Tooth size patterns in patients with hypodontia and supernumerary teeth

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.

Occlusal characteristics in modern humans with tooth agenesis

Non-syndromic permanent tooth agenesis affects a significant proportion of the population, especially if third molars are considered. Although tooth agenesis has been linked to a smaller craniofacial size, reduced facial convexity and a shorter skeletal face, the occlusal characteristics of individuals with tooth agenesis remain largely unexplored. Therefore, this study investigated potential associations between tooth agenesis and metric occlusal traits in 806 individuals (491 with 4.1 missing teeth per subject, including third molars, and 315 without any tooth agenesis). Dentoskeletal morphology was defined through anatomical landmarks on pre-treatment cephalometric radiographs. Multivariate regression models, adjusted for sex and age, showed that tooth agenesis was significantly associated with a reduced overjet, an increased interincisal angle, and shorter upper and lower dental arch lengths, but not with overbite. Moreover, apart from reduced tooth length and dentoalveolar effects, as the number of missing teeth increased the upper front teeth were progressively retruded according to the craniofacial complex and to the face. Thus, tooth agenesis has a substantial influence on dental and occlusal characteristics, as well as on the sagittal position and inclination of anterior teeth. These findings emphasize the necessity for personalized, multidisciplinary approaches in individuals with multiple agenesis to successfully meet treatment goals.

The genetic basis of hypodontia in dental development

Dental agenesis is one of the most common developmental anomalies in humans, characterised by the developmental absence of one or more teeth. It can present as an isolated condition (non-syndromic hypodontia) or associated with a syndrome (syndromic hypodontia). This paper aims to review the genetic basis of hypodontia with reference to aetiology, classification and the subsequent clinical features.Significant progress has been made to identify the developmental basis of tooth formation, though there is still a lack of knowledge within the literature of the aetiological basis of inherited tooth loss.Gene anomalies or mutations in WNT10A, MSX1, PAX9, AXIN2 and EDA appear to be most critical during tooth development, leading to various forms of tooth agenesis.

Few dental indices in modern Bulgarian population from southern Bulgaria

AIM

The aim of the present study is to evaluate the reduction of the distal teeth towards the medial ones in one functional dental group in southern Bulgarian population.

MATERIALS AND METHODS

The study included 232 Bulgarians aged 20-40 years. Mesiodistal dimensions of the teeth were measured by Dentistry Sliding Vernier Caliper and analyzed with SPSS 23.0. Four interdental indices were calculated: inter-incisive, premolar, upper, and lower molar indices.

RESULTS

We found a decrease in the percentage ratio of the lateral to the central incisors of people from the Bulgarian population compared to those dating from the Eneolithic period on the territory of Bulgaria. Furthermore, we found a reduction in the percentage ratio of the upper and lower second molars compared to the first ones. The biggest reduction in the percentage ratio (more than 6%) was found in the lower second premolars compared to the first ones, which is characteristic for southern Bulgarians.

CONCLUSION

There was a dental reduction in all the distal members compared to the medial ones participating in one morphological dental group. As a result, we think that interdental indices can be used for explaining historical, cultural, and biological macro and microevolutionary processes and thus for understanding the origin, formation, contacts, and migration pathways of the different populations leading to ethnic variation of humanity. Therefore, they can be a reliable source of information in physiological anthropology.

Genetic, Epigenetic and Environmental Factors Influence the Phenotype of Tooth Number, Size and Shape: Anterior Maxillary Supernumeraries and the Morphology of Mandibular Incisors

The aim of this study is to investigate whether the genetic, epigenetic and environmental factors that give rise to supernumeraries in the maxillary incisor region and larger dimensions of the adjacent maxillary incisors are also associated with variations in the morphology of the mandibular incisors. If so, this would contribute to understanding the distribution and interactions of factors during dental development and how these can be modelled. The sample consisted of 34 patients with supernumerary teeth in the maxillary anterior region, matched for gender, age and White Caucasian ethnicity with 34 control subjects. The average ages of the supernumerary and control groups were 12.8 and 12.2 years, respectively. Study models of all subjects were constructed and imaged using a previously validated system. Using custom software, each of the mandibular incisor teeth were measured to obtain 17 parameters from the labial view and 17 from the occlusal view. Principal component analysis (PCA) was used to summarize the measurements into a smaller set representing distinct features of the clinical crowns, followed by a comparison between the supernumerary and control groups using 2-way ANOVA. Seven factors of tooth size of the mandibular central incisors and six factors of the mandibular lateral incisors were identified as major features of the clinical crowns. All parameters of both mandibular incisors were greater in the supernumerary group than in the control, with three of these, located in the incisal and cervical regions of the mandibular lateral incisors, being statistically significantly larger. The findings of this study indicate that the aetiological factors associated with supernumerary teeth in the maxillary anterior region also affect tooth crown dimensions of mandibular incisors. This new evidence enhances several models of the interactions of genetic, epigenetic and environmental components of dental development and supports a multi-model approach to increase understanding of this process and its variations.

