Characteristics of incisor-premolar hypodontia in families

TGFB3 and BMP4 polymorphism are associated with isolated tooth agenesis

OBJECTIVE

To evaluate the association of the polymorphisms in the TGFB3 gene (rs2268626) and the BMP4 gene (rs17563) with isolated human tooth agenesis.

MATERIALS AND METHODS

One hundred and seventy-five unrelated individuals (125 control individuals without tooth agenesis and 50 cases with tooth agenesis) were evaluated using a case-control design. The participants of the study were recruited through the Dental School of the Federal University of Rio de Janeiro, Brazil. Genotyping of the selected polymorphisms for TGFB3 (48 individuals with tooth agenesis and 125 control cases) and BMP4 (46 individuals with tooth agenesis and 88 control cases) were carried out by real-time PCR using the Taqman assay method from a genomic DNA isolated from buccal epithelial cells of all individuals.

RESULTS

Significant statistical differences were found for genotype frequencies between tooth agenesis and TGFB3 control samples (p = 0.026). In addition, significant differences were also observed for allele and genotype frequencies between unilateral tooth agenesis and TGFB3 control samples (p = 0.014 and 0.004 for allele and genotype frequencies, respectively). For BMP4, genotype distribution had a statistically significant difference between groups (p = 0.047). The GG genotype of BMP4 was more frequent in individuals with three or more missing teeth than in the control group (p < 0.0001).

CONCLUSIONS

These results indicate that polymorphisms in the TGFB3 gene and in BMP4 genes contribute to tooth agenesis. Nonetheless, the extents to which this polymorphism may actually contribute to the tooth agenesis status should be clarified.

A novel nonsense mutation in PAX9 is associated with sporadic hypodontia

The most important events during the regulation of tooth development were inductive interactions between the epithelial and mesenchymal tissues. The expression of Pax9 had been shown to specifically mark the mesenchymal regions at the prospective sites of all teeth prior to any morphological manifestations. Here, we investigated the PAX9 gene as a candidate gene for hypodontia in five unrelated Chinese patients with tooth agenesis. Direct sequencing and restriction enzyme analysis revealed a novel heterozygous mutation c.480C>G (p.160Tyr>X, Y160X) in a patient who was missing 20 permanent teeth (the third molars excluded) and 6 primary teeth. The mutation was a nonsense mutation, leading to a premature stop codon in exon 2 of PAX9 gene. PCR analysis of complementary DNA from cultured lymphocytes of the affected individual could not indicate the complete degradation of the mutated transcript. Promoter reporter assays revealed reduced transcriptional activity of the mutated PAX9 protein suggesting that the severe phenotype may result from haploinsufficiency of PAX9. In another patient with 15 missing permanent teeth (the third molars excluded), we found the c.219insG mutation previously reported by Stockton.

Craniofacial and dental features in kabuki syndrome patients

Objective : To describe oral manifestations in Brazilian individuals with Kabuki syndrome, a multiple congenital anomaly/mental retardation syndrome. Study Design : A total of 16 Kabuki syndrome individuals, aged between 8 to 24 years and of both sexes, were referred by the Department of Clinical Genetics for oral treatment and follow-up to the Oral Care Center for Inherited Diseases, University Hospital of Brasília, Brasília, Brazil. Each individual underwent complete physical examination, as well as intraoral and radiographic examinations. Results : Craniofacial and dental alterations were observed in all Kabuki syndrome patients examined. In addition, atypical shape of the molars' crowns, occlusal convergence of the premolars' crowns, and root dilaceration were also observed. Enamel diffuse opacities were observed in permanent dentition (n  =  10). Conclusion : A great clinical heterogeneity was observed in Kabuki syndrome individuals in line with previous studies in the literature. Further clinical and molecular studies are necessary in order to better understand the presence of dental anomalies in this syndrome.

Implant-prosthetic rehabilitation of a patient with nonsyndromic oligodontia: a clinical report

Oligodontia is defined as the absence of 6 or more permanent teeth due to the hypodevelopment of tooth germs. This familial abnormality is attributable to various mutations or polymorphisms of genes and associated with malformative syndromes. This clinical report presents the multidisciplinary dental treatment planning for a 27-year-old woman who exhibited oligodontia. After radiographic and clinical evaluations, 7 retained primary teeth and 2 mandibular third molars were extracted. Three dental implants were placed into the maxillary alveolar process. After the osseointegration period, complete-arch fixed prostheses in both maxilla and mandible, supported by a combination of implants and teeth, were fabricated. Osseointegration of the implants, peri-implant mucosa health, and prosthesis function were assessed every 6 months. At the end of the 3-year clinical follow-up, the patient was satisfied with the esthetics, function, and phonation of her prosthesis. To attain the best esthetic and biological results, an interdisciplinary approach could be used to synergistically combine surgery and restorative dentistry for the restoration of maximal esthetics and function.

