Shape variation and covariation of upper and lower dental arches of an orthodontic population

The Relationship between Unilateral Palatal Maxillary Canine Impaction and the Morphology of the Maxilla: A CBCT Study in Eastern Province of Saudi Arabia

OBJECTIVE

 This study aimed to examine the correlation between the morphology of the maxilla and unilateral palatally impacted maxillary canine (PIMC) among the Saudi population in the Eastern Province of Saudi Arabia.

MATERIALS AND METHODS

In this retrospective study, 36 patients' records [(17 PIMC, 8 male, 9 female, mean age 16.75 ± 2.12 years) (19 control; 9 male,10 female, mean age: 17.16 ± 2.12 years)] were included from a teaching dental hospital. On cone-beam computed tomographic images, measurements of maxillary arch length (MAL), palatal vault depth (PVD), intermolar width, sum of widths of 4 maxillary incisors, available arch space (AAS), palatal maxillary width (PMW) in the molar and premolar regions, nasal cavity width (NCW), maxillary arch shape (MAS) (arch length/intermolar width x 100), and palatal vault shape (PVS) (the PVD/intermolar width x100) were performed. Data were analyzed by SPSS-20.0. p-value less than or equal to 0.05 reflected statistical significance.

RESULTS

 This study's findings depicted that AAS (p = 0.012), PVD (p = 0.028), and PMW in the molar and premolar regions at the level of the alveolar crest (p = 0.002 and p = 0.034) and mid-root (p = 0.004 and p = 0.022) were significantly higher in the control compared to the PIMC group. PVS showed a significant difference between the PIMC and control groups (p = 0.037). However, regarding MAS, no significant difference was observed (p = 0.707).

CONCLUSION

 MAS was narrower in PIMC compared to the control group. The control group had a deeper palatal vault and greater AAS compared to the PIMC group. However, no significant difference was observed between groups regarding tooth size or NCW.

Palatal shape covariation in extraction versus nonextraction borderline patients: A geometric morphometric study

INTRODUCTION

This study aimed to evaluate changes in palatal shape after orthodontic treatment from a borderline sample of extraction and nonextraction patients with a Class I relationship.

METHODS

A borderline sample regarding premolar extractions was obtained through discriminant analysis and comprised 30 nonextraction and 23 extraction patients. The digital dental casts of these patients were digitized with 3 curves and 239 landmarks placed on the hard palate. Procrustes superimposition and principal component analysis were implemented to assess group shape variability patterns.

RESULTS

The success of the discriminant analysis in identifying a borderline sample regarding the extraction modality was validated using geometric morphometrics. Concerning palatal shape, no sexual dimorphism was found (P = 0.78). The first 6 principal components that were statistically significant accounted for 79.2% of the total shape variance. Palatal changes were 61% more pronounced in the extraction group, which exhibited a decrease in palatal length (P = 0.02; 10,000 permutations). In contrast, the nonextraction group showed an increase in the palatal width (P <0.001; 10,000 permutations). Intergroup comparisons indicated that the nonextraction group exhibited longer palates, whereas the extraction group exhibited higher palates (P = 0.02; 10,000 permutations).

CONCLUSIONS

Considerable changes in palatal shape were seen for the nonextraction and extraction treatment group, with the latter exhibiting more pronounced changes, mainly in terms of palatal length. Further investigations are needed to clarify the clinical significance of the palatal shape changes in borderline patients after extraction and nonextraction treatment.

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.

Morphological Comparison of the Maxillary Arch in Buccal and Palatal Canine Impaction among Asian Population of Gujarati Origin: A Hospital-Based Study

