Morphologic determinants in the etiology of class III malocclusions: a review

Prevalence of Malocclusion Traits in Primary Dentition, 2010-2024: A Systematic Review

The present review was aimed to describe the prevalence and the regional distribution of malocclusion among preschool children worldwide. Two independent reviewers performed a systematic literature search to identify English publications from January 2010 to May 2024 using PubMed, ISI Web of Science and Embase. Search MeSH key words were "malocclusion", "primary dentition" and "child, preschool". The reporting quality was assessed by the modified Newcastle-Ottawa Quality Assessment Scale. We identified 2599 publications and recruited 47 articles. Fourteen of the included studies were conducted in Asia, four in Europe, twenty-eight in South America and one in Africa. The prevalence of malocclusion ranged from 28.4% to 83.9%, and half of the reported prevalences were higher than 50%. The highest percentage was in Asia (61.81%), followed by Europe (61.50%), South America (52.69%) and Africa (32.50%). Statistically significant differences existed in deep overbite, anterior open bite, posterior crossbite, edge-to-edge incisor relationship and distal step between continents (p < 0.05). Europe showed the highest prevalence (33.08%) of deep overbite. Africa showed the highest prevalence (18.60%) of anterior open bite. Europe showed the highest prevalence (15.38%) of posterior crossbite. The most common malocclusion traits were increased overjet and deep overbite. To conclude, malocclusion remained prevalent in the primary dentition and varied between countries.

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.

Skeletal Class III phenotype: Link between animal models and human genetics: A scoping review

This study aimed to identify evidence from animal studies examining genetic variants underlying maxillomandibular discrepancies resulting in a skeletal Class III (SCIII) malocclusion phenotype. Following the Manual for Evidence Synthesis of the JBI and the PRISMA extension for scoping reviews, a participant, concept, context question was formulated and systematic searches were executed in the PubMed, Scopus, WOS, Scielo, Open Gray, and Mednar databases. Of the 779 identified studies, 13 met the selection criteria and were included in the data extraction. The SCIII malocclusion phenotype was described as mandibular prognathism in the Danio rerio, Dicentrarchus labrax, and Equus africanus asinus models; and as maxillary deficiency in the Felis silvestris catus, Canis familiaris, Salmo trutta, and Mus musculus models. The identified genetic variants highlight the significance of BMP and TGF-β signaling. Their regulatory pathways and genetic interactions link them to cellular bone regulation events, particularly ossification regulation of postnatal cranial synchondroses. In conclusion, twenty genetic variants associated with the skeletal SCIII malocclusion phenotype were identified in animal models. Their interactions and regulatory pathways corroborate the role of these variants in bone growth, differentiation events, and ossification regulation of postnatal cranial synchondroses.

Towards Genetic Dissection of Skeletal Class III Malocclusion: A Review of Genetic Variations Underlying the Phenotype in Humans and Future Directions

INTRODUCTION

Skeletal abnormalities and malocclusions have varied features that impact populations globally, impairing aesthetics and lowering life quality. The prevalence of the Skeletal Class III disease is the lowest among all angle malocclusions, with varied prevalence across nations. Environmental, genetic, and societal factors play a role in its numerous etiologies. In this study, we conducted a thorough search across the published data relating to quantitative trait loci (QTL) and the genes associated with Class III progression in humans, discussed these findings and their limitations, and proposed future directions and strategies for studying this phenotype.

METHODS

An inclusive search of published papers in the PubMed and Google Scholar search engines using the following terms: 1. Human skeletal Class III; 2. Genetics of Human skeletal Class III; 3. QTL mapping and gene associated with human skeletal Class III; 4. enriched skeletal Class-III-malocclusion-associated pathways.

RESULTS

Our search has found 53 genes linked with skeletal Class III malocclusion reported in humans, genes associated with epigenetics and phenomena, and the top 20 enriched pathways associated with skeletal Class III malocclusion.

CONCLUSIONS

The human investigations yielded some contentious conclusions. We conducted a genome-wide association study (GWAS), an epigenetics-wide association study (EWAS), RNA-seq analysis, integrating GWAS and expression quantitative trait loci (eQTL), micro- and small-RNA, and long non-coding RNA analysis in tissues connected to skeletal Class III malocclusion phenotype in tissues connected with the skeletal phenotype. Finally, we invite regional, national, and international orthodontists and surgeons to join this effort by contributing human samples with skeletal Class III malocclusion following the accepted Helsinki ethical protocol to challenge these phenomena jointly.

Effects produced by the facemask with and without skeletal anchorage for the orthopaedic treatment of Class III malocclusion in growing patients: a systematic review and meta-analysis of RCTs

BACKGROUND

Skeletally anchored facemask has been proposed to maximize skeletal effects and minimize dental effects in the treatment of Class III malocclusion in growing patients.

OBJECTIVE

To compare the dento-skeletal effects produced by the facemask with or without skeletal anchorage for the treatment of Class III malocclusion in growing patients.

MATERIALS AND METHODS

PubMed, Cochrane Library, Scopus, Embase, Web of Science, and OpenGrey were used for the electronic search without language, publication status, and year restrictions. Only RCTs were included. Inclusion criteria were: growing patients (age under 18 years) with Class III malocclusion, with indications for treatment with the facemask. Data were extracted by two independent reviewers. GRADE statement was executed. The mean of differences (MD) and the risk ratio (RR) were used.

RESULTS

Three articles with a total of 123 patients were included. One article was at low risk of bias while two were at high risk of bias. There were no significant differences between the two groups in ANB angle, Wits appraisal, SNB angle, and SN-MP angle. SNA angle was significantly increased in the skeletally anchored facemask (pooled MD = 0.80 favouring skeletal anchorage, 95% CI from 0.29 to 1.31, P = 0.002, I2 = 12 per cent, three studies, GRADE moderate). The U1-SN angle was significantly reduced in the skeletally anchored facemask (pooled MD = -5.91 favouring skeletal anchorage, 95% CI from -7.64 to -4.27, P < 0.00001, I2 = 0 per cent, two studies, GRADE moderate). There were significantly less complications in tooth-anchored facemask (pooled RR = 7.98 favouring dental anchorage, 95 per cent CI from 1.04 to 61.27, P = 0.05, I2 = 0 per cent, two studies, GRADE low).

LIMITATIONS

Few RCTs (three) were included, and two studies were at high risk of bias. There were no long-term RCTs comparing skeletally anchored facemask with dental-anchored facemask. Only Asiatic patients were included in this systematic review.

CONCLUSIONS

Skeletally anchored facemask was associated to a greater increase of SNA angle at the end of treatment though clinically not significant. Facemask with skeletal anchorage determined a reduced inclination of maxillary incisors compared to dental-anchored facemask with greater risks of complications.

REGISTRATION

PROSPERO register (CRD42020221982).

Analysis of MYO1H Gene Polymorphism in Skeletal Class-III Malocclusion Due to Mandibular Prognathism

Background  Mandibular prognathism (MP) is a craniofacial deformity resulting from the combined effects of environmental and genetic factors. Although various linkage and genome-wide association studies for mandibular prognathism have identified multiple strongly associated regions and genes, the causal genes and variants responsible for the deformity remained ambiguous.

