MSX1, PAX9, and TGFA contribute to tooth agenesis in humans

"Examining the link between tooth agenesis and papillary thyroid cancer: is there a risk factor?" Observational study

BACKGROUND

Mutations in one or multiple genes can lead to hypodontia and its characteristic features. Numerous studies have shown a strong genetic influence on the occurrence of hypodontia, and identified several genes, including AXIN2, EDA, FGF3, FGFR2, FGFR10, WNT10A, MSX1, and PAX9, that are directly associated with dental agenesis and carcinogenesis. The objective of this study was to investigate the occurrence and pattern of tooth agenesis, microdontia, and palatally displaced canine (PDC) in women diagnosed with papillary thyroid cancer (PTC), compared to a control group of women without any malignancy or thyroid disease.

MATERIALS AND METHODS

This case-control study was carried at the Department of Orthodontics, School of Dental Medicine University of Zagreb, and Department of Oncology and Nuclear Medicine Sestre Milosrdnice University Hospital Centre. The study involved a clinical examination and evaluation of dental status, panoramic X-ray analysis, and assessment of medical and family history of 116 female patients aged 20-40 with PTC, as well as 424 females in the control group who were of similar age.

RESULTS

The prevalence of hypodontia, microdontia, and PDC was statistically higher in women with PTC than in the control group. The prevalence rate of hypodontia was 11.3% in the experimental group and 3.5% in the control group. The experimental group showed a higher occurrence of missing upper lateral incisors, lower left central incisors, and all the third molars (except the upper left) compared to the control group. Women with PTC showed the prevalence of PDC significantly higher than the control group (3.5%, 0.7%, p = 0.002). The probability of hypodontia as a clinical finding increases 2.6 times, and microdontia occurs 7.7 times more frequently in women with PTC.

CONCLUSION

Our study suggests a possible link between odontogenesis and PTC. The absence of permanent teeth may increase the likelihood of PTC in women. Leveraging the age-7 orthopantomogram to identify women at high risk for PTC within a critical early detection window could significantly improve oral health outcomes and PTC prognosis through proactive interventions.

Correlation of Dental Anomalies with Cleft Type and Gender in Non-Syndromic Oral Cleft Patients: A Cross-Sectional Study

To investigate the distribution of dental anomalies between non-syndromic orofacial cleft patients and their association with the cleft type and gender.

Retrospective cross-sectional study involving examination of intraoral dental records and radiographs.

300 non-syndromic orofacial cleft patients included (161 males and 139 females, mean age: 10.23 ± 2.3 years).

Variables analyzed: tooth agenesis, microdontia, and supernumerary teeth. Data analysis: Chi-square and Fisher's exact tests to investigate the correlation between dental anomalies, cleft type, and gender.

Agenesis occurred in 66% of the subjects, supernumerary teeth in 19.6%, and microdontia in 18.3%. In females with unilateral left cleft lip and palate (CLP), agenesis was significantly higher compared to males. Both genders presented significant agenesis of maxillary lateral incisors and right central incisor. Significant agenesis of central incisor, canine and second premolar on the upper left side and lower second premolars were observed only in males, with significant microdontia for maxillary lateral incisors and left central incisor. Significant agenesis of maxillary first premolars was seen only in females. Agenesis in maxillary quadrants was significant for patients with unilateral right and left CLP, and bilateral CLP. In mandibular quadrants, agenesis was substantially higher for patients with isolated CP.

Results suggest that tooth agenesis and microdontia might not be directly associated with the cleft area's anatomical irregularity but are affected by gender and other genetic factors that regulate the development of the anomaly and the orofacial clefting mutually.

Genetic Factors of Teeth Impaction: Polymorphic and Haplotype Variants of PAX9, MSX1, AXIN2, and IRF6 Genes

In recent research, there has been a growing awareness of the role of genetic factors in the positioning and eruption of teeth in the maxilla and mandible. This study aimed to evaluate the potential of specific polymorphic markers of single nucleotide polymorphisms (SNPs) located within the PAX9, MSX1, AXIN2, and IRF6 genes to determine the predisposition to tooth impaction. The study participants were divided into two groups: the first group consisted of individuals with at least one impacted secondary tooth. In contrast, the second group (control group) had no impacted teeth in their jaws. To analyze the genes, real-time PCR (polymerase chain reaction) and TaqMan probes were utilized to detect the selected polymorphisms. The findings suggest that disruptions in the structure and function of the mentioned genetic factors such as polymorphic and haplotype variants of PAX9, MSX1, AXIN2, and IRF6 genes, which play a direct role in tooth and periodontal tissue development, might be significant factors in tooth impaction in individuals with genetic variations. Therefore, it is reasonable to hypothesize that tooth impaction may be influenced, at least in part, by the presence of specific genetic markers, including different allelic variants of the PAX9, AXIN2, and IRF6 genes, and especially MSX1.

Relationship between the TGFBR1 Gene and Molar Incisor Hypomineralization

BACKGROUND

Molar Incisor Hypomineralization Syndrome (MIH) is a problem of increasing incidence that represents a new challenge in the dental treatment of many of the children we see in our dental offices. Understanding the etiology of this syndrome (still unknown) will help us to prevent the appearance of this process. Lately a certain genetic relationship has been suggested in the syndrome. The aim of the present study was to explore the relationship between activation of the TGFBR1 gene and the development of MIH, as recent studies suggest that there may be an association in this regard.

MATERIALS AND METHODS

The study sample consisted of 50 children between 6-17 years of age with MIH, each with at least one parent and a sibling with or without MIH, and a group control of 100 children without MIH. The condition of the permanent molars and incisors was evaluated and recorded based on the criteria of Mathu-Muju and Wright. Saliva samples were collected after washing and rinsing of the oral cavity. Genotyping was performed with the saliva samples for the selection of a target polymorphism of the studied gene (TGFBR1).

RESULTS

The mean age was 9.7 years (SD 2.36). Of the 50 children with MIH, 56% were boys and 44% girls. The degree of MIH was predominantly severe (58%), with moderate and mild involvement in 22% and 20% of the cases, respectively, according to the classification of Mathu-Muju. The allelic frequencies were seen to behave as expected. The logistic regression analysis aimed to relate each polymorphism to the presence or absence of the factors. These results were inconclusive, with no evidence suggesting an alteration of the TGFBR1 gene to be related to the appearance of MIH.

CONCLUSIONS

Within the limitations posed by a study of these characteristics, it can be affirmed that no relationship has been found between the TGFBR1 gene and the appearance of molar incisor hypomineralization.

Permanent Tooth Agenesis and Associated Dental Anomalies among Orthodontically Treated Children

(1) Background: Tooth agenesis is one of the most common developmental dental anomalies often affecting the maxillary incisors area and premolar regions. (2) Purpose: The aim of this study was to assess the prevalence and distribution of permanent tooth agenesis and the associated dental abnormalities among orthodontically treated children. (3) Materials and Methods: This study was carried out utilizing 3000 pretreatment records of children who underwent orthodontic treatment, 1780 (59%) females and 1220 (41%) males, aged 10-25 years (mean age 15 years). Tooth agenesis and other dental anomalies were surveyed using their panoramic radiographs, according to gender, pattern, and location. The level of statistical significance was set at p < 0.05 using t-test or Chi-Square tests. (4) Results: The total number of missing teeth, excluding third molars, was 518 (17%) found in 326 (11%) children. The majority were the maxillary lateral incisors, which was 176 teeth (34%) (p < 0.05). Of them, 111 (63%) were in females, and 65 (37%) were in males. The second most common missing tooth was mandibular second premolars, which was 137 teeth (26%), followed by missing 73 (14%) maxillary second premolars. Impacted teeth had the highest associated dental anomaly prevalence (14.3%), while transposition showed the lowest anomaly prevalence (0.5%). (5) Conclusions: A prevalence of 11% for tooth agenesis was detected in this study. More teeth were missing in the maxilla compare with the mandible. A significant association was found between missing maxillary lateral incisors and missing premolars (p < 0.05). Associated dental anomalies included an increased number of peg-shaped maxillary lateral incisors, palatally displaced and impacted maxillary canines, ectopic teeth, and infra-occluded (submerged) primary second molars.