Tooth agenesis in German orthodontic patients with non-syndromic craniofacial disorder: a retrospective evaluation of panoramic radiographs

Objectives

The study objective was to evaluate the tooth agenesis in German orthodontic patients with non-syndromic cleft lip and/or palate and Robin sequence compared to a control group without craniofacial disorder.

Materials/methods

A total of 108 panoramic radiographs were examined using the binary system of Tooth Agenesis Code (TAC) (excluding the third molar). Patients were divided into the craniofacial disorder group 1 (n = 43) and the healthy control group 2 (n = 65). Parameters such as skeletal class malformation, sex, localization of the cleft, craniofacial disorder, and interobserver reliability were assessed.

Results

Permanent tooth agenesis was observed in 44% of group 1 and 14% in group 2 with a statistically significant higher prevalence (p = 0.00162 (χ²)). Fourteen different TAC patterns were observed in group 1, ten of these occurring only once in separate patients. The distribution of the TAC codes in group 2 showed nine different possibilities of TAC code patterns; seven TACs were unique. In group 1, the most frequently absent teeth were the maxillary lateral incisor of the left side (30%); in group 2, the second premolar of the lower jaw on the right side (9%). Male patients with craniofacial disorder showed a higher percentage of tooth agenesis than female.

Conclusion

The data presented here shows a statistically significant higher prevalence of tooth agenesis in German patients with non-syndromic craniofacial disorder.

Clinical relevance

Radiographic evaluation enables the diagnosis of tooth agenesis. Recognizing early on the higher prevalence of tooth agenesis in patients exhibiting a craniofacial disorder is an important issue when developing long-term and comprehensive interdisciplinary treatment.

Assessment of risk factors and molecular biomarkers in children with supernumerary teeth: a single-center study

Background

Supernumerary teeth are considered one of the commonly observed dental anomalies in children. Several theories have been proposed to explain the presence of supernumerary teeth, including environmental and genetic factors. This study aimed to identify the different risk factors and molecular biomarkers in patients presented with supernumerary teeth.

Methods

This case–control study included 240 children, 6 to 12-year-old. They were divided into a test group (n = 120 children presented with supernumerary teeth) and a control group (n = 120 children with no supernumerary teeth). Questionnaires were distributed to assess demographics and exposure to several environmental factors. Ten extracted supernumerary teeth from the test group were processed for histopathological analysis.

Results

Male gender, dental history of severe oral infection or medical history of chemotherapy treatment, previous history of taking medication or illness during pregnancy, family history of neoplastic disorders, use of electronic devices, and living beside agricultural fields or industrial areas were found to be statistically significant associated with the risk of supernumerary teeth development. Immunohistochemistry panel revealed that supernumerary teeth showed enhanced expression of wingless (Wnt) and sonic hedgehog (SHH) proteins as well as a reduced expression of adenomatous polyposis coli (APC) protein, denoting molecular derangement in a group of pathways classically believed to be involved in its pathogenesis.

Conclusions

Males were more frequently affected by supernumerary teeth than females. Several risk factors were notably correlated with the existence of supernumerary teeth. Additionally, molecular biomarkers assessment demonstrated a high expression level of pro-tumorigenic proteins such as Wnt and SHH in patients with supernumerary teeth.

Rehabilitation Considerations for Very Young Children with Severe Oligodontia due to Ectodermal Dysplasia: Report of Three Clinical Cases with a 2-Year Follow-Up

Introduction

Management of oligodontia can be complicated and requires multidiscipline care, involving a wide spectrum of interventions. The aim of this report is to describe the challenges of oral rehabilitation of three very young children with oligodontia. Report. Three preschool aged Caucasian males, diagnosed with ectodermal dysplasia, were treated with interim removable dentures in order to replace missing teeth, reclaim vertical dimension, and improve function and aesthetics. The main challenges faced were patient cooperation, dental and skeletal characteristics, and parental expectations. Two years post-treatment, both patients and parents reported excellent adaptation to prosthesis and satisfaction with aesthetics.

Conclusion

Rehabilitation of oligodontia may be challenging due to accompanying oral findings, dentofacial growth considerations, and behavioral issues. Establishment of good rapport between patients, parents, and clinician is the key for the success of the treatment even with the use of nonpharmacological behavioral management techniques.

How Does Hypodontia Compare in Nonsyndromic Pierre Robin Sequence Versus Isolated Cleft Palate and Isolated Cleft Lip?

OBJECTIVE

To assess the prevalence and patterns of hypodontia in nonsyndromic Pierre Robin sequence (PRS) and compare it with hypodontia in nonsyndromic isolated cleft palates and isolated cleft lips.

DESIGN

Retrospective cohort study.

SETTING

Alder Hey Children's Hospital, United Kingdom.

PATIENTS

Patients with nonsyndromic PRS (group 1), isolated cleft palate (group 2), and isolated cleft lip (group 3).