Aim  This research work was aimed to study the association between polymorphism rs10850110 of the MYO1H gene and skeletal class-III malocclusion in our local population.

Materials and Methods  Thirty patients with skeletal class III due to mandibular prognathism in the study group and 30 patients with skeletal class I in the control group were selected for this study. These patients were from both sexes and above age 10 years. Based on the cephalometric values, patients were categorized into study and control groups. SNB (angle between sella, nasion and point B at nasion) greater than 82 degrees with an ANB (angle between point A, nasion and point B at nasion) of less than 0 degrees in the study group and ANB (angle between point A, nasion and point B at nasion) of 2 to 4 degrees in the control group were categorized. The polymorphism (rs10850110) of the MYO1H gene was genotyped using polymerase chain reaction and restriction fragment length polymorphism. Associations were tested with SNP exact test using SNPstats software.

Results  The single-nucleotide polymorphism rs10850110 showed a statistically significant association with mandibular prognathism. The G allele of marker rs10850110 (5′ of myosin1H - MYO1H ) was overrepresented when compared with the “A” allele in mandibular prognathism cases ( p  < 0.0001), and this was very significant.

Conclusion  These results suggest that the rs10850110 polymorphism of the MYO1H gene is associated with an increased risk for mandibular prognathism.

Targeted sequencing of NOTCH signaling pathway genes and association analysis of variants correlated with mandibular prognathism

Introduction

The purpose of this study was to systematically identify variants in NOTCH signaling pathway genes that correlate with mandibular prognathism (MP) in the general Chinese population.

Methods

Targeted sequencing of NOTCH signaling pathway genes was conducted in 199 MP individuals and 197 class I malocclusion control individuals. The associations of common and rare variants with MP, cephalometric parameters, and continuous cephalometric phenotypes were analyzed by principal component (PC) analysis. The associations between rare variants and MP were tested for each gene.

Results

Six SNPs, including rs415929, rs520688, and rs423023 in an exonic region of NOTCH4; rs1044006 in an exonic region of NOTCH3; rs1051415 in an exonic region of JAG1; and rs75236173 in the 3′-untranslated region (3′-UTR) of NUMB were associated with MP (P < 0.05). One common variant, rs1051415, in an exonic region of JAG1 was significantly related to PC1 (P  = 3.608 × 10^− 4), which explained 24.3% of the overall phenotypic variation observed and corresponded to the sagittal mandibular position towards the maxilla, ranging from a posterior positioned mandible to an anterior positioned mandible. Additionally, 41 other variants were associated with PC1–5 (P  <  0.05). With respect to rare variant analysis, variants within the EP300, NCOR2, and PSEN2 gene showed an association with MP (t   < 0 .05).

Conclusions

An association between NOTCH signaling pathway genes and MP has been identified.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13005-021-00268-0.

Developmental Abnormalities of the Skull Base in Patients with Turner Syndrome

The skull base is one of the most complex anatomic structures of the skeleton that is responsible for protecting and supporting the brain and is also involved in the development of the facial structures. The main objective of our study was to evaluate skull base abnormalities in a group of patients diagnosed with Turner syndrome by assessing lateral cephalometric radiographs. A total of 7 patients diagnosed with Turner syndrome in the Endocrinology Department of the Emergency Clinical County Hospital of Craiova were included in the study. The following cephalometric variables were measured in our study: total skull base (N-Ba): Nasion (N)-Basion (Ba); anterior skull base (N-S): Nasion (N)-Sella (S); posterior skull base (S-Ba): Sella (S)-Basion (Ba). Regarding the investigated cephalometric variables, the mean±standard deviation (SD) recorded values in our study were 86.34±4.26mm for the total skull base (N-Ba), 63.87±2.54mm for the anterior skull base (N-S) and 38.33±4.87mm for the posterior skull base (S-Ba). The results of our study were compared to the ones provided by one of the most representative studies described in the literature. A reduced size of the posterior base of the skull is considered pathognomonic in subjects diagnosed with Turner syndrome. Also, the posterior base of the skull directly influences the maxillomandibular skeletal relationships and it is therefore necessary to calculate this cephalometric variable, which is easily highlighted on a lateral cephalometric radiograph.

Timing of Spheno-Occipital Synchondrosis Ossification in Children and Adolescents with Cleft Lip and Palate: A Retrospective Case-Control Study

Background: Cleft lip and palate (CLP) can affect the development of the maxilla; which may create a midfacial deficiency as well as an interference of the facial growth pattern and dentofacial esthetics. Objective: This study aimed to estimate the chronological age of complete fusion of the spheno-occipital synchondrosis (SOS) in cleft lip and palate patients and a control group; using cone beam computed tomography (CBCT) images. Methods: In this retrospective study; 125 patients were enrolled (cleft lip and palate group (n = 91); control group (n = 34)). Age comparison was made with a chi-square test; and a Kaplan–Meier analysis determined the median time to reach complete fusion of the spheno-occipital synchondrosis (p < 0.05). Results: The experimental group showed statistically significant differences in the median time for complete ossification between males and females (p = 0.019). The median time for complete ossification of the spheno-occipital synchondrosis was; for males; 15.0 years in both groups; for females; it was 14.0 years and 13.0 years in the experimental group and in the control group; respectively. Both for males and females; there were no statistically significant differences between experimental and control groups (p = 0.104). Conclusions: The present study showed no differences in the ossification of the spheno-occipital synchondrosis between individuals with and without cleft lip and/or palate.

Malocclusion in individuals with osteogenesis imperfecta: A systematic review and meta-analysis

OBJECTIVE

To evaluate whether individuals with osteogenesis imperfecta (OI) are more affected by malocclusion than individuals without OI.

MATERIALS AND METHODS

Searches in PubMed, Ovid, Web of Science, Scopus, Lilacs and gray literature were performed. Data extraction was conducted by two researchers. Risk of bias assessment employing the Newcastle-Ottawa Scale and meta-analysis were conducted. Results were provided with mean difference (MD), odds ratio (OR) and 95% confidence interval (CI). Strength of evidence was determined.

RESULTS

Six cross-sectional studies were included. In comparison with individuals without OI, the group with OI had 19.69-fold greater chance of exhibiting Angle Class III malocclusion (OR = 19.69, CI: 9.00-43.09) and presenting anterior crossbite greater (MD = 6.08, CI: 2.40-9.77). Individuals without OI had a significantly greater ANB angle (MD = 3.88, CI: 1.15-6.61) and SNA angle (MD = 2.11, CI: 0.24-3.98) in comparison with those with OI. No difference between groups was found for SNB (MD = -0.50, CI: -2.21 to 1.21) and open bite (MD = 0.98, CI: -0.29 to 2.25). Most studies included had moderate methodological quality. Strength of evidence was low or very low.

