Prevalence and patterns of permanent tooth agenesis in individuals with Down syndrome: a meta-analysis

Syndromic and Non-Syndromic Primary Failure of Tooth Eruption: A Genetic Overview

Primary failure of tooth eruption (PFE) is a rare genetic disorder characterized by the failure of teeth to erupt in the absence of obvious physical obstructions, often resulting in a progressive open bite that is resistant to orthodontic treatment. While PFE can be caused by genetic or systemic factors (such as cysts, tumors, and endocrine imbalances), the non-syndromic causes are primarily genetic, with an autosomal dominant inheritance pattern with variable expressivity. Several genes have been closely associated with the non-syndromic PFE form. The PTH1R (parathyroid hormone 1 receptor) is the most commonly PFE-associated gene. Additional genes associated with minor frequency are Transmembrane protein 119 (TMEM119), which reduces the glycolytic efficiency of bone cells, limiting their mineralization capacity and causing bone fragility; Periostin (POSTN), which regulates the extracellular matrix and the bone's response to mechanical stress; and Lysine (K)-specific methyltransferase 2C (KMT2C), which establishes histone methylation near the Wnt Family Member 5A (WNT5A) gene involved in dental development (odontogenesis). Syndromic forms of PFE are typically associated with complex multisystem disorders, where dental eruption failure is one of the clinical features of the spectrum. These syndromes are often linked to genetic variants that affect ectodermal development, craniofacial patterning, and skeletal growth, leading to abnormal tooth development and eruption patterns. Notable syndromes include GAPO syndrome, ectodermal dysplasia, and cleidocranial dysplasia, each contributing to PFE through distinct molecular mechanisms, such as disruptions in dental structure development, cranial abnormalities, or systemic developmental delays. The main aim of this review is to provide a comprehensive overview of the genetic basis underlying both syndromic and non-syndromic forms of PFE to facilitate precision diagnosis, foster the development of personalized therapeutic strategies, and offer new insights into managing this complex dental anomaly.

Main genetic entities associated with tooth agenesis

BACKGROUND

Tooth agenesis refers to the absence of one or more of the deciduous or permanent teeth. Tooth agenesis results from a series of disrupted reciprocal ectodermal mesenchymal interactions taking place during the early stages of tooth development.

METHODS

A narrative literature review was performed to describe the main genetic syndromes associated with tooth agenesis.

RESULTS AND CONCLUSIONS

The etiology of congenital tooth agenesis is multifactorial and include genetic, epigenetic, and environmental influences. Syndromes associated with chromosomal alterations, ectodermal dysplasia, Axenfeld-Rieger syndrome, oral-facial cleft syndromes, and syndromes with cancer predisposition are among the main entities presenting with tooth agenesis.

CLINICAL RELEVANCE

Tooth agenesis disorders can affect the masticatory function and cause disfigurement leading to physiological and psychological complications. Early recognition of these entities is crucial to guide the management of the patient and to provide families with the appropriate genetic counseling.

Patterns of tooth agenesis in individuals with Down syndrome: A secondary analysis using the Tooth Agenesis Code

AIMS

Tooth agenesis (TA) is common in Down syndrome (DS). It is unknown whether this agenesis occurs in specific patterns, which is important regarding treatment planning and aetiological research. This study aimed to aggregate and analyze patterns of TA, excluding third molars, in individuals with DS using the tooth agenesis code (TAC).

METHODS AND RESULTS

The study was designed as a secondary analysis, following STROSA guidelines. The search (MEDLINE-PubMed) and selection process resulted in six included studies encompassing 241 individuals with DS. TA data were systematically converted into TACs and analyzed per dentition, per jaw, and per tooth type. Symmetry was evaluated. The prediction was calculated for oligodontia. In the 155 cases with TA 86 distinct Overall-TAC patterns were identified. The most common patterns were bilateral maxillary lateral incisor agenesis (TAC002.002.000.000;10.3%), bilateral mandibular second premolar agenesis (TAC000.000.016.016;5.8%), and unilateral left maxillary lateral incisor agenesis (TAC000.002.000.000;5.2%). Symmetry in TA patterns was observed in 49.6% of TA cases in the maxilla and 52.3% in the mandible. The simultaneous absence of both mandibular central incisors had a large predictive value for oligodontia (OR12.44;95% CI:4.97-31.84; p < .001).