Non-syndromic hypodontia in an Iranian orthodontic population

To investigate the prevalence, characteristics (ie, malocclusion, location, type), and sex distribution of hypodontia in an Iranian orthodontic population. A retrospective study was conducted using periapical and panoramic radiographs and study models of 1,751 subjects attending university orthodontic clinics (870 females, 881 males, age 9-27 years). The Chi-square test was used to analyze differences in the distribution of hypodontia, after stratification by sex and malocclusion type. A total of 197 congenitally missing teeth were observed in 160 patients (9.1%; 74 boys and 86 girls); there were no statistically significant differences between sexes (Chi-square = 0.832, P = 0.36). Hypodontia was more common in patients with Class III malocclusion (45.2%), and was more prevalent in the maxilla (71%) than in the mandible (29%). Maxillary lateral incisors (35.6%) and maxillary second premolars (13.0%) were the most commonly missing teeth, followed by mandibular lateral incisors (9.6%) and mandibular second premolars (8.2%). The prevalence of missing teeth was higher in the anterior segment (incisors and canines) than in the posterior segment (premolars and molars). The prevalence of oligodontia was 0.34%. The prevalence and characteristics of the most frequently missing teeth accorded with the findings of most studies conducted in other countries.

The association of aggressive and chronic periodontitis with systemic manifestations and dental anomalies in a jordanian population: a case control study

Background

The relationship between dental anomalies and periodontitis has not been documented by earlier studies. Although psychological factors have been implicated in the etiopathogenesis of periodontitis, very little information has so far been published about the association of anxiety and depression with aggressive periodontitis. The aim of this study was to investigate the association of chronic periodontitis and aggressive periodontitis with certain systemic manifestations and dental anomalies.

Methods

A total of 262 patients (100 chronic periodontitis, 81 aggressive periodontitis and 81 controls), attending the Periodontology clinics at Jordan University of Science and Technology, Dental Teaching Centre) were included. All subjects had a full periodontal and radiographic examination to assess the periodontal condition and to check for the presence of any of the following dental anomalies: dens invaginatus, dens evaginatus, congenitally missing lateral incisors or peg-shaped lateral incisors. Participants were interrogated regarding the following: depressive mood, fatigue, weight loss, or loss of appetite; and their anxiety and depression status was assessed using the Hospital Anxiety and Depression (HAD) scale.

Results

Patients with aggressive periodontitis reported more systemic symptoms (51%) than the chronic periodontitis (36%) and control (30%) patients (p < 0.05). Aggressive periodontitis patients had a higher tendency for both anxiety and depression than chronic periodontitis and control patients. Dental anomalies were significantly (p < 0.05) more frequent among both of chronic and aggressive periodontitis patients (15% and 16%, respectively), compared to controls.

Conclusion

In this group of Jordanians, systemic symptoms were strongly associated with aggressive periodontitis, and dental anomalies were positively associated with both aggressive and chronic periodontitis.

PAX9 and MSX1 transcription factor genes in non-syndromic dental agenesis

OBJECTIVE

The molecular variation of paired domain box gene 9 (PAX9) was previously investigated by our research group and a high degree of evolutionary conservation in coding and non-coding regions was observed except in exon 3. PAX9 is a transcription factor important in tooth development, and we wanted to verify its role in dental agenesis in detail. Since dental development is a complex trait we also decided to examine the influence of another transcription factor, muscle segment homeodomain-homeobox 1 (MSX1) on it.

DESIGN

A total of 360 consecutively ascertained patients seeking orthodontic treatment were screened for tooth agenesis and 33% of them were found to have it. Thirty-five of those with agenesis and 15 controls had their DNA studied for PAX9 exons 2, 3, 4 and adjacent regions (total of 1476 base pairs, bp) as well as MSX1 exon 2 (698bp). A trio (a proband and her parents) was also studied.

RESULTS

Six polymorphic sites were found, three in PAX9 exon 3 and three in MSX1 exon2. MSX1 rs1095 derived allele occurred in individuals with agenesis only, and two other mutations in this gene had been earlier associated with tooth agenesis. Homozygosity for the PAX9 Ala240Pro mutation was studied in a family (proband and her parents), suggesting recessive inheritance with variable expressivity for the dental agenesis found.

CONCLUSION

Common variants located out of the DNA binding domain of the two PAX9 and MSX1 genes can also be related to tooth agenesis.

MMP1 and MMP20 contribute to tooth agenesis in humans

OBJECTIVE

Variations in genes that are critical for tooth formation may contribute to the tooth agenesis. MMPs are potential candidate genes for dental alterations based on the roles they play during embryogenesis. The aim of this study was to investigate the possible association between MMP1, MMP3, and MMP20 and tooth agenesis.