CONCLUSIONS

The occurrence of Angle Class III malocclusion and anterior crossbite was greater among individuals with OI compared to those without OI. These findings can assist stakeholders about the occlusal abnormalities affecting OI individuals.

Active unilateral condylar hyperplasia: Assessment of the usefulness of single photon emission computed tomography

Background

This study aims to evaluate whether the uptake difference by the condyles evaluated using single photon emission computed tomography (SPECT) examination is useful for predicting the activity of the feature and the advance of this pathology.

Material and Methods

An observational and prospective study has been carried out on nine patients affected by unilateral condylar hyperplasia (UCH) with complete bone maturation, with a follow-up over 18 months. At the beginning of the study, a test-battery was conducted including dental casts, articular examination, teleradiography and cephalometry, computed tomography and SPECT, creating two groups of patients from a difference in uptake between both condyles greater than 10% over the follow-up period. Evolution of data obtained with the rest of the diagnostic tests were compared to confirm UCH activity predicted by SPECT.

Results

The comparison of both groups did not show hardly any significant differences, with little clinical significance. Deviation of the mandibular line, the size of the branches or condyles behaved similarly in both study groups.

Conclusions

From the data obtained in our study, we can conclude that the use of the difference in uptake between both condyles by applying the SPECT technique is not a valid approach for predicting clinical activity in cases of UCH.

Key words:Temporomandibular joint, facial asymmetry, single photon emission computed tomography, scintigraphy, condylar hyperplasia.

Differential Diagnosis of Skeletal Class III

Skeletal Class III is a relatively rare malocclusion of the craniofacial complex and the accurate differential diagnosis of its aetiology is necessary so that it may be correctly treated. Differential diagnosis of Class III aetiopathogenesis should distinguish between: a) true skeletal Class III as opposed to pseudo Class III; b) three forms of Skeletal Class III, in which there is either maxillary deficiency only or mandibular excess only or combination of both; and c) skeletal Class III that may be treated with orthodontic treatment alone, as opposed to Class III that is difficult to manage with orthodontic treatment alone and requires combine orthodontic and surgical approach. Differential diagnosis is mainly based on clinical examination and cephalometric analysis. The aim of this paper is to present the basic principles and modes of achieving differential diagnosis in skeletal Class III cases.

Whole-exome sequencing in a Japanese pedigree implicates a rare non-synonymous single-nucleotide variant in BEST3 as a candidate for mandibular prognathism

Mandibular prognathism is a phenotype of facial deformity seen in populations around the world, but with higher incidence among East Asian populations. Five genome-wide nonparametric linkage analyses and a genome-wide association study to identify susceptibility loci of the phenotype have shown inconsistent results. To explore variants related to mandibular prognathism, we undertook whole-exome sequencing in a Japanese pedigree. The pedigree was ascertained as mandibular prognathism. The pedigree comprised 15 individuals from 4 generations. Four affected individuals across 2 generations and 5 unaffected individuals were chosen for whole-exome sequencing. Five non-synonymous single-nucleotide variants (SNVs) of UBASH3B, OR6M1, OR8D4, OR8B4, and BEST3 genes were detected in all 4 affected individuals, but in none of the 5 unaffected individuals. A non-synonymous SNV of the BEST3 gene, Chr12(GRCh37):g.70048878G>T, NM_032735.2:c.1816C>A, p.(L606I), was identified as rare missense variant. BEST3 is located on chromosome 12q15 and encodes bestrophin 3 from the bestrophin family of anion channels. The 4 other non-synonymous SNVs of UBASH3B, OR6M1, OR8D4, and OR8B4 were not considered plausible candidates for mandibular prognathism. Our whole-exome sequencing implicates a rare non-synonymous SNV of BEST3 as a candidate for mandibular prognathism in the Japanese pedigree.

Premaxillary-maxillary suture development in the first trimester : An ultrasound study

PURPOSE

Our study was designed to investigate premaxillary-maxillary suture growth in fetuses from the first trimester of pregnancy using the B‑ultrasound technique in order to determine the suture fusion time.

METHODS

We selected 169 healthy Han singleton pregnancies as subjects. All subjects received routine pregnancy tests and were divided into three groups based on the gestational age of the fetus: group 1, the 11th gestational week; group 2, the 12th gestational week; and group 3, the 13th gestational week. Fetal biometric measurements were recorded during consecutive prenatal ultrasonographic examinations. These measurements included nuchal translucency thickness, crown-rump length, and premaxillary-maxillary length. Intergroup comparisons were performed using analysis of variance (ANOVA).

RESULTS

The premaxillary-maxillary suture grows gradually and its measured length at the 11th, 12th and 13th week was 0.54 cm, 0.65 cm, and 0.74 cm, respectively. We observed a significant linear correlation between the premaxillary-maxillary length and the week of gestation in the first trimester. The growth rate of the maxilla at the 11th, the 12th and the 13th week are significantly different with a descending order of growth rates being week 12, week 11 and week 13, with the 12th week rate being the most rapid.

CONCLUSION

The premaxillary and maxillary growth at 11 and 12 gestational weeks in the first trimester steadily accelerated, peaking at the 12th week. The rate of growth slows down after week 12 which may be associated with the fusion of the premaxillary-maxillary suture.

Time and pattern of the fusion of the spheno-occipital synchondrosis in patients with skeletal Class I and Class III malocclusion

OBJECTIVES

To investigate the time and pattern of fusion of the spheno-occipital synchondrosis in patients with skeletal Class I and Class III malocclusion using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

A total of 262 CBCT images were collected: 140 skeletal Class I (0° < ANB < 4°; 71 males, 69 females) and 122 skeletal Class III (ANB ≤ 0°; 61 males and 61 females). The fusion stages were identified using CBCT images of a six-stage system defined by the appearance of osseous cores and ossifying vestige in the synchondrosis. The age distributions of each stage and the pattern of fusion were evaluated.

RESULTS

The stages of fusion progressed with increasing age (P < .05, r = .824), and the age distributions in the female groups were generally 1 to 3 years younger than those in the male groups. However, no significant differences were observed between the skeletal Class I and Class III groups regarding the time of ossification of the synchondrosis. The osseous cores appeared most frequently in the supero-center part, followed by the mid-center part of the synchondrosis.

CONCLUSIONS

The time and pattern of fusion of the spheno-occipital synchondrosis are not apparently different between patients with Class I malocclusion and those with Class III malocclusion. The osseous cores appear frequently in the supero-center and mid-center of the synchondrosis with various patterns before the end of the pubertal growth spurt period.

