated with the eruption guidance appliance over a mean period of 1.72 ± 0.48 years. The control group comprised 22 untreated subjects (12 males, 10 females, mean age 7.21 ± 0.60 years) with Class III malocclusion. Lateral cephalometric radiographs were obtained at pretreatment (T1) and posttreatment (T2). Intergroup comparisons were performed with Mann-Whitney and t-tests (P < .05).

RESULTS

In the experimental and control groups, the anteroposterior relationship between the maxilla and mandible (ANB angle) remained stable during the treatment period (T1 to T2). The mandibular plane angle decreased in the experimental group and increased in the control group. In the experimental group, the lower anterior face height increase and maxillary molar vertical development were significantly smaller compared to controls. Positive overjet was achieved in 54% of the experimental group.

CONCLUSIONS

The eruption guidance appliance produced no change in the skeletal anteroposterior relationship. The anterior cross-bite/edge-to-edge relationship was corrected in only about half of the treated subjects.

Evaluation of three-dimensional reconstructed palatal morphology in skeletal class III subjects with different vertical patterns using cone beam computed tomography

BACKGROUND

This study aims to evaluate the difference of three-dimensional (3D) reconstructed palatal morphology between subjects with skeletal Class III and skeletal Class I in different vertical patterns using cone beam computed tomography (CBCT).

METHODS

In this study, 89 subjects with skeletal Class III (49 females, 40 males; 25.45 ± 3.81 years) and 85 subjects with skeletal Class I (45 females, 40 males; 23.95 ± 4.45 years) were collected retrospectively and divided into hyperdivergent, normodivergent and hypodivergent groups. Dolphin software was used to reorient the CBCT images of these subjects. After segmenting 3D object of maxilla from the 3D skull by ProPlan software, Geomagic Studio was used to reconstruct 3D palatal morphology and establish an average 3D palatal morphology for each group. The differences of 3D palatal morphology between different groups were compared by deviation patterns on 3D colored map analysis.

RESULTS

3D colored map analysis showed the posterior part of male's palate was higher and wider than that of female's palate in skeletal Class III subjects. In skeletal Class III subjects, males with hyperdivergent pattern had a higher and narrower palate compared with hypodivergent subjects, while females with hyperdivergent had a higher but not obviously narrower palate compared with hypodivergent subjects. In the similar vertical patterns, skeletal Class III subjects had a flatter but not narrower palate compared with skeletal Class I subjects, along with a smaller palate volume.

CONCLUSIONS

This method allows more intuitive between-group comparisons of the differences of 3D palatal morphology. In skeletal Class III subjects, as the vertical dimension increased, the palate tends to be higher and narrower. Therefore, the influence of vertical patterns on the palatal morphology should be fully considered in the orthodontic and orthognathic treatment of skeletal Class III subjects.

East Asian and Southern European craniofacial class III phenotype: two sides of the same coin?

OBJECTIVES

The skeletal class III phenotype is a heterogeneous condition in populations of different ethnicities. This study aimed to analyse the joint and ethnicity-specific clustering of morphological features in skeletal class III patients of Asian and European origins.

MATERIALS AND METHODS

This cross-sectional study involved South Korean and Spanish participants who fulfilled the cephalometric, clinical, and ethnic-related selection criteria. Radiographic records were standardised, calibrated, and measured. A total of 54 skeletal variables were selected for varimax factorial analysis (VFA). Subsequently, a cluster analysis (CA) was performed (mixed method: k-means and hierarchical clustering). Method error and precision were assessed using ICC, Student's t-test, and the Dahlberg formula.

RESULTS

A total of 285 Korean and Spanish participants with skeletal class III malocclusions were analysed. After performing VFA and CA, the joint sample revealed three global clusters, and ethnicity-specific analysis revealed four Korean and five Spanish clusters. Cluster_1_global was predominantly Spanish (79.2%) and male (83.01%) and was characterised by a predominantly mesobrachycephalic pattern and a larger cranial base, maxilla, and mandible. Cluster_2_global and Cluster_3_global were mainly South Korean (73.9% and 75.6%, respectively) and depicted opposite phenotypes of mandibular projection and craniofacial pattern.