CONCLUSION

Predominant TA patterns exist in DS. Observation of mandibular central incisor agenesis can promote early diagnosis of oligodontia in DS.

A Narrative Review of the Association between Dental Abnormalities and Chemotherapy

Dental abnormalities are often detected in childhood and are reported to occur with high prevalence in patients who have undergone cancer treatment or chemotherapy. We performed a literature search of PubMed from 2004 to 2024 using the terms "dental anomaly" and "panoramic examination", and 298 potentially relevant articles were found. Thirty-one articles about dental abnormalities matched the eligibility criteria and were extracted for this review. Although the prevalence of tooth agenesis and microdontia in the general population was reported to be approximately 10% and 3%, respectively, the prevalence in patients who had undergone cancer treatment or chemotherapy was higher in all surveys, suggesting that the treatment is related to the occurrence of dental abnormalities. It is important to continue long-term follow-up with patients not only during treatment but also after the completion of treatment. Dental professionals should provide information about dental abnormalities to patients, their guardians, and medical professionals, which may lead to improvement in the quality of life of patients.

Pan-cancer analysis reveals the characteristics and roles of tooth agenesis mutant genes

Tooth development is regulated by numerous genes and signaling pathways. Some studies suggest that mutations in these genes may be associated with several cancer types. However, the tooth agenesis mutated genes role in the prognosis and their clinical therapeutic potentials in pan-cancer have not been elaborately explored. Moreover, the intrinsic correlation between tooth agenesis and cancers also needs to be further verified. We preliminarily analyzed expression levels and prognostic values of causative genes of tooth agenesis, and explored the correlation between the expression of tooth agenesis mutated genes and TME, Stemness score, clinical characteristic, immune subtype, and drug sensitivity in pan-cancer, which based on updated public databases and integrated some bioinformatics analysis methods. In addition, we conducted the enrichment analysis of tooth agenesis mutant genes from KOBAS database. We observed that TA mutant genes had significant gene expression differences in multiple cancer types compared with normal tissues. The expression of causative genes of TA is associated with the prognosis in several cancers from different databases. For example, AXIN2 and MSX1 were correlated to the overall survival (OS) of uterine corpus endometrial carcinoma. PAX9 and TP63 were related to OS of lung squamous cell carcinoma. And TP63 was associated with OS in breast invasive carcinoma and pancreatic adenocarcinoma. Furthermore, the expression of TA mutant genes also has a significant correlation with stromal and immune scores, and RNA stemness score and DNA stemness score in pan-cancer. Besides, we observed that all causative genes of TA were significantly correlated with immune subtypes. Moreover, KEGG pathway analysis showed that causative genes of TA were associated with the development and progression of breast cancer, basal cell carcinoma, gastric cancer, and hepatocellular carcinoma. Finally, AXIN2 expression has a significantly positive or negative correlation with drug sensitivity. Our study indicates the great potential of TA mutant genes as biomarkers for prognosis and provides valuable strategies for further investigation of TA mutant genes as potential therapeutic targets in cancers. Our study can further verify that there may be an intrinsic correlation between tooth agenesis and the occurrence of multiple cancers.