Evaluation of Nasal Airway Volume of Operated Unilateral Cleft Lip and Palate Patients Compared With Skeletal Class III Individuals

Cleft lip and palate (CLP) patients have various problems with nasal anatomy beyond just oronasal separation. The alar base, concha, and septum are over impressed in these individuals. Additionally, skeletal class III deformity is seen. These conditions may limit nasal function. In our study, 15 unilateral patients with CLP older than 15 years (10 females, 5 males; mean age: 19.13) who had received surgery were included as the study group, and 15 participants with noncleft skeletal class III deformities were included as the control group (10 females, 5 males; mean age: 19.20). The individuals' nasal airway volumes (total/cleft side/noncleft side/control/ nasal passages) were examined and compared statistically. The results showed that the study group had significantly higher values in terms of total airway volume ( P < .05). Additionally, there were significant differences between the cleft side and noncleft side volumes, between the cleft side volumes and the volumes of the control group participants, and between the noncleft side volumes and the volumes of the control group participants ( P < .05). There was no difference between the groups in terms of nasopharyngeal ( P = .39) and nasal passage volumes ( P = .73). The results show there are some problems regarding nasal airway volume in patients with CLP, even when lip, palate, and alveolar cleft operations have been performed. The aim of this study was to evaluate differentiation of nasal airway volumes between unilateral patients with CLP and individuals with noncleft skeletal class III serving as the control group.

Craniofacial growth studies in orthodontic research — lessons, considerations and controversies

The distinguishing features of Class I, Class II and Class III craniofacial growth have been subjects of orthodontic research since the middle of the 20th century. However, the moral and practical issues related to studying craniofacial growth in modern times have presented unresolved challenges to researchers. While previous longitudinal growth investigations are typically based on historical data sets, the cephalometric growth studies of contemporary populations must now rely on cross-sectional data. Furthermore, clinical orthodontic research has faced similar ethical challenges in which therapeutic outcomes are analysed using historical control data. These limitations, amongst others, have obscured the conclusions that can be drawn from both types of studies. This article begins with a review of the defining characteristics of Class I, Class II and Class III growth and then explores the limitations of growth studies and the use of historical control groups in orthodontic research.

Understanding interactions among cephalometrics variables during growth in untreated Class III subjects

Objective

The aim of the present study was to apply a computational method commonly used in data mining discipline, classification trees (CTs), to evaluate the growth features in untreated Class III subjects.

Materials and methods

CT was applied to data from 91 untreated Class III subjects (48 females and 43 males) and compared with the results of discriminant analysis (DA). For all subjects, lateral cephalograms were available at T1 (mean age 10.4 ± 2.0 years) and at T2 (mean age 15.4 ± 1.9 years). A cephalometric analysis comprising 11 variables was performed. The subjects were divided into two subgroups, unfavourable ('Bad') and favourable ('Good') growers, according to the quality of the skeletal growth rate in comparison with the normal craniofacial growth.

Results

CTs showed that the most informative attribute for the prediction of favourable/unfavourable skeletal growth was the SNA angle. Subjects with SNA values lower than 79.1 degrees showed a risk of 94 per cent of growing unfavourably. DA was able to select palatal plane to mandibular plane angle as predictors. DA, however, showed a statistically significant higher rate of misclassification when compared with CTs (40.7 per cent versus 12.1 per cent, binomial exact test: odds ratio = 6.20; P < 0.0001).

Conclusions

CTs provided a valid measure of elucidating the effective contribution of craniofacial characteristics in predicting favourable/unfavourable growth in untreated Class III subjects.

Genetic polymorphisms underlying the skeletal Class III phenotype

INTRODUCTION

Our goal was to verify the association between candidate polymorphisms and skeletal Class III malocclusion in a well-characterized homogeneous sample set.

METHODS

Thirty-five single-nucleotide polymorphisms were studied from 10 candidate loci in 54 Class III subjects and 120 controls. Skeletal Class III characteristics included ANB angle less than 0°, SNB angle greater than 83° (mandibular prognathism), SNA angle less than 79° (maxillary deficiency), Class III molar relationship, and negative overjet. Inclusion criteria for the controls were ANB angle between 0° and 4°, Class I molar relationship, and normal overjet. Chi-square and Fisher exact tests and principal component (PC) analysis were used to determine overrepresentation of marker alleles with alpha of 0.05. Odds ratios and 95% confidence intervals were calculated.

RESULTS

MYO1H (rs10850110 A<G) (P <0.01; odds ratio, 7.44 [4.02-13.77]) was associated with an increased risk for the mandibular prognathism phenotype. These results were confirmed by PC analysis, which showed 4 PCs representing the sample variations (PC1, 37.24%; PC2, 20.02%; PC3, 12.18%; and PC4, 11.40%), and PC1 was associated with MYO1H (P <0.001). We also found by PC analysis associations between MYO1H (P <0.001) and GHR (rs2973015 A>G) (P = 0.001) with PC2 and between FGF10 (rs593307 A<G) (P = 0.001) with PC4.

CONCLUSIONS

Polymorphism in MYO1H could be used as a marker for genetic susceptibility to Class III malocclusion with mandibular prognathism, and polymorphisms in GHR and FGF were associated with maxillomandibular discrepancies. This study may contribute to improved diagnosis and further research assessing possible differences in treatment responses based on genetic polymorphisms.

The Growth Hormone Receptor Gene is Associated with Mandibular Height in a Chinese Population

Genetic influences are important in the determination of mandibular morphology, and growth hormone receptor ( GHR) is believed to have an important influence on the growth of craniofacial bone. In this study, we used quantitative trait locus methods to evaluate the relationship between craniofacial morphology and single-nucleotide polymorphisms (SNPs) in GHR in an unselected healthy Chinese population. We systematically screened the 10 exons and nearby introns of GHR and identified 6 SNPs. Using 4 SNPs as markers, we studied the relationships between genotypes and craniofacial linear measurements. Individuals with the genotype CC of polymorphism I526L had a significantly greater mandibular ramus length (condylion-gonion/ articulare-gonion) than those with genotype AC or AA. Haplotype analysis showed that there were also significant differences between the long and short mandibular height groups in an extreme population. Our results indicate that the GHR gene polymorphism I526L is associated with mandibular height in the Chinese population.

Cranial base characteristics in anteroposterior malocclusions: A meta-analysis

OBJECTIVE

To investigate cranial base characteristics in malocclusions with sagittal discrepancies.

MATERIALS AND METHODS

An electronic search was performed in PubMed, Embase, Web of Science, and the Cochrane Library. A fixed- or random-effect model was applied to calculate weighted mean difference with 95% confidence intervals (CIs) according to statistical heterogeneity. Outcome measures were anterior, posterior, and total cranial base length and cranial base angle. Sensitivity analysis and publication bias were conducted.

RESULTS

Twenty studies that together included 1121 Class I, 1051 Class II, and 730 Class III cases qualified for the final analysis. Class III malocclusion demonstrated significantly reduced anterior (95% CI: -1.74, -0.53; P < .001 vs Class I; 95% CI: -3.30, -2.09; P < .001 vs Class II) and total cranial base length (95% CI: -3.33, -1.36; P < .001 vs Class I; 95% CI: -7.38, -4.05; P < .001 vs Class II). Further, Class II patients showed significantly greater anterior and total cranial base length than did Class I patients (95% CI: 0.51, 1.87; P < .001 for SN; 95% CI: 2.20, 3.30; P < .001 for NBa). Cranial base angle was significantly smaller in Class III than in Class I (95% CI: -3.14, -0.93; P < .001 for NSBa; 95% CI: -2.73, -0.68; P  =  .001 for NSAr) and Class II malocclusions (95% CI: -5.73, -1.06; P  =  .004 for NSBa; 95% CI: -6.11, -1.92; P < .001 for NSAr) and greater in Class II than in Class I malocclusions (95% CI: 1.38, 2.38; P < .001 for NSBa).