MAIN OUTCOME MEASURES

Hypodontia in the permanent dentition assessed from orthopantomographs.

RESULTS

A total of 154 patients were included. Group 1 had the highest incidence of hypodontia with 47% having at least one tooth congenitally absent. Groups 2 and 3 had reduced rates of hypodontia with 27% and 19% of the groups missing teeth, respectively; 93% of cases of hypodontia in group 1 involved the absence of at least one second premolar. Of these patients, there was found to be bilateral agenesis of second premolars in 50% of cases.

CONCLUSIONS

Patients with PRS and cleft palates are more likely to have hypodontia than those with isolated cleft palates or unilateral cleft lips. Patients with PRS have more severe hypodontia than those with isolated cleft palates or unilateral cleft lips. Bilateral agenesis of lower second premolars is a commonly seen pattern among patients with PRS. In this large UK study, a similar prevalence and pattern of hypodontia to other nonsyndromic PRS populations worldwide has been demonstrated.

FGF10 and FGF13 genetic variation and tooth-size discrepancies

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

The effect of Ekman-Westborg and Julin trait (generalized megadontia) and localized megadontia on tooth components size and ion content

AIMS

The objective of this study is to compare size, enamel thickness and ion relative concentration in generalized megadontia (Ekman- Westborg and Julin trait) and a localized megadont upper third molar to normal teeth.

MATERIALS AND METHODS

The MD dimensions of permanent teeth were compared to controls. Tooth components of molars were measured from X-rays and compared to controls. The enamel and dentin relative amounts of elements of mandibular first permanent molar and deciduous canines of E-WJ trait girl, and megadont upper third molar were determined using ESD program of SEM and compared to match-paired normal teeth.

RESULTS

The teeth of the girl diagnosed with E-WJ trait were true megadont (larger than mean ± 2SD). The ratio of enamel thickness to M-D dimension of molars of E-WJ trait and localized megadontia molars is reduced in comparison with normal similar teeth. In the enamel, carbon and silica concentrations were different in E-WJ trait teeth.

CONCLUSIONS

The enamel thickness was reduced in the E-WJ trait and megadont molars, but the relative amount of elements in enamel and dentin was similar to normal. The megadontia is due to a very large tooth germ, as determined by the DEJ, while the ratio of enamel apposition from the total M-D dimension is reduced.

CLINICAL RELEVANCE

Generalized megadontia, as observed in E-WJ trait, is due to large tooth germ, but the enamel thickness is similar to normal. Extractions of permanent teeth are necessary in order to allow normal eruption of teeth.

Three-dimensional geometric morphometric analysis of tooth shape in hypodontia: II size variation

The study aimed to evaluate differences in tooth size between patients with hypodontia and those with normal complement of permanent teeth using three-dimensional geometric morphometric analysis. The number of anatomical landmarks was recorded on the clinical crown of the permanent teeth on three-dimensional scanned study models of hypodontia and in control subjects. The study sample comprised 120 patients with hypodontia (mild, moderate, severe) and 40 controls matched for age and sex. Tooth size differences were tested statistically using multivariate statistics. Size variation was for the most part found to be significant, especially when the control subjects were compared with the hypodontia groups. The explained variance among group membership was generally larger in the anterior and premolar region than in the molar region Sexual dimorphism was found less in the anterior region than in the posterior region; therefore, the sexes were pooled more often for teeth in the anterior region. Quantitative measurement of tooth size in patients with hypodontia may enhance the multidisciplinary management of these patients.

Dental development in children with supernumerary teeth in the anterior region of maxilla

OBJECTIVE

Development of human dentition has been used as a predictor for evaluating the growth and maturity of an individual. It is fairly identical in a specific population, but the effect of development on subjects with dental anomalies had not been fully explored, particularly on subjects with supernumerary teeth (ST). This study hence aims to evaluate the dental development of children with and without ST.

MATERIALS AND METHODS

Sample size calculation was conducted and 320 radiographs of subjects with and without supernumerary teeth (ST) were obtained from the archives of a teaching hospital. The subjects in both groups were age and sex matched. All the subjects belong to southern Chinese ethnicity aged 2 to 14 years. The left-side dentition was scored, and dental age (DA) was estimated by obtaining scores from the southern Chinese dental reference dataset. Paired t test was used to calculate the difference between chronological age and dental age (CA-DA) for boys and girls with and without ST and further based on the number and position of ST.

RESULTS

The difference between chronological age and dental age (CA-DA) was 0.10 years for boys and 0.19 years for girls with ST whilst 0.01 and 0.05 years for boys and girls without ST (p > 0.05). The boys with bilateral ST showed significant delay in dental development of 0.23 years (p < 0.05). Position of the ST did not have any influence on dental age.

CONCLUSIONS

No significant difference was observed in the dental development of children with and without supernumerary teeth.

CLINICAL RELEVANCE

Understanding dental development of children with supernumerary teeth may be useful in appropriate treatment planning of such conditions.