METHODS

One hundred sixty-seven nuclear families from two different populations were analysed, 116 from Brazil and 51 from Turkey. Probands had at least one congenitally missing tooth. DNA samples were obtained from blood or saliva samples and genotyping was performed using TaqMan chemistry. In addition, Mmp20 was selected for quantitative real-time polymerase chain reaction analysis with SYBR Green I Dye in mouse tooth development.

RESULTS

Associations between tooth agenesis and MMP1 (p=0.007), and MMP20 (p=0.03) were found in Brazilian families. In the total dataset, MMP20 continued to be associated with tooth agenesis (p=0.01). Mmp20 was not expressed during the initial stages of tooth development.

CONCLUSION

Our findings provide evidence that MMP1 and MMP20 play a role in human tooth agenesis.

Familial aggregation of maxillary lateral incisor agenesis

In spite of recent developments, data regarding the genes responsible for the less severe forms of hypodontia are still scarce and controversial. This study addressed the hypothesis that agenesis of maxillary lateral incisors (MLIA) is a distinct type of hypodontia, by evaluating its familial aggregation and the occurrence of other types of ageneses or microdontia in probands' relatives. Sixty-two probands with MLIA were identified, and information was collected on 142 first-degree relatives. Relative risk (RR) was calculated and compared by re-assessment of data previously published for the Swedish, Utah, and Israeli populations, for the same trait. A RR of 15 was obtained in the Portuguese, 16 in the Swedish, 12 in Utah, and 5 in the Israeli population. Our results support a significant familial aggregation of MLIA, show that MLIA almost never segregates with other forms of agenesis, and suggest that microdontia of maxillary lateral incisors is part of the same phenotype.

Oral health-related quality of life of children with oligodontia

OBJECTIVES

To assess the functional and psychosocial impact of oligodontia in children aged 11-14 years.

METHODS

Children aged 11-14 years with oligodontia were recruited from orthodontic clinics when they presented for orthodontic evaluation. All completed a copy of the Child Perceptions Questionnaire for 11- to 14-year olds, a measure of the functional and psychosocial impact of oral disorders. Information on the number and pattern of missing teeth for each child were obtained from charts and radiographs.

RESULTS

Thirty-six children were included in the study. The number of missing teeth ranged from one to 14 (mean = 6.8). Just over three-quarters of the subjects reported experiencing one or more functional and psychosocial impacts 'Often' or 'Everyday/almost everyday'. Correlations between scale and sub-scale scores and the number of missing teeth were weak and nonsignificant.

CONCLUSIONS

Children with oligodontia experience substantial functional and psychosocial impacts from the condition. When compared with other clinical groups, children with oligodontia appear to have worse oral health-related quality of life than children with dental decay and malocclusion, but better oral health-related quality of life than children with oro-facial conditions.

Prevalence of hypodontia in orthodontic patients in Brasilia, Brazil

The purpose of this retrospective study was to determine the prevalence of hypodontia and associated dental anomalies in patients undergoing orthodontic treatment in Brasília, Brazil, over a 2 year period (1998-2000). The records of 1049 orthodontic patients between 10 and 15.7 years of age (507 males and 542 females) from 16 orthodontic clinics were analysed. Descriptive statistics were performed for the study variables. A chi-square test was used to determine the difference in the prevalence of hypodontia between genders. The prevalence of hypodontia was 6.3 per cent (39.4 per cent males and 60.6 per cent females) with no statistically significant difference between the genders. One case of oligodontia was observed. The maxillary lateral incisor was the most frequently missing tooth, followed by the mandibular second premolar. All cases of hypodontia, except one, were associated with at least one other dental anomaly. These associated dental anomalies were retained primary teeth (30.3 per cent), ectopic canine eruption (25.8 per cent), taurodontism (21.2 per cent), and peg-shaped maxillary lateral incisors (16.7 per cent).

Genetic basis of tooth agenesis

Tooth agenesis or hypodontia, failure to develop all normally developing teeth, is one of the most common developmental anomalies in man. Common forms, including third molar agenesis and hypodontia of one or more of the incisors and premolars, constitute the great majority of cases. They typically affect those teeth that develop latest in each tooth class and these teeth are also most commonly affected in more severe and rare types of tooth agenesis. Specific vulnerability of the last developing teeth suggests that agenesis reflects quantitative defects during dental development. So far molecular genetics has revealed the genetic background of only rare forms of tooth agenesis. Mutations in MSX1, PAX9, AXIN2 and EDA have been identified in familial severe agenesis (oligodontia) and mutations in many other genes have been identified in syndromes in which tooth agenesis is a regular feature. Heterozygous loss of function mutations in many genes reduce the gene dose, whereas e.g. in hypohidrotic ectodermal dysplasia (EDA) the complete inactivation of the partially redundant signaling pathway reduces the signaling centers. Although these mechanisms involve quantitative disturbances, the phenotypes associated with mutations in different genes indicate that in addition to an overall reduction of odontogenic potential, tooth class-specific and more complex mechanisms are also involved. Although several of the genes so far identified in rare forms of tooth agenesis are being studied as candidate genes of common third molar agenesis and incisor and premolar hypodontia, it is plausible that novel genes that contribute to these phenotypes will also become identified.