Aim: To estimate the differences in the maxillary arch morphology in buccal and palatal canine impaction in an Asian population of Gujarati origin. Methodology: An institutional ethics committee’s approval was acquired before the commencement of this study. Sixty subjects were enrolled in the study. Thirty subjects (20 females and 10 males) had a maxillary impacted canine either buccal or palatal and thirty control group participants were selected aged 13 to 18 years who sought orthodontic treatment at the tertiary health care center in Ahmedabad, Gujarat, in western India. Routine pre-treatment radiographs and dental plaster models with good anatomic details were recorded. Measurements of the inter-molar width, palatal depth, arch length, sum of the mesio-distal width of the upper incisors, and available arch space were recorded from prepared orthodontic study models using digital vernier calipers with an accuracy of 0.01 mm and brass wire. The ratio of palatal depth to inter-molar width (Ratio 1), arch length to inter-molar width (Ratio 2), and width of the maxillary incisors to available arch space (Ratio 3) were also secondarily calculated. Data were analyzed using Statistical Package for Social Sciences (SPSS) version 21, IBM Inc. The normality of the data was assessed by the Shapiro−Wilk test. As the data was found to be normally distributed, bivariate analyses were also performed (one-way ANOVA test, Bonferroni post hoc correction). The level of statistical significance was set at a p-value less than 0.05. Results: The comparison of the inter-molar width, palatal depth, arch length, sum of the mesio-distal width of the upper incisors, available arch space, Ratio 1, Ratio 2, and Ratio 3 among controls and subjects with buccal and palatal canine impaction showed overall significant differences in the inter-molar width, palatal depth, arch length, sum of the mesio-distal width of the upper incisors, and available arch space when compared using one-way ANOVA as p < 0.05. Ratios 1, 2, and 3 also showed significant differences between the buccal and palatal canine impaction. Conclusion: An inadequate arch length (p < 0.0001) and a higher degree of crowding with reduced available arch space (p < 0.0001) may be considered as early risk factors for buccal maxillary canine impaction. An inadequate inter-molar width (p < 0.0001), and an increased palatal depth (p < 0.0001) with a clinically reduced mesiodistal width of the sum of maxillary incisors may be considered as risk factors for palatal maxillary canine impaction in an Asian population of Gujarati origin.

Accuracy of dental arch form in customized fixed labial orthodontic appliances

INTRODUCTION

This study evaluated arch form accuracy with or without premolar extraction in customized fixed labial orthodontic appliance treatment.

METHODS

Setup and posttreatment digital models of 27 samples (15 extractions and 12 nonextractions) were selected and superimposed by best-fit surface-based registration in both the maxilla and the mandible. The facial axis points were identified and converted into Cartesian coordinates. A sixth-order polynomial equation was used to fit dental arches. Arch discrepancies (the mean distance between 2 arch forms) and similarities were compared between extraction and nonextraction groups, maxilla and mandible, and anterior and posterior arches.

RESULTS

The arch discrepancy between extraction and nonextraction groups showed no statistically significant difference, but a statistically significant difference in arch similarity was found in the mandible. There were statistically significant differences between anterior and posterior arch discrepancies in the extraction (mandible) and the nonextraction (maxilla and mandible) groups. However, no statistically significant correlation was shown between anterior and posterior arch discrepancies. The arch similarities were 96.18% and 97.38% in the maxilla and 96.01% and 97.49% in the mandible between extraction and nonextraction groups. Arch form discrepancies and similarities showed a moderate correlation but no statistically significant differences between the maxilla and the mandible.

CONCLUSIONS

In customized fixed labial orthodontic appliance treatment, arch form setup can be accurately achieved with and without premolar extraction. Anterior arch form acquires fewer discrepancies than the posterior arch, and overcorrection should be added to the end of the customized archwire to reduce posterior arch discrepancies. The discrepancy of the maxillary and mandibular arches is interrelated, and adjustments should be made on both maxillary and mandibular archwires to correct single-jaw transverse malposition.

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.

Fully automated estimation of arch forms in cone-beam CT with cubic B-spline approximation: Evaluation of digital dental models with missing teeth

BACKGROUND AND OBJECTIVE

To evaluate the automatic determination method for the arch form in cone-beam computed tomography (CBCT) images with cubic B-spline approximation on digital dental models using various types of missing teeth.

METHODS

The maxilla and mandible from eight dental CBCT images with Class I occlusion and no missing teeth were used in this study. The dental arch determination algorithm using cubic B-spline approximation was modified by applying a smoothing function for reliable curve fitting to the digital dental models with various types of missing teeth. For evaluation, 31 scenarios with missing teeth were simulated, and cases with 1-8 missing teeth were divided into three groups: solitary, consecutive, and multiple (more than 4) missing teeth. The prediction accuracies of the dental arch forms were evaluated through comparisons with the gold standards for the digital dental models by two expert orthodontists.

RESULTS

The distance errors between the gold standards and the estimated results of the dental arch forms in all types of models were 0.237-1.740 mm. The mean distance errors of the solitary, consecutive, and multiple groups were 0.436 ± 0.124 mm (0.237-0.964 mm), 0.591 ± 0.250 mm (0.256-1.482 mm), and 0.679 ± 0.310 mm (0.254-1.740 mm), respectively.

CONCLUSIONS

The algorithm for predicting the arch form functioned reliably, even for digital dental models with various types of missing teeth, and could be applied to digital dentistry for applications such as orthodontic tooth setup, artificial tooth arrangement for denture fabrication, and implant guides.

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.

