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Sun R, Li S, Xia B, Zhu J. Detection of Novel Variant and Functional Study in a Chinese Family with Non-syndromic Oligodontia. Oral Dis 2022. [PMID: 35596231 DOI: 10.1111/odi.14259] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 03/13/2022] [Accepted: 03/20/2022] [Indexed: 11/28/2022]
Abstract
OBJECTIVES To investigate the pathogenic gene of a patient with non-syndromic oligodontia, and analyze its possible pathogenic mechanism. SUBJECTS AND METHODS The variant was detected by whole exome sequencing (WES) and Sanger sequencing in a family with oligodontia. Bioinformatic and structural analyses were used to analyze variant. Functional studies including western blotting and immunofluorescent analyses and luciferase reporter assay were conducted to explore the functional effects. RESULTS We identified a novel frameshift variant of PAX9 (c.491-510delGCCCT-ATCACGGCGGCGGCC, p.P165Qfs*145) outside the DNA-binding domain causing an autosomal-dominant non-syndromic oligodontia in a Chinese family. Bioinformatic and structural analyses revealed that the variant is pathogenic and conserved evolutionarily, and the changes might affect protein stability or folding. Functional studies demonstrate dramatically reduced ability in activating transcription activity of BMP4 promoter and a marked decrease in protein production, as evaluated by western blotting and immunofluorescent analyses. CONCLUSIONS We found a novel frameshift variant of PAX9 causing non-syndromic oligodontia in a Chinese family. Our findings indicate that frameshift variants cause loss of function of PAX9 protein during the patterning of the dentition and the subsequent tooth agenesis, providing new molecular insights into the role of frameshift variant of PAX9 and broaden the pathogenic spectrum of PAX9 variants.
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Affiliation(s)
- Ruiqing Sun
- Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health & Beijing Key Laboratory of Digital Stomatology & National Clinical Research Center for Oral Diseases, Beijing 100081, China
| | - Shuangying Li
- Department of Pediatric Dentistry, Yinchuan Stomatology Hospital, Ningxia 750001, China
| | - Bin Xia
- Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health & Beijing Key Laboratory of Digital Stomatology & National Clinical Research Center for Oral Diseases, Beijing 100081, China
| | - Junxia Zhu
- Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health & Beijing Key Laboratory of Digital Stomatology & National Clinical Research Center for Oral Diseases, Beijing 100081, China
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Çarıkçıoğlu B, Sezer B. Dental age estimation with fewer than mandibular seven teeth: An accuracy study of Bedek models in Turkish children. Clin Oral Investig 2022; 26:5773-5784. [PMID: 35562511 DOI: 10.1007/s00784-022-04534-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 05/03/2022] [Indexed: 11/30/2022]
Abstract
OBJECTIVES One or more missing teeth, such as hypodontia, make it difficult to obtain accurate results in age estimation methods. This paper aims to test the accuracy of the models developed by Bedek et al. that can estimate age with fewer than seven teeth for Turkish children. MATERIALS AND METHODS Panoramic radiographs of 1118 children (540 girls and 578 boys) aged between 6 and 16 years were evaluated using the Willems method and Bedek models for the entire sample and for different ages and sexes. Differences between dental age (DA) and chronological age (CA) calculated for all methods for each sex and all age groups were analyzed the paired sample t-test and Wilcoxon signed rank test. The accuracy of the DA estimation methods was determined by the proximity of DA to CA by calculating mean absolute error (MAE). RESULTS While all Bedek models underestimated CA by 0.2 to 0.1 years, the Willems method overestimated CA by 0.3 years. DA-CA difference in the total sample and girls was statistically significant in all methods. In the total sample, the seven- and four-teeth models had the lowest MAE, while the one-tooth model had the highest MAE. CONCLUSIONS Seven- and four-teeth models were the most suitable for age estimation, and all models except the one-tooth model were found to be more accurate than the Willems method in northwestern Turkish children. CLINICAL RELEVANCE Especially in children with hypodontia, it may be possible to estimate DA with the use of Bedek models.
