Alveolar and Skeletal Chin Dimensions Associated with Lower Facial Height Among Different Divergent Patterns

Evaluation of Incisor Position in a Sample of Orthodontic Patients

BACKGROUND

To achieve a successful result, the orthodontist must use a systematic approach to plan the orthodontic treatment. Defining the correct position of the upper and lower incisors and evaluating their relationship with intermaxillary discrepancy and facial divergence have been recognized as the starting point for the diagnostic decision regarding extractions and anchorage requirements. The aim of our study was to analyze the relationship between intermaxillary discrepancy (ANPg^), mandibular inclination (SN^GoGn), lip incompetence, and the positioning of the upper and lower incisors (UIPs and LIPs) in a group of orthodontic patients. This retrospective study included 290 lateral cephalograms in 122 males (42.1%) and 168 females (57.9%) aged 8 to 53 years (median 14; interquartile range IQR 12-17). Data were analyzed by means of one-way Analysis of Variance (ANOVA) and linear regression analysis.

RESULTS

This study showed a statistically significant increase in LIP values in patients with lip incompetence (p < 0.001). Moreover, the distribution of LIPs in groups with various SN^GoGn and ANPg^ angles was significantly different (p < 0.001). The regression analysis also showed a positive association between the LIP and SN^GoGn and between the LIP and ANPg^.

CONCLUSION

The LIP presented a statistically significant difference in patients with and without lip incompetence, which varied significantly in subjects with different sagittal malocclusions and vertical face patterns.

Correlation Between Horizontal and Vertical Skeletal Components in Dental Malocclusions Among the Jazan Population

INTRODUCTION

The dentoskeletal morphology of various malocclusions has been analyzed in cephalometric studies. It is important to understand the vertical and horizontal components of orthodontic treatment. To provide accurate treatment, an orthodontist needs to understand the facial types of an individual. This study aims to evaluate a correlation between vertical and horizontal components of skeletal and dental malocclusion by assessing cephalometric radiographs of the population of Jazan province.

METHODS

The cephalometric radiographs of 267 eligible participants were assessed digitally. Fourteen skeletal and dental parameters were used to evaluate the association. Reliability was checked with the intra-class coefficient. Statistical analyses included descriptive statistics and Spearman's rho test. Statistical significance was set at P ≤ 0.05.

RESULTS

Correlations were found between anterior facial height (AFH), posterior facial height (PFH), FH ratio (Jarabak ratio), upper incisor to NA (U1-NA), lower incisor to NB (L1-NB), and upper incisor to the palatal plane (U1/PP). In dental class I, AFH (N-Me) had a strong positive correlation with L1-NB (0.300), U1/PP (0.164), and L1/MP (0.215). In dental class II, AFH negatively correlated with U1-NA (-0.735) and positively correlated with L1-NB (0.292), L1/MP (0.085), and U1-NA. PFH (S-Go) positively correlated with L1-NB (0.525) in class I but negatively correlated in class II. However, a negative relation was observed between all the vertical and horizontal components in class III.

CONCLUSION

This study suggests potential associations between vertical and horizontal components in developing skeletal and dental discrepancies.

The relation between mandibular symphysis and the Angle class in orthodontic treatment

Objectives

Facial perception depends on the different components of the face. The chin is a striking anatomical structure in the individual's identity and mandibular symphysis (MS) shape influences the adjacent soft tissue, determining facial harmony. In lateral cephalometry, the MS corresponds to the image of the mandibular body in its anterior curvature. It shape, inclination and thickness provide valuable information for orthodontic diagnosis and prognosis. Since facial features are associated with malocclusions, the present investigation aims to relate the height, thickness and inclination of the MS using Angle's Class.

Methods

495 lateral incidence cephalograms of an orthodontic population were analyzed using a previously developed and tested software. The sample was randomly selected and the height, thickness and inclination of the MS were measured. The values were statistically analyzed (p ≤ 0.05).

Results

The distribution according to Angle's Class was 48.9% for Class I, 34.7% for Class II Division 1, 7.4% for Class II Division 2 and 8.9% for Class III. The MS height did not't show significant differences between the three dental classes. The MS thickness was significantly increased in Class II Division 2 and Class I subjects (p = 0,037). The MS inclination was significantly less in Class III subjects when compared to Class I and Class II Division 1 (p ≤ 0.001).

Conclusions

The MS presented variations, which may be associated with a natural compensation against malocclusion, influencing the position of the teeth and their relationship with the other dento-craniofacial structures and with consequences on the facial harmony.