CONCLUSIONS

A distinct distribution of Spanish and South Korean participants was observed in the global analysis. Interethnic and interethnic differences were observed, primarily in the cranial base and maxilla size, mandible projection, and craniofacial pattern.

CLINICAL RELEVANCE

Accurate phenotyping, reflecting the complexity of skeletal class III phenotype across diverse populations, is critical for improving diagnostic predictability and future personalised treatment protocols.

Three-dimensional phenotype characteristics of skeletal class III malocclusion in adult Chinese: a principal component analysis-based cluster analysis

BACKGROUND

Skeletal class III malocclusion has a diverse and complicated aetiology involving environmental and genetic factors. It is critical to correctly classify and define this malocclusion to be diagnosed and treated on a clinically sound basis. Thus, this study aimed to provide reliable and detailed measurements in a large ethnically homogeneous sample of Chinese adults to generate an adequate phenotypic clustering model to identify and describe the skeletal variation present in skeletal class III malocclusion.

MATERIALS AND METHODS

This is a retrospective cross-sectional study in which 500 pre-treatments cone-beam computed tomography (CBCT) scans of patients with skeletal class III malocclusion (250 males and 250 females) were selected following specific selection criteria. Seventy-six linear, angular, and ratios measurements were three-dimensionally analysed using InVivo 6.0.3 software. These measurements were categorised into 47 skeletal, 18 dentoalveolar, and 11 soft tissue variables. Multivariate reduction methods: principal component analyses and cluster analyses were used to present the most common phenotypic groupings of skeletal class III malocclusion in Han ethnic group of Chinese adults.

RESULTS

The principal component analysis revealed eight principal components accounted for 72.9% of the overall variation of the data produced from the seventy-six variables. The first four principal components accounted for 53.37% of the total variations. They explained the most variation in data and consisted mainly of anteroposterior and vertical skeletal relationships. The cluster analysis identified four phenotypes of skeletal class III malocclusion: C1, 34%; C2, 11.4%; C3, 26.4%; and C4, 28.2%.

CONCLUSION

Based on three-dimensional analyses, four skeletal class III malocclusion distinct phenotypic variations were defined in a large sample of the adult Chinese population, showing the occurrence of phenotypic variation between identified clusters in the same ethnic group. These findings might serve as a foundation for accurate diagnosis and treatment planning of each cluster and future genetic studies to determine the causative gene(s) of each cluster.

Comparison of alveolar bone width and sagittal tooth angulation of maxillary central incisors in Class I and Class III canine relationships: a retrospective study using CBCT

Background

Canine relationship is a key reference identifying anterior malocclusion and an important implication for evaluating preimplantation bone morphology at maxillary esthetic zone. This study aimed to compare the differences of maxillary central incisor-related measurements (alveolar bone thickness and tooth sagittal angulation) between Class I and Class III canine relationship and further explore the risk factors for immediate implant placement in the anterior maxilla based on cone beam computed tomography (CBCT) data.

Methods

CBCT digital imaging and communications in medicine (DICOM) files of 107 patients (54 with Class I canine relationship and 53 with Class III canine relationship) were collected and the alveolar bone thickness at mid-root (mid-root buccal thickness/MBT; palatal/MPT), apical regions (apical buccal thickness/ABT; palatal/APT) and sagittal angulation (SA) of the maxillary central incisor at the examined side were measured on the mid-sagittal observation plane. Descriptive statistical analysis and frequency distributions of the measurements based on Class I or Class III canine relationship were established. Statistical analyses were performed using Fisher’s exact test, independent samples t test and Pearson correlation test with the significance level set at p < 0.05.