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Affiliation(s)
- Burak Çarıkçıoğlu
- Department of Pediatric Dentistry, School of Dentistry, Çanakkale Onsekiz Mart University, Çanakkale, Turkey.
| | - Berkant Sezer
- Department of Pediatric Dentistry, School of Dentistry, Çanakkale Onsekiz Mart University, Çanakkale, Turkey
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New model for dental age estimation: Willems method applied on fewer than seven mandibular teeth. Int J Legal Med 2019; 134:735-743. [PMID: 31041502 DOI: 10.1007/s00414-019-02066-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 04/09/2019] [Indexed: 10/26/2022]
Abstract
Willems method measures the developmental stages of the seven left permanent mandibular teeth and is frequently used for dental age estimation. The aim of this study was to test its accuracy on a large sample of the Croatian population and to develop new models for estimation based on one to seven mandibular teeth. The developmental stages were evaluated on the digital, standardized orthopantomograms of 1868 Croatian children aged 5 to 16. Univariate regression was used for age estimation based on one tooth and regression with forward and backward elimination for selection of the best combination on two to six teeth. Tested in parallel with Willems method, the accuracy of the new models was assessed within intervals of ± 0.5, ± 1, ± 1.5 and ± 2 years and shows the percentage of correct estimations. Using Willems method, the average overestimation was 0.41 years for boys and 0.22 years for girls. Newly developed models that use two to seven teeth proved to be significantly more accurate (p < 0.001). The accuracy of age estimation increases significantly with the number of teeth in a model. Predictably, within the interval ± 0.5 years, a model with three teeth has 3% fewer accurate age estimations than a model including seven teeth. In both theory and practice, Willems method has been considered suitable for age estimation among Croatian children. However, these newly developed models significantly surpass its accuracy. Models using two to seven teeth represent a simple, reliable, and accurate method for age estimation, even in cases with missing mandibular teeth.
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Gracco ALT, Zanatta S, Forin Valvecchi F, Bignotti D, Perri A, Baciliero F. Prevalence of dental agenesis in a sample of Italian orthodontic patients: an epidemiological study. Prog Orthod 2017; 18:33. [PMID: 29034420 PMCID: PMC5641500 DOI: 10.1186/s40510-017-0186-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 08/14/2017] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The congenital absence of one or more teeth is a dental anomaly that frequently occurs in the world's population with a wide variability of distribution. The aim of this study is to assess the current prevalence of dental agenesis in the permanent dentition (excluding third molars) using a sample of Italian orthodontic patients. METHODS Panoramic radiographs of 4006 Caucasian children between 9 and 16 years of age (1865 males and 2141 females) performed over a 5-year period (from 2010 to 2015) were carefully examined to identify congenital missing teeth. A chi-square test was used to determine the difference in the prevalence of hypodontia between genders and between arches. RESULTS The prevalence of dental agenesis was 9% (9.1% for females and 8.7% for males). The most common congenitally missing teeth were the mandibular second premolars (20.3 and 18.1%) followed by the upper lateral incisors (17.8 and 17.7%) and the maxillary second premolars (7.4 and 6.3%). The absence of one tooth to five teeth was observed in 344 patients (8.6%), while 15 patients showed from six to nine missing teeth (0.4%). The analysis showed 363 cases of agenesis in the upper arch (0.64%) and 339 in the lower arch (0.60%). Unilateral (4.6%) and bilateral (4.4%) agenesis demonstrated a similar frequency. The most common bilateral missing teeth were the mandibular second premolars (1.9%) and the maxillary lateral incisors (1.6%). CONCLUSIONS The results of this study observed a higher prevalence of hypodontia compared to previous studies conducted on the Italian population. Thus, a detailed and careful radiographic examination was important in diagnosing one or more missing teeth. This could help plan the best possible treatments, both esthetically and functionally, for these patients.