Morphometric analysis of the palatal shape and arch dimension in subjects with buccally displaced canine

OBJECTIVES

To analyse morphological variations of the palate shape and maxillary arch dimension between a group of subjects with unilaterally or bilaterally buccally impacted maxillary canines and a control group (CG) by means of 3D geometric morphometric (GMM).

MATERIALS

Pre-treatment records of 50 subjects (16 males and 34 females; mean age 13.9 years ± 1.8) with one or both canines buccally displaced were collected retrospectively. A CG of 50 subjects was selected from a list of orthodontic patients at the same dental hospital. The experimental group, buccally displaced canine (BDC) was divided in two groups: unilateral buccally displaced canine (UBDC) and bilateral buccally displaced canine (BBDC). To analyse the palate's shape and maxillary arch dimension, study casts were scanned. To study the entirety of the palatal shape, 3D GMM analysis was used. To analyse the maxillary arch dimension, the virtual three-dimensional models were measured with a specific software (VAM, Vectra, Canfield Scientific, Fairfield, New Jersey, USA).

RESULTS

When comparing the groups with the GMM analysis, patients with BDC showed a statistically significant narrower and higher palatal vault. About the analysis of linear measurements, the intercanine width, the anterior and posterior segment length were significantly smaller in BDC, UBDC, and BBDC subjects when compared with the controls and there were no differences between UBDC versus BBDC groups.

CONCLUSIONS

Patients with buccally displaced permanent canine tended to have maxillary transverse constriction and variation in palatal vault morphology. The morphometric variation of the palatine vault and arch dimensions can be considered a clinical factor associated with the presence of BDC.

Geometric morphometric analysis of the palatal morphology in growing subjects with skeletal open bite

OBJECTIVES

To assess the morphological shape variations of the palatal vault in Open Bite (OB) growing subjects when compared with a Control Group (CG) by means of Geometric Morphometric Method (GMM).

MATERIALS AND METHODS

The OB Group (OBG) consisted of 75 subjects (39 females, 36 males; mean age: 8.5 ± 0.8 years) who were collected retrospectively with the following inclusion criteria: European ancestry, overbite less than 0 mm, mixed dentition stage, prepubertal skeletal maturation (CS1-CS2), hyperdivergent skeletal pattern (SN^GoGn > 37°). The OBG was compared with a CG of 46 prepubertal subjects presenting normal occlusion (24 females, 22 males; mean age of 8.3 ± 1.7 years). For each subject, lateral cephalograms and maxillary dental casts were available. Landmarks and semilandmarks were digitized on digital dental casts and GMM was applied. Procrustes analysis and principal component analysis (PCA) were performed. OBG was divided in two subgroups: Sucking Habits Group (SHG) (39 subjects) and Non-Sucking Habits Group (NSHG) (36 subjects).

RESULTS

PC1 showed significant morphological changes in transverse and vertical dimensions with OBG palates higher and narrower when compared with CG. When comparing the two subgroups no statistically significant differences were found. NSHG demonstrated a slight reduction of the transverse dimension and a deeper palatal vault respect to SHG.

LIMITATIONS

The limitations of this study were the division of OBG in two subgroups based on referral of thumb sucking habits without assessing the duration and the intensity of thumb sucking.

CONCLUSIONS

OB subjects presented with a significant constriction of the maxillary arch when compared with CG. The morphological palatal shape variations in OBG were not influenced by the presence or absence of non-nutritive sucking habits.

Evaluation of the morphometric covariation between palatal and craniofacial skeletal morphology in class III malocclusion growing subjects

Background

To study the covariation between palatal and craniofacial skeletal morphology in Class III growing patients through geometric morphometric analysis (GMM).

Methods

In this retrospective study, 54 Class III subjects (24F,30M;7.6 ± 0.8yy) were enrolled following these inclusion criteria: European ancestry, Class III skeletal and dental relationship, early mixed dentition, prepubertal skeletal maturation, familiarity for Class III malocclusion, no pseudo Class III malocclusion. Each patient provided upper digital cast and cephalogram before starting the therapy. Landmarks and semilandmarks were digitized (239 on the casts;121 on the lateral radiographs) and GMM was used. Procrustes analysis and principal component analysis (PCA) were applied to show the principal components of palatal and craniofacial skeletal shape variation. Two-block partial least squares analysis (PLS) was used to assess pattern of covariation between palatal and craniofacial morphology.

Results

Regarding palatal shape variation, PC with largest variance (PC1) described morphological changes in the three space dimensions, while, concerning the craniofacial complex components, PC1 revealed morphological differences along the vertical plane. A significant covariation was found between palatal and craniofacial shape. PLS1 accounted for more than 61,7% of the whole covariation, correlating the craniofacial divergence to palatal height and width.