CONCLUSIONS

This meta-analysis showed that anterior and total cranial base length and cranial base angle were significantly smaller in Class III malocclusion than in Class I and Class II malocclusions, and that they were greater in Class II subjects compared to controls.

Patterns of morphological integration in the dental arches of individuals with malocclusion

OBJECTIVES

In humans, there is a large range of variation in the form of the maxillary and mandibular dental arches. This variation can manifest as either prognathism or retrognathism in either or both arches, which can cause malocclusion and lead to abnormal masticatory function. This study aims to identify aspects of variation and morphological integration existing in the dental arches of individuals with different types of malocclusion.

METHODS

Coordinate landmark data were collected along the gingival margins of 397 scanned dental casts and then analyzed using geometric morphometric techniques to explore arch form variation and patterns of morphological integration within each malocclusion type.

RESULTS

Significant differences were identified between Class II forms (increased projection of upper arch relative to the lower arch) and Class III forms (lower arch projection beyond the upper arch) in symmetrical shape variation, including anteroposterior arch discrepancies and abnormal anterior arch divergence or convergence. Partial least squares analysis demonstrated that Class III dental arches have higher levels of covariance between upper and lower arches (RV = 0.91) compared to the dental arches of Class II (RV = 0.78) and Class I (RV = 0.73). These high levels of covariance, however, are on the lower end of the overall range of possible masticatory blocks, indicating weaker than expected levels of integration.

CONCLUSIONS

This study provides evidence for patterns of variation in dental arch shape found in individuals with Class II and Class III malocclusions. Moreover, differences in integration found between malocclusion types have ramifications for how such conditions should be studied and treated. Am. J. Hum. Biol. 28:879-889, 2016. © 2016Wiley Periodicals, Inc.

The distribution of cervical vertebrae anomalies among dental malocclusions

Aims:

The aims of our study were to investigate the distribution of cervical vertebrae anomalies (CVAs) among dental Angle Class I, II, and III malocclusions in Turkish population and whether a correlation between CVA and dental malocclusion.

Materials and Methods:

The study was performed on lateral cephalometric radiographs which were taken at the Department of Orthodontics, Faculty of Dentistry, Kirikkale University. The final sample of 318 orthodontic patients was included in the study. Dental malocclusions were performed according to Angle classification. CVAs were categorized: (1) fusion and (2) posterior arch deficiency (PAD). The Chi-square test was used to the analysis of the potential differences among dental malocclusions.

Results:

The final sample of 318 patients was examined. CVA was observed in 42 individuals (of 26 [8.17%] had fusion and 16 [5.03%] had PAD), with a frequency of 13.2%. Of the 26 fusion defect, 8 (30.7%) had Angle Class I, 8 (30.7%) had Angle Class II, and 10 (38.4%) had Angle Class III malocclusion. Of the 16 PAD, 8 (50%) had Angle Class I, 8 (50%) had Angle Class II but no patients with Angle Class III malocclusion was observed. The distribution of dental malocclusions regarding CVA was not statistically significant (P = 0.076). Of these 42 individuals with CVA, 52.3% (15 fusions and 7 PAD) were females and 47.7% (11 fusions and 9 PAD) were males.

Conclusion:

In our study, the prevalence of fusion and PAD were found 8.1% and 5.0% in Turkish population, respectively. Besides, no statistically significant correlation between CVA and Angle Class I, II, and III malocclusions were found. Our findings support the studies showing no gender dimorphism.

Accuracy of two cephalometric analyses in the treatment of patients with skeletal class III malocclusion

The aim of the present study was to compare the treatment plan outlined from the diagnosis obtained by two different cephalometric analyses with the clinical decision made for surgical treatment of patients with skeletal Class III malocclusion. For this purpose, 82 skeletal Class III patients were evaluated, divided into three groups according to the surgical procedure performed for dentofacial deformity correction. Their preoperative cephalometric radiographs were submitted to McNamara and Steiner cephalometric analyses. The association of variables was evaluated by Kappa correlation (α=5%). The agreement between indication of surgical procedures performed based on clinical decision and surgical treatment indicated based on the evaluation of McNamara and Steiner cephalometric analyses were not significant (p=0.609 and p=0.544, respectively). McNamara and Steiner analyses showed reasonable agreement with each other as to the diagnosis, but did not agree with the clinical decision to treat skeletal CIII patients. Both tests were equally inaccurate in the indication of the surgical treatment.

Genetic association of ARHGAP21 gene variant with mandibular prognathism

Mandibular prognathism (MP) is a recognizable phenotype associated with dentoskeletal class III malocclusion. MP is a complex genetic trait, although familial recurrence also suggests the contribution of single inherited variations. To date, the genetic causes of MP have been investigated using linkage analysis or association studies in pooled families. Here for the first time, next-generation sequencing was used to study a single family with a large number of MP-affected members and to identify MP-related candidate genes. A 6-generation kindred with MP segregating as an autosomal dominant character was recruited. To identify family members affected by MP, a standard cephalometric procedure was used. In 5 MP subjects separated by the largest number of meioses, whole-exome sequencing was performed. Five promising missense gene variants (BMP3, ANXA2, FLNB, HOXA2, and ARHGAP21) associated with MP were selected and genotyped in most other family members. In this family, MP seemed to consist of 2 distinct genetic branches. Interestingly, the Gly1121Ser variant in the ARHGAP21 gene was found to be shared by all MP individuals in the larger branch of the family with nearly complete penetrance. This variant is rare in the Caucasian population (frequency 0.00034) and is predicted as damaging by all bioinformatic algorithms. ARHGAP21 protein strengthens cell-cell adhesions and may be regulated by bone morphogenetic factors, thus influencing mandibular growth. Further studies in both animal models and human patients are required to clarify the significance of this association.

Prediction of Class III treatment outcomes through orthodontic data mining

OBJECTIVE

To determine whether it is possible to predict Class III treatment outcomes on the basis of a model derived from a combination of computational analyses derived from complexity science, such as fuzzy clustering repartition and network analysis.

METHODS

Cephalometric data of 54 Class III patients (32 females, 22 males) taken before (T1, mean age 8.2 ± 1.6 years) and after (T2, mean age 14.6 ± 1.8 years) early rapid maxillary expansion and facemask therapy followed by fixed appliances were analysed. Patients were classified at T1 on the basis of high membership grade into three main dentoskeletal fuzzy cluster phenotypes: hyperdivergent (HD), hypermandibular (HM), and balanced (Bal) phenotypes. The prevalence rate of successful and unsuccessful cases at T2 was calculated for the three clusters and compared by means of Fisher's exact test corrected for multiple testing (Holm-Bonferroni method).