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Affiliation(s)
- Antonio L. T. Gracco
- Department of Neurosciences, Section of Dentistry, University of Padua, Via Giustiniani 2, Padua, Italy
| | - Serena Zanatta
- Department of Neurosciences, Section of Dentistry, University of Padua, Via Giustiniani 2, Padua, Italy
| | - Filippo Forin Valvecchi
- Department of Neurosciences, Section of Dentistry, University of Padua, Via Giustiniani 2, Padua, Italy
| | - Denis Bignotti
- Department of Neurosciences, Section of Dentistry, University of Padua, Via Giustiniani 2, Padua, Italy
| | - Alessandro Perri
- Department of Neurosciences, Section of Dentistry, University of Padua, Via Giustiniani 2, Padua, Italy
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Zeng B, Zhao Q, Li S, Lu H, Lu J, Ma L, Zhao W, Yu D. Novel EDA or EDAR Mutations Identified in Patients with X-Linked Hypohidrotic Ectodermal Dysplasia or Non-Syndromic Tooth Agenesis. Genes (Basel) 2017; 8:genes8100259. [PMID: 28981473 PMCID: PMC5664109 DOI: 10.3390/genes8100259] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 09/21/2017] [Accepted: 09/29/2017] [Indexed: 01/02/2023] Open
Abstract
Both X-linked hypohidrotic ectodermal dysplasia (XLHED) and non-syndromic tooth agenesis (NSTA) result in symptoms of congenital tooth loss. This study investigated genetic causes in two families with XLHED and four families with NSTA. We screened for mutations of WNT10A, EDA, EDAR, EDARADD, PAX9, MSX1, AXIN2, LRP6, and WNT10B through Sanger sequencing. Whole exome sequencing was performed for the proband of NSTA Family 4. Novel mutation c.1051G>T (p.Val351Phe) and the known mutation c.467G>A (p.Arg156His) of Ectodysplasin A (EDA) were identified in families with XLHED. Novel EDA receptor (EDAR) mutation c.73C>T (p.Arg25*), known EDA mutation c.491A>C (p.Glu164Ala), and known Wnt family member 10A (WNT10A) mutations c.511C>T (p.Arg171Cys) and c.742C>T (p.Arg248*) were identified in families with NSTA. The novel EDA and EDAR mutations were predicted as being pathogenic through bioinformatics analyses and structural modeling. Two variants of WNT10A, c.374G>A (p.Arg125Lys) and c.125A>G (p.Asn42Ser), were found in patients with NSTA. The two WNT10A variants were predicted to affect the splicing of message RNA, but minigene experiments showed normal splicing of mutated minigenes. This study uncovered the genetic foundations with respect to six families with XLHED or NSTA. We identified six mutations, of which two were novel mutations of EDA and EDAR. This is the first report of a nonsense EDAR mutation leading to NSTA.
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Affiliation(s)
- Binghui Zeng
- Guanghua School of Stomatology, Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
| | - Qi Zhao
- Department of Oncology, Xianning Central Hospital, The First Affiliated Hospital of Hubei University of Science and Technology, Xianning 437100, China.
| | - Sijie Li
- Guanghua School of Stomatology, Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
| | - Hui Lu
- Guanghua School of Stomatology, Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
| | - Jiaxuan Lu
- Guanghua School of Stomatology, Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
| | - Lan Ma
- Guanghua School of Stomatology, Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
| | - Wei Zhao
- Guanghua School of Stomatology, Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
| | - Dongsheng Yu
- Guanghua School of Stomatology, Hospital of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
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Peled A, Sarig O, Samuelov L, Bertolini M, Ziv L, Weissglas-Volkov D, Eskin-Schwartz M, Adase CA, Malchin N, Bochner R, Fainberg G, Goldberg I, Sugawara K, Baniel A, Tsuruta D, Luxenburg C, Adir N, Duverger O, Morasso M, Shalev S, Gallo RL, Shomron N, Paus R, Sprecher E. Mutations in TSPEAR, Encoding a Regulator of Notch Signaling, Affect Tooth and Hair Follicle Morphogenesis. PLoS Genet 2016; 12:e1006369. [PMID: 27736875 PMCID: PMC5065119 DOI: 10.1371/journal.pgen.1006369] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 09/16/2016] [Indexed: 11/19/2022] Open
Abstract