Advances in tooth agenesis and tooth regeneration

The lack of treatment options for congenital (0.1%) and partial (10%) tooth anomalies highlights the need to develop innovative strategies. Over two decades of dedicated research have led to breakthroughs in the treatment of congenital and acquired tooth loss. We revealed that by inactivating USAG-1, congenital tooth agenesis can be successfully ameliorated during early tooth development and that the inactivation promotes late-stage tooth morphogenesis in double knockout mice. Furthermore, Anti- USAG-1 antibody treatment in mice is effective in tooth regeneration and can be a breakthrough in treating tooth anomalies in humans. With approximately 0.1% of the population suffering from congenital tooth agenesis and 10% of children worldwide suffering from partial tooth loss, early diagnosis will improve outcomes and the quality of life of patients. Understanding the role of pathogenic USAG-1 variants, their interacting gene partners, and their protein functions will help develop critical biomarkers. Advances in next-generation sequencing, mass spectrometry, and imaging technologies will assist in developing companion and predictive biomarkers to help identify patients who will benefit from tooth regeneration.

Tooth number abnormality: from bench to bedside

Tooth number abnormality is one of the most common dental developmental diseases, which includes both tooth agenesis and supernumerary teeth. Tooth development is regulated by numerous developmental signals, such as the well-known Wnt, BMP, FGF, Shh and Eda pathways, which mediate the ongoing complex interactions between epithelium and mesenchyme. Abnormal expression of these crutial signalling during this process may eventually lead to the development of anomalies in tooth number; however, the underlying mechanisms remain elusive. In this review, we summarized the major process of tooth development, the latest progress of mechanism studies and newly reported clinical investigations of tooth number abnormality. In addition, potential treatment approaches for tooth number abnormality based on developmental biology are also discussed. This review not only provides a reference for the diagnosis and treatment of tooth number abnormality in clinical practice but also facilitates the translation of basic research to the clinical application.

PAX9 Is Involved in Periodontal Ligament Stem Cell-like Differentiation of Human-Induced Pluripotent Stem Cells by Regulating Extracellular Matrix

Periodontal ligament stem cells (PDLSCs) play central roles in periodontal ligament (PDL) tissue homeostasis, repair, and regeneration. Previously, we established a protocol to differentiate human-induced pluripotent stem cell-derived neural crest-like cells (iNCs) into PDLSC-like cells (iPDLSCs) using human PDL cell-derived extracellular matrix (ECM). However, it remained unclear what factors principally regulate the differentiation of iNCs into iPDLSCs. In this study, we aimed to identify the transcription factor regulating production of human PDL cell-derived ECM, which is responsible for the generation of iPDLSCs. We cultured iNCs on ECMs of two human PDL cell lines (HPDLC-3S and HPDLC-3U) and of human dermal fibroblasts (HDF). iNCs cultured on HPDLC-3U demonstrated higher iPDLSC-associated gene expression and mesenchymal differentiation capacity than cells cultured on HDF or HPDLC-3S. The transcription factor PAX9 was highly expressed in HPDLC-3U compared with HDF and HPDLC-3S. iNCs cultured on siPAX9-transfected HPDLC-3U displayed downregulation of iPDLSC-associated marker expression and adipocytic differentiation capacity relative to controls. Our findings suggest that PAX9 is one of the transcription factors regulating ECM production in human PDL cells, which is responsible for the differentiation of iNCs into iPDLSCs.

Prevalence of dental anomalies in different facial patterns and malocclusions in an Iranian population

Objective

This study aimed to evaluate the prevalence and association of dental anomalies with different types of malocclusions and facial patterns.

Methods

In this cross-sectional study, the records of patients referred to the Orthodontics Department at 12-20 years of age were collected. The patients were classified into four types of malocclusion: Cl I, Cl II div 1, Cl II div 2, and Cl III, and three types of facial patterns: normal, long, and short. Fifteen dental anomalies were searched within the documents. The statistical analysis of data was performed with chi-squared and Fisher's exact test.

Results

Among 602 patients evaluated in this study, 28.6% were males, and 71.4% were females. The prevalence of Cl I, Cl II div1, Cl II div 2, and Cl III was 58.3%, 28.7%, 5.5%, and 7.5%, respectively. The normal facial pattern was most prevalent (47.2%), followed by the long facial pattern (41.4%) and short facial pattern (11.5%); 60.7% of the study population had at least one dental anomaly. Dilaceration was the most common anomaly (27.7%), followed by impaction (21.8%) and hypodontia (18.9%). Most dental anomalies were found in females, Cl II malocclusion, and long face samples. A statistically significant association was found between transposition and male gender (P = 0.006) and between short roots and Cl II malocclusion (P = 0.047). No significant association was found between dental anomalies and facial patterns.

Conclusion

Significant associations were reported between transposition and male gender and between short roots and Cl II malocclusion. In our population, dilaceration was the most common dental anomaly.

WNT10A variants: following the pattern of inheritance in tooth agenesis and self-reported family history of cancer

OBJECTIVES

The aim of this study was the analysis of WNT10A variants in seven families of probands with various forms of tooth agenesis and self-reported family history of cancer.

MATERIALS AND METHODS

We enrolled 60 young subjects (aged 13 to 17) from the Czech Republic with various forms of tooth agenesis. Dental phenotypes were assessed using Planmeca ProMax 3D (Planmeca Oy, Finland) with Planmeca Romexis software (version 2.9.2) together with oral examinations. After screening PAX9, MSX1, EDA, EDAR, AXIN2 and WNT10A genes on the Illumina MiSeq platform (Illumina, USA), we further analyzed the evolutionarily highly conserved WNT10A gene by capillary sequencing in the seven families.

RESULTS

All the detected variants were heterozygous or compound heterozygous with various levels of phenotypic expression. The most severe phenotype (oligodontia) was found in a proband who was compound heterozygous for the previously identified WNT10A variant p.Phe228Ile and a newly discovered c.748G > A variant (p.Gly250Arg) of WNT10A. The newly identified variant causes substitution of hydrophobic glycine for hydrophilic arginine.

CONCLUSIONS

We suggest that the amino acid changes in otherwise highly conserved sequences significantly affect the dental phenotype. No relationship between the presence of WNT10A variants and a risk of cancer has been found.

CLINICAL RELEVANCE

Screening of PAX9, MSX1, EDA, EDAR, AXIN2 and WNT10A genes in hope to elucidate the pattern of inheritance in families.

The Human Genetics of Dental Anomalies

The development of tooth is a highly complex procedure and mastered by specific genetic programs. Genetic alterations, environmental factors, and developmental timing can disturb the execution of these programs, and result in various dental anomalies like hypodontia/oligodontia, and supernumerary teeth, which are commonly seen in our clinical practice. Advances in molecular research enabled the identification of various genes involved in the pathogenesis of dental anomalies. In the near future, it will help provide a more accurate diagnosis and biological-based treatment for these anomalies. In this article, we present the molecular phenomenon of tooth development and the genetics of various dental anomalies.

Dental caries and periodontitis risk factors in cleft lip and palate patients

Cleft lip and palate (CLP) is the most common congenital facial malformation and has a significant developmental, physical, and psychological impact on those with the deformity and their families. Risk factors contributing to CLP may conclude as genetic factors and environmental factors. The anatomical and morphological abnormalities related to CLP are favorable for dental plaque accumulation on the tooth surface. Therefore, patients with CLP undergo poorer oral hygiene and higher susceptibility to dental caries and periodontitis. In this review, we aim to conclude and update probable causes underlying the association between CLP and poor oral health and provide novel ideas of targeted early prevention for such oral diseases.