Results

The frequency distributions of maxillary central incisors’ MPT, ABT, APT and SA showed significant differences between Class I and Class III canine relationships (p = 0.030, 0.024, 0.000 and 0.000, respectively). MPT (2.48 ± 0.88 mm vs. 3.01 ± 1.04 mm, p = 0.005), APT (6.79 ± 1.65 mm vs. 8.47 ± 1.93 mm, p = 0.000) and SA (12.23 ± 5.62° vs. 16.42 ± 4.49°, p = 0.000) were significantly smaller in patients with Class III canine relationship. Moreover, SA showed a strong positive correlation with APT (R = 0.723, p = 0.000) and a moderate negative correlation with ABT (R = − 0.554, p = 0.000).

Conclusions

In populations with Class III canine relationship, maxillary central incisors were significantly more labially inclined and have a thinner palatal bone plate at the apex compared with Class I relationship. Clinicians should avoid palatal perforation during immediate implantation at sites of originally protrusive maxillary incisors.

Development of a new category system for the profile morphology of temporomandibular disorders patients based on cephalograms using cluster analysis

Objective

This study aims to develop a new category scheme for the profile morphology of temporomandibular disorders (TMDs) based on lateral cephalometric morphology.

Methods

Five hundred and one adult patients (91 males and 410 females) with TMD were enrolled in this study. Cluster tendency analysis, principal component analysis and cluster analysis were performed using 36 lateral cephalometric measurements. Classification and regression tree (CART) algorithm was used to construct a binary decision tree based on the clustering results.

Results

Twelve principal components were discovered in the TMD patients and were responsible for 91.2% of the variability. Cluster tendency of cephalometric data from TMD patients were confirmed and three subgroups were revealed by cluster analysis: (a) cluster 1: skeletal class I malocclusion; (b) cluster 2: skeletal class I malocclusion with increased facial height; (c) cluster 3: skeletal class II malocclusion with clockwise rotation of the mandible. Besides, CART model was built and the eight key morphological indicators from the decision tree model were convenient for clinical application, with the prediction accuracy up to 85.4%.

Conclusion

Our study proposed a novel category system for the profile morphology of TMDs with three subgroups according to the cephalometric morphology, which may supplement the morphological understanding of TMD and benefit the management of the categorical treatment of TMD.

Multi-disciplinary treatment of maxillofacial skeletal deformities by orthognathic surgery combined with periodontal phenotype modification: A case report

BACKGROUND

Maxillofacial deformities are skeletal discrepancies that cause occlusal, functional, and esthetic problems, and are managed by multi-disciplinary treatment, including careful orthodontic, surgical, and periodontal evaluations. However, thin periodontal phenotype is often overlooked although it affects the therapeutic outcome. Gingival augmentation and periodontal accelerated osteogenic orthodontics (PAOO) can effectively modify the periodontal phenotype and improve treatment outcome. We describe the multi-disciplinary approaches used to manage a case of skeletal Class III malocclusion and facial asymmetry, with thin periodontal phenotype limiting the correction of deformity.

CASE SUMMARY

A patient with facial asymmetry and weakness in chewing had been treated with orthodontic camouflage, but the treatment outcome was not satisfactory. After examination, gingiva augmentation and PAOO were performed to increase the volume of both the gingiva and the alveolar bone to allow further tooth movement. After orthodontic decompensation, double-jaw surgery was performed to reposition the maxilla-mandibular complex. Finally, implant placement and chin molding were performed to restore the dentition and to improve the skeletal profile. The appearance and function were significantly improved, and the periodontal tissue remained healthy and stable.

CONCLUSION

In patients with dentofacial deformities and a thin periodontal phenotype, multi-disciplinary treatment that includes PAOO could be effective, and could improve both the quality and safety of orthodontic-orthognathic therapy.

Characterization of phenotypes of skeletal Class III malocclusion in Korean adult patients treated with orthognathic surgery using cluster analysis

OBJECTIVES

To characterize the phenotypes of skeletal Class III malocclusion in adult patients who underwent orthognathic surgery (OGS).

MATERIALS AND METHODS

The sample consisted of 326 patients with Class III malocclusion treated with OGS (170 men and 156 women; mean age, 22.2 years). Using lateral cephalograms taken at initial visits, 13 angular variables and one ratio cephalometric variable were measured. Using three representative variables obtained from principal components analysis (SNA, SNB, and Björk sum), K-means cluster analysis was performed to classify the phenotypes. Statistical analysis was conducted to characterize the differences in the cephalometric variables among the clusters.