Gene mutations and chromosomal abnormalities in syndromes with tooth agenesis

This study aims to review the pathogenic mechanisms and clinical manifestations in syndromes with tooth agenesis (TA). Online Mendelian Inheritance in Man and PubMed databases were searched for a comprehensive review. Previous publications reported complicated aetiologies of syndromic TA. Gene mutations in conserved signalling pathways (WNT, EDA, SHH, FGF, and TGF-β/BMP) and crucial molecules (PAX9, PIXT2, IRF6, the p53 family, and subunits of RNA polymerase III) are the main causes of syndromic TA. In the process of odontogenesis, antagonistic or synergistic interactions are demonstrated in patients and murine models. Mutations in some genes (WNT10A, WNT10B, AXIN2, ANTXR1, MSX1, EDA, EDAR, and EDARADD) can result in both syndromic and isolated TA. In addition, chromosomal anomalies are also responsible for syndromic TA (Down syndrome, Wolf-Hirschhorn syndrome, Williams syndrome, and Pierre Robin sequence). The causes and manifestations of syndromic TA are highly complex, and this constitutes a clinical challenge. Mutations in signalling pathways and crucial molecules as well as chromosomal anomalies are responsible for syndromic TA. And there are overlaps between the causative genes of syndromic and isolated TA.

Treatment of Class II malocclusion with anterior open bite and posterior crossbite with the aid of mini-implants in a patient with Down syndrome: Clinical case report

OBJECTIVE

We report the orthodontic treatment of a class II malocclusion with anterior open bite and posterior crossbite in a patient with Down syndrome (DS) treated with mini-implants.

METHODS

Treatment began with rapid maxillary expansion with a Haas appliance, followed by dental alignment and leveling with a fixed appliance and the correction of class II dental relationships with the use of orthodontic mini-implants associated with a sliding jig.

RESULTS

The results obtained at the end of the treatment were satisfactory, with improvements in occlusion, including bite closure; maxillary expansion; and the correction of dental relationships.

CONCLUSION

When well-planned, orthodontic treatment in a patient with DS achieves satisfactory results from a skeletal, occlusal, and facial perspective.

Lateral cephalometric characteristics in individuals with Down Syndrome compared to non-syndromic controls: A meta-analysis

OBJECTIVES

The aim of the present meta-analysis was to provide a complete synthesis of all studies involving lateral cephalometric measurements in populations with Down Syndrome (DS).

METHODS

A literature search was carried out using six electronic databases to identify studies comparing cephalometric characteristics between populations with DS and control (healthy) populations. Studies were selected according to the research objectives, and predefined inclusion and exclusion criteria. Only the cephalometric measurements included in three or more studies selected were analyzed. The random-effects meta-analysis model was used for data analysis, and all analyses were carried out using RevMan5 software.

RESULTS

From an initial 871 articles identified through the literature search, ten cross-sectional studies were finally selected based on the inclusion and exclusion criteria. Ten cephalometric measurements underwent meta-analysis, five linear and five angular measurements. Concerning the five linear measurements, namely S-N, ANS-PNS, Go-Gn, Ar-Go, and N-ANS, all were significantly smaller in the DS group with the exception of Go-Gn. Of the five angular measurements, only three were statistically different between the DS and control groups. SNB and ANB angles were smaller in individuals with DS, whereas the basilar angle was larger. Subgroup analysis was also carried out based on age, and it was found that the gonial angle was significantly smaller before puberty, in individuals with DS. No differences between groups were found for the SNA angle.

CONCLUSION

There are significant cephalometric differences between individuals with and without DS. Individuals with DS have a shorter anterior cranial base, maxillary length, upper anterior facial height and mandibular height. The ANB and SNB angles were also smaller in those with DS, but the SNA angle showed no differences. These findings may indicate that the Class III malocclusion commonly found in individuals with DS does not seem to be due to mandibular prognathism.

CLINICAL RELEVANCE

Lateral cephalometric measurements in individuals with DS show significant differences from individuals without DS. Practitioners need to be aware of this and monitor growth from an early age in these children.

A comparative retrospective study on the prevalence and therapeutic treatment of dental agenesis between healthy children and children with systemic disease or congenital malformation

BACKGROUND

Dental agenesis (DA) in the permanent dentition is one of the most common dental anomalies, with a prevalence up to 2-10%. Therefore, the aim of this retrospective study was to investigate the prevalence and therapeutic treatment of DA in healthy children (HC) compared to children with systemic disease or congenital malformation (SD/CM).