Frequency of missing teeth and reduction of mesiodistal tooth width in Japanese patients with tooth agenesis

Background

Tooth agenesis can involve one or more congenitally missing teeth (CMT) and is the most common congenital dental anomalies in humans. Tooth agenesis and reduction of mesiodistal tooth width are reportedly associated, suggesting that the pathogenesis of the two conditions is related. The current study analyzed the frequency of tooth agenesis and mesiodistal tooth width in cases of hypodontia (1–5 CMT) and oligodontia (≥ 6 CMT) in Japanese patients based on the hypothesis that reductions in mesiodistal tooth width are more frequently associated with oligodontia than hypodontia.

Methods

Japanese patients with tooth agenesis were divided into hypodontia cases (60 female and 25 male, mean age 19.6 years, mean CMT number 1.31 ± 1.65) and oligodontia cases (26 female and 25 male, mean age 14.6 years, mean CMT number 8.07 ± 2.39). Controls included patients with a skeletal class I relationship and no CMT (female and 60 male, mean age 20.8 years). Dental casts and orthopantomograms were used to analyze the CMT frequency and mesiodistal tooth width for each group. The Kruskal-Wallis test, the Mann-Whitney U test, and Spearman’s rank correlation were used for statistical analysis.

Results

In the hypodontia group, mandibular second premolars were the most frequently missing tooth type (25.9%), followed by mandibular and maxillary lateral incisors (19.4 and 17.1%, respectively). In the oligodontia group, mandibular second premolars were the most frequently missing tooth type (88.2%), followed by maxillary second premolars (87.3%) and first premolars (63.7%). In female subjects in the hypodontia group, only maxillary lateral incisors and mandibular first molars were significantly smaller than those of the female control subjects. In contrast, in the oligodontia group, more tooth types were significantly smaller than those of the control, for both sexes. Except for maxillary second premolars in female subjects, correlations were apparent for all tooth types in both sexes.

Conclusions

Compared to hypodontia, more tooth types exhibited reduced mesiodistal tooth width in oligodontia. Correlations between CMT number and mesiodistal tooth width support the hypothesis that reduction of mesiodistal tooth width are more frequently observed in Japanese oligodontia patients than in Japanese hypodontia patients.

Mesiodistal and Buccolingual Dimensions in Croatian Orthodontic Hypodontia Patients' Teeth

OBJECTIVE

This study compared mesiodistal (MD) and buccolingual (BL) tooth dimensions of hypodontia patients with a control group with complete dentition. The null hypothesis was that there was no difference in tooth sizes between hypodontia patients and the controls.

METHODS

The sample comprised 76 patients with hypodontia (50 female and 26 male) aged between 11 and 18 years. The control group comprised 50 females and 26 males with the same age range as the study group. Mesiodistal (MD) and buccolingual (BL) dimensions were measured on pretreatment dental casts with a digital caliper to the nearest 0.01 mm. The data were analyzed using Statistica 7.1 (StatSoft Inc.) statistical package (descriptive statistics, test of distribution normality, parametric statistics).

RESULTS

The most common congenitally missing teeth were the lower second premolars (left 13.45% and right 13.90%) and upper lateral incisors (both left and right 12.56%), followed by upper second premolars (right 9.4o% and left 10.31%). The greatest differences between the study and control group were found in upper lateral incisors, 8.08% in MD and 6.40% in BL dimension. The smallest difference was found in BL dimension of lower lateral incisor (2.37%), MD dimension of lower second premolars and upper first molar (2.61%) and MD dimension of lower central incisor (2.26%).

CONCLUSION

The teeth are smaller in subjects with hypodontia than those of the controls on average 4.02% in MD dimension and 3.85% in BL dimension. The tooth that showed the greatest difference in tooth dimension was maxillary lateral incisor.

Three-dimensional evaluation of root dimensions and alveolar ridge width of maxillary lateral incisors in patients with unilateral agenesis

Background

The objective of this retrospective case-control study was to measure the maxillary lateral incisor root dimensions and quantify the labial and palatal bone in patients with unilateral maxillary lateral incisor agenesis (MLIA) after orthodontic treatment and compare them to non-agenesis controls using cone beam computed tomography.

Methods

The labiopalatal and mesiodistal root dimensions, mesiodistal coronal dimensions, and labiopalatal bone and alveolar ridge widths of the maxillary lateral incisor were assessed on posttreatment cone beam computed tomography scans of 15 patients (mean age 16.5 ± 3.4 years, 9 females and 6 males) with maxillary lateral incisor agenesis and 15 gender-matched patients (mean age 16.08 ± 3.23 years) with no dental agenesis or anterior Bolton discrepancy. The Mann-Whitney test was used to distinguish any differences in root width, crown width, or changes in labial or palatal bone width between the two groups.