Mutations in the human homeobox MSX1 gene in the congenital lack of permanent teeth

Tooth agenesis is the congenital lack of permanent teeth, which is called oligodontia, when the number of missing teeth is 6 or more. Oligodontia affects more than 1 of 100 humans, but its pathogenesis is largely unknown. Tooth genesis depends on the complex interactions between environmental and genetic factors. The MSX1 gene, a member of homeobox gene family, encodes a DNA-binding protein, which is involved in many epithelial-mesenchymal interactions, leading to vertebrate organogenesis, and appears to be most critical during early tooth development. The MSH1 gene has 2 exons, separated by an intron, and its mutations, such as missense or frame-shift mutations, have been reported to be associated with tooth agenesis. In the present study, we sequenced the MSX1 gene of three unrelated patients with sporadic, non-syndromic oligodontia: 2 boys aged 8.5 and 15 years old and one girl aged 15.5 years old. We have thus identified a homozygotic deletion of 11 nucleotides in the intron, near the 5' splicing site, in two patients, who also carry a different exonic transition. The base changes we detected were not present in an open reading-frame of the MSX1 gene, but the newly identified deletion of 11 nucleotides might interfere with the splicing of the MSX1 gene. In contrast, the third patient, a 15-year boy, displayed no base change in the examined regions. Therefore, the identified 11-nucleotide deletion may decrease the expression level of the MSX1 protein, but the link with oligodontia needs further study.

Skeletal and dental patterns in patients with severe congenital absence of teeth

INTRODUCTION

Children with severe congenital absence of teeth present uncommon morphologies and therapeutic challenges. This study was designed to investigate the characteristic skeletal and dental features of this group.

METHODS

A group of 28 children with at least 10 congenitally missing teeth (excluding third molars) was examined roentgenographically. The data were collected from their intraoral series or panoramic views and lateral cephalograms. The results of their cephalometric analyses were compared with classic cephalometric norms and with local population norms.

RESULTS

Specific patterns of incisor, premolar, and third molar absence emerged. The cephalometric parameters of the children with severe absence differed from the classic norms in bimaxillary retrognathism, chin angle, and maxillary incisor inclination. These children differed from the Israeli norms in almost all parameters examined.

CONCLUSIONS

Patients with severe congenital absence of teeth have unique dental and skeletal patterns.

Dento-craniofacial phenotypes and underlying molecular mechanisms in hypohidrotic ectodermal dysplasia (HED): a review

The hypohidrotic ectodermal dysplasias (HED) belong to a large and heterogeneous nosological group of polymalfomative syndromes characterized by dystrophy or agenesis of ectodermal derivatives. Molecular etiologies of HED consist of mutations of the genes involved in the Ectodysplasin (EDA)-NF-kappaB pathway. Besides the classic ectodermal signs, craniofacial and bone manifestations are associated with the phenotypic spectrum of HED. The dental phenotype of HED consists of various degrees of oligodontia with other dental abnormalities, and these are important in the early diagnosis and identification of persons with HED. Phenotypic dental markers of heterozygous females for EDA gene mutation-moderate oligodontia, conical incisors, and delayed dental eruption-are important for individuals giving reliable genetic counseling. Some dental ageneses observed in HED are also encountered in non-syndromic oligodontia. These clinical similarities may reflect possible interactions between homeobox genes implicated in early steps of odontogenesis and the Ectodysplasin (EDA)-NF-kappaB pathway. Craniofacial dysmorphologies and bone structural anomalies are also associated with the phenotypic spectrum of persons with HED patients. The corresponding molecular mechanisms involve altered interactions between the EDA-NF-kappaB pathway and signaling molecules essential in skeletogenic neural crest cell differentiation, migration, and osteoclastic differentiation. Regarding oral treatment of persons with HED, implant-supported prostheses are used with a relatively high implant survival rate. Recently, groundbreaking experimental approaches with recombinant EDA or transgenesis of EDA-A1 were developed from the perspective of systemic treatment and appear very promising. All these clinical observations and molecular data allow for the specification of the craniofacial phenotypic spectrum in HED and provide a better understanding of the mechanisms involved in the pathogenesis of this syndrome.