Congenitally missing second permanent molars in non‑syndromic patients (Review)

Hypodontia (tooth agenesis) is regarded as the most common congenital dental anomaly. The present review discusses the epidemiological characteristics of congenitally missing second permanent molars (CMSPMs) within a systematic review of the literature. The review was based on Pubmed library associated with the search of various scientific databases or academic resources, improved by hand search of reference lists. The terms ‘hypodontia’ or ‘anodontia’ in combination with ‘prevalence’ or ‘epidemiology’ were searched in the data sources for studies published between January 2001 and December 2020. Abstracts of non-English papers were also analyzed. The inclusion criteria were as follows: i) Study provided precise data about CMSPMs, even if no second permanent molar was reportedly missing; ii) the number of CMSPMs distributed by jaw was provided and iii) studies on subjects >3 years were used. The exclusion criteria were as follows: i) Studies on patients with history of trauma of the maxilla or the mandible, any type of syndrome affecting bone metabolism, metabolic disorders, previous extraction or tooth loss due to dental caries, cleft lip and palate; ii) studies performed on cohorts of patients with hypodontia and iii) studies reporting data including third molars, except for those that presented sufficient data to perform correct calculations. A total of 79 studies were selected, accumulating a population of 281,968 people, with an average sample size of 3,524.60±11,255.25. The prevalence of CMSPMs (IpHSPM) was 2.79±3.16% among all missing teeth (1.03±1.59% for upper CMSPMs and 1.76±2.32% for lower CMSPMs; P=0.011). There were no significant differences (P=0.250) in IpHSPM between men (1.59±1.52%) and women (2.13±1.67%). However, significant differences were recorded between continents. Furthermore, lower CMSPMs were found more frequently in orthodontic samples (P=0.033). The prevalence of CMSPMs is low compared with the overall prevalence of CM teeth. Despite the rarity of these anomalies, early detection is important to enable practitioners to plan and start treatment at the best time for optimal results.

Missing and unerupted teeth in osteogenesis imperfecta

INTRODUCTION

Osteogenesis imperfecta (OI) is a genetic disorder characterized by bone fragility and craniofacial and dental abnormalities such as congenitally missing teeth and teeth that failed to erupt which are believed to be doubled in OI patients than normal populations and were associated with low oral health quality of life. However, the etiology of these abnormalities remains unclear. To understand the factors influencing missing and unerupted teeth, we investigated their prevalence in a cohort of OI patients as a function of the clinical phenotype (OI type), the genetic variant type, the tooth type and the onset of bisphosphonate treatment.

METHOD

A total of 144 OI patients were recruited from The Shriners Hospital, Montreal, Canada, between 2016 and 2017. Patients were evaluated using intraoral photographs and panoramic radiographs. Missing teeth were evaluated in all patients, and unerupted teeth were assessed only in patients ≥15 years old (n = 82).

RESULTS

On average, each OI patient had 2.4 missing teeth and 0.8 unerupted teeth, and the most common missing and unerupted teeth were the premolars and the upper second molars, respectively. These phenomena were more prominent in OI type III and IV than in OI type I, and were not sex or age-related. Missing teeth were significantly more common in patients with C-propeptide variants than all other variants (p-value <0.05). Unerupted teeth were significantly more common in patients with α1 and α2 glycine variants or substitutions than in those with haploinsufficiency variants. Early-onset of bisphosphonate treatment would significantly increase the risk of unerupted teeth in patients with OI types III and IV (OR = 1.68, 95% CI (1.15-1.53)).

CONCLUSION

The prevalence of missing and unerupted teeth at the tooth type level in OI patients varies according to the nature of the collagen variants and the OI type. These findings highlight the role of collagen in tooth development and eruption.

Use of a Modified Nance Appliance for Esthetic Rehabilitation of a Child Patient with Rare Nonfamilial and Nonsyndromic Oligodontia

Congenital absence of more than 6 teeth except the third molar is known as oligodontia. It can affect both primary and permanent dentitions. The affected individuals usually demonstrate esthetic, functional, and psychological concerns. The present case report is about a 4-year-old female patient with multiple missing (both primary and permanent) teeth with esthetic and social problems. On extraoral examination, the patient demonstrated upper lip relapse due to missing anterior teeth. On physical examination, no other abnormality was detected in relation to the hair, appendages, or presence of a cleft. On intraoral and radiographic examination, 21 teeth were missing, which included both the primary and the permanent tooth buds. To encourage a positive behavioral change, it was decided to carry out prosthetic intervention using a modified fixed Nance appliance and acrylic teeth. After the replacement of the missing teeth, a marked improvement in the profile and esthetics was seen.

The clinical significance and correlative signaling pathways of paired box gene 9 in development and carcinogenesis

Paired box 9 (PAX9) gene belongs to the PAX family, which encodes a family of metazoan transcription factors documented by a conserved DNA binding paired domain 128-amino-acids, critically essential for physiology and development. It is primarily expressed in embryonic tissues, such as the pharyngeal pouch endoderm, somites, neural crest-derived mesenchyme, and distal limb buds. PAX9 plays a vital role in craniofacial development by maintaining the odontogenic potential, mutations, and polymorphisms associated with the risk of tooth agenesis, hypodontia, and crown size in dentition. The loss-of-function of PAX9 in the murine model resulted in a short life span due to the arrest of cleft palate formation and skeletal abnormalities. According to recent studies, the PAX9 gene has a significant role in maintaining squamous cell differentiation, odontoblast differentiation of pluripotent stem cells, deregulation of which is associated with tumor initiation, and malignant transformation. Moreover, PAX9 contributes to promoter hypermethylation and alcohol- induced oro-esophageal squamous cell carcinoma mediated by downregulation of differentiation and apoptosis. Likewise, PAX9 activation is also reported to be associated with drug sensitivity. In summary, this current review aims to understand PAX9 function in the regulation of development, differentiation, and carcinogenesis, along with the underlying signaling pathways for possible cancer therapeutics.

FGF10 and FGF13 genetic variation and tooth-size discrepancies

OBJECTIVES

To explore whether variations in odontogenesis-related genes are associated with tooth-size discrepancies.

MATERIALS AND METHODS

Measurements of the width of permanent teeth were obtained from dental casts of 62 orthodontic patients (age 15.65 ± 6.82 years; 29 males and 33 females). Participants were classified according to the anterior and overall Bolton ratios as without tooth-size discrepancy or with maxillary or mandibular tooth-size excess. Genomic DNA extracted from buccal cells was used, and 13 single nucleotide polymorphisms (SNPs) across nine genes were genotyped by polymerase chain reaction using TaqMan chemistry. χ2 or Fisher exact tests were applied to determine the overrepresentation of genotypes/alleles depending on the type of tooth-size discrepancy (α = .05; corrected P value: P < 5.556 × 10-3). Odds ratios (ORs) and their correspondent 95% confidence intervals (CIs) were also calculated to investigate the risk of this phenotype for the SNPs having significant association.

RESULTS

Individuals carrying the FGF10 rs900379 T allele were more likely to have larger mandibular teeth (OR = 3.74; 95% CI: 1.65-8.47; P = .002). This effect appeared to be stronger when two copies of the risk allele (TT) were found (recessive model, OR = 6.16; 95% CI: 1.71-22.16; P = .006). On the other hand, FGF13 rs5931572 rare homozygotes (AA, or male A hemizygotes) had increased risk of displaying tooth-size discrepancies when compared with the common homozygotes (GG, or male G hemizygotes; OR = 10.32; 95% CI: 2.20-48.26; P = .003).

CONCLUSIONS

The results suggest that FGF10 and FGF13 may contribute to the presence of tooth-size discrepancies.

Genetics of Dentofacial and Orthodontic Abnormalities

The development of craniofacial complex and dental structures is a complex and delicate process guided by specific genetic mechanisms. Genetic and environmental factors can influence the execution of these mechanisms and result in abnormalities. An insight into the mechanisms and genes involved in the development of orofacial and dental structures has gradually gained by pedigree analysis of families and twin studies as well as experimental studies on vertebrate models. The development of novel treatment techniques depends on in-depth knowledge of the various molecular or cellular processes and genes involved in the development of the orofacial complex. This review article focuses on the role of genes in the development of nonsyndromic orofacial, dentofacial variations, malocclusions, excluding cleft lip palate, and the advancements in the field of molecular genetics and its application to obtain better treatment outcomes.