Results

The median labiopalatal root width was narrower in the MLIA group at the level of the cementoenamel junction (CEJ) to 8 mm apical of the CEJ compared to controls (p ≤ 0.009). The mesiodistal root width was significantly reduced in the MLIA group at the CEJ and at 4 mm apical to the CEJ. The labiopalatal alveolar ridge width was significantly decreased at 2 mm apical to the CEJ in MLIA group. The mesiodistal crown width was significantly smaller in the MLIA group at both the incisal edge and at the crown midpoint. The bone thickness was similar in both groups.

Conclusions

Coronal and root dimensions in patients with MLIA were reduced compared to controls. Alveolar ridge width was also reduced in patients with MLIA, although bone thickness was not different than controls.

Tooth Size in Patients with Mild, Moderate and Severe Hypodontia and a Control Group

Objectives:

To compare tooth size between subjects with mild, moderate and severe hypodontia and a control group.

Material and Methods:

The study comprised 120 patients with hypodontia divided into three groups of 40 mild (≤2 teeth congenitally missing), 40 moderate (3-5 teeth congenitally missing) and 40 severe (≥6 teeth congenitally missing) hypodontia; and 40 age and sex matched controls. Tooth size was recorded by measuring the mesiodistal and buccolingual dimensions of all fully erupted teeth on study models using digital callipers and compared between all hypodontia and control groups using Two-way ANOVA and Post Hoc Tests of subgroup comparison.

Results:

Two-way ANOVA revealed patients with hypodontia had significantly smaller mesiodistal and buccolingual tooth dimensions compared with controls (p<0.05). Furthermore patients with more severe hypodontia demonstrated significantly smaller tooth dimensions than those in the mild and moderate hypodontia subgroups (p<0.05). The most affected tooth in terms of tooth size reduction was the maxillary lateral incisor and the least affected tooth was the mandibular first molar.

Conclusion:

Patients with hypodontia have smaller tooth dimensions than control. Tooth size appears to be affected by the degree of hypodontia, with severe hypodontia having a greater effect on tooth size reduction. The findings of this study may contribute to understanding the aetiology of hypodontia and aid the multidisciplinary management of this complex condition.

Rehabilitation of a patient with non-syndromic partial oligodontia

Oligodontia is defined as a congenital tooth agenesis with the absence of six or more permanent teeth. This clinical report describes a patient with non-syndromic partial oligodontia, with retained deciduous teeth and the absence of 16 permanent teeth. Anterior esthetic problems were caused by interarch tooth size discrepancy, interdental space, aberrant tooth dimensions, and the absence of centric contacts of the anterior teeth. Prosthetic restoration after orthodontic and implant treatment was performed with a multi-disciplinary team approach. Favorable functional and esthetic results were obtained using a definitive prosthesis.

Effects of Usag-1 and Bmp7 deficiencies on murine tooth morphogenesis

BACKGROUND

Wnt5a and Mrfzb1 genes are involved in the regulation of tooth size, and their expression levels are similar to that of Bmp7 during morphogenesis, including during the cap and early bell stages of tooth formation. We previously reported that Usag-1-deficient mice form supernumerary maxillary incisors. Thus, we hypothesized that BMP7 and USAG-1 signaling molecules may play important roles in tooth morphogenesis. In this study, we established double genetically modified mice to examine the in vivo inter-relationships between Bmp7 and Usag-1.

RESULTS

We measured the volume and cross-sectional areas of the mandibular incisors using micro-computed tomography (micro-CT) in adult Bmp7- and Usag-1-LacZ knock-in mice and their F2 generation upon interbreeding. The mandibular incisors of adult Bmp7+/- mice were significantly larger than those of wild-type (WT) mice. The mandibular incisors of adult Usag-1-/- mice were the largest of all genotypes examined. In the F2 generation, the effects of these genes were additive; Bmp7+/- was most strongly associated with the increase in tooth size using generalized linear models, and the total area of mandibular supernumerary incisors of Usag-1-/-Bmp7+/- mice was significantly larger than that of Usag-1-/-Bmp7 +/+ mice. At embryonic day 15 (E15), BrdU assays demonstrated that the labeling index of Bmp7+/- embryos was significantly higher than that of WT embryos in the cervical loop. Additionally, the labeling index of Usag-1-/- embryos was significantly the highest of all genotypes examined in dental papilla.

CONCLUSIONS

Bmp7 heterozygous mice exhibited significantly increased tooth sizes, suggesting that tooth size was controlled by specific gene expression. Our findings may be useful in applications of regenerative medicine and dentistry.

The prevalence and distribution of hypodontia in a sample of Qatari patients

OBJECTIVE

The aims of this study were to determine the prevalence of hypodontia in the permanent dentition in a sample of Qatari patients attending a dental center and to compare the results with the reported findings of other populations.

MATERIALS AND METHODS

Orthodontic files including orthopantomographs of 1000 patients (655 females and 345 males, 11-36-year-old) were examined and inspected for evidence of hypodontia.