Despite recent advances in our understanding of the pathogenesis of ectodermal dysplasias (EDs), the molecular basis of many of these disorders remains unknown. In the present study, we aimed at elucidating the genetic basis of a new form of ED featuring facial dysmorphism, scalp hypotrichosis and hypodontia. Using whole exome sequencing, we identified 2 frameshift and 2 missense mutations in TSPEAR segregating with the disease phenotype in 3 families. TSPEAR encodes the thrombospondin-type laminin G domain and EAR repeats (TSPEAR) protein, whose function is poorly understood. TSPEAR knock-down resulted in altered expression of genes known to be regulated by NOTCH and to be involved in murine hair and tooth development. Pathway analysis confirmed that down-regulation of TSPEAR in keratinocytes is likely to affect Notch signaling. Accordingly, using a luciferase-based reporter assay, we showed that TSPEAR knock-down is associated with decreased Notch signaling. In addition, NOTCH1 protein expression was reduced in patient scalp skin. Moreover, TSPEAR silencing in mouse hair follicle organ cultures was found to induce apoptosis in follicular epithelial cells, resulting in decreased hair bulb diameter. Collectively, these observations indicate that TSPEAR plays a critical, previously unrecognized role in human tooth and hair follicle morphogenesis through regulation of the Notch signaling pathway. Ectodermal dysplasias refer to a large group of inherited disorders characterized by developmental defects in tissues of ectodermal origin. The study of these conditions has been instrumental in the discovery of biological pathways involved in the regulation of epithelial tissue morphogenesis. In this report, through the delineation of the molecular basis of a novel form of autosomal recessive ectodermal dysplasia, we identified a new key player in ectodermal development. We detected a number of mutations in TSPEAR co-segregating with abnormal hair and tooth development in three families. TSPEAR encodes the thrombospondin-type laminin G domain and EAR repeats (TSPEAR) protein, whose function is poorly understood. TSPEAR was found to be strongly expressed in murine hair and tooth. Using a reporter assay, we showed that it regulates Notch activity. Accordingly, NOTCH1 expression was altered in patient skin, and NOTCH1, as well as many of its known targets, was down-regulated in TSPEAR deficient keratinocytes. Moreover, Tspear silencing in mouse hair follicle organ cultures was found to induce apoptosis in follicular epithelial cells, resulting in decreased hair bulb diameter. Collectively, these observations indicate that TSPEAR plays a critical, previously unrecognized role in human tooth and hair follicle morphogenesis through regulation of the Notch pathway. As such, these new data are likely to lead to further investigations aimed at characterizing the role of Notch signaling pathway in other forms of ectodermal dysplasias as well as acquired hair and tooth pathologies.
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Affiliation(s)
- Alon Peled
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
- Department of Human Molecular Genetics and Biochemistry, Tel-Aviv University, Tel Aviv, Israel
| | - Ofer Sarig
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
| | - Liat Samuelov
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
- Division of Dermatology, University of California, San Diego, San Diego, California, United States of America
| | - Marta Bertolini
- Department of Dermatology, University of Münster, Münster, Germany
| | - Limor Ziv
- Sheba Medical Center, Ramat Gan, Israel
| | | | - Marina Eskin-Schwartz
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
- Department of Human Molecular Genetics and Biochemistry, Tel-Aviv University, Tel Aviv, Israel
| | - Christopher A. Adase
- Division of Dermatology, University of California, San Diego, San Diego, California, United States of America
| | - Natalia Malchin
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
| | - Ron Bochner
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
| | - Gilad Fainberg
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
| | - Ilan Goldberg
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
| | - Koji Sugawara
- Department of Dermatology, Osaka City University, Osaka, Japan
| | - Avital Baniel
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
| | - Daisuke Tsuruta
- Department of Dermatology, Osaka City University, Osaka, Japan
| | - Chen Luxenburg
- Department of Cell and Developmental Biology, Tel Aviv University, Tel Aviv, Israel
| | - Noam Adir
- Faculty of Chemistry, Technion, Haifa, Israel
| | - Olivier Duverger
- Laboratory of Skin Biology, National Institute of Health, Bethesda, Maryland, United States of America
| | - Maria Morasso
- Laboratory of Skin Biology, National Institute of Health, Bethesda, Maryland, United States of America
| | - Stavit Shalev
- Institute of Human Genetics, Haemek Medical Center, Afula, Israel
- Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Richard L. Gallo
- Division of Dermatology, University of California, San Diego, San Diego, California, United States of America
| | - Noam Shomron
- Department of Cell and Developmental Biology, Tel Aviv University, Tel Aviv, Israel
| | - Ralf Paus
- Department of Dermatology, University of Münster, Münster, Germany
- Centre for Dermatology Research, Institute of Inflammation and Repair, University of Manchester, Manchester, United Kingdom