METHODS

Out of 3407 patients treated at the Department of Paediatric Dentistry of the Justus Liebig University Giessen (Germany) between January 2015 and December 2020, a total of 1067 patients (594 female, 473 male) aged between 4.5 and 18 years were included in this study due to DA. Besides the patients' general medical history and therapeutic treatments, panoramic radiographs were analysed.

RESULTS

In contrast to the HC group with 9.7% DA, the SD/CM group showed a significantly higher prevalence of DA (19.8%; p < 0.05). The latter group was further classified into children with ectodermal dysplasia (4.4%), down syndrome (8.2%), cleft lip and palate (4.4%), intellectual disability/developmental delay (16.4%), and other genetic/organic diseases without intellectual disability (45.9%). Regarding therapeutic treatments, the HC group (59.5%) was significantly more often treated with an orthodontic gap opening compared to the SD/CM group (42.6%; p < 0.05), followed by orthodontic gap closing 36.5% in the HC group and 22.9% in the SD/CM group (p < 0.05), whereas no treatment was predominantly performed in the SD/CM group (37.7%) compared to the HC group (4%; p < 0.05). Furthermore, 50% in the SD/CM group required general anaesthesia for therapeutic treatment (vs. 8.1% in the HC group; p < 0.05).

CONCLUSIONS

Children with SD/CM suffered more often from DA compared to HC that underlines multi- and interdisciplinary treatment of utmost importance. Furthermore, due to intellectual disability, common treatment methods can be complicated by insufficient compliance. This fact underlines the importance of an early attempt to establish the necessary cooperation enabling children with SD/CM to receive therapy.

Panoramic radiographs and dental patients with Down syndrome: A scoping review

INTRODUCTION

Life expectancy for people with Down syndrome (DS) has increased to 60 years, although poor oral health affects their quality of life. Panoramic radiographs (PRs) are usually well-tolerated by people with DS and can provide valuable diagnostic data for treatment planning and research. Methods A scoping review of peer-reviewed articles published between 1971and 2021 was conducted in accordance with the PRISMA extension for scoping reviews to determine the scope of use of PRs for people with DS.

RESULTS

937 papers were screened, and 52 papers were included and charted into seven categories in this review. A high prevalence of tooth agenesis (TA) and other anomalies were reported in 45% of papers. Severe periodontal disease was considered characteristic of DS in the 1970s-80s and the benefit of time-consuming treatment was questioned. Since 2000 case reports illustrate that improved oral care, orthodontic treatment, and dental implants under local or general anaesthetic can improve the quality of life for people with DS.

CONCLUSION

PRs play an important role in the diagnosis of anomalies, periodontal disease, and implant planning for patients with DS. This review highlights the gaps in research of caries, pathology, TMJ, systemic disease indicators, and guidelines for dentists. Systematic PR viewing, with a knowledge of characteristic features of DS, will assist diagnosis of pathology and improve comprehensive dental care treatment planning for children and adults with DS.

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.

Establishment of Down's syndrome periodontal ligament cells by transfection with SV40T-Ag and hTERT

Down's syndrome is one of the most common human congenital genetic diseases and affected patients have increased risk of periodontal disease. To examine involvement of the disease with periodontal disease development, we established immortalized periodontal ligament cells obtained from a Down's syndrome patient by use of SV40T-Ag and hTERT gene transfection. Expressions of SV40T-Ag and hTERT were observed in periodontal ligament cell-derived immortalized cells established from healthy (STPDL) and Down's syndrome patient (STPDLDS) samples. Primary cultured periodontal ligament cells obtained from a healthy subject (pPDL) had a limited number of population doublings (< 40), while STPDL and STPDLDS cells continued to grow with more than 80 population doublings. Primary cultured periodontal ligament cells obtained from the patient showed a chromosome pattern characteristic of Down's syndrome with trisomy 21, whereas STPDLDS samples showed a large number of abnormal chromosomes in those results. Gene expression analysis revealed that expression of DSCR-1 in STPDLDS is greater than that in STPDL. These results suggest that the newly established STPDLDS cell line may be a useful tool for study of periodontal disease in Down's syndrome patients.