RESULTS

Unsuccessful cases were 9 out of 54 patients (16.7%). Once patients were framed into their cluster membership, the individualized pre-treatment prediction of unsuccessful cases was largely differentiated: HD and HM patients showed a significantly greater prevalence rate of unsuccessful cases than Bal patients (0% in Bal cluster, 28.6% in HM cluster, and 33.3% in HD cluster). Network analysis captured some noticeable interdependencies of Class III patients, showing a more connected interactive structure of cephalometric data sets in HM and HD patients compared with Bal patients. The results were confirmed after minimizing the geometrical connections between cephalometric variables in the model.

CONCLUSIONS

Fuzzy clustering repartition can be usefully used to estimate an individualized risk of unsuccessful treatment outcome in Class III patients.

Lip closing force of Class III patients with mandibular prognathism: a case control study

INTRODUCTION

To compare the lip closing force of patients with mandibular prognathism to that of patients without dentofacial anomalies.

METHODS

The subject group included 62 female patients of Class III relationship with mandibular prognathism. The control group been comprised of 71 patients of Class I relationships without skeletal deformities. Maximum lip closing force and average lip closing force were measured using a Y-meter. Student's t-test was carried out to analyse the differences between the groups. Correlation and stepwise multiple linear regression analyses were performed to analyse the relationship between lip closing force and craniofacial morphology.

RESULTS

The lower lip closing force of subjects with mandibular prognathism was significantly greater than that of patients in the control group (P < 0.001), while the upper lip closing force showed no difference (P > 0.05). The lower lip closing force of patients with mandibular prognathism was strongly correlated with IMPA (Lower Incisor - Mandibular Plane angle, P < 0.001) and FMA (Frankfort Plane-Mandibular Plane angle, P < 0.001). Multiple regression equations: (MaxLL) = 12.192 - 0.125 * (IMPA) + 0.082 (FMA); (AveLL) = 9.112 - 0.091 * (IMPA) + 0.054 (FMA).

CONCLUSIONS

The lower lip closing force was markedly increased in Class III patients with mandibular prognathism and was strongly correlated with lower incisor position and mandibular plane angle.

Cephalometric investigation of craniomaxillofacial structures during the prenatal period: a cadaver study

INTRODUCTION

We aimed to investigate the morphometric development of the cranial base and its related structures, and their growth rate changes from the ninth gestational week to full term in a large group of human fetuses.

METHODS

We selected 203 (109 male, 94 female) fetuses between 9 and 40 weeks of gestation and without any external anomalies. From each fetus, standard lateral and posteroanterior cephalometric images were taken using a dental digital panoramic and cephalometric x-ray machine. Fourteen linear and 9 angular parameters were measured.

RESULTS

The cranial base angle showed a statistically significant increase between the groups from only the second to the third trimester periods. The sagittal translation of the maxilla increased during the prenatal period, whereas the mandibular sagittal relation grew at a steady rate. The vertical plane angles of the maxilla and the mandible did not show any significant changes. The maxillary length to mandibular length ratio remained stable.

CONCLUSIONS

The cranial base angle increased, especially in the second through the third trimesters. The maxilla and the mandible demonstrated different growth patterns in the sagittal direction. The findings of this study could be a guide for interpreting the relationships among the craniofacial structures.

The evaluation of maximum bite force in the occlusal rehabilitation of patient with Angle Class III malocclusion: a case report

The case report describes the occlusal rehabilitation of a male patient with Angle Class III malocclusion and its effect on maximum bite force. The main complaints of patient were masticatory difficulty and poor esthetic. The patient's expectations from the treatment were a good esthetic and function with a less invasive and relatively promptly way. Therefore, increasing of the occlusal vertical dimension (OVD) and then restoring the maxillary and mandibular teeth was chosen by the patient among the treatment options. At the beginning of treatment maximum bite force of patient was measured. Then an occlusal splint was provided to evaluate the adaptation of the patient to the altered OVD. Full mouth rehabilitation with metal ceramic restorations was made. After the completion of full mouth restoration, bite force measurement was repeated and patient exhibited increased maximum bite force. Full mouth restorative treatment in a patient with Class III malocclusion could be an effective treatment approach to resolve esthetic concern and to improve masticatory function related to maximum bite force.

A missense mutation in DUSP6 is associated with Class III malocclusion

Class III malocclusion is a common dentofacial phenotype with a variable prevalence according to ethnic background. The etiology of Class III malocclusion has been attributed mainly to interactions between susceptibility genes and environmental factors during the morphogenesis of the mandible and maxilla. Class III malocclusion shows familial recurrence, and family-based studies support a predominance of an autosomal-dominant mode of inheritance. We performed whole-exome sequencing on five siblings from an Estonian family affected by Class III malocclusion. We identified a rare heterozygous missense mutation, c.545C>T (p.Ser182Phe), in the DUSP6 gene, a likely causal variant. This variant co-segregated with the disease following an autosomal-dominant mode of inheritance with incomplete penetrance. Transcriptional activation of DUSP6 has been presumed to be regulated by FGF/FGFR and MAPK/ERK signaling during fundamental processes at early stages of skeletal development. Several candidate genes within a linkage region on chromosome 12q22-q23--harboring DUSP6--are implicated in the regulation of maxillary or mandibular growth. The current study reinforces that the 12q22-q23 region is biologically relevant to craniofacial development and may be genetically linked to the Class III malocclusion.

Aspects of orthodontic-prosthetic rehabilitation of dentofacial anomalies

Skeletal class III malocclusion is one of the most difficult dentofacial anomalies, characterized by deviation in the development of the mandible and maxilla in the sagittal plane, where the mandible is dominant in relation to the maxilla. In patients with class III malocclusion, anomalies in the dentoalveolar level and esthetic discrepancies are also frequent. The etiology of class III malocclusion is multifactorial due to the interaction of hereditary and environmental factors. Rehabilitation and treatment of malocclusion is one of the major goals of modern dentistry. This article presents the orthodontic-prosthetic therapy and rehabilitation of a 45-year-old patient with an abnormal occlusal vertical dimension and a skeletal class III malocclusion. The patient came to the clinic complaining about degraded esthetics and disordered functions of the orofacial region (functions of eating, swallowing, speech) and also pain in the temporomandibular joint. After the diagnosis was made, the patient was first referred to orthodontic treatment with fixed orthodontic appliances (self-ligating brackets system Rot 0.22). Upon completion of the orthodontic treatment, the patient was sent for further prosthetic treatment. Fixed prosthetic restorations were made in the upper and lower jaw, thus achieving a satisfactory result in terms of esthetics and function of the stomatognathic system.