| | - Eli Sprecher
- Department of Dermatology, Tel Aviv Medical Center, Tel Aviv, Israel
- Department of Human Molecular Genetics and Biochemistry, Tel-Aviv University, Tel Aviv, Israel
- * E-mail:
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Tooth agenesis and orofacial clefting: genetic brothers in arms? Hum Genet 2016; 135:1299-1327. [PMID: 27699475 PMCID: PMC5065589 DOI: 10.1007/s00439-016-1733-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 09/21/2016] [Indexed: 12/16/2022]
Abstract
Tooth agenesis and orofacial clefts represent the most common developmental anomalies and their co-occurrence is often reported in patients as well in animal models. The aim of the present systematic review is to thoroughly investigate the current literature (PubMed, EMBASE) to identify the genes and genomic loci contributing to syndromic or non-syndromic co-occurrence of tooth agenesis and orofacial clefts, to gain insight into the molecular mechanisms underlying their dual involvement in the development of teeth and facial primordia. Altogether, 84 articles including phenotype and genotype description provided 9 genomic loci and 26 gene candidates underlying the co-occurrence of the two congenital defects: MSX1, PAX9, IRF6, TP63, KMT2D, KDM6A, SATB2, TBX22, TGFα, TGFβ3, TGFβR1, TGFβR2, FGF8, FGFR1, KISS1R, WNT3, WNT5A, CDH1, CHD7, AXIN2, TWIST1, BCOR, OFD1, PTCH1, PITX2, and PVRL1. The molecular pathways, cellular functions, tissue-specific expression and disease association were investigated using publicly accessible databases (EntrezGene, UniProt, OMIM). The Gene Ontology terms of the biological processes mediated by the candidate genes were used to cluster them using the GOTermMapper (Lewis-Sigler Institute, Princeton University), speculating on six super-clusters: (a) anatomical development, (b) cell division, growth and motility, (c) cell metabolism and catabolism, (d) cell transport, (e) cell structure organization and (f) organ/system-specific processes. This review aims to increase the knowledge on the mechanisms underlying the co-occurrence of tooth agenesis and orofacial clefts, to pave the way for improving targeted (prenatal) molecular diagnosis and finally to reflect on therapeutic or ultimately preventive strategies for these disabling conditions in the future.
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Rakhshan V, Rakhshan H. Meta-analysis and systematic review of the number of non-syndromic congenitally missing permanent teeth per affected individual and its influencing factors. Eur J Orthod 2015; 38:170-7. [PMID: 25840586 DOI: 10.1093/ejo/cjv008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND AND PURPOSE Dental aplasia (or hypodontia) is a frequent and challenging anomaly and thus of interest to many dental fields. Although the number of missing teeth (NMT) in each person is a major clinical determinant of treatment need, there is no meta-analysis on this subject. Therefore, we aimed to investigate the relevant literature, including epidemiological studies and research on dental/orthodontic patients. METHODS Among 50 reports, the effects of ethnicities, regions, sample sizes/types, subjects' minimum ages, journals' scientific credit, publication year, and gender composition of samples on the number of missing permanent teeth (except the third molars) per person were statistically analysed (α = 0.05, 0.025, 0.01). LIMITATIONS The inclusion of small studies and second-hand information might reduce the reliability. Nevertheless, these strategies increased the meta-sample size and favoured the generalisability. Moreover, data weighting was carried out to account for the effect of study sizes/precisions. RESULTS The NMT per affected person was 1.675 [95% confidence interval (CI) = 1.621-1.728], 1.987 (95% CI = 1.949-2.024), and 1.893 (95% CI = 1.864-1.923), in randomly selected subjects, dental/orthodontic patients, and both groups combined, respectively. The effects of ethnicities (P > 0.9), continents (P > 0.3), and time (adjusting for the population type, P = 0.7) were not significant. Dental/orthodontic patients exhibited a significantly greater NMT compared to randomly selected subjects (P < 0.012). Larger samples (P = 0.000) and enrolling younger individuals (P = 0.000) might inflate the observed NMT per person. CONCLUSIONS Time, ethnic backgrounds, and continents seem unlikely influencing factors. Subjects younger than 13 years should be excluded. Larger samples should be investigated by more observers.
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Affiliation(s)
- Vahid Rakhshan
- *Iranian Tissue Bank and Research Centre, Tehran University of Medical Sciences, **Department of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran and
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