Determination of prognostic factors for orthognathic surgery in children with cleft lip and/or palate

OBJECTIVE

To determine the prognostic factors for orthognathic surgery (OGS) in children with cleft lip and/or palate (CL/P) using artificial intelligence (AI) systems.

DESIGN

Retrospective cohort study.

SETTING

An orthodontic department at a university dental hospital.

PARTICIPANTS

This study included 126 patients with bilateral and unilateral CL/P for whom lateral cephalograms were obtained at three time points: 7 (T1), 10 (T2) and 15 (T3) years of age.

MAIN OUTCOME MEASURES

Cleft type, severity of lip separation at birth, number of missing teeth, sex, palatal repair methods and surgeons, cephalometric variables at T1 and T2, and the total duration of orthodontic treatment were examined as predictors. The need for OGS and skeletal and dental discrepancies at T3 was examined as outcomes.

RESULTS

A total of six models were developed, with a mean area under the receiver operating characteristic curve of 0.93. Multiple prognostic factors for OGS were identified. In particular, the number of clefts in the lip and alveolus showed relatively high odds ratios, as did anterior crossbite at T3. Achieving palatal closure with the push-back method, rather than Furlow's method, was also found to be a predictive factor for anterior crossbite at T3, with high odds ratios.

CONCLUSIONS

The prognostic factors for OGS determined by the AI systems were the number of clefts in the lip and alveolus, the palatal repair method, male sex, several cephalometric variables for the sagittal and vertical dimensions, growth patterns and the number of missing teeth.

Are developmentally missing teeth a predictive risk marker of malignant diseases in non-syndromic individuals? A systematic review

Background:

Different genes and loci that are associated with non-syndromic developmental tooth agenesis (TA) have the same causation pathway in the development of tumours including breast cancer (BC), epithelial ovarian cancer (EOC), colorectal cancer (CRC) and lung cancer (LC).

Objectives:

To assess the link between TA and the development of cancer.

Search sources:

This registered review included a comprehensive search of electronic databases (Cochrane Central Register of Controlled Trials [CENTRAL], LILACS, Scopus, Web of Science and Medline via Ovid) until 1 April 2020, supplemented by manual, grey literature and reference lists search. There was no restriction in term of date of publication, gender, race or type of hypodontia.

Data selection:

The primary outcome was the relationship between TA and cancer. The secondary outcome was to identify the genetic correlation between TA and cancer.

Data extraction:

Study selection, data extraction and risk of bias assessment were performed independently and induplicate by two reviewers, with disputes resolved by a third reviewer.

Results:

Eight studies with a moderate-high risk of bias were included in the final review, with a total of 5821 participants. Due to the heterogeneity among the included studies, the data were presented narratively. Limited studies reported a high prevalence of EOC (19.2%–20%) and CRC (82%–100%) in individuals with TA (depending on the study) compared to those without TA (3% for EOC and 0% for CRC). While others reported a weak correlation between EOC and CRC and TA ( P > 0.05). Weak evidence suggested a strong correlation between breast, cervical uterine and prostate cancers and TA ( P < 0.05).

Conclusions:

Though low-quality evidence suggests a link between TA and cancer, it was not possible to verify that TA can hold a predictive value as a marker for cancers. Further research is needed to confirm the association.

Registration:

PROSPERO (CRD42020139751).

IRF6, MSX1, TGFA, dental anomalies, and skeletal malocclusion

OBJECTIVE

Verify the presence of association between four variables-transforming growth factor α (TGFA; C/T rs1523305), interferon regulatory factor 6 (IRF6; A/C rs2013162), muscle segment homeobox 1 (MSX1; A/G rs12532), and dental anomalies-with skeletal malocclusion by comparing these four variables with Angle Classes I, II, and III, and normal, hyperdivergent, and hypodivergent growth patterns.

METHODS

A total of 505 orthodontic records of patients older than 8 years were evaluated. The sample consisted of 285 (56.4 per cent) females, 220 (43.6 per cent) males, 304 (60.2 per cent) Whites (the rest were mixed Blacks with Whites), with a mean age of 20.28 (±10.35) years (ranging from 8 to 25 years). Eight cephalometric points, which served as the anatomical framework for obtaining angles and cephalometric measurements, were used for skeletal characterization using the Dolphin Software. Samples of saliva were collected and the DNA was extracted, diluted and quantified. Markers in TGFA, IRF6, and MSX1 were used and genotypes were obtained using TaqMan chemistry. Odds ratio (OR) and 95 per cent confidence interval (CI) calculations, chi-square, Fisher's Exact, Mann-Whitney, and correlation coefficient tests (significance level: 95 per cent) were performed. Bonferroni correction was applied and an alpha of 0.0006 was considered statistically significant.

RESULTS

There was no statistically significant associations between markers in TGFA or IRF6 with skeletal malocclusions. Tooth agenesis was associated with facial convexity (P < 0.001). MSX1 was associated with Class II skeletal malocclusion (P = 0.0001, OR = 0.6, CI = 0.46-0.78).

CONCLUSION

Individuals with tooth agenesis were more likely to have a convex face. MSX1 was associated with Class II skeletal malocclusion.

Association of rs2862851 in TGFA Gene with Peripheral TGFA Levels and the Severity of Knee Osteoarthritis in the Han Chinese Population

Background: Osteoarthritis (OA) is a complex joint disorder characterized by sclerosis of subchondral bone. The knee is one of the most commonly affected joints. Given that the genetic mechanisms underlying knee OA remain elusive, our study aims were to first confirm the association of the TGFA gene alleles with the risk of knee OA and, second, to evaluate the relationship between peripheral TGFA concentrations and knee OA in an independent Han Chinese population. Materials and Methods: We performed a case-control study consisting of 392 knee OA patients and 808 unrelated healthy controls. Single-marker-based association analyses and haplotype-based analyses using 3 single nucleotide polymorphisms (SNPs) were performed to confirm the association of TGFA gene alleles with the risk of knee OA. Furthermore, we used enzyme-linked immunosorbent assay (ELISA) kits to detect the peripheral blood TGFA concentrations in patients and healthy controls and then evaluated the relationships between the TGFA alleles and genotypes with serum TGFA levels. Results: We replicated the genetic association of the rs2862851 T allele with the risk of knee OA (p = 1.68 × 10^-4, OR = 1.41). Moreover, we observed that the peripheral TGFA concentrations were higher in knee OA patients than in healthy controls (p = 8.15 × 10^-13). The peripheral TGFA concentrations were significantly different among the various rs2862851 genotypes for both cases (p = 4.16 × 10^-16) and controls (p = 7.24 × 10^-19). The individuals with the TT genotype in both cases and controls, had the highest peripheral TGFA concentrations. Moreover, with the increase in knee OA grade, peripheral TGFA concentration also increased (p = 1.36 × 10^-72). Conclusion: Our study confirmed the association of the TGFA gene with the risk of knee OA and identified a positive correlation between peripheral TGFA levels and the severity of knee OA in the Han Chinese population, providing clues for understanding the etiology of knee OA.

Family-based association study of genetic analysis of paired box gene 9 polymorphisms in the peg-shaped teeth in the Jordanian Arab population

OBJECTIVE

The aim of this study is to genotype thirteen Single Nucleotide Polymorphisms (SNPs) within the paired box gene 9 (PAX9) in 36 Jordanian Arab families with peg-shaped teeth, and also to investigate the association between the PAX9 gene and peg-shaped teeth disorder.

METHODS

Genomic DNA samples were extracted from families according to distinguished processes. Then, DNA was amplified by polymerase chain reaction technique (PCR) using specified primers for the exons of the PAX9 gene. In addition, single nucleotide polymorphisms analysis was conducted using the DNA sequencing genotyping method to identify specific single nucleotide polymorphisms in the PAX9 gene associated with peg-shaped teeth.