Factors associated with the morphology of the mandibular symphysis and soft tissue chin

Objectives:

This study aimed to (I) assess the morphology of the symphysis and soft tissue chin associated with sex, age and sagittal/vertical skeletal patterns, and (II) identify the individual and combined contributions of these variables to different portions of the symphysis.

Methods:

This cross-sectional study included 195 lateral cephalometric radiographs from untreated adults. Alveolar, basal, and soft tissue of the symphysis were measured by an X/Y cranial base coordinate system, and divided in accordance to four predictor variables: sex, age, and sagittal/vertical skeletal patterns. Parametric tests were conducted for comparison and correlation purposes, while multiple regression analysis was performed to explore combined interactions.

Results:

Alveolar inclination is related to sagittal and vertical patterns, and both explained 71.4% of the variations. Alveolar thickness is weakly predicted and poorly influenced by age. Symphysis height was 10% higher in males, and associated with a vertical skeletal pattern and sex, and both explained 43.6% of variations. Basal symphyseal shows an individual thickness, is larger in males, and vertically short-positioned with age. Soft tissue chin is not necessarily related to the size of the underling skeletal pattern, and enlarges with age, even in adulthood.

Conclusions:

The symphysis and surrounding tissues are influenced by sex, age, and sagittal and vertical patterns, acting differently on the alveolar, basal and soft tissue portions. Sagittal and vertical skeletal patterns are the strongest association on alveolar symphysis inclination, whereas sex and age acts on the vertical symphysis position and soft tissues thickness.

Differences in skeletal growth patterns: an exploratory approach using elliptic Fourier analysis

OBJECTIVE

Apply elliptic Fourier analysis to find shape differences among the hypodivergent, normodivergent, and hyperdivergent growth patterns in skeletal classes I, II and, III in mandibular and maxillary curves and evaluate the discriminatory capacity of these differences.

MATERIALS AND METHODS

A total of 626 adult patients were included: 354 Brazilian patients (52 with tomographic information and 302 with radiographic information) and 272 Colombian patients with radiographic information. Lateral views were selected. The maxillary and mandibular curves were digitized. Elliptic Fourier analysis was employed considering with 20 harmonics as well as filtering size, rotation, and translation properties. One-way non-parametric MANOVA was employed to determine differences. A confusion matrix tool was employed to analyze the discriminatory capacity of the model.

RESULTS

Significant shape differences in the mandibular and maxillary contours were found among the hypodivergent, normodivergent, and hyperdivergent growth patterns in classes I, II, and III (p < 0.05). The accuracies obtained from the confusion matrix were respectively 74.1, 79.5, and 90.1% in classes I, II, and III in the mandibular curves and respectively 71.9, 73.9, and 75% in classes I, II, and III in the maxillary curves.

CONCLUSIONS

Elliptic Fourier analysis can be used to find shape differences with an acceptable discriminatory capacity, especially in the mandible contour. Maxillary and mandibular bone curves each significantly defined facial biotypes regardless of the size and position properties.

CLINICAL RELEVANCE

This exploration offers a way to quantify mandibular morphology for the construction of an economic mandibular prediction system applicable to the Latin American population.

Relationship between the maxillofacial skeletal pattern and the morphology of the mandibular symphysis: Structural equation modeling

Objective

The purpose of this study was to investigate the relationship between the facial skeletal patterns and the shape of the mandibular symphysis in adults with malocclusion by using a structural equation model (SEM).

Methods

Ninety adults who had malocclusion and had records of facial skeletal measurements performed using cone-beam computed tomography were selected for this study. The skeletal measurements were classified into three groups (vertical, anteroposterior, and transverse). Cross-sectional images of the mandibular symphysis were analyzed using generalized Procrustes and principal component (PC) analyses. A SEM was constructed after the factors were extracted via factor analysis.

Results

Two factors were extracted from the transverse, vertical, and anteroposterior skeletal measurements. Latent variables were extracted for each factor. PC1, PC2, and PC3 were selected to analyze the variations of the mandibular symphyseal shape. The SEM was constructed using the skeletal variables, PCs, and latent variables. The SEM showed that the vertical latent variable exerted the most influence on the mandibular symphyseal shape.

Conclusions

The relationship between the skeletal pattern and the mandibular symphysis was analyzed using a SEM, which showed that the vertical facial skeletal pattern had the highest effect on the shape of the mandibular symphysis.