The effects of C-type natriuretic peptide on craniofacial skeletogenesis

C-type natriuretic peptide (CNP) is a potent stimulator of long bone and vertebral development via endochondral ossification. In the present study, we investigated the effects of CNP on craniofacial skeletogenesis, which consists of both endochondral and membranous ossification. Morphometric analyses of crania from CNP knockout and transgenic mice revealed that CNP stimulates longitudinal growth along the cranial length, but does not regulate cranial width. CNP markedly increased the length of spheno-occipital synchondrosis in fetal murine organ cultures, and the thickness of cultured murine chondrocytes from the spheno-occipital synchondrosis or nasal septum, resulting in the stimulation of longitudinal cranial growth. Mandibular growth includes endochondral and membranous ossification; although CNP stimulated endochondral bone growth of condylar cartilage in cultured fetal murine mandibles, differences in the lengths of the lower jaw between CNP knockout or transgenic mice and wild-type mice were smaller than those observed for the lengths of the upper jaw. These results indicate that CNP primarily stimulates endochondral ossification in the craniofacial region and is crucial for midfacial skeletogenesis.

Nasal septal and craniofacial form in European- and African-derived populations

As a component of the chondrocranium, the nasal septum influences the anteroposterior dimensions of the facial skeleton. The role of the septum as a facial growth center, however, has been studied primarily in long-snouted mammals, and its precise influence on human facial growth is not as well understood. Whereas the nasal septum may be important in the anterior growth of the human facial skeleton early in ontogeny, the high incidence of nasal septal deviation in humans suggests the septum's influence on human facial length is limited to the early phases of facial growth. Nevertheless, the nasal septum follows a growth trajectory similar to the facial skeleton and, as such, its prolonged period of growth may influence other aspects of facial development. Using computed tomography scans of living human subjects (n = 70), the goal of the present study is to assess the morphological relationship between the nasal septum and facial skeleton in European- and African-derived populations, which have been shown to exhibit early developmental differences in the nasal septal-premaxillary complex. First we assessed whether there is population variation in the size of the nasal septum in European- and African-derived samples. This included an evaluation of septal deviation and the spatial constraints that influence variation in this condition. Next, we assessed the relationship between nasal septal size and craniofacial shape using multivariate regression techniques. Our results indicate that there is significant population variation in septal size and magnitude of septal deviation, both of which are greater in the European-derived sample. While septal deviation suggests a disjunction between the nasal septum and other components of the facial skeleton, we nevertheless found a significant relationship between the size of the nasal septum and craniofacial shape, which appears to largely be a response to the need to accommodate variation in nasal septal size.

Id2 controls chondrogenesis acting downstream of BMP signaling during maxillary morphogenesis

Maxillofacial dysmorphogenesis is found in 5% of the population. To begin to understand the mechanisms required for maxillofacial morphogenesis, we employed the inhibitors of the differentiation 2 (Id2) knock-out mouse model, in which Id proteins, members of the regulator of basic helix-loop-helix (bHLH) transcription factors, modulate cell proliferation, apoptosis, and differentiation. We now report that spatially-restricted growth defects are localized at the skull base of Id2 KO mice. Curiously, at birth, neither the mutant Id2 KO nor wild-type (WT) mice differed, based upon cephalometric and histological analyses of cranial base synchondroses. In postnatal week 2, a narrower hypertrophic zone and an inhibited proliferative zone in presphenoid synchondrosis (PSS) and spheno-occipital synchondrosis (SOS) with maxillary hypoplasia were identified in the Id2 mutant mice. Complementary studies revealed that exogenous bone morphogenetic proteins (BMPs) enhanced cartilage growth, matrix deposition, and chondrocyte proliferation in the WT but not in the mutant model. Id2-deficient chondrocytes expressed more Smad7 transcripts. Based on our results, we assert that Id2 plays an essential role, acting downstream of BMP signaling, to regulate cartilage formation at the postnatal stage by enhancing BMP signals through inhibiting Smad7 expression. As a consequence, abnormal endochondral ossification was observed in cranial base synchondroses during the postnatal growth period, resulting in the clinical phenotype of maxillofacial dysmorphogenesis.

Exclusion of Class III malocclusion candidate loci in Brazilian families

The role played by genetic components in the etiology of the Class III phenotype, a class of dental malocclusion, is not yet understood. Regions that may be related to the development of Class III malocclusion have been suggested previously. The aim of this study was to search for genetic linkage with 6 microsatellite markers (D1S234, D4S3038, D6S1689, D7S503, D10S1483, and D19S566), near previously proposed candidate regions for Class III. We performed a two-point parametric linkage analysis for 42 affected individuals from 10 Brazilian families with a positive Class III malocclusion segregation. Analysis of our data indicated that there was no evidence for linkage of any of the 6 microsatellite markers to a Class III locus at = zero, with data supporting exclusion for 5 of the 6 markers evaluated. The present work reinforces that Class III is likely to demonstrate locus heterogeneity, and there is a dependency of the genetic background of the population in linkage studies.

Polymorphisms in the Matrilin-1 gene and risk of mandibular prognathism in Koreans

Previous linkage analysis of an Asian population proposed possible candidate genes for mandibular prognathism, such as Matrilin-1 (cartilage matrix protein). To investigate the association between the single-nucleotide polymorphisms (SNPs) in Matrilin-1 and mandibular prognathism, we investigated three sequence variants (-158 T>C, 7987 G>A, 8572 C>T) in 164 mandibular prognathism patients and 132 control individuals with a normal occlusion. The results showed that the 8572 TT genotypes in Matrilin-1 showed increased risk of mandibular prognathism (OR = 9.28, 95% Cl = 1.19~197.57, P < 0.05), whereas the 7987 AA genotype showed a protective effect for mandibular prognathism (OR = 0.16, 95% Cl = 0.05~0.47, P < 0.05). Genotyping results showed that the Matrilin-1 polymorphism haplotype TGC (ht4; 158T, 7987G, and 8572C alleles) had a pronounced risk effect for mandibular prognathism compared with controls (OR = 5.16, 95% Cl = 2.03~13.93, P < 0.01). The results suggest that polymorphisms in Matrilin-1 could be used as a marker for genetic susceptibility to mandibular prognathism.

Induced premaxillary suture fusion: class III malocclusion model

The etiology of class III malocclusion remains unknown. The present study investigates the relationship between craniofacial morphology and premaxillary suture fusion to test the hypothesis that class III malocclusion may be related to premaxillary suture fusion. Cyanoacrylate was applied to immobilize the left premaxillary suture in the experimental group. Sham surgeries in rats were used for controls. Dental impressions and radiographs were taken before and after surgery for comparison of craniofacial differences between groups. Overall cranial base lengths, craniofacial widths, and craniofacial angulations related to the anterior base showed significant differences between groups. At the end of the experiment, the growth of the snout in the experimental group was inhibited and deviated to the treated side, while no obvious change was seen in the control group. The results show that induced premaxillary suture fusion can affect craniofacial morphology and indicate that premature premaxillary suture fusion may result in class III malocclusion.

Cranial base features in skeletal Class III patients

OBJECTIVE

To investigate the cranial base configuration in skeletal Class III patients to clarify the conflicting findings from literature.

MATERIALS AND METHODS

Initial lateral radiographs of 54 skeletal Class III patients and 54 matched controls (Class I, II/1, II/2) aged 14 to 24 years were analyzed retrospectively for 21 cephalometric basicranial variables and jaw lengths relative to anterior cranial base length.