Conclusions

In Class III subjects increments of angle divergence are related to a narrow and high palate.

Adolescent dental arch development among Southern Chinese in Hong Kong: a geometric morphometric approach

This study aimed to investigate changes in types of dental arch form during adolescence and explore adolescent changes in size and form of dental arch. Hong Kong Chinese were recruited and digital dental arch models were obtained at ages 12, 15, and 18 years. Geometric morphometrics was used to investigate adolescent changes of dental arch form. There were 225 participants from whom digital models at all three age periods were available. Three types of dental arch form were identified through clustering. Significant changes (p < 0.001) in types of dental arch form were noted during age 12–18 years. During age 12–18 years, significant changes in centroid size and form of dental arch were observed (p < 0.001). No significant changes were observed during 15–18 years. Adolescent changes of dental arch form occur primarily during age 12–15 years, whereas dental arch form was relatively stable during age 15–18 years.

Morphometric analysis of the palatal shape and arch dimension in subjects with palatally displaced canine

OBJECTIVES

The aim of this study is to analyse the morphological variations of the palate shape and maxillary arch dimension in a group of subjects with unilaterally or bilaterally impacted maxillary canines compared with a control group, using three-dimensional (3D) geometric morphometric.

MATERIALS

The subject of this study consisted of pre-treatment records of 46 (18 males and 28 females) patients with one or both canines palatally displaced. A control group of 26 subjects was selected from a list of orthodontic patients at the same dental hospital. The subjects were divided in two study groups: unilateral palatally displaced canine (UPDC) and bilateral palatally displaced canine (BPDC). Study casts were scanned to analyse the palate's shape and maxillary arch dimension. The 3D geometric morphometric analysis was used to study the entirety of the shape of the palate. The virtual 3D models were measured with a specific software to analyse the maxillary arch dimension. (VAM, Vectra; Canfield Scientific, Fairfield, New Jersey, USA).

RESULTS

When comparing the groups with the geometric morphometrics analysis, no significant palatal shape change was found. For the analysis of linear measurements, only a significant reduction of intercanine width was found in the UPDC and BPDC groups when compared with the control subjects.

CONCLUSIONS

Patients with palatally displaced permanent canine showed no maxillary transverse constriction or variation in palatal vault morphology but the absence of permanent teeth was associated with a reduction in the intercanine width.

Analysis of the relationship between the morphology of the palate and facial skeletal patterns in Class III malocclusion using structural equation modelling

INTRODUCTION

The present study investigated the relationship between facial skeletal patterns and morphology of the palate in adult patients with Class III malocclusion using structural equation modelling (SEM).

SETTING AND SAMPLE POPULATION

One hundred cone beam computed tomography images of Class III adults were evaluated for skeletal measurements.

MATERIALS AND METHODS

The skeletal measurements were classified into the vertical, anteroposterior and transverse group based on factor analysis. 3D scanning model of the maxilla was analysed by Generalized procrustes analysis (GPA) and principal component analysis (PCA). Structural equation modelling was used to analyse relationship among the skeletal and morphometric factors.

RESULTS

According to the factor analysis, latent variables were extracted by each skeletal variable. First principal component (PC1) and PC2 of palatal morphology were used to analyse relationship with skeletal variables. As results of the structural equation model, the transverse latent variable had the most influence on PC1, followed by vertical and anteroposterior variables. This result means that as the facial width increases, the palate becomes narrower, deeper and longer.

CONCLUSIONS

The relationship between the skeletal pattern with Class III malocclusion and palatal morphology was analysed through SEM. The transverse facial skeletal pattern showed the highest correlation with PC1 of palatal morphology.

Prediction of dental arch width increase in the early mixed dentition using craniofacial parameters

BACKGROUND

The dimensions of the dental arch have considerable impact on treatment planning. Since the dental arch development has a relationship with the craniofacial growth, we designed a cohort study to find a regression model for predicting the mandibular arch width increase using craniofacial parameters.

METHODS

A total of 148 children, all in early mixed dentition, were selected randomly from primary schools by cluster sampling. Craniofacial anthropometric parameters were measured by a caliper bow and intercanine and intermolar widths were assessed on each subject's dental casts by a digital caliper at baseline and after 12 months. Data were analyzed with SPSS v. 15. Student's t-test and linear regression test were applied separately for girls and boys.

RESULTS

Out of 153 children, 148 returned for one-year follow-up meeting the inclusion criteria. The results of regression analysis showed a significant inverse correlation between intercanine width and facial index. The bigonial dimension showed a high correlation with both the intermolar width and the intercanine width increase.