Prevalence and incidence of physical health conditions in people with intellectual disability - a systematic review

OBJECTIVE

To synthesize evidence on the prevalence and incidence of physical health conditions in people with intellectual disability (ID).

METHODS

We searched Medline, PsycInfo, and Embase for eligible studies and extracted the prevalence, incidence, and risk of physical health conditions in people with ID.

RESULTS

Of 131 eligible studies, we synthesized results from 77 moderate- to high-quality studies, which was mainly limited to high-income countries. The highest prevalence estimates were observed for epilepsy, ear and eye disorders, cerebral palsy, obesity, osteoporosis, congenital heart defects, and thyroid disorders. Some conditions were more common in people with a genetic syndrome. Compared with the general population, many health conditions occur more frequently among people with ID, including asthma and diabetes, while some conditions such as non-congenital circulatory diseases and solid cancers occur at the same or lower rate. The latter associations may reflect under-detection.

CONCLUSIONS

People with ID have a health profile more complex than previously known. There is a pressing need for targeted, evidence-informed population health initiatives including preventative programs for this population.

Tooth agenesis: What do we know and is there a connection to cancer?

Like all developmental processes, odontogenesis is highly complex and dynamically regulated, with hundreds of genes co-expressed in reciprocal networks. Tooth agenesis (missing one or more/all teeth) is a common human craniofacial anomaly and may be caused by genetic variations and/or environmental factors. Variants in PAX9, MSX1, AXIN2, EDA, EDAR, and WNT10A genes are associated with tooth agenesis. Currently, variants in ATF1, DUSP10, CASC8, IRF6, KDF1, GREM2, LTBP3, and components and regulators of WNT signaling WNT10B, LRP6, DKK, and KREMEN1 are at the forefront of interest. Due to the interconnectedness of the signaling pathways of carcinogenesis and odontogenesis, tooth agenesis could be a suitable marker for early detection of cancer predisposition. Variants in genes associated with tooth agenesis could serve as prognostic or therapeutic targets in cancer. This review aims to summarize existing knowledge of development and clinical genetics of teeth. Concurrently, the review proposes possible approaches for future research in this area, with particular attention to roles in monitoring, early diagnosis and therapy of tumors associated with defective tooth development.

Craniofacial morphology in down syndrome: a systematic review and meta-analysis

The aim of this study was to evaluate the craniofacial cephalometric characteristics of individuals with Down syndrome (DS), comparing them with healthy subjects. An electronic search was made in Pubmed, Embase, Lilacs, Scopus, Medline and Web of Science without imposing limitations on publication date or language. Studies were selecting following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. The PECO acronym was applied as follows: P (population), individuals with DS; E, (exposition) diagnosis of DS; C (comparison), individuals without DS; O (outcomes) craniofacial characteristics based on cephalometric measurements. Independent reviewers performed data extraction and assessed the methodological quality of the articles using the Newcastle–Ottawa Quality-Assessment-scale. Seven case–control studies were included in meta-analysis. Given the variability of the cephalometric measurements used, only those that had been reported in at least three or more works could be included. Anterior cranial base length (SN), posterior cranial base length (SBa), total cranial base length (BaN), effective length of the maxilla (CoA), sagittal relationship between subspinale and supramentale (ANB), anterior facial height (NMe), and posterior facial height (SGo) values were significantly lower in the DS population than among control subjects. No significant differences were found in sagittal position of subspinale relative to cranial base (SNA) and sagittal position of supramentale relative to cranial base (SNB). Summarizing, individuals with DS present a shorter and flatter cranial base than the general population, an upper jaw of reduced sagittal dimension, as well as a tendency toward prognatic profile, with the medium third of the face flattened and a reduced anterior and posterior facial heights.