RESULTS

Thirteen single nucleotide polymorphisms in the PAX9 gene (Chromosome 14q13.3) were used; seven of them (rs104894467, rs104894469, rs28933373, rs28933970, rs28933971, rs28933972, and rs7143727) were non-polymorphic, and the other six were polymorphic (rs2073244, rs2073246, rs2295222, rs4904155, rs4904210, and rs12881240). Both rs12881240 and rs2295222 SNPs showed significant association with peg-shaped teeth disorder (P < 0.05). Moreover, the haplotype genetic analysis revealed that there is a genetic association with peg-shaped teeth disorder susceptibility (P < 0.05) in the Jordanian families of Arab descent.

CONCLUSION

Our findings exhibited significant variations compared to the data recorded from other countries.

Functional study of novel PAX9 variants: The paired domain and non-syndromic oligodontia

OBJECTIVES

To investigate pathogenic variants of the paired box 9 (PAX9) gene in patients with non-syndromic oligodontia, and the functional impact of these variants.

SUBJECTS AND METHODS

Whole exome sequencing and Sanger sequencing were utilized to detect gene variants in a cohort of 80 patients diagnosed with non-syndromic oligodontia. Bioinformatic and conformational analyses, fluorescence microscopy and luciferase reporter assay were employed to explore the functional impact.

RESULTS

We identified three novel variants in the PAX9, including two frameshift variants (c.211_212insA; p.I71Nfs*246 and c.236_237insAC; p.T80Lfs*6), and one missense variant (c.229C > G; p.R77G). Familial co-segregation verified an autosomal-dominant inheritance pattern. Conformational analyses revealed that the variants resided in the paired domain, and could cause corresponding structural impairment of the PAX9 protein. Fluorescence microscopy showed abnormal subcellular localizations of frameshift variants, and luciferase assay showed impaired downstream transactivation activities of the bone morphogenetic protein 4 (BMP4) gene in all variants.

CONCLUSIONS

Our findings broaden the spectrum of PAX9 variants in patients with non-syndromic oligodontia and support that paired domain structural impairment and the dominant-negative effect are likely the underlying mechanisms of PAX9-related non-syndromic oligodontia. Our findings will facilitate genetic diagnosis and counselling, and help lay the foundation for precise oral health therapies.

Common variants of EDA are associated with non-syndromic hypodontia

OBJECTIVE

The aim of this case-control study was to investigate the association between non-syndromic hypodontia and nineteen common variants of candidate genes ectodysplasin A (EDA), paired box 9 (PAX9), msh homeobox 1 (MSX1) and axis inhibition protein 2 (AXIN2).

SETTINGS AND SAMPLE POPULATION

Sixty-one hypodontia cases were frequency-matched to 253 controls with no missing teeth (excluding the third molars).

MATERIAL AND METHODS

Self-report data and DNA samples were collected from each participant.

RESULTS

The sample had a mean age of 16.6 years (SD = 7.3), with most participants being female (59.6%), and of New Zealand European origin (75.4%). Using multiple logistic regression analysis, it was found that the T-allele of rs12853659 (EDA) and the G-allele of rs2428151 (EDA) were both associated with a higher risk of hypodontia (odds ratio, OR = 2.79, 95% CI = 1.11-7.01; and OR = 2.87, 95% CI = 1.04-7.94, respectively). The G-allele of rs2520378 (EDA) showed a protective effect with an OR of 0.61 (95% CI = 0.38-0.99). The EDA SNP findings were consistent with previous reports included in a meta-analysis. No associations were found with the PAX9, AXIN2 and MSX1 genes, after adjusting for sex and ethnicity.

CONCLUSIONS

Common variants of the EDA genes are associated with specific phenotypes of non-syndromic hypodontia, thus confirming their role in the regulatory pathways of normal tooth development. However, larger samples are needed to investigate the association further.

Genetic variants in tooth agenesis-related genes might be also involved in tooth size variations

OBJECTIVE

The present study aimed to evaluate if genetic variants in PAX9, MSX1, TGFα, FGF3, FGF10, FGF13, GLI2 and GLI3 are involved in TS of permanent teeth.

MATERIALS AND METHODS

Pretreatment dental records from orthodontic patients were assessed prior to recruitment. Patients with tooth agenesis and congenital anomalies (including oral cleft) and/or syndromes were excluded. Dental casts were used to measure the maximum crown dimensions of all fully erupted permanent teeth except second and third molars in mesiodistal direction. Teeth with caries, occlusal wear, mesiodistal restorations, and obvious deformities were not evaluated. Genomic DNA samples were used for genotyping. The allelic discrimination of 13 genetic variants was performed. The associations between TS and genotype were analyzed by linear regression, adjusted by gender at a significance level of p ≤ 0.05.

RESULTS

Genetic polymorphisms in the tooth agenesis-related genes studied here were associated with increased and decreased TS, in both maxilla and mandible (p < 0.05).

CONCLUSION

This study reported associations of novel tooth agenesis-related gene variants with permanent tooth size variations.

CLINICAL RELEVANCE

The presence of some genetic variants could allow the prediction of permanent tooth size.

Association between craniofacial morphological patterns and tooth agenesis-related genes

Background

The aim of the present study was to assess if genetic polymorphisms in tooth agenesis (TA)-related genes are associated with craniofacial morphological patterns.

Methods

This cross-sectional, multi-center, genetic study evaluated 594 orthodontic Brazilians patients. The presence or absence of TA was determined by analysis of panoramic radiography. The patients were classified according to their skeletal malocclusion and facial growth pattern by means of digital cephalometric analysis. Genomic DNA was extracted from squamous epithelial cells of buccal mucosa and genetic polymorphisms in MSX1 (rs1042484), PAX9 (rs8004560), TGF-α (rs2902345), FGF3 (rs1893047), FGF10 (rs900379), and FGF13 (rs12838463, rs5931572, and rs5974804) were genotyped by polymerase chain reaction using TaqMan chemistry and end-point analysis.

Results

Genotypes (p = 0.038) and allele (p = 0.037) distributions for the FGF3 rs1893047 were significantly different according to the skeletal malocclusion. Carrying at least one G allele increased in more than two times the chance of presenting skeletal class III malocclusion (OR = 2.21, CI 95% = 1.14–4.32; p = 0.017). There was no association between another skeletal craniofacial pattern and some polymorphism assessed in the present study.

Conclusion

Our results suggest that the genetic polymorphism rs1893047 in FGF3 might contribute to variations in the craniofacial sagittal pattern.

Association between MSX1 rs12532 polymorphism with nonsyndromic unilateral complete cleft lip and palate and tooth agenesis

OBJECTIVES

To investigate the association of MSX1 rs12532 polymorphism with the risk of nonsyndromic unilateral complete cleft lip and palate (NSCLP) and tooth agenesis.

MATERIALS AND METHODS

The study is comprised of 384 individuals divided into 4 groups: group 1, patients with unilateral complete NSCLP and premolar agenesis (n = 57); group 2, patients with unilateral NSCLP without tooth agenesis (n = 117); group 3, patients with premolar agenesis without oral cleft (n = 53) and group 4 (n = 157), a control group with individuals without tooth agenesis and oral cleft. Genotyping of rs12532 was carried out with Taqman chemistry, and associations were investigated using logistic regression analyses.

RESULTS

Overall rs12532 allele and genotype distributions revealed no significant differences between the groups of NSCLP or tooth agenesis.

CONCLUSION

Although our results are consistent with a lack of association of MSX1 rs12532 and the risk of unilateral NSCLP and tooth agenesis, further studies with additional SNPs and a more diverse ethnic cohort are warranted.