RESULTS

The prevalence of hypodontia in the present Qatari sample was 7.8%; 6.9% was in males and 8.2% in females. Hypodontia was found more frequently in the maxilla than in the mandible. The distribution of missing teeth was noticed in the left side more than the right side. The most frequently missing teeth were the maxillary lateral incisors followed by the mandibular second premolars, maxillary second premolars, and mandibular left lateral incisor. The majority of patients with hypodontia had one or two teeth missing, but rarely more than four teeth were missing in the same patient. Bilateral missing teeth in the current study was commonly seen in the maxillary lateral incisor (14.1%) followed by mandibular second premolar (12.8%) and maxillary second premolar (6.4%).

CONCLUSIONS

The prevalence of hypodontia in a sample of Qatari individuals was within the range reported in the literature for other populations. The incidence of hypodontia in the anterior segment requires multidisciplinary team approach (orthodontic and prosthodontic) to restore the esthetic and function and improve patient self-esteem.

Prevalence of hypodontia and associated factors: a systematic review and meta-analysis

OBJECTIVES

To determine the prevalence and factors associated with hypotonia.

DESIGN

Systematic review and meta-analysis.

DATA SOURCE

A search strategy was developed along with inclusion criteria and run in MEDLINE and EMBASE (published from 2002 to August 2012) databases to reveal all studies on the prevalence of hypodontia or associated factors. A hand search of reference lists and a Google search aimed to improve the sensitivity of the literature search.

SELECTION CRITERIA

All studies on the prevalence of hypodontia or associated factors published from 2002 onwards were included. Abstracts of non-English papers were also analyzed.

DATA SELECTION AND EXTRACTION

All potential articles were checked against the inclusion criteria independently, and in duplicate by two investigators. A checklist was used to assess the quality of selected studies.

MAIN OUTCOME

Prevalence of hypodontia, excluding third molars.

RESULTS

The overall prevalence of hypodontia was found to be 6.4% (95% CI: 5.7, 7.2). There was a statistically significant difference in the prevalence of hypodontia by continent (Q = 34.18, P<0.001). Prevalence of hypodontia was the highest in Africa: 13.4% (95% CI: 9.7, 18.0), followed by Europe (7% CI: 6.0-8.0%), Asia (6.3% CI: 4.4, 9.1) and Australia (6.3% CI: 5.3, 7.4) with a lower prevalence in North America (5.0% CI: 4.1-5.9) and Latin America and Caribbean (4.4% CI: 3.2-6.1). Females were found to have a higher prevalence than males (combined OR 1.22; 95% CI: 1.14, 1.30). The most commonly affected teeth were mandibular second premolars followed by maxillary lateral incisors and maxillary second premolars. The prevalence of mild, moderate and severe hypodontia was found to be 81.6, 14.3 and 3.1% respectively.

CONCLUSIONS

There was a high variation in the prevalence of hypodontia between the studies. African populations were found to have a higher risk for tooth agenesis and there was an increased risk for females to have hypodontia than males.

Assessing the association of taurodontism with numeric dentition anomalies in an adult central Indian population

AIM

To study the association between taurodontism and numeric anomalies in adult population.

MATERIALS AND METHODS

Out of 1,012; 946 panoramic radiographs and dental records were retrospectively assessed to determine the presence of dental agenesis and supernumerary and taurodont teeth.

RESULTS

Taurodontism of one or more teeth was observed in 164 cases (97 females and 67 males). Hypodontia was observed in 148 patients (84 females and 64 males) with 62 patients having associated taurodontism (38 females, 24 males), oligodontia in 12 patients (five females and seven males) of whom nine patients also had taurodontism of one or more teeth (five females and four males). Forty-five patients (32 females and 13 males) presented with 57 supernumerary teeth (ST) with 12 patients having simultaneous presence of taurodontic tooth (seven females and five males).

CONCLUSION

Our study suggests a preferential association between tooth agenesis and taurodontism; however, such association was not observed in individuals with hyperdontia. Understanding the nature of this preferential association may be of importance in determining the etiology of both conditions. This association may also define a subphenotype for future genetic studies on dental development. Further molecular studies are necessary to verify the etiology and mechanism of taurodontism associated with tooth agenesis.

3D-Geomorphometrics tooth shape analysis in hypodontia

Assessment of tooth morphology is an important part of the diagnosis and management of hypodontia patients. Several techniques have been used to analyze tooth form in hypodontia patients and these have shown smaller tooth dimensions and anomalous tooth shapes in patients with hypodontia when compared with controls. However, previous studies have mainly used 2D images and provided limited information. In the present study, 3D surface-imaging and statistical shape analysis were used to evaluate tooth form differences between hypodontia and control patients. Eighteen anatomical landmarks were recorded on the clinical crown of the lower left first permanent molar of 3D scanned study models of hypodontia and control subjects. The study sample group comprised of 120 hypodontia patients (40 mild, 40 moderate, and 40 severe hypodontia patients) and 40 age- and sex-matched controls. Procrustes coordinates were utilized to scale and superimpose the landmark coordinate data and then were subjected to principal component analysis (PCA). Subsequently, differences in shape as well as size were tested statistically using allometric analysis and MANOVA. Significant interaction was found between the two factor variables “group” and “sex” (p < 0.002). Overall expected accuracies were 66 and 56% for females and males, respectively, in the cross-validated discriminant-analysis using the first 20 PCs. Hypodontia groups showed significant shape differences compared with the control subjects (p < 0.0001). Significant differences in tooth crown shape were also found between sexes (p < 0.0001) within groups. Furthermore, the degree of variation in tooth form was proportional to the degree of the severity of the hypodontia. Thus, quantitative measurement of tooth shape in hypodontia patients may enhance the multidisciplinary management of those patients.