Comparison of the Visibility of Fetal Tooth Buds on 1.5 and 3 Tesla MRI

Dental anomalies coincide with genetic disorders, and prenatal identification may contribute to a more accurate diagnosis. The aim of this study was to assess whether fetal Magnet Resonance Imaging (MRI) is suitable to visualize and investigate intrauterine dental development in the upper jaw, and to compare the quality of visibility of tooth buds between 1.5 Tesla (T) and 3T images. MR images of fetuses Gestational Week (GW) 26.71 ± 4.97 from 286 pregnant women with diagnoses unrelated to dental anomalies were assessed by three raters. We compared the visibility between groups and field strengths in five gestational age groups, using chi square and Fisher’s exact tests. All ten primary tooth buds were identifiable in 5.4% at GW 18–21, in 75.5% at GW 26–29, and in 90.6% at GW 34+. Before GW 30, more tooth buds were identifiable on 3T images than on 1.5T images. Statistical significance was only reached for identification of incisors (p = 0.047). Therefore, 1.5T and 3T images are viable to visualize tooth buds, particularly after GW 25, and their analysis may serve as diagnostic criterion. MRI tooth bud data might have an impact on various fields of research, such as the maldevelopment of teeth and their causes. Analyzing tooth buds as an additional diagnostic criterion is not time consuming, and could lead to an improvement of syndrome diagnosis.

Size and bridging of the sella turcica in Japanese orthodontic patients with tooth agenesis

The purpose of this study was to investigate the association between the size and bridging of the sella turcica and tooth agenesis, and whether the likelihood of second premolar agenesis can be predicted from the sella turcica size and bridging in Japanese orthodontic patients. Patients were divided into four groups of 32: groups 1 and 2 consisted of patients with agenesis of the maxillary and mandibular second premolars, respectively; group 3, patients with severe tooth agenesis; and group 4, patients without tooth agenesis. Each group was divided into two subgroups of 16 each based on the patient's age: patients under 14 years of age (groups 1A through 4A, group A) and patients 14 years of age or older (groups 1B through 4B, group B). Lateral cephalograms were used to evaluate the size and bridging of the sella turcica. The interclinoidal distance (ID) was significantly shorter in groups 1 and 3 than in group 4, and in group 3 than in group 2. Group B exhibited significantly greater depth, diameter, area, and perimeter of the sella turcica than group A. Groups 3 and 1B had a significantly higher prevalence of sella turcica bridging than groups 4 and 4B, respectively. Maxillary second premolar agenesis and severe tooth agenesis were associated with a reduced ID irrespective of age and increased occurrence of sella turcica bridging. The early emergence in life of a short ID might be a predictor of possible second premolar agenesis in later life.

Mind the gap: A novel technique for space closure - a case report

Patients presenting with severe hypodontia can be challenging to manage. They often present with significant spaces within the dental arches and the lack of permanent teeth can make anchorage control difficult. This case report demonstrates a novel technique for diastema closure in a 14-year-old with severe hypodontia. The technique allows maintenance of root parallelism during space closure in cases with reduced anchorage support. The treatment plan was agreed on a multidisciplinary hypodontia clinic and involved an upper sectional fixed orthodontic appliance to close a 7-mm midline diastema aiding subsequent partial denture provision. Treatment commenced by bonding upper primary canines and central incisors. However, attempting space closure on a 0.019 × 0.025-inch stainless-steel working archwire resulted in tipping of the incisor crowns. Two brackets were therefore placed on the labial surface of each central incisor (one incisal and one gingival). Subsequently two stainless steel working archwires and elastomeric chain were used for diastema closure. This four-bracket system provided superior control allowing space closure by bodily tooth movement. Excellent root parallelism was achieved with this innovative technique.