The Changing Landscape in the Genetic Etiology of Human Tooth Agenesis

Despite much progress in understanding the genetics of syndromic tooth agenesis (TA), the causes of the most common, isolated TA remain elusive. Recent studies have identified novel genes and variants contributing to the etiology of TA, and revealed new pathways in which tooth development genes belong. Further, the use of new research approaches including next-generation sequencing has provided increased evidence supporting an oligogenic inheritance model for TA, and may explain the phenotypic variability of the condition. In this review, we present current knowledge about the genetic mechanisms underlying syndromic and isolated TA in humans, and highlight the value of incorporating next-generation sequencing approaches to identify causative and/or modifier genes that contribute to the etiology of TA.

Tooth Abnormalities In Individuals With Unilateral Alveolar Clefts: A Comparison Between Sides Using Cone-Beam Computed Tomography

Background

Tooth abnormalities are most often present in individuals with oral clefts than general population, and lead to a long-term impact on facial anatomy and self-esteem. The purpose of this study was to compare the proportion of dental anomalies between the cleft side and non-cleft side in individuals with non-syndromic unilateral alveolar clefts (AC).

Material and Methods

Twenty cone beam computed tomography (CBCT) scans were converted into three-dimensional (3D) virtual models. The dental anomalies considered were: tooth agenesis; supernumerary teeth; giroversion; and microdontia. Statistical analysis was performed using the McNemar’s test and Fisher’s exact test (p<0.05).

Results

Statistically significant differences were not found either between the prevalence of individuals with dental abnormalities on the non-cleft side and the sides of the AC (p = 1.00), or sex (p = 0.36). Tooth agenesis was the most prevalent dental anomaly (55.6%). On the cleft side the lateral incisor was tooth most involved by dental anomalies; and the second premolar was the most affected on the non-cleft side.

Conclusions

This study showed a high frequency of dental anomalies in the cleft individuals and indicated that the side of AC and sex do not interfere in the proportion of dental anomalies on non-cleft side.

Key words:Cone beam computed tomography, Hypodontia, Tooth abnormalities.

Genetic study of non-syndromic tooth agenesis through the screening of paired box 9, msh homeobox 1, axin 2, and Wnt family member 10A genes: a case-series

Non-syndromic tooth agenesis (NSTA) is the most common developmental anomaly in humans. Several studies have been conducted on dental agenesis and numerous genes have been identified. However, the pathogenic mechanisms responsible for NSTA are not clearly understood. We studied a group of 28 patients with sporadic NSTA and nine patients with a family history of tooth agenesis. We focused on four genes - paired box 9 (PAX9), Wnt family member 10A (WNT10A), msh homeobox 1 (MSX1), and axin 2 (AXIN2) - using direct Sanger sequencing of the exons and intron-exon boundaries. The most prevalent variants identified in PAX9 and AXIN2 genes were analyzed using the chi-square test. The sequencing results revealed a number of variants in the AXIN2 gene, including one novel missense mutation in one patient with agenesis of a single second premolar. We also identified one variant in the AXIN2 gene as being a putative risk factor for tooth agenesis. Only one missense mutation was identified in the WNT10A gene and this mutation was found in two patients. Interestingly, WNT10A is reported as the most prevalent gene mutated in the European population with NSTA.

Nonsyndromic oligodontia : Does the Tooth Agenesis Code (TAC) enable prediction of the causative mutation?

OBJECTIVES

The literature suggests an association between phenotype and causative mutation in nonsyndromic oligodontia. Thus, the present study was designed to verify this hypothesis in a consecutive cohort of patients.

METHODS

All patients with nonsyndromic oligodontia who had been treated at the study center (Department of Orthodontics, University of Giessen, Germany) over the period 1986-2013 were contacted. Candidates were included only if at least one more family member had hypo- or oligodontia (i.e., without regard to the number of congenitally missing teeth). A total of 20 patients were included. After evaluating the dental status of each participant, the Tooth Agenesis Code (TAC) was applied. On this basis, a tentative diagnosis was made to predict which gene (MSX1, AXIN2, EDA, or PAX9) was likely to show mutation. Afterwards this hypothesis was confirmed or rejected by analyzing a saliva sample for mutation of the predicted gene. If confirmed, any available family members were also genetically analyzed.

RESULTS

Based on their TAC scores and sums, gene mutations were predicted for MXS1 in 11, AXIN2 in 3, EDA in 6, and PAX9 in none of the patients. The evaluation of MSX1 yielded variants in 4 of 11 cases, all of which were classified as nonpathogenic since they were not considered as functional mutations. The evaluation of EDA yielded a pathogenic exon-7 mutation in 2 of 6 patients, both being brothers with different TAC scores; the same mutation, which represents a novel missense mutation, was also found in other members of the same family. The evaluation of AXIN2 yielded variants in 3 of 3 cases, all of which were classified as nonpathogenic.

CONCLUSIONS

Our findings obtained in consecutive patients with nonsyndromic oligodontia did not reveal any clinically relevant associations between oligodontia phenotype (based on TAC) and causative mutations for nonsyndromic oligodontia.

Dental Anomalies in a Brazilian Cleft Population

Objective

The aim of this study was to radiographically investigate the prevalence of dental anomalies outside the cleft area in a group of Brazilian patients with nonsyndromic cleft lip and/or palate (NSCL/P).

Design, Participants, and Setting

A retrospective analysis of 207 panoramic radiographs of patients with NSCL/P aged 12 to 45 years without history of tooth extraction and orthodontic treatment was performed.

Results

Dental anomalies were found in 75.4% of the patients, and tooth agenesis (29.2%) and supernumerary tooth (2.6%) were the most common anomalies. The risk of agenesis was higher among the individuals with cleft palate (CP) compared with individuals with cleft lip (CL) and cleft lip and palate (CLP) (agenesis: CP versus CL: odds ratio 6.27, 95% confidence interval 2.21-17.8, P = .0003; CP versus CLP: odds ratio 2.94; 95% confidence interval 1.27-6.81, P = .01). The frequency of dental agenesis was higher in patients with unilateral complete CLP (agenesis: P < .0001), incomplete bilateral CLP (agenesis: P = .0013), complete CP (agenesis: P < .0001), and incomplete CP (agenesis: P < .0001). The frequency of supernumerary teeth was higher in patients with bilateral complete CLP ( P < .0001). The frequency of dental agenesis ( P < .0001) and ectopic tooth ( P = .009) was higher than the frequency estimated for general population.

Conclusions

The prevalence of dental anomalies in patients with NSCL/P was higher than that reported in overall population. This study found preferential associations between dental anomalies and specific extensions of NSCL/P, suggesting that dental agenesis and ectopic tooth may be part of oral cleft subphenotypes.

Radiographic Study of the Prevalence and Distribution of Hypodontia Associated with Unilateral and Bilateral Clef Lip and Palate in a Hungarian Population

Background

Cleft defects are one of the most frequent birth-deformities of the orofacial region and they are commonly associated with anomalies of the tooth structure, size, shape, formation, eruption, and tooth number. The aim of our study was to evaluate the prevalence, distribution, and potential association of combined hypodontia in cleft-affected patients with regard to all types of teeth in both jaws in the permanent dentition.

Material/Methods

This retrospective radiographic analysis included patients with various types of clefts treated orthodontically in the Department of Orofacial Orthopedics and Orthodontics at Heim Pàl Children’s Hospital, Budapest. There were 150 patients (84 males, 66 females) with non-syndromic unilateral (UCLP; n=120 patients) or bilateral (BCLP; n=30 patients) cleft formation (lip, alveolus and palate) who met the inclusion criteria. Statistical analysis was performed using the chi-square test and Fisher’s exact test (significance level p<0.05).

Results

Hypodontia was significantly more frequent in patients with cleft-sided lateral incisor (104 patients, 69%), with a total of 235 missing teeth, followed by the second premolars of the upper and lower jaw. A significant correlation of congenital missing teeth was observed in left-sided clefts between the upper and lower second premolar in the cleft area.

Conclusions

Hypodontia inside and outside the cleft area was frequently observed. This should affect the therapy plans, especially if the cleft-sided premolar is also absent. Further comprehensive research including numerous random samples is necessary for better estimating other possible associations.