RESULTS

Class III phenotypes were classified into nine clusters from the following four major groups: (1) retrusive maxilla group, clusters 7 and 9 (7.1% and 5.5%; severely retrusive maxilla, normal mandible, severe and moderate hyperdivergent, respectively) and cluster 6 (9.2%; retrusive maxilla, normal mandible, normodivergent); (2) relatively protrusive mandible group, cluster 2 (20.9%; normal maxilla, normal mandible, hyperdivergent); (3) protrusive mandible group, clusters 3 and 1 (11.7% and 15.3%; normal maxilla, protrusive mandible, normodivergent and hyperdivergent, respectively) and clusters 8 and 4 (15.3% and 3.7%; normal maxilla, severe protrusive mandible, normodivergent and hypodivergent, respectively); and (4) protrusive maxilla and protrusive mandible group, cluster 5 (11.4%; protrusive maxilla, severely protrusive mandible, normodivergent). Considerations for presurgical orthodontic treatment and OGS planning were proposed based on the Class III phenotypes.

CONCLUSIONS

Because the anteroposterior position of the maxilla and rotation of the mandible by a patient's vertical pattern determine Class III phenotypes, these variables should be considered in diagnosis and treatment planning for patients who have skeletal Class III malocclusion.

Toxicological Profile of Biological Environment of Two Elastodontic Devices

Malocclusion and teething problems are common health problems globally, affecting people of all ages, especially children and adolescents. In addition to the pathophysiological complications associated with orthodontic problems, they also affect the well-being of the individual. Orthodontic appliances are frequently used, even from an early age, and their activity in different biological environments is very varied and incompletely described. Due to these considerations, the purpose of the study was to evaluate the toxicological profile of the biological environment (saliva at three pH values: 3, 7, and 10) of two elastodontic orthodontic appliances: Myobrace (MB) and LM TrainerTM 2 (LMD). In vitro techniques applied were conducted on human keratinocytes to evaluate cell viability (Alamar blue assay) and gene expression real-time reverse transcription–polymerase chain reaction (RT-PCR technique). In addition, it was assessed the irritating effect on the vascular plexus using as a biological model the chorioallantoic membrane of the hen’s egg by applying the hen’s egg-chorioallantoic membrane (HET-CAM) method. The obtained results showed a decrease in cell viability up to 82% in the case of LMD at pH = 3, a slight increase in mRNA expression for the anti-apoptotic marker (Bcl-2 and Bcl-xL), and a decrease in mRNA expression for the pro-apoptotic marker (Bad), and any type of toxic change at the capillary level (irritation score being below 0.9). Based on the data obtained, it can be stated that MB and LMD biological environments, at different pH values, present a safe toxicological profile.

Genetic factors contributing to skeletal class III malocclusion: a systematic review and meta-analysis

OBJECTIVES

The present systematic review aims to report and critically assess the findings of the available scientific evidence from genetic association studies examining the genetic variants underlying skeletal class III malocclusion and its sub-phenotypes.

MATERIAL AND METHODS

A pre-piloted protocol was registered and followed. The PubMed, Scopus, WOS, Cochrane Library, Gray Open literature, and CADTH databases were explored for genetic association studies following PICOS-based selection criteria. The research was reported in accordance with PRISMA statement and HuGE guidelines. The Q-genie tool was applied to assess the quality of genetic studies. Meta-analysis of genetic association studies was done by means of Meta-Genyo tool.

RESULTS

A total of 8258 articles were retrieved, of which 22 were selected for in-depth analysis. Most of the studies did not differentiate between sub-phenotypes, and the cohorts were heterogeneous regarding ethnicity. Four to five principal components of class III malocclusion explained the phenotypic variation, and gene variants at MYO1H(rs10850110), BMP3(rs1390319), GHR (rs2973015,rs6184, rs2973015), FGF7(rs372127537), FGF10(rs593307), and SNAI3(rs4287555) (p < .05) explained most of the variation across the studies, associated to vertical, horizontal, or combined skeletal discrepancies. Meta-analysis results identified a statistically significant association between risk of class III malocclusion of A allele of the FBN3 rs7351083 [OR 2.13; 95% CI 1.1-4.1; p 0.02; recessive model].