RESULTS

In contrast to overall cranial base length, the anterior (N-S) and posterior (S-Ba, S-Ar) sections failed to show a significant reduction in Class III patients. The significantly more acute angles Ca-S-Ba and Se-S-Ba reflected increased cranial base flexure. Resulting anterior condylar displacement was shown by significant reduction of Se-S-Cd and Ar-Ca. Relative mandibular length was significantly increased.

CONCLUSIONS

Decreased basicranial angulation associated with Class III mandibular protrusion was clearly confirmed for skeletal Class III patients. Overall shortening of the cranial base apparently resulted from various minor alterations. The results are compatible with the deficient orthocephalization hypothesis of Class III morphogenesis. The basicranial-maxillary relationship in skeletal Class III remains unclear.

Growth of cranial synchondroses and sutures requires polycystin-1

In vertebrates, coordinated embryonic and postnatal growth of the craniofacial bones and the skull base is essential during the expansion of the rostrum and the brain. Identification of molecules that regulate skull growth is important for understanding the nature of craniofacial defects and for development of non-invasive biologically based diagnostics and therapies. Here we report on spatially restricted growth defects at the skull base and in craniofacial sutures of mice deficient for polycystin-1 (Pkd1). Mutant animals reveal a premature closure of both presphenoid and sphenooccipital synchondroses at the cranial base. Furthermore, knockout mice lacking Pkd1 in neural crest cells are characterized by impaired postnatal growth at the osteogenic fronts in craniofacial sutures that are subjected to tensile forces. Our data suggest that polycystin-1 is required for proliferation of subpopulations of cranial osteochondroprogenitor cells of both mesodermal and neural crest origin during skull growth. However, the Erk1/2 signalling pathway is up-regulated in the Pkd1-deficient skeletal tissue, similarly to that previously reported for polycystic kidney.

Major gene and multifactorial inheritance of mandibular prognathism

Mandibular prognathism typically shows familial aggregation. Various genetic models have been described and it is assumed to be a multifactorial and polygenic trait, with a threshold for expression. Our goal was to examine specific genetic models of the familial transmission of this trait. The study sample comprised of 2,562 individuals from 55 families. Complete family histories for each proband were ascertained and the affection status of relatives were confirmed by lateral cephalograms, photographs, and dental models. Pedigrees were drawn using PELICAN and complex segregation analysis was performed using POINTER. Parts of some pedigrees were excluded to create one founder pedigrees, so the total N was 2,050. Analysis showed more affected females than males (P = 0.030). The majority of the pedigrees suggest autosomal dominant inheritance. Incomplete penetrance was demonstrated by the ratio of affected/unaffected parents and siblings. The heritability of mandibular prognathism was estimated to be 0.316. We conclude that there is a major gene that influences the expression of mandibular prognathism with clear signs of Mendelian inheritance and a multifactorial component.

Cervical column morphology in patients with skeletal Class III malocclusion and mandibular overjet

INTRODUCTION

The cervical column morphology of adults with skeletal Class III malocclusion and mandibular overjet was examined and compared with the cervical column morphology of a control group with neutral occlusion and normal craniofacial morphology.

METHODS

The mandibular overjet group consisted of 57 patients (32 women, 25 men). The control group consisted of 21 subjects (15 women, 6 men). A visual assessment of the cervical column and measurements of the craniofacial dimensions were performed on a profile radiograph of each subject.

RESULTS

In the mandibular overjet group, 61.4% had cervical column fusion, and 12.3% had posterior arch deficiency. Morphologic cervical column deviations occurred significantly more often in the mandibular overjet group than in the control group (P <.001). The most important craniofacial parameters for fusion of the cervical column were maxillary retrognathism (P <.05) and mandibular overjet (P <.05) (R2 = 0.22). The most important factor for posterior arch deficiency was mandibular inclination (P <.05) (R2 = 0.12).

CONCLUSIONS

These results are considered an important first step in phenotypic differentiation of skeletal Class III malocclusions that can be associated with different genotypes. This is important for the diagnosis and the correct treatment of these patients.

Pressure from the lips and the tongue in children with class III malocclusion

OBJECTIVE

To discuss possible relationships between class III malocclusion and perioral forces by measuring the pressure from the lips and the tongue of children with class III malocclusion.

METHODS

Thirty-one children with class III malocclusion were investigated and their perioral forces were measured at rest and during swallowing under natural head position by a custom-made miniperioral force computer measuring system.

RESULTS

The resting pressures exerted on the labial side and palatine side of the upper left incisor, as well as the labial side and lingual side of the lower left incisor, were 0 g/cm(2), 0 g/cm(2), 0.57 g/cm(2) and 0.23 g/cm(2), respectively. Correspondingly, the swallowing forces were 2.87 g/cm(2), 5.97 g/cm(2), 4.09 g/cm(2) and 7.89 g/cm(2), respectively. No statistical difference between muscular pressure and gender existed. During swallowing, the lingual forces were significantly higher than the labial forces (P<0.01), however, at rest there was no significantly different force between these two sides. Compared to the normal occlusion patients, children with class III malocclusion had lower perioral forces. The upper labial resting forces (P<0.01), the lower labial resting forces (P<0.05) and all the swallowing pressures from the lips and the tongue (P<0.01) showed statistical differences between the two different occlusion conditions. Meanwhile, no significant difference was found for the resting pressure from the tongue between class III malocclusion and normal occlusion.

CONCLUSION

Patients with class III malocclusion have lower perioral forces and this muscle hypofunction may be secondary to the spatial relations of the jaws. The findings support the spatial matrix hypothesis.

Mandibular prognathism in Japanese families ascertained through orthognathically treated patients

INTRODUCTION

Patients with severe mandibular prognathism frequently require orthognathic surgery to correct skeletal disharmony. Genetic and environmental factors are suggested in the etiology of mandibular prognathism, but the precise contribution of these factors is unknown.

METHODS

To clarify the impact of genetic factors on mandibular prognathism, we gave a questionnaire to 105 subjects with severe skeletal Class III mandibular prognathism who planned to undergo or had undergone orthognathic surgery. The questionnaire assessed mandibular prognathism in 3 generations of each subject's family. All answers were confirmed in a careful interview that included differentiation of "maxillary deficiency" and "mandibular excess." This is the first 3-generation family study of mandibular prognathism in orthognathically treated patients.

RESULTS

The average ANB, SNA, and SNB angles in the probands were -3.7 degrees , 80.9 degrees , and 84.6 degrees, respectively. A total of 1480 family members were examined, and 11.2% had mandibular prognathism. Men were slightly more affected than women; 68.6% of families had at least 1 member other than the proband with mandibular prognathism. The affected ratio of first-degree relatives was more than twice that of second-degree relatives (17.5% and 7.6%, respectively). There was no difference in the occurrence between fathers and mothers of probands, and siblings showed a high affected ratio of 25.0%. Falconer's heritability was calculated as 84.3% in first-degree relatives.

CONCLUSIONS

A high occurrence of mandibular prognathism was seen in families of orthognathically treated skeletal Class III patients, suggesting a profound genetic influence.