Genetic Basis of Nonsyndromic and Syndromic Tooth Agenesis

Human dentition development is a long and complex process which involves a series of reciprocal and sequential interactions between the embryonic stomodeal epithelium and the underlying neural crest-derived mesenchyme. Despite environment disturbances, tooth development is predominantly genetically controlled. To date, more than 200 genes have been identified in tooth development. These genes implied in various signaling pathways such as the bone morphogenetic protein, fibroblast growth factor, sonic hedgehog homolog, ectodysplasin A, wingless-type MMTV integration site family (Wnt), and transform growth factor pathways. Mutations in any of these strictly balanced signaling cascades may cause arrested odontogenesis and/or other dental defects. This article aims to review current knowledge about the genetic mechanisms responsible for selective nonsyndromic tooth agenesis in humans and to present a detailed summary of syndromes with hypodontia as regular features and their causative genes.

Mutation analysis by direct and whole exome sequencing in familial and sporadic tooth agenesis

Dental agenesis is one of the most common congenital craniofacial abnormalities. Dental agenesis can be classified, relative to the number of missing teeth (excluding third molars), as hypodontia (1 to 5 missing teeth), oligodontia (6 or more missing teeth), or anodontia (lack of all teeth). Tooth agenesis may occur either in association with genetic syndromes, based on the presence of other inherited abnormalities, or as a non-syndromic trait, with both familiar and sporadic cases reported. In this study, we enrolled 16 individuals affected by tooth agenesis, prevalently hypodontia, and we carried out direct Sanger sequencing of paired box 9 (PAX9) and Msh homeobox 1 (MSX1) genes in 9 subjects. Since no mutations were identified, we performed whole exome sequencing (WES) in the members of 5 families to identify causative gene mutations either novel or previously described. Three individuals carried a known homozygous disease mutation in the Wnt family member 10A (WNT10A) gene (rs121908120). Interestingly, two of these individuals were siblings and also carried a heterozygous functional variant in EDAR-associated death domain (EDARADD) (rs114632254), another disease causing gene, generating a combination of genetic variants never described until now. The analysis of exome sequencing data in the members of other 3 families highlighted new candidate genes potentially involved in tooth agenesis and considered suitable for future studies. Overall, our study confirmed the major role played by WNT10A in tooth agenesis and the genetic heterogeneity of this disease. Moreover, as more genes are shown to be involved in tooth agenesis, WES analysis may be an effective approach to search for genetic variants in familiar or sporadic tooth agenesis, at least in more severe clinical manifestations.

On the Etiology of Molar-Incisor Hypomineralization

Molar-incisor hypomineralization (MIH) is a condition that is defined based on its peculiar clinical presentation. Reports on the etiology of the condition and possible risk factors are inconclusive and the original suggestion that MIH is an idiopathic condition is often cited. Our group was the first to suggest MIH has a genetic component that involves genetic variation in genes expressed during dental enamel formation. In this report, we provide a rationale to explain the preferential affection of molars and incisors. We suggest that MIH is a genetic condition based on its prevalence, which varies depending on the geographic location, and the evidence that on occasion second primary molars, permanent canines, and premolars can show signs of hypomineralization of enamel when molars and incisors are affected.

Systematic analysis of copy number variants of a large cohort of orofacial cleft patients identifies candidate genes for orofacial clefts

Orofacial clefts (OFCs) represent a large fraction of human birth defects and are one of the most common phenotypes affected by large copy number variants (CNVs). Due to the limited number of CNV patients in individual centers, CNV analyses of a large number of OFC patients are challenging. The present study analyzed 249 genomic deletions and 226 duplications from a cohort of 312 OFC patients reported in two publicly accessible databases of chromosome imbalance and phenotype in humans, DECIPHER and ECARUCA. Genomic regions deleted or duplicated in multiple patients were identified, and genes in these overlapping CNVs were prioritized based on the number of genes encompassed by the region and gene expression in embryonic mouse palate. Our analyses of these overlapping CNVs identified two genes known to be causative for human OFCs, SATB2 and MEIS2, and 12 genes (DGCR6, FGF2, FRZB, LETM1, MAPK3, SPRY1, THBS1, TSHZ1, TTC28, TULP4, WHSC1, WHSC2) that are associated with OFC or orofacial development. Additionally, we report 34 deleted and 24 duplicated genes that have not previously been associated with OFCs but are associated with the BMP, MAPK and RAC1 pathways. Statistical analyses show that the high number of overlapping CNVs is not due to random occurrence. The identified genes are not located in highly variable genomic regions in healthy populations and are significantly enriched for genes that are involved in orofacial development. In summary, we report a CNV analysis pipeline of a large cohort of OFC patients and identify novel candidate OFC genes.

Spectrum of Dental Phenotypes in Nonsyndromic Orofacial Clefting

Children with oral clefts show a wide range of dental anomalies, adding complexity to understanding the phenotypic spectrum of orofacial clefting. The evidence is mixed, however, on whether the prevalence of dental anomalies is elevated in unaffected relatives and is mostly based on small samples. In the largest international cohort to date of children with nonsyndromic clefts, their relatives, and controls, this study characterizes the spectrum of cleft-related dental anomalies and evaluates whether families with clefting have a significantly higher risk for such anomalies compared with the general population. A total of 3,811 individuals were included: 660 cases with clefts, 1,922 unaffected relatives, and 1,229 controls. Dental anomalies were identified from in-person dental exams or intraoral photographs, and case-control differences were tested using χ(2) statistics. Cases had higher rates of dental anomalies in the maxillary arch than did controls for primary (21% vs. 4%, P = 3 × 10(-8)) and permanent dentitions (51% vs. 8%, P = 4 × 10(-62)) but not in the mandible. Dental anomalies were more prevalent in cleft lip with cleft palate than other cleft types. More anomalies were seen in the ipsilateral side of the cleft. Agenesis and tooth displacements were the most common dental anomalies found in case probands for primary and permanent dentitions. Compared with controls, unaffected siblings (10% vs. 2%, P = 0.003) and parents (13% vs. 7%, P = 0.001) showed a trend for increased anomalies of the maxillary permanent dentition. Yet, these differences were nonsignificant after multiple-testing correction, suggesting genetic heterogeneity in some families carrying susceptibility to both overt clefts and dental anomalies. Collectively, the findings suggest that most affected families do not have higher genetic risk for dental anomalies than the general population and that the higher prevalence of anomalies in cases is primarily a physical consequence of the cleft and surgical interventions.

Taurodontism, Root Dilaceration, and Tooth Transposition: A Radiographic Study of a Population With Nonsyndromic Cleft Lip and/or Palate

OBJECTIVES

In an effort to contribute to proper dental planning and define possible dental phenotypes of nonsyndromic cleft lip and/or palate (CL/P), this study aimed to investigate the occurrence of taurodontism, root dilaceration, and tooth transposition in persons with nonsyndromic CL/P, specifically analyzing the differences among gender, cleft types, and the most affected teeth.

DESIGN

This retrospective study analyzed 974 panoramic x-rays from nonsyndromic Brazilians older than 16 years and categorized into the following four groups: group 1, 250 persons with unilateral cleft lip and palate; group 2, 250 persons with unilateral cleft lip; group 3, 224 persons with cleft palate; and a control group of 250 persons without clefts. Radiographs were digitalized with a scanner and analyzed.

RESULTS

In the Brazilian population studied, the prevalence of taurodontism was 60.4% in group 1, 62.4% in group 2, 67.0% in group 3, and 42.8% in the control group. Root dilacerations had a prevalence of 31.2% in group 1, 29.6% in group 2, 26.3% in group 3, and 27.2% in the control group. The teeth most affected by taurodontism were 17 and 27; whereas root dilacerations were most common in teeth 38 and 48. No tooth transpositions were found in any radiograph analyzed.

CONCLUSIONS

Taurodontism is significantly more prevalent in Brazilians with nonsyndromic CL/P than in persons without clefts; whereas the prevalence of root dilaceration no different from that in the control group. However, root dilacerations in anterior teeth were increased in groups 1 and 2 when compared to the control group.