Hypodontia prevalence over four decades in a Slovenian population

AIM

This study was performed to determine the prevalence of hypodontia of permanent teeth in the Slovenian population and whether such prevalence is associated with the year of birth.

MATERIAL AND METHODS

The prevalence of hypodontia in the Slovenian population, both male and female, and the association between tooth types, the upper or lower arch, the associated dental anomalies, and orthodontic treatment were studied using interviews and oral and panoramic radiographic examinations of 2,546 Slovenians born in years 1966, 1976, 1986, and 1996. The data were processed using Chi-square test.

RESULTS

Among the 2,546 subjects studied, 307 teeth were missing in 175 subjects. The overall prevalence of hypodontia, excluding the third molars, was 6.9%; and there was no statistically significant difference with the year of birth. The most commonly missing teeth were the mandibular second premolar (38.8%), followed by the maxillary lateral incisors (32.6%). The majority (86.9%) of patients with hypodontia were missing only one or two teeth. Subjects with hypodontia (54.9%) were more often involved in orthodontic treatment than subjects without hypodontia (20.5%).

CONCLUSIONS

The relatively high prevalence of hypodontia and its frequent association with other dental anomalies emphasizes the importance of dental examination in early childhood with radiographic screening for hypodontia as standard public oral health policy.

CLINICAL SIGNIFICANCE

The relatively high prevalence of hypodontia in Slovenians and its frequent association with other dental anomalies emphasizes the importance of dental examination with radiographic screening of hypodontia in childhood as part of public oral health policy.

Anomalous findings of number, morphology and size of permanent teeth in 7-10 years children living in the Czech Republic

6,043 children, who were ordinary patients and children of Caucasian population, were examined clinically and radiographically. 430 children were aged 7-10 years. Dental anomalies were diagnosed in 14.1% (61 children) of those observed between 7-10 years. We aimed at numerical anomalies (78.6% of children with anomalies), morphological anomalies (19.6% of children with anomalies), size anomalies (3.2% of children with anomalies) and combinations of diagnoses (1.4% reflects the combinations of teeth 2 times calculated in combinations of diagnoses). Congenital numerical variations, i.e. hypodontia and hyperodontia, are among the most common deviations of the permanent dentition. Both conditions can occur as isolated traits or in association with other syndromes. Many studies indicate that hereditary factors are involved in the aetiology of anomalies. Gen MSX1 involves a primary position in mediating interactions between epithelium and mesenchyme in the development of teeth. Occurrence of dental anomalies is not very frequent; problems can arise with diagnosis of those affected teeth. It can be done using Orthopantomogram or Computed Tomography and 3D reconstruction. Some of the children with anomalies may have difficulties in treatment of affected teeth but in most cases the prognosis is good.

Evaluation of tooth size in patients with congenitally-missing teeth

Background and aims

Hypodontia is a common developmental abnormality of dentition. This study aimed to determine tooth width in patients affected with mild hypodontia and compare the results with a control group without tooth agenesis.

Materials and methods

The orthodontic records of 25 patients with congenital missing of one or two teeth (hypodontia group), and 25 subjects with full dentition (control group) were selected. The greatest mesiodistal width of each tooth was measured on the study models by a digital caliper. Tooth width measurements were compared between the groups using a student t-test at p < 0.05 of significance.

Results

Patients with hypodontia showed narrower teeth than the control subjects. The differences in tooth size between the two groups were statistically significant for the first and second premolars and first molar in the maxillary right and for the second premolar in the maxillary left quadrants (p < 0.05). In the lower arch, the first and second premolars and also first molar in both sides of hypodontia patients demonstrated significant reduction in tooth size compared to the control group (p < 0.05).

Conclusion

These findings suggest that patients with mild hypodontia have narrower teeth than normal subjects especially in posterior segments, which may have clinical implications during the orthodontic treatment process.

Three-dimensional analysis of tooth dimensions in the MSX1-missense mutation

OBJECTIVES

A novel, 3D technique to measure the differences in tooth crown morphology between the MSX1 cases and non-affected controls was designed to get a better understanding of dental phenotype-genotype associations.

MATERIALS AND METHODS

Eight Dutch subjects from a single family with tooth agenesis, all with an established nonsense mutation c.332 C > A, p. Ser 111 Stop in exon 1 of MSX1, were compared with unaffected controls regarding several aspects of tooth crown morphology of incisor and molar teeth. A novel method of quantitative three-dimensional analysis was used to detect differences.