Dental age estimation in children with chromosomal syndromes

When the age of an individual is unknown, age assessment refers to the procedures through which authorities try to establish the chronological age of an individual. Dental evidence demonstrated to be very effective in estimating age and dental mineralization is largely deemed a process scarcely influenced by major diseases and nutritional or environmental factors which can affect child growth. This research aims to understand the possible influence of genetic syndromes on dental maturation of affected individuals. The sample is composed of a test sample of 159 chromosomal affected children, 69 males and 90 females, and a control sample of 157 healthy children, 77 males and 80 females aged between 4,49 and 19,8years. London Atlas was applied to estimate dental age on OPGs (orthopantompographies). No statistical significant difference has been found in dental estimates between syndromic and healthy individuals. Moreover no statistical significant difference emerged between sexes and age cohorts. Children affected by Down or Williams syndromes nor mean error neither the mean accuracy per cohort of age show differences compared to non-affected subjects. The London Atlas can be validly applied to age estimation of individuals with multiple agenesis as in Down and Williams syndromes, even if it a slight overestimation of age occurs systematically in syndromic as well as in healthy samples. The current findings suggest that dental maturation is a very stable biological process scarcely affected by even serious illnesses as genetic syndromes.

A Radiographic Evaluation of Missing of Permanent First Molars in a Group of Iranian Children and Adults: A Retrospective Study

The missing of permanent first molars influences the occlusal status and dental health. The purpose of this study was to determine the prevalence of missing first molar teeth in a selected population of Shiraz, Iran. Methods. A total of 2206 panoramic views of patients aged from 7 to 75 years old were inspected for missing of permanent first molars. Patients were categorized into five age groups: from 7 to 15, 16 to 30, 31 to 45, 46 to 60, and more than 60 years old. Data were categorized according to sex, age, and number of lost teeth using SPSS software. Results. No first molar was missing in 59.9% of the cases, 17.05% had lost one, 10.4% had lost two, 7.2% had lost three, and 5% were missing all four of their permanent first molars. The mandibular first molar was the most commonly lost tooth, and the left side in both jaws was more affected than the right side. There was a positive relation between age and missing first molar. Conclusions. A missing first molar is a common finding in southern Iran population. Due to the important role of permanent first molars in occlusion, more education and dental care is recommended to preserve these teeth.

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.

Permanent tooth agenesis in individuals with non-syndromic Robin sequence: a systematic review and meta-analysis

OBJECTIVES

To evaluate prevalence rates and patterns of permanent tooth agenesis in individuals with non-syndromic Robin sequence (ns-RS).

MATERIAL AND METHODS

Two investigators independently carried out a literature search, using PubMed, Web of Science, Ovid, EMBASE and the Cochrane Library, identifying articles relating to permanent tooth agenesis, diagnosed using panoramic radiographs, in individuals with ns-RS. The outcomes desired were prevalence rates and patterns of permanent tooth agenesis. The final search was carried out in January 2017.

RESULTS

Six articles were selected for inclusion, with a total of 448 individuals with ns-RS. Data available in each study varied which allowed conducting further specific meta-analyses only on sample sizes of 339 or 378 individuals from three or four of the six included articles. The overall estimated prevalence rate of permanent tooth agenesis was 42% (95% CI: 35%-48%), excluding third molars, with no sex predilection. In individuals with tooth agenesis, approximately 30% had one missing tooth while 40% had two missing teeth. Tooth agenesis was more commonly bilateral (Relative Risk 2) and found in the mandible (Relative Risk 1.6). The highest prevalence of permanent tooth agenesis was found for mandibular second premolars (26%) followed by maxillary second premolars (14%). The most common tooth agenesis patterns were the agenesis of both mandibular second premolars, followed by the agenesis of all second premolars.

CONCLUSION

Individuals with ns-RS have high prevalence rates of permanent tooth agenesis. The most prevalent tooth agenesis patterns are bilateral symmetric tooth agenesis, most commonly agenesis of both mandibular second premolars.