CONCLUSIONS

We found that the arch width increase in the early mixed dentition could be predicted precisely based on certain craniofacial parameters.

[Does gender make a difference in orthodontics? A literature review]

OBJECTIVES

The objective of this literature review is to investigate whether the gender of patients and practitioners makes any difference to orthodontic treatment.

MATERIALS AND METHODS

Sixty-nine articles were selected, the vast majority of which studied patient gender.

RESULTS

Young females are the category of patients which most often apply for orthodontic treatment, probably because of their higher aesthetic demands, despite their objective needs being no greater. Aesthetic, skeletal and dental analyses reveal an obvious dimorphism with larger dimensions in males, especially for the nose, cheekbones, mouth and mandibular canines. Nevertheless, cephalometric angular values do not vary significantly between male and female individuals. Growth is quantitatively greater in males. It also occurs later, as does eruption and maturation of their teeth. Response to the different orthodontic / orthopedic therapies would appear not to differ according to the sex of the patient.

DISCUSSION

These results, however, need to be qualified according to the country concerned, the patients' life style and mind frames, as these can modify or influence the studied parameters.

Candidate gene analyses of 3-dimensional dentoalveolar phenotypes in subjects with malocclusion

INTRODUCTION

Genetic studies of malocclusion etiology have identified 4 deleterious mutations in genes DUSP6,ARHGAP21, FGF23, and ADAMTS1 in familial Class III cases. Although these variants may have large impacts on Class III phenotypic expression, their low frequency (<1%) makes them unlikely to explain most malocclusions. Thus, much of the genetic variation underlying the dentofacial phenotypic variation associated with malocclusion remains unknown. In this study, we evaluated associations between common genetic variations in craniofacial candidate genes and 3-dimensional dentoalveolar phenotypes in patients with malocclusion.

METHODS

Pretreatment dental casts or cone-beam computed tomographic images from 300 healthy subjects were digitized with 48 landmarks. The 3-dimensional coordinate data were submitted to a geometric morphometric approach along with principal component analysis to generate continuous phenotypes including symmetric and asymmetric components of dentoalveolar shape variation, fluctuating asymmetry, and size. The subjects were genotyped for 222 single-nucleotide polymorphisms in 82 genes/loci, and phenotpye-genotype associations were tested via multivariate linear regression.

RESULTS

Principal component analysis of symmetric variation identified 4 components that explained 68% of the total variance and depicted anteroposterior, vertical, and transverse dentoalveolar discrepancies. Suggestive associations (P < 0.05) were identified with PITX2, SNAI3, 11q22.2-q22.3, 4p16.1, ISL1, and FGF8. Principal component analysis for asymmetric variations identified 4 components that explained 51% of the total variations and captured left-to-right discrepancies resulting in midline deviations, unilateral crossbites, and ectopic eruptions. Suggestive associations were found with TBX1AJUBA, SNAI3SATB2, TP63, and 1p22.1. Fluctuating asymmetry was associated with BMP3 and LATS1. Associations for SATB2 and BMP3 with asymmetric variations remained significant after the Bonferroni correction (P <0.00022). Suggestive associations were found for centroid size, a proxy for dentoalveolar size variation with 4p16.1 and SNAI1.

CONCLUSIONS

Specific genetic pathways associated with 3-dimensional dentoalveolar phenotypic variation in malocclusions were identified.

Geometric morphometric analysis of the palatal morphology in children with impacted incisors: A three-dimensional evaluation

OBJECTIVE

To analyze variations in palatal morphology in subjects presenting unilaterally impacted maxillary permanent central incisors compared with a control group of subjects without eruption anomalies using a three-dimensional (3D) analysis.

MATERIALS AND METHODS

Twenty-six white subjects (10 girls and 16 boys; mean age 9.5 ± 1.5 years) with unilaterally impacted maxillary permanent central incisors (impacted incisor group [IIG]) were compared with a control group (CG) of 26 subjects (14 girls and 12 boys, mean age 8.7 ± 1.6 years) presenting no eruption disorders. For each subject, dental casts were taken and the upper arch was scanned using a 3D laser scanner. To study the entirety of the shape of the palate in any point of the surface, 3D geometric morphometrics was applied.

RESULTS

Subjects with impacted maxillary incisors showed skeletal adaptations of the maxilla. In the IIG, both the superior palatal region and lateral palatal surface showed significantly different morphology when compared with CG, with a narrower and higher palatal vault.

CONCLUSION

The absence of maxillary central incisors over the physiological age of eruption influenced the development of the palatal morphology compared with subjects without eruption anomalies.