Geometric morphometrics of different malocclusions in lateral skull radiographs

Assessing cervical spine and craniofacial morphology in Class II and Class III malocclusions: A geometric morphometric approach

To compare craniofacial and cervical morphology between skeletal Classes II and III applying Geometric Morphometric Methods (GMM). Twenty-six cervical and craniofacial landmarks of 40 Class II and 39 Class III individuals were digitalized on lateral cephalograms. Procrustes ANOVA, generalized Procrustes, principal component analyses, and thin-plate spline function were applied to assess the pattern of shape variation of craniofacial structure and the cervical spine in relation to skeletal classes. Compared with Class III, Class II individuals presented a maxillary protrusion, mandibular retrusion, shorter mandibular corpus, posterior mandibular ramus rotation, anterior cranial base rotation, and a smaller centroid size. Furthermore, a forward and smaller cervical spine were observed. With GMM, the shape and size differences between skeletal classes can be analyzed visually and numerically.

Dynamic Morphological Growth Trajectory of Crouzon Population: A Geometric Morphometric Analysis

This study is to visualize the morphological growth trajectory of the Crouzon population and provide a more comprehensive and perceptual understanding of pathologic aggregation in terms of maxillofacial and soft tissue surfaces. Twenty-two patients with Crouzon syndrome were included in this retrospective surgery. Preoperative computed tomography was segmented into maxillofacial and soft tissue surface morphologies. Fifty-two anatomical landmarks and a standardized template were used to extract the morphological phenotypes and transform them into spatial coordinates. Geometric morphometrics (GM) were applied to visualize the growth trajectory and estimate the morphological variation of the Crouzon population. Cephalometric analysis was conducted to validate the growth trajectory in a clinical aspect. It was found that both maxillofacial and soft tissue surface morphologies were strongly covaried with age. Morphological development of the Crouzon population was characterized by (1) maxillary retrusion and clockwise rotation, (2) mandibular counterclockwise rotation, (3) facial width narrowing and aggregated concave face, and (4) sunken nasal bone. Pathologic maxillary retrusion continuously existed from infancy to adulthood, and rapid aggravation took place at 3 to 6 years old. In conclusion, this study is the first to visualize the dynamic growth trajectories on both maxillofacial and soft tissue surface morphologies. More attention and monitoring of breathing, snoring, intelligence, and global development should be cast on Crouzon patients between 3 and 6 years old in family care. If any functional abnormalities occur during this period, professional consultations and evaluations should be conducted timely to avoid pathologic aggravation. Consistency between GMs and cephalometry validates the reliability of GM potentials in the clinical field, allowing a promising and revolutionary methodology for dynamically and qualitatively analyzing pathologic changes in some rare congenital diseases.

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.

An interpretable machine learning approach to study the relationship beetwen retrognathia and skull anatomy

Mandibular retrognathia (C2Rm) is one of the most common oral pathologies. Acquiring a better understanding of the points of impact of C2Rm on the entire skull is of major interest in the diagnosis, treatment, and management of this dysmorphism, but also permits us to contribute to the debate on the changes undergone by the shape of the skull during human evolution. However, conventional methods have some limits in meeting these challenges, insofar as they require defining in advance the structures to be studied, and identifying them using landmarks. In this context, our work aims to answer these questions using AI tools and, in particular, machine learning, with the objective of relaying these treatments automatically. We propose an innovative methodology coupling convolutional neural networks (CNNs) and interpretability algorithms. Applied to a set of radiographs classified into physiological versus pathological categories, our methodology made it possible to: discuss the structures impacted by retrognathia and already identified in literature; identify new structures of potential interest in medical terms; highlight the dynamic evolution of impacted structures according to the level of gravity of C2Rm; provide for insights into the evolution of human anatomy. Results were discussed in terms of the major interest of this approach in the field of orthodontics and, more generally, in the field of automated processing of medical images.

Gender Dimorphism of Skeletal Measurements and Dental Angle Classification in Orthodontic Patients

AIM

The present study aimed to evaluate gender dimorphism of the skeletal and dental angles and measurements among different types of malocclusions in the Population of Jizan, Kingdom of Saudi Arabia (KSA).

MATERIALS AND METHODS

Cephalometric data were retrieved from the archived records of 272 dental patients, comprising 134 males and 138 females. Skeletal and dental malocclusions in both the sub-groups were digitally studied.