Taurodontism and Van der Woude syndrome. Is there an association?

OBJECTIVE

To report the occurrence of taurodontism in a clinical sample of Van der Woude syndrome (VWS) and describe its association with hypodontia and cleft type.

MATERIALS AND METHODS

This retrospective, cross-sectional study was carried out on chart reviews and radiographs of 13 persons with VWS. Mean age was 10 years 11 months +/- 1 year 5 months. Panoramic radiographs were used to confirm the presence or absence of teeth and to measure crown body and root lengths of mandibular first molars. Three-dimensional cone beam computed tomography (CT) scans were available on two persons with VWS. Both volumetric and linear measurements were obtained.

RESULTS

The occurrence of taurodontism of the mandibular first molar was 35%: 27% hypodont and 8% mesodont. Of the 13 subjects with VWS, 6 (4 males and 2 females) had at least one tooth identified with taurodontism. Half of the cases were unilateral and half were bilateral, and all of the unilateral cases were on the left side. Five of the six subjects with taurodontism had missing incisors and premolars. Taurodontism was two times more frequent in those who were missing their second premolars than in those who had their second premolars. There was no correlation between cleft type and presence of taurodontism. The cone beam CT pilot study on two persons showed very abnormal morphology of both crown and roots, which was not apparent on the standard panoramic radiograph. Both the volumetric and linear measurements of the ratio of crown body to root were highly indicative of taurodontism. Further genetic studies are needed.

CONCLUSION

There is a likely association between VWS and taurodontism.

Dental agenesis: genetic and clinical perspectives

Dental agenesis is the most common developmental anomaly in humans and is frequently associated with several other oral abnormalities. Whereas the incidence of missing teeth may vary considerably depending on dentition, gender, and demographic or geographic profiles, distinct patterns of agenesis have been detected in the permanent dentition. These frequently involve the last teeth of a class to develop (I2, P2, M3) suggesting a possible link with evolutionary trends. Hypodontia can either occur as an isolated condition (non-syndromic hypodontia) involving one (80% of cases), a few (less than 10%) or many teeth (less than 1%), or can be associated with a systemic condition or syndrome (syndromic hypodontia), essentially reflecting the genetically and phenotypically heterogeneity of the condition. Based on our present knowledge of genes and transcription factors that are involved in tooth development, it is assumed that different phenotypic forms are caused by different genes involving different interacting molecular pathways, providing an explanation not only for the wide variety in agenesis patterns but also for associations of dental agenesis with other oral anomalies. At present, the list of genes involved in human non-syndromic hypodontia includes not only those encoding a signaling molecule (TGFA) and transcription factors (MSX1 and PAX9) that play critical roles during early craniofacial development, but also genes coding for a protein involved in canonical Wnt signaling (AXIN2), and a transmembrane receptor of fibroblast growth factors (FGFR1). Our objective was to review the current literature on the molecular mechanisms that are responsible for selective dental agenesis in humans and to present a detailed overview of syndromes with hypodontia and their causative genes. These new perspectives and future challenges in the field of identification of possible candidate genes involved in dental agenesis are discussed.

Morphogenetic fields within the human dentition: a new, clinically relevant synthesis of an old concept

This paper reviews the concept of morphogenetic fields within the dentition that was first proposed by Butler (Butler PM. Studies of the mammalian dentition. Differentiation of the post-canine dentition. Proc Zool Soc Lond B 1939;109:1–36), then adapted for the human dentition by Dahlberg (Dahlberg AA. The changing dentition of man. J Am Dent Assoc 1945;32:676–90; Dahlberg AA. The dentition of the American Indian. In: Laughlin WS, editor. The Physical Anthropology of the American Indian. New York: Viking Fund Inc.; 1951. p. 138–76). The clone theory of dental development, proposed by Osborn (Osborn JW. Morphogenetic gradients: fields versus clones. In: Butler PM, Joysey KA, editors Development, function and evolution of teeth. London: Academic Press, 1978. p. 171–201), is then considered before these two important concepts are interpreted in the light of recent findings from molecular, cellular, genetic and theoretical and anthropological investigation. Sharpe (Sharpe PT. Homeobox genes and orofacial development. Connect Tissue Res 1995;32:17–25) put forward the concept of an odontogenic homeobox code to explain how different tooth classes are initiated in different parts of the oral cavity in response to molecular cues and the expression of specific groups of homeobox genes. Recently, Mitsiadis and Smith (Mitsiadis TA, Smith MM. How do genes make teeth to order through development? J Exp Zool (Mol Dev Evol) 2006; 306B:177–82.) proposed that the field, clone and homeobox code models could all be incorporated into a single model to explain dental patterning. We agree that these three models should be viewed as complementary rather than contradictory and propose that this unifying view can be extended into the clinical setting using findings on dental patterning in individuals with missing and extra teeth. The proposals are compatible with the unifying aetiological model developed by Brook (Brook AH. A unifying aetiological explanation for anomalies of tooth number and size. Archs Oral Biol 1984;29:373–78) based on human epidemiological and clinical findings. Indeed, this new synthesis can provide a sound foundation for clinical diagnosis, counselling and management of patients with various anomalies of dental development as well as suggesting hypotheses for future studies.