CONCLUSION

Skeletal class III is a polygenic trait substantially modulated by ethnicity. A multicentric approach should be considered in future studies to increase sample sizes, applying multivariate analysis such as PCA and cluster analysis to characterize existing sub-phenotypes warranting a deeper analysis of genetic variants contributing to skeletal class III craniofacial disharmony.

CLINICAL RELEVANCE

Grasping the underlying mechanisms of this pathology is critical for a fuller understanding of its etiology, allowing generation of preventive strategies, new individualized therapeutic approaches and more accurate treatment planification strategies.

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

The main aim of this study was to generate an adequate sub-phenotypic clustering model of class III skeletal malocclusion in an adult population of southern European origin. The study design was conducted in two phases, a preliminary cross-sectional study and a subsequent discriminatory evaluation by main component and cluster analysis to identify differentiated skeletal sub-groups with differentiated phenotypic characteristics. Radiometric data from 699 adult patients of southern European origin were analyzed in 212 selected subjects affected by class III skeletal malocclusion. The varimax rotation was used with Kaiser normalization, to prevent variables with more explanatory capacity from affecting the rotation. A total of 21,624 radiographic measurements were obtained as part of the cluster model generation, using a total set of 55 skeletal variables for the subsequent analysis of the major component and cluster analyses. Ten main axes were generated representing 92.7% of the total variation. Three main components represented 58.5%, with particular sagittal and vertical variables acting as major descriptors. Post hoc phenotypic clustering retrieved six clusters: C1:9.9%, C2:18.9%, C3:33%, C4:3.77%, C5:16%, and C6:16%. In conclusion, phenotypic variation was found in the southern European skeletal class III population, demonstrating the existence of phenotypic variations between identified clusters in different ethnic groups.

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

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.

Subclustering in Skeletal Class III Phenotypes of Different Ethnic Origins: A Systematic Review

OBJECTIVE

We aimed to systematically review articles investigating the efficiency of the clustering of skeletal class III malocclusion phenotypic subtypes of different ethnic origins as a diagnostic tool.

METHODS

The review protocol was structured in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement and registered in Prospero (CRD42016053865). A survey of articles published up to March 2018 investigating the identification of different subgroups of skeletal class III malocclusion via cluster analysis was performed using 11 electronic databases. Any type of study design that addressed the classification of subclusters of class III malocclusion was considered. The Newcastle-Ottawa scale for cohort and cross-sectional (modified) studies was used for quality assessment.

RESULTS

The final selection included 7 studies that met all the criteria for eligibility (% overall agreement 0.889, free marginal kappa 0.778). All studies identified at least 3 different types of class III clusters (ranging from 3 to 14 clusters; the total variation of the prevalence of each cluster ranged from 0.2% to 36.0%). The main shared variables used to describe the more prevalent clusters in the studies included were vertical measurements (Ar-Go-Me: 117.51°-135.8°); sagittal measurements: maxilla (SNA: 75.3°-82.95°), mandible (SNB: 77.03°-85.0°). With regard to ethnicity, a mean number of 8.5 and 3.5 clusters of class III were retrieved for Asian and Caucasian population, respectively.

CONCLUSIONS

The total number of clusters identified varied from 3 to 14 to explain all the variability in the phenotype class III malocclusions. Although each extreme may be too simple or complex to facilitate an exhaustive but useful classification for clinical use, a classification system including 4 to 7 clusters may prove to be efficient for clinical use in conjunction with complete and meticulous subgrouping.

CLINICAL SIGNIFICANCE

The identification and description of a subclustering classification system may constitute an additional step toward more precise orthodontic/orthopedic diagnosis and treatment of skeletal class III malocclusion.