An aberrant splice acceptor site due to a novel intronic nucleotide substitution in MSX1 gene is the cause of congenital tooth agenesis in a Japanese family

Congenital tooth agenesis is caused by mutations in the MSX1, PAX9, WNT10A, or AXIN2 genes. Here, we report a Japanese family with nonsyndromic tooth agenesis caused by a novel nucleotide substitution in the intronic region between exons 1 and 2 of the MSX1 gene. Because the mutation is located 9 bp before exon 2 (c.452-9G>A), we speculated that the nucleotide substitution would generate an abnormal splice site. Using cDNA analysis of an immortalized patient blood cell, we confirmed that an additional 7-nucleotide sequence was inserted at the splice junction between exons 1 and 2 (c.451_452insCCCTCAG). The consequent frameshift generated a homeodomain-truncated MSX1 (p.R151fsX20). We then studied the subcellular localization of truncated MSX1 protein in COS cells, and observed that it had a whole cell distribution more than a nuclear localization, compared to that of wild-type protein. This result suggests a deletion of the nuclear localization signal, which is mapped to the MSX1 homeodomain. These results indicate that this novel intronic nucleotide substitution is the cause of tooth agenesis in this family. To date, most MSX1 variants isolated from patients with tooth agenesis involve single amino acid substitutions in the highly conserved homeodomain or deletion mutants caused by frameshift or nonsense mutations. We here report a rare case of an intronic mutation of the MSX1 gene responsible for human tooth agenesis. In addition, the missing tooth patterns were slightly but significantly different between an affected monozygotic twin pair of this family, showing that epigenetic or environmental factors also affect the phenotypic variations of missing teeth among patients with nonsyndromic tooth agenesis caused by an MSX1 haploinsufficiency.

A Nonsyndromic Autosomal Dominant Oligodontia with A Novel Mutation of PAX9-A Clinical and Genetic Report

Oligodontia is congenital absence of one or more teeth which has familial abnormality and attributable to various mutations or polymorphisms of genes often associated with malformative syndromes. The present case reports a rare case of non syndromic oligodontia in an 8-year-old girl with missing 14 permanent teeth excluding third molars in mixed dentition. It is a rare finding which has not been frequently documented in Indian children. Mutations in MSX1 and PAX9 have been described in families in which inherited oligodontia characteristically involves permanent incisors, lateral incisors, premolars and molars. Our study analysed one large family with dominantly inherited oligodontia clinically and genetically. This phonotype is distinct from oligodontia phenotypes associated with mutations in PAX9. Sequencing of the PAX9 revealed a novel mutation in the paired domain of the molecule. The multiple sequence alignment and SNP analysis of the PAX9 exon 2 revealed two mutations.

Mutations in the MSX1 gene in Turkish children with non-syndromic tooth agenesis and other dental anomalies

Aim:

To search for mutations on the MSX1 gene and to present a genetic basis for non-syndromic tooth agenesis in conjunction with dental anomalies in a Turkish population.

Materials and Methods:

The patients included in this study were otherwise healthy, with ages ranging from seven to eighteen years. Eighty-two of them had one to six teeth missing (Group I) and 26 had more than six teeth missing (Group II), except for the third molars,. The missing teeth and dental anomalies were examined clinically and radiographically. The MSX1 gene was sequenced from the blood samples of patients who consented to the study.

Results:

Mutations or polymorphisms on the MSX1 gene were identified in six patients. Taurodontism was seen in patients from both groups I and II. The nucleotide changes were identified by mutation screening.

Conclusions:

Performing family studies, screening other candidate genes, and investigation of interactions between genes will provide a basis for better analysis of tooth agenesis models and their association with other dental anomalies.

Congenitally missing teeth (hypodontia): A review of the literature concerning the etiology, prevalence, risk factors, patterns and treatment

Congenitally missing teeth (CMT), or as usually called hypodontia, is a highly prevalent and costly dental anomaly. Besides an unfavorable appearance, patients with missing teeth may suffer from malocclusion, periodontal damage, insufficient alveolar bone growth, reduced chewing ability, inarticulate pronunciation and other problems. Treatment might be usually expensive and multidisciplinary. This highly frequent and yet expensive anomaly is of interest to numerous clinical, basic science and public health fields such as orthodontics, pediatric dentistry, prosthodontics, periodontics, maxillofacial surgery, anatomy, anthropology and even the insurance industry. This essay reviews the findings on the etiology, prevalence, risk factors, occurrence patterns, skeletal changes and treatments of congenitally missing teeth. It seems that CMT usually appears in females and in the permanent dentition. It is not conclusive whether it tends to occur more in the maxilla or mandible and also in the anterior versus posterior segments. It can accompany various complications and should be attended by expert teams as soon as possible.

Pediatric sleep-disordered breathing: New evidence on its development

Sleep-disordered breathing (SDB) in children could be resolved by adenotonsillectomy (T&A). However, incomplete results are often noted post-surgery. Because of this partial resolution, long-term follow-up is needed to monitor for reoccurrence of SDB, which may be diagnosed years later through reoccurrence of complaints or in some cases, through systematic investigations. Children undergoing T&A often have small upper airways. Genetics play a role in the fetal development of the skull, the skull base, and subsequently, the size of the upper airway. In non-syndromic children, specific genetic mutations are often unrecognized early in life and affect the craniofacial growth, altering functions such as suction, mastication, swallowing, and nasal breathing. These developmental and functional changes are associated with the development of SDB. Children without genetic mutations but with impairment of the above said functions also develop SDB. When applied early in life, techniques involved in the reeducation of these functions, such as myofunctional therapy, alter the craniofacial growth and the associated SDB. This occurs as a result of the continuous interaction between cartilages, bones and muscles involved in the growth of the base of the skull and the face. Recently collected data show the impact of the early changes in craniofacial growth patterns and how these changes lead to an impairment of the developmental functions and consequent persistence of SDB. The presence of nasal disuse and mouth breathing are abnormal functions that are easily amenable to treatment. Understanding the dynamics leading to the development of SDB and recognizing factors affecting the craniofacial growth and the resulting functional impairments, allows appropriate treatment planning which may or may not include T&A. Enlargement of lymphoid tissue may actually be a consequence as opposed to a cause of these initial dysfunctions.

Presentation of a keratocystic odontogenic tumor with agenesis: a case report

Introduction

We analyzed the etiopathogenetic, clinical, radiographic, and histopathologic aspects of keratocystic odontogenic tumors, particularly in association with dental anomalies of number, with the aim of providing useful information for their correct diagnosis, treatment, and prognosis within a multidisciplinary approach.

Case presentation

A 14-year-old Caucasian girl presented for observation of bilateral agenesis of the upper incisors, which was diagnosed by orthopantomography. Approximately one year after starting orthodontic treatment, the patient went to the emergency department because of a phlegmonous tumefaction of the lateroposterior upper left maxillary region. Diagnostic orthopantomography and axial computed tomography scan results of the facial skeleton revealed a large lesion occupying the left maxillary sinus, rhizolysis of dental elements 26 and 27, and dislocation of dental element 28. The lesion and infected sinus mucosa were removed through surgical antral-cystectomy with the Caldwell-Luc approach. Histological examination of the lesion confirmed the suspected diagnosis of keratocystic odontogenic tumor. The 12-month follow-up orthopantomography and computed tomography scan results showed good trabecular bone formation in the lesion area. The 24-month follow-up results showed optimal healing in the area of the lesion, positive pulp vitality tests for teeth 26 and 27, and good periodontal tissue healing, as verified through periodontal probing.

Conclusions

Combined with our observations from a careful review of the literature, the results of the case study suggest that keratocystic odontogenic tumor and dental agenesis probably do not develop through a common genetic cause. More likely, they are caused by related environmental factors. Management of this case required the multidisciplinary collaboration of different specializations and careful planning to devise a correct therapeutic protocol and reach a favorable prognosis.