Studies of dental anomalies in a large group of school children

The identification of specific patterns of dental anomalies would allow testing the hypothesis that certain genetic and environmental factors contribute to distinct dental anomaly subphenotypes. A sexual dimorphism in tooth agenesis and its association with other dental anomalies has been suggested. The aim of this study was to investigate a large group of children to define dental anomaly subphenotypes that may aid future genetic studies. Orthopantamograms of 1198 subjects were examined and 1167 were used in this study. The frequency of tooth agenesis in the studied population was 4.8%. Male:female ratios varied from 2:1 in the agenesis of upper lateral incisors to 0.5:1 in premolar agenesis. The risk of infra-occlusion of primary molars and double formation of primary incisors was increased in individuals with tooth agenesis.

Assessing the proposed association between tooth agenesis and taurodontism in 975 paediatric subjects

BACKGROUND

An association between tooth agenesis and taurodontism has been suggested. The identification of subpopulations with specific associated dental anomalies (subphenotype) would allow testing of the specific hypothesis that certain genetic factors contribute to the specific subphenotype.

AIM

This work aims to assess a large cohort to verify if the association between tooth agenesis and taurodontism is present.

DESIGN

Panoramic radiographs of 1002 patients were examined and 975 were used in this study. The presence of tooth agenesis and taurodontism was assessed in the study population.

RESULTS

The frequency of tooth agenesis was 4.6% and the frequency of taurodontism was 1.6%. There were, however, no observations of concomitant tooth agenesis and taurodontism.

CONCLUSIONS

Our data do not support the hypothesis that isolated tooth agenesis is associated with isolated taurodontism.

Identification of a novel missense mutation of MSX1 gene in Chinese family with autosomal-dominant oligodontia

OBJECTIVES

Oligodontia is defined as the congenital absence of 6 or more permanent teeth excluding the third molar. The occurrence of non-syndromic still remains poorly understood, but in recent years some cases have been reported where mutations or polymorphisms of PAX9 and MSX1 had been associated with non-syndromic oligodontia. The objective of the present work was to study the phenotype and genotype of three generations of a Han Chinese family affected by non-syndromic autosomal-dominant oligodontia.

DESIGN

We examined all individuals of the oligodontia family by clinical and radiographic examinations. Based on clinical manifestations, candidate genes MSX1 and PAX9 were picked up to analyse and screen mutations.

RESULTS

Dental evaluation showed that the most commonly missing teeth are the mandibular second premolars, followed by the maxillary second premolars and maxillary lateral incisors, and subsequently the maxillary first premolars. The probability of missing a particular type of tooth is not always bilaterally symmetrical, and differences exist between maxilla and mandible. PCR-SSCP analysis and DNA sequencing revealed a novel missense mutation c.662C>A in a highly conserved homeobox sequence of MSX1 and a known polymorphisms c.347C>G.

CONCLUSION

Our finding suggests the missense transversion (c.662C>A) and the polymorphisms (c.347C>G) may be responsible for oligodontia phenotype in this Chinese family.

Labial cervical vertical groove (LCVG) distribution and morphometric characteristics

OBJECTIVE

Labial cervical vertical groove (LCVG), a dental anomaly found at the cervical region of upper permanent incisors, can be of esthetic, periodontal and prosthetic concern. The aim of this study was to define the prevalence and characteristics of LCVG.

DESIGN

Of the 1250 examined subjects, 66 exhibited an LCVG. This group (age 19.7+/-11.4 years) was then compared with a matched No-LCVG (control) group of 49 subjects (age 17.9+/-5.7 years). Six LCVG characteristics were examined: distribution, severity and location of LCVG in central (I(1)) and lateral (I(2)) permanent maxillary incisors, Angle's classification, gender and presence of LCVG in siblings.

RESULTS

Total LCVG prevalence was 5.3% (single 3.76%; multiple 1.53%), found predominantly in I(1) (93.9%) compared with I(2) (p=0.001). The anomaly presented mostly as a single configuration (71.21%); double configuration was predominantly homological bilateral, i.e., I(1)+I(1), or I(2)+I(2) (88%). LCVG in I(2) was mainly associated with multi-configuration (75%). The severe form occurred only in I(1). A mid-crown LCVG allocation was distinctive in I(1) (62.2%, p=0.001) and mesial-crown in I(2) (66.7%, p=0.038). LCVG was found mostly in males (p=0.045). In the LCVG group 16.7% were siblings.

CONCLUSIONS

LCVG primarily involved I(1) in single configuration as the target assaulted tooth and secondarily I(2) mostly as a multi-configuration. The genetic impact on LCVG formation was primarily supported by the high prevalence in siblings and secondarily by the favourable occurrence in males, exclusive pattern of allocation within the crown and high occurrence of bilateral double-configuration LCVG.

Familial human hypodontia--is it all in the genes?

The congenital absence of teeth is one of the commonest developmental abnormalities seen in human populations. Familial hypodontia or oligodontia represents an absence of varying numbers of primary and/or secondary teeth as an isolated trait. While much progress has been made in understanding the developmental basis of tooth formation, knowledge of the aetiological basis of inherited tooth loss remains poor. The study of mouse genetics has uncovered a large number of candidate genes for this condition, but mutations in only three have been identified in human pedigrees with familial hypodontia or oligodontia: MSX1, PAX9 and AXIN2. This suggests that these conditions may represent a more complex multifactorial trait, influenced by a combination of gene function, environmental interaction and developmental timing. Completion of the human genome project has made available the DNA sequence of the collected human chromosomes, allowing the localisation of all human genes and, ultimately, determination of their function. Therefore it is likely that our understanding of this complex developmental process will continue to improve, not only during normal development but also when things go wrong.

Congenital Missing Permanent Teeth in Korean Unilateral Cleft Lip and Alveolus and Unilateral Cleft Lip and Palate Patients

Objective: To investigate the differences in the congenital missing teeth pattern in terms of tooth type (permanent maxillary lateral incisor [MLI] and maxillary second premolar [MSP]) and sidedness (cleft vs noncleft) between boys and girls in Korean unilateral cleft lip and alveolus (UCLA) and unilateral cleft lip and palate (UCLP) patients.

Materials and Methods: This study used the charts, models, radiographs, and intraoral photographs of 90 UCLA patients and 204 UCLP patients (ages 6 to 13 years). Binomial test, chi-square test, Fisher exact test, maximum likelihood analysis of variance, and the odds ratio were performed.

Results: According to the relationship between the congenital missing teeth pattern and the cleft type, the UCLP patients had 2.98 times more missing MLIs and 1.80 times more missing MSPs than did the UCLA patients. The MLI was congenitally missing more in boys than in girls, but the MSP showed the opposite tendency. Boys had a higher frequency of congenital missing MLIs and MSPs on the cleft side than did girls. However, on the noncleft side and both sides, girls had a higher frequency of congenital missing MLIs and MSPs than did boys. Results showed a gender-dominant pattern of congenital missing MLIs and MSPs.

Conclusion: These results suggest that gender and cleft type might affect the congenital missing teeth pattern in terms of tooth type and sidedness.

Endodontic treatment of an unusual connation of permanent mandibular molars: a case report

A 27-year-old patient with an anomalous mandibular molar was referred for endodontic therapy. Clinical and radiographic examination revealed the connation of a second mandibular molar with a third molar. Challenging endodontic therapy was performed in the unusual connated molars. A 2-year recall showed good treatment result.

A novel missense mutation in MSX1 underlies autosomal recessive oligodontia with associated dental anomalies in Pakistani families

Tooth agenesis constitutes the most common anomaly of dental development in humans. In the majority of familial cases of hypodontia alone or in association with other anomalies, the mode of inheritance is autosomal dominant. In the present study, we have identified two distantly related consanguineous Pakistani kindreds with an autosomal recessive form of oligodontia with associated dental anomalies. Locus in this case has been mapped on chromosome 4p16.1-p16.3. The maximum two-point LOD score of 2.85 (theta=0.0) was obtained at markers D4S2925 and D4S2285. A maximum multipoint LOD score exceeding 4 was obtained at the same markers. Recombination events observed in affected individuals localized the disease locus between markers D4S412 and D4S2935, spanning a 9.24-cM region on chromosome 4p16.1-p16.3. Sequence analysis of candidate gene MSX1 revealed a novel recessive missense mutation resulting in substitution of alanine to threonine amino acid (p. A219T), located in the MSX1 homeodomain, which is important for DNA binding and protein-protein interaction. The mutation, p. A219T, is the first recessive mutation identified in MSX1.

Maxillary canine anomalies and tooth agenesis

The aims of the study were to analyse the records of 26 subjects (18 females, eight males) with maxillary canine-first premolar transposition (Mx.C.P1) together with 160 subjects with a palatally displaced canine (PDC) to determine the pattern of tooth agenesis in these cases and to compare them with similar samples reported in the literature. A strong association between Mx.C.P1, lateral incisor and lower second premolar agenesis was found, with a 20 per cent prevalence of lateral incisor agenesis and a 24 per cent prevalence of lower second premolar agenesis. There was a lesser association with third molar (M.3) agenesis, with a prevalence of 52.2 per cent. Weaker associations were found for a PDC, with a prevalence of 5 per cent for lateral incisor agenesis. The prevalence of lower second premolar (5 per cent) and M.3 (27.5 per cent) agenesis approached reference values. Evidence for the implication of the MSX1 or PAX9 genes in the aetiology of PDC was weak.

Prosthodontic management of older severe hypodontia patients in general dental practice: A case series

Although a detailed understanding of the etiology of hypodontia is lacking, there is a need for awareness among dental professionals of the social and psychological consequences of severe hypodontia, as well as knowledge of those affected by hypodontia have ongoing dental treatment needs. Although, there may be a need for immediate referral of children to different specialists for optimal multidisciplinary treatment planning, most older patients with severe hypodontia can be treated by general practitioners. Practitioners therefore need to be aware of the ramifications of the condition and be capable of providing adequate oral health care for these patients and referring them for additional services when necessary. A case-report series is used to illustrate routine prosthodontic treatments that can be offered to older patients in general dental practice.

Peg-shaped and small lateral incisors not at higher risk for root resorption

The purpose of this study was to examine the pattern of external root resorption for peg-shaped and small lateral incisors according to various conditions and to compare it with that of normal-shaped lateral incisors. The periapical radiographs of 114 patients with 60 peg-shaped and 54 small lateral incisors were measured before and after treatment. Crown shape was assessed by examining pretreatment study casts. Findings showed that there was no significant difference in external root resorption between peg-shaped (1.09 mm) and normal lateral incisors (0.88 mm). However, a statistically significant difference in apical root resorption between small lateral incisors (1.03 mm) and normal lateral incisors (1.62 mm) was found. Peg-shaped laterals were also coincidentally found to occur more frequently on the left side of the arch.

Is tooth agenesis related to brainstem anomalies in myelomeningocele patients with Chiari II malformations?

Defects in the prenatal development of the brainstem can result in cranial nerve deficiencies. As the development of tooth germ is dependent on n. trigeminus, which originates from the brainstem, the hypothesis underlying this study was that anomalies of the brainstem would lead to an increased prevalence of tooth agenesis. Twenty-three patients (13 F and 10 M, age range 6-37 years) were studied, all with myclomeningocele and brainstem anomalies (Chiari II). They were examined retrospectively from the data in journals and dental radiographs and compared to available data on the prevalence of tooth agenesis in the Swedish population. Our hypothesis was rejected, since there was insignificant difference in the frequency of agenesis in our material (8.7%) compared with that of the Swedish population (7.4%).

Prevalence of short-root anomaly in healthy young adults

Short-root anomaly (SRA), occurring mostly in maxillary incisors, is defined as developmentally very short, blunt dental roots. The condition has a genetic background and is related to hypodontia. Earlier population studies have been based on schoolchildren with developing dentitions and have indicated prevalence figures between 1% and 10%. We studied a random sample of existing panoramic radiographs of 2000 university students for SRA. Roots as long as or shorter than the crowns in the incisors and visually evaluated as very short, blunt roots bilaterally in the posterior teeth were classified as SRA. The prevalence was 1.3%. According to anamnestic information, half the SRA patients had undergone orthodontic therapy, but pre-treatment radiographs were unavailable. In 70% of the SRA patients the short-rooted tooth pairs were upper incisors, but also involved were maxillary premolars, lateral incisors, and lower second premolars. Women were significantly more often affected. We discuss other factors known to cause short-rooted teeth and conclude that the population prevalence for genetic SRA in fully developed dentitions is close to our 1.3%.

Identification of a nonsense mutation in the PAX9 gene in molar oligodontia

Development of dentition is controlled by numerous genes, as has been shown by experimental animal studies and mutations that have been identified by genetic studies in man. Here we report a nonsense mutation in the PAX9 gene that is associated with molar tooth agenesis in a Finnish family. The A340T transversion creates a stop codon at lysine 114, and truncates the coded PAX9 protein at the end of the DNA-binding paired-box. All the affected members of the family were heterozygous for the mutation. The tooth agenesis phenotype involves all permanent second and third molars and most of the first molars and resembles the earlier reported phenotype that was also associated with a PAX9 mutation. The phenotype is presumably a consequence of haploinsufficiency of PAX9. In another Finnish family with molar tooth agenesis, we could not find similar sequence changes in PAX9.