RESULTS

Statistically significant shape differences were observed for the maxillary incisor in the MSX1 family compared with the controls on the following parameters: surface area, buccolingual dimension, squareness, and crown volume (P ≤ 0.002). Molar crown shape was unaffected.

CONCLUSIONS

A better understanding of dental phenotype-genotype associations may contribute to earlier diagnosis of some multiple-anomaly congenital syndromes involving dental anomalies.

CLINICAL RELEVANCE

A "shape database" that includes associated gene mutations resulting from developmental syndromes may facilitate the genetic identification of hypodontia cases.

Case report: identical twins revealing discordant hypodontia. The rationale of dental arch differences in monozygotic twins

BACKGROUND

While it is generally accepted that monozygotic (MZ) twins are identical with respect to inherited traits, because they share 100% of their genetic material, clinical findings and scientific evidence does not support this belief. In addition to environmental factors and stochastic developmental events, a number of genetic mechanisms, detectable by new techniques in molecular genetics, explain the differences frequently observed in MZ twins.

CASE REPORT

Nine-year-old twin girls requested treatment for a dental malocclusion. Their facial and occlusal features were very similar. Panoramic radiographs revealed hypodontia of two permanent teeth in one twin (35 and 45) and of only one tooth in the other (45). An incorrect diagnosis of dizygosity (DZ) had been made at birth based on the presence of two amniotic sacs. Despite discordance in the dental complement of both girls their orthodontist suspected that the twins might be identical. A genetic study performed by quantitative fluorescence-polymerase chain reaction (QFPCR) analysis of chromosomes 13, 15, 16, 18, 21, 22, and X confirmed that the twins were MZ.

CONCLUSION

Discordances in dental complement between MZ twins are not uncommon and do not exclude monozygosity.

Multilevel complex interactions between genetic, epigenetic and environmental factors in the aetiology of anomalies of dental development

Dental anomalies are caused by complex interactions between genetic, epigenetic and environmental factors during the long process of dental development. This process is multifactorial, multilevel, multidimensional and progressive over time. In this paper the evidence from animal models and from human studies is integrated to outline the current position and to construct and evaluate models, as a basis for future work. Dental development is multilevel entailing molecular and cellular interactions which have macroscopic outcomes. It is multidimensional, requiring developments in the three spatial dimensions and the fourth dimension of time. It is progressive, occurring over a long period, yet with critical stages. The series of interactions involving multiple genetic signalling pathways are also influenced by extracellular factors. Interactions, gradients and spatial field effects of multiple genes, epigenetic and environmental factors all influence the development of individual teeth, groups of teeth and the dentition as a whole. The macroscopic, clinically visible result in humans is a complex unit of four different tooth types formed in morphogenetic fields, in which teeth within each field form directionally and erupt at different times, reflecting the spatio-temporal control of development. Even when a specific mutation of a single gene or one major environmental insult has been identified in a patient with a dental anomaly, detailed investigation of the phenotype often reveals variation between affected individuals in the same family, between dentitions in the same individual and even between different teeth in the same dentition. The same, or closely similar phenotypes, whether anomalies of tooth number or structure, may arise from different aetiologies: not only mutations in different genes but also environmental factors may result in similar phenotypes. Related to the action of a number of the developmental regulatory genes active in odontogenesis, in different tissues, mutations can result in syndromes of which dental anomalies are part. Disruption of the antagonistic balance between developmental regulatory genes, acting as activators or inhibitors can result in dental anomalies. There are critical stages in the development of the individual tooth germs and, if progression fails, the germ will not develop further or undergoes apoptosis. The reiterative signalling patterns over time during the sequential process of initiation and morphogenesis are reflected in the clinical association of anomalies of number, size and form and the proposed models. An initial step in future studies is to combine the genetic investigations with accurate recording and measurement of the phenotype. They also need to collate findings at each level and exploit the accurate definition of both human and murine phenotypes now possible.

A curriculum vitae of teeth: evolution, generation, regeneration

The ancestor of recent vertebrate teeth was a tooth-like structure on the outer body surface of jawless fishes. Over the course of 500,000,000 years of evolution, many of those structures migrated into the mouth cavity. In addition, the total number of teeth per dentition generally decreased and teeth morphological complexity increased. Teeth form mainly on the jaws within the mouth cavity through mutual, delicate interactions between dental epithelium and oral ectomesenchyme. These interactions involve spatially restricted expression of several, teeth-related genes and the secretion of various transcription and signaling factors. Congenital disturbances in tooth formation, acquired dental diseases and odontogenic tumors affect millions of people and rank human oral pathology as the second most frequent clinical problem. On the basis of substantial experimental evidence and advances in bioengineering, many scientists strongly believe that a deep knowledge of the evolutionary relationships and the cellular and molecular mechanisms regulating the morphogenesis