STATISTICAL ANALYSIS

The measurement reliability was assessed using the intra-class correlation coefficient (ICC). Non-parametric Mann-Whitney U tests were performed to evaluate the difference in skeletal and dental parameters between genders. The Chi-square test was done to determine the difference in malocclusion patterns amongst the gender.

RESULTS

Statistical significance was noted in dental malocclusion (p-value = 0.003) and facial height, with females having a steeper mandible plan than males. The Sella-nasion-Nasion-Vertical line angles were reported high in females with no statistical significance. Linear cephalometric values were measured higher in males than females, whereas angular values and facial height parameters were lower in females than male.

CONCLUSION

Within the limitation of this study, it could be concluded that there is a prominent difference measured in facial profiles of males and females with higher facial height in males. Clinical significance and limitations: These clinical outcomes will help orthodontists to analyze the accurate base angles and points to draft proper treatment plans considering the variation in the profile of males and females.

Maxillary dimensions and arch shape with palatally displaced canines

BACKGROUND/OBJECTIVES

The aim of this study was to explore the effect of palatally displaced canines on maxillary dimensions and arch shape.

METHODS

Occlusal and skeletal landmarks were plotted on cone beam computed tomography (CBCT) images of 156 orthodontic patients: 78 with palatally displaced canines (PDC) (27 left, 28 right, and 23 bilateral) and 78 controls using Mimics™ (Materialise, Belgium). Arch forms were created, and arch width, depth, and skeletal dimensions were measured. T-test (P < 0.05) was used to compare the groups. Geometric Morphometrics (GM) analysis was used to compare the groups and to explore the pattern of covariation between two sets of landmarks.

RESULTS

The unilateral PDC group showed an increased first premolar, second premolar, molar widths, and an increased molar depth. No significant difference was found in arch form. The skeletal measurements were generally larger in the PDC group, but the transverse measurements were the most significant. Discriminant Function Analysis (DFA) with cross-validation allowed an accurate classification of 85.9% of the control group and 66.7% of the PDC group. The Mahalanobis distance displayed significant differences among three combinations of groups. Strong covariance was found between the second premolar and all other landmarks.

LIMITATIONS

The small sample sizes of the stratified groups precluded recognition of statistical significance.

CONCLUSIONS

Patients with unilateral PDC displayed significantly wider first, second premolar, and first molar widths, and increased first molar depths. There were no significant differences in arch form; however, GM showed significant differences between the groups and a prominent covariance function for the 2nd premolars.

Soft-Tissue Analysis of Different Sagittal Skeletal Patterns Using the Geometric Morphometric Method

OBJECTIVES

 This study aimed to investigate the size and shape variations of soft-tissue patterns in different sagittal skeletal patterns using the geometric morphometrics method (GMM) obtained from lateral cephalograms.

MATERIALS AND METHODS

 This is a retrospective study, where the sample comprised of 188 Malaysian Malay subjects aged between 18 and 40 years and with different sagittal skeletal patterns. Overall, 71 males and 117 females were gathered for all size and shape analyses. This study incorporated 11 soft-tissue landmarks, which underwent landmark application using tpsDig2 software version 2.31, while the shape analysis was done using MorphoJ software version 1.07a.

STATISTICAL ANALYSIS

 Statistical analyses were performed using IBM SPSS Statistics 26. The result of the analysis of variance (ANOVA) test showed significant differences in some of the parameters between the landmarks. Length D, Length E, Length F, Length H, and Length I showed significant differences (p < 0.05), while other parameters showed no difference (p > 0.05).

RESULTS

 The shape variation of soft-tissue landmarks in different skeletal patterns existed in 18 different dimensions which showed by 18 principal components (PCs). Procrustes ANOVA and canonical variate analysis showed the size and shape differences of soft-tissue patterns between Class II and III and gender groups (p < 0.0001). In discriminant function analysis for Class II subjects, the classification accuracy was 98.4%, whereas subsequent to cross-validation, the classification accuracy was 90.6%. For Class III subjects, the classification accuracy was 96.6%, while after cross-validation, the classification accuracy was 90%.

CONCLUSION

 Different sagittal skeletal patterns demonstrated different soft-tissue shape variations. Class III showed the most protrusive upper and lower lips, while Class II demonstrated the most retrusive lower lip.

Evaluation of maxillary and mandibular growth patterns with cephalometric analysis based on cervical vertebral maturation: A Japanese cross-sectional study

Background

Appropriate maxillofacial growth and development evaluation is important for effective orthodontic treatment. Growth evaluation is based on physiological age determined by individual development, but not chronological age. One strategy for determining physiological age is using the cervical vertebral bone age.

Objectives

This study aimed to clarify the standard size of the upper and lower jawbones in Japanese patients using the cervical vertebral maturation stages (CVMS) as an index and clarify the growth pattern. And to use the cervical spine age as a diagnostic aid in orthodontic treatment.

Material and methods

Random sampling was performed from the outpatients who visited the Orthodontics department, Tokyo Medical and Dental University Dental Hospital, and 400 patients were enrolled before treatment. Lateral cephalometric radiographs were obtained to measure the height and length of the mandible and the maxilla length with cephalometric analysis. Standard values were calculated for each cervical-spine-age group to analyze changes during mandibular and maxillary growth. Furthermore, we compared the differences between males and females. The Kruskal–Wallis test was used to compare cervical-spine-age groups, and the Steel–Dwass test was used for multiple comparisons. The reliability of CVMS was confirmed by calculating the weighted kappa coefficient (κ).

Results

κ for the degree of intra-evaluator agreement and the degree of the inter-evaluator agreement were calculated, and both indicated almost perfect agreement. We found that the distance between the anterior nasal spine (ANS) and posterior nasal spine (PNS) (i.e., ANS–PNS) increased significantly between CVMS II and CVMS III in males. The distance between Articulare (Ar) and Gonion (Go) (i.e., Ar–Go) and the distance between Go and Pogonion (Pog) (i.e., Go–Pog) increased significantly between CVMS III and CVMS IV in males.

Conclusion

The findings suggested that CVMS is a reliable indicator of the growth stage of the maxilla and mandible.

Mandibular shape prediction model using machine learning techniques

OBJECTIVE

To create a mandibular shape prediction model using machine learning techniques and geometric morphometrics.

MATERIALS AND METHODS

Six hundred twenty-nine radiographs were used to select the most appropriate craniomaxillary variables in different craniofacial pattern classifications using a support vector machine. To obtain the three-dimensional mandibular shape, a Procrustes fit was used on 55 tomograms, in which 17 three-dimensional landmarks were digitized. A partial least square regression was employed to find the best covariation between craniomaxillary angles and the symmetric components of mandibular shape. The model was applied to a new sample of six tomograms and evaluated by the mean absolute error. Each mandible predicted was assessed using the Hausdorff distance (HDu) and a color scale. The model was also exploratively applied to six new radiographs.

RESULTS

Covariation was 88.66% with a significance of < 0.0001 explained by twelve craniomaxillary variables. Low differences between the original and predicted models were obtained, with a mean absolute error of 0.0143. The mean distance between meshes ranged from 0.0033 to 0.0059 HDu and each color scale demonstrated general similarity between the surfaces.

CONCLUSIONS

This approach offered promising results in obtaining a mandibular prediction model that enhances shape properties in an economical way and is applicable to a Latin American population. Clinical proof of this method will require further studies with larger samples.

CLINICAL RELEVANCE

This method offers a reliable, economic alternative to traditional mandibular prediction methods and is applicable to the Latin American population.

A geometric morphometric evaluation of facial hard tissue patterns

OBJECTIVE:

The purpose of this study was to investigate the size and shape variations of hard tissue patterns in different skeletal relations in Malaysian Malay subjects using the two-dimensional geometric morphometrics method.

MATERIALS AND METHODS:

A total of 188 lateral cephalograms of adult Malay subjects (aged between 18 and 40 years) with Class I, II, and III skeletal relations were collected. Ten two-dimensional hard tissue landmarks were applied on lateral cephalograms which underwent landmark application and shape analyses as Procrustes ANOVA analysis, principal component analysis, canonical variate analysis, and discriminant function analysis. Statistical analyses were performed to find the mean and variance of each landmark using one-way ANOVA. The raw data from shape analysis were used to calculate the link between landmarks.

RESULTS:

Skeletal relations showed 16 Principal Components which indicated that variances existed in 16 different dimensions. In Procrustes ANOVA, the Centroid size was significantly different in genders and skeletal relations (P < 0.01). Canonical variate analysis showed the highest Mahalanobis distances and Procrustes distances between Class II and III among skeletal relations and between gender groups (P < 0.0001). Discriminant function analysis showed the classification was mostly accurate, especially for Class II and Class III with success rates of 90.6% and 83.3%, respectively, after cross-validation. The statistical analysis showed significant differences (P < 0.05) in hard tissue landmarks.

CONCLUSION:

There were different ANB angles in different skeletal relations. The GMM could be used as an alternative tool for diagnosis and treatment planning for craniofacial shape evaluations for future orthodontists and maxillofacial surgeons.

Palatal vault morphometric analysis of the effects of two early orthodontic treatments in anterior open bite growing subjects: a controlled clinical study

Background

The purpose of this study was to evaluate the palatal morphological changes in Anterior Open Bite (AOB) pre-pubertal subjects treated with Rapid Maxillary Expansion and Bite-Block (RME/BB) or Quad Helix with crib (QH/C) when compared with a Control Group (CG) by using Geometric Morphometric Analysis (GMM).

Methods

AOB group (AOBG) included 30 subjects (20 females, 10 males, mean age 8.1 ± 0.8ys) with dentoskeletal AOB. AOBG was divided in two subgroups according to the treatment strategy: RME/BB group (RME/BBg) included 15 subjects (10 females, 5 males, QH/C group (QH/Cg) comprised 15 subjects (10 females, 5 males). The two subgroups were compared with a CG of 15 subjects (10 females, 5 males) matched for sex, age, vertical pattern, and observation period. Digital upper dental casts were collected before treatment (T1) and at the end of the active treatment (T2). Landmarks and semilandmarks were digitized on dental casts and GMM was applied. Procrustes analysis and principal component analysis (PCA) were performed.

Results

At T2, RME/BBg when compared with QH/Cg evidenced no statistically significant differences. Instead, RME/BBg showed an increased maxillary transverse dimension and a decreased palatal depth when compared with CG. The comparison QH/Cg vs. CG demonstrated a slight transversal maxillary expansion.

Conclusions

RME/BBg showed significant changes in the transversal and vertical dimensions with a clear maxillary expansion and a decrease of the palatal depth when compared with QH/Cg and CG. QH/Cg showed a significant slight maxillary expansion and no variation in vertical and sagittal planes when compared with CG.

The Expanding Role of Geometric Morphometrics in Craniofacial Surgery

INTRODUCTION

Geometric morphometrics (GM) is an advanced landmark-based quantitative method used to study biological shape and form. Historically, GM has been limited to non-biomedical fields such as comparative biology; however, this technique confers advantages over traditional cephalometric methods, warranting a review of current applications of GM to human craniofacial disorders.

METHODS

The RISmed package was used to extract metadata associated with PubMed publications referencing GM analysis techniques in craniofacial and reconstructive surgery. PubMed search terms included "geometric AND morphometric AND craniofacial;" and "geometric AND morphometric AND reconstructive surgery." Duplicate search results were eliminated.

RESULTS

Search yielded 139 studies between 2005 and 2020, of which 27 met inclusion criteria. Human craniofacial studies constituted 2% of all queried GM studies. Among these, cleft lip and palate were the most commonly studied craniofacial conditions (7 studies, 26%), followed by sagittal craniosynostosis (4 studies, 15%). Seventeen studies (63%) used GM to assess skeletal structures, seven studies (26%) examined both skeletal and soft tissues, and three studies (11%) analyzed soft tissues only. Eleven studies (40.1%) employed a GM approach to evaluate postoperative changes in craniofacial morphology. Two studies (7%) systematically compared GM analysis with conventional shape measurements.

CONCLUSION

The ability to study shape while controlling for variability in structure size and imaging technique make GM a promising tool for understanding growth patterns in complex craniofacial diseases. Furthermore, GM overcomes many limitations of traditional cephalometric techniques, and hence may claim an expanded role in the study of human craniofacial disorders in clinical and research settings.

Shape differences among symmetrically shaped skeletal growth patterns in a panoramic view: a Fourier analysis

The objective of this study was to apply elliptic Fourier analysis (EFA) to find shape differences among skeletal growth patterns in both radiographic and tomographic panoramic views, controlling for asymmetry. Lateral and panoramic images were obtained from 350 patients. After screening patients with asymmetric linear and angular values and natural asymmetric hemimandibular shape, 240 patients were included in the study: 48 with tomographic information and 192 with radiographic information. The images were classified according to the mandibular plane angle and the ANB angle. Mandibular contours were digitized on the panoramic images and EFA was performed with 20 harmonics, filtering rotation, translation and size properties. As there were no differences between radiographic and tomographic panoramic mandibular contours and normal distribution was found in all groups, MANOVA was conducted to determine differences using a Hotelling's p-values with Bonferroni correction and an XY graph tool was applied to visualize these differences graphically. A 95% confidence level was used. Significative differences were found among hypodivergent, normodivergent, and hyperdivergent patterns in Class I, II, and III (p < 0.05), located mainly in the symphyseal region. The results of this study suggest that EFA is a useful tool to mathematically analyze mandibular contours and their morphological differences given by facial biotypes. This method could improve the precision of the mandibular prediction models.

Changes in mandibular shape after early treatment in subjects with open bite: a geometric morphometric analysis

OBJECTIVES

To evaluate the mandibular modifications in anterior open bite (OB) growing subjects treated with Rapid Maxillary Expansion and bite block (RME/BB) or Quad Helix with crib (QH/C) when compared with a Control Group (CG) by using Geometric Morphometric Method (GMM) and conventional cephalometric.

MATERIALS

The OB group comprised 34 subjects (26 girls, 8 boys) with dentoskeletal OB and a mean age of 8.0 ± 1.0 years. OB group was divided in two subgroups: RME/BB group comprised 17 subjects (13 girls, 4 boys), while QH/C group included 17 subjects (13 girls, 4 boys). The two subgroups were compared with a CG of 17 subjects (13 girls, 4 boys) matched for sex, age, vertical pattern, and observation periods. Two consecutives lateral cephalograms were available: the first one was taken before treatment (T1), and the second one was acquired at a follow-up observation at least 4 years after the completion of treatment (T2). Landmarks and semilandmarks were digitized on lateral cephalograms and GMM was applied. Procrustes analysis and principal component analysis were performed. Analysis of variance (ANOVA) with Tukey post hoc tests was used to compare the T2-T1 cephalometric changes between the RME/BB, QH/C, and CG.

RESULTS

In the long term, RME/BB showed a significantly greater decrease of the Condylar axis to mandibular plane angle when compared to CG and QH/C. GMM showed an increased in height of the mandibular ramus in RME/BB group with tendency to counterclockwise rotation of the mandible when compared with QH/C and CG groups.

CONCLUSIONS

RME/BB subjects showed significant changes in the shape of the mandibular ramus with a counterclockwise rotation tendency when compared with QH/C and CG subjects.

Mandibular shape prediction using cephalometric analysis: applications in craniofacial analysis, forensic anthropology and archaeological reconstruction

Background

The human mandible is variable in shape, size and position and any deviation from normal can affect the facial appearance and dental occlusion.

Objectives

The objectives of this study were to determine whether the Sassouni cephalometric analysis could help predict two-dimensional mandibular shape in humans using cephalometric planes and landmarks.

Materials and methods

A retrospective computerised analysis of 100 lateral cephalometric radiographs taken at Kingston Hospital Orthodontic Department was carried out.

Results

Results showed that the Euclidean straight-line mean difference between the estimated position of gonion and traced position of gonion was 7.89 mm and the Euclidean straight-line mean difference between the estimated position of pogonion and the traced position of pogonion was 11.15 mm. The length of the anterior cranial base as measured by sella-nasion was positively correlated with the length of the mandibular body gonion-menton, r = 0.381 and regression analysis showed the length of the anterior cranial base sella-nasion could be predictive of the length of the mandibular body gonion-menton by the equation 22.65 + 0.5426x, where x = length of the anterior cranial base (SN). There was a significant association with convex shaped palates and oblique shaped mandibles, p = 0.0004.

Conclusions

The method described in this study can be used to help estimate the position of cephalometric points gonion and pogonion and thereby sagittal mandibular length. This method is more accurate in skeletal class I cases and therefore has potential applications in craniofacial anthropology and the ‘missing mandible’ problem in forensic and archaeological reconstruction.

Effects of Multi-Generational Soft Diet Consumption on Mouse Craniofacial Morphology

Variations in craniofacial morphology may arise as a result of adaptation to different environmental factors such as soft diet (SD), which lessens functional masticatory load. Prior studies have shown that changes in the masticatory muscle function associated with a switch to short-term SD led to changes in craniofacial morphology and alveolar bone architecture. However, the long-term effects of SD and the associated adaptive changes in craniofacial shape are unclear. Our novel study set out to profile prospective skull changes in mice fed with SDs over multiple generations using three-dimensional (3D) geometric morphometric analysis (GMA). Our results revealed that short-term SD consumption led to a significant decrease in craniofacial size, along with numerous shape changes. Long-term SD consumption over 15 continuous generations was not associated with changes in craniofacial size; however, shape analysis revealed mice with shortened crania and mandibles in the anteroposterior dimension, as well as relative widening in the transverse dimension compared to the average shape of all mice analyzed in our study. Moreover, changes in shape and size associated with different functional loads appeared to be independent - shape changes persisted after diets were switched for one generation, whereas size decreased after one generation and then returned to baseline size. Our study is the first to study the role of prolonged, multi-generational SD consumption in the determination of craniofacial size and shape.

Geometric morphometric analysis of malocclusion on lateral cephalograms in Malaysian population

Geometric morphometrics is a new approach for shape identification in diagnosis of malocclusion. Lateral cephalogram is an X-ray that taken for diagnosing malocclusion in dental setting. The aim of this study was to determine the differences of craniofacial shape in malocclusion by application of two-dimensional geometric morphometrics and to compile the database of malocclusion in adult Malaysian population. Lateral cephalogram radiographs of 381 adults Malaysia (age 18-45) were retrieved retrospectively and assigned to three groups according to their occlusion: class I, class II, and class III. The geometric morphometric shape study incorporated nine landmarks and was analyzed in details using tpsUtil p software. Geometric morphometric analysis such was done using MorphoJ software. The results of the principal component's analysis (PCA) yielded 14 main components responsible for 100% of the variation exhibited by the malocclusion with three highly significant PCA. The highest Mahalanobis distances were exhibited by the malocclusion class II and III population. The Procrustes ANOVA showed that the shape effect was highly significant (P<0.01). The discriminant function analysis showed the high percentage of 80% discriminate among the malocclusions after cross-validation. There are significant differences for ANB angle (A point-Nasion-B point) in all malocclusion groups. Class II has the widest ANB angle while class III has the most acute ANB angle. Skeletal shape was clearly associated with dental malocclusion and showed considerable variation. Geometric morphometrics is an alternative research tool and can be used for diagnosing individual classification of malocclusion.

Morphometric analysis of sella turcica in growing patients: an observational study on shape and dimensions in different sagittal craniofacial patterns

The aim of this study was to evaluate the differences in sella dimensions and shape between growing patients with Class I, Class II, and Class III skeletal malocclusions, evaluated through morphometric analysis. Seventy-eight subjects aged between 9 and 13 years were selected and assigned to either the Class I, Class II, or Class III groups according to the measured ANB angle (the angle between the Nasion, skeletal A-point and skeletal B-point). Six landmarks were digitised to outline the shape of the sella turcica. Linear measurements of the sella length and depth were also performed. Procrustes superimposition, principal component analysis, and canonical variate analysis were used to evaluate the differences in sella shape between the three groups. A one-way MANOVA and Tukey’s or Games-Howell tests were used to evaluate the presence of differences in sella dimensions between the three groups, gender, and age. The canonical variate analysis revealed a statistically significant difference in sella shape between the Class I and the Class II groups, mostly explained by the CV1 axis and related to the posterior clinoidal process and the floor of the sella. No differences were found regarding linear measurements, except between subjects with different age. These differences in sella shape, that are present in the earlier developmental stages, could be used as a predictor of facial growth, but further studies are needed.

Dentoalveolar compensation in different anterioposterior and vertical skeletal malocclusions

Background

To evaluate the position and inclination of maxillary and mandibular incisors in adults with different anteroposterior and vertical skeletal malocclusions.

Material and Methods

In this retrospective study, lateral cephalometry of 272 adults (134 males and 138 females) who met the selection criteria were digitally analyzed. They were classified based on both linear and angular measurements, anterioposteriorly into skeletal Class I, Class II and Class III and vertically into hypodivergent, normodivergent and hyperdivergent individuals. Sixteen linear and angular measurements were used to assess both positions and inclinations of maxillary base, mandibular base, maxillary incisors, mandibular incisors, and inter-incisors relationship. Descriptive statistics were calculated and presented. The intra-class correlation coefficient (ICC) was applied for the reliability of measurements. Pearson correlation was used to present the degree of correlation between all variables. A P value of < 0.05 was considered significant.

Results

There was a significant correlation between anteroposterior skeletal discrepancy and maxillary and mandibular dentoalveolar compensation (P<0.001). There was significant correlation between vertical skeletal discrepancy and maxillary and mandibular dentoalveolar compensation except for maxillary incisor position. Anterioposterior skeletal jaw position had greater significant effect on the dentoalveolar changes than the vertical skeletal jaw inclination did with variant degree.

Conclusions

There may be an association between dentoalveolar changes and the skeletal anteroposterior and vertical positions, inclinations and intermaxillary relation. Key words:Dentoalveolar compensation, anteroposterior, vertical, skeletal malocclusions, Cephalometry.

Association of anterior and posterior occlusal planes with different Angle and skeletal classes in permanent dentitions : A lateral cephalometric radiograph study

Objectives

Malocclusions affect about two-thirds of the population and orthodontic treatment is justified in 65% of these. However, the associations between anterior and posterior occlusal plane (AOP, POP) inclinations and Angle classification are lacking.

Patients and methods

In a retrospective study, lateral cephalometric radiograph tracings of 230 previously untreated Caucasians, aged 13 to 49 years, yielded inclines of the bisector occlusal plane, AOP, and POP. All inclinations were referenced to the Sella-Nasion line and the Frankfort horizontal and were assigned to the Angle classification as well as skeletal groups (retrognathic, neutral, prognathic). Quantile regressions were calculated.

Results

In the skeletal groups the angles between Sella-Nasion line and both AOP and POP were significantly different between the groups (p < 0.01), showing steep inclines in skeletal class II and flat inclines in skeletal class III. The angles Frankfort horizontal-to-POP and Frankfort horizontal-to-AOP showed the same trends but only the latter differed significantly between the groups (p = 0.02). Among the Angle groups, AOP inclinations did not differ significantly for both reference planes whereas POP inclinations were significantly different (p = 0.01 to Frankfort horizontal, p = 0.02 to Sella-Nasion). Angle class I patients showed the flattest POP.

Conclusion

Occlusal plane inclines, measured to Sella-Nasion, were more consistent than those referenced to Frankfort horizontal. Sella-Nasion related anterior and posterior occlusal plane inclinations were steep in skeletal class II and flat in skeletal class III patients over all quantiles. Using the Angle classification, anterior and posterior occlusal plane inclinations did not follow this principle.

Influence of anthropometry, TMD, and sex on molar bite force in adolescents with and without orthodontic needs

PURPOSE

Bite force has been studied as representative of functional indices of mastication and its value may have diagnostic significance in disorders of the musculoskeletal system of facial bones. This study aimed to evaluate bite force in adolescents with and without orthodontic needs considering presence of temporomandibular disorders (TMD) as well as anthropometry: craniofacial dimensions and body mass index (BMI).

METHODS

A total of 80 subjects were screened (61 females, 19 males; 18 ± 3 years old). Unilateral molar bite force was measured using a digital dynamometer with a fork thickness of 12 mm. Direct anthropometry was used to quantify craniofacial measurements. Dental Health Component of the Index of Orthodontic Treatment Need (IOTN-DHC) and the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were used to classify samples according to malocclusion and to TMD, respectively. Data were analyzed using normality tests, Mann-Whitney U test, and multiple linear regression analyses with stepwise backward elimination, controlling for the presence of malocclusion and TMD (p ≤ 0.05).

RESULTS

The cephalic index was greater in females with malocclusion and the longitudinal cranial diameter was reduced in females with malocclusion. BMI was not different between normal and malocclusion groups for either gender. Bite force was negatively related with vertical dimension of the face, and positively related with facial width and facial index. The model explained 32% of bite force variability, considering the sample size (coefficient of determination R ² = 0.324).

CONCLUSIONS

Even when orthodontic needs and TMD signs and symptoms are present, stronger bite force is still observed in males and in subjects with smaller anterior facial heights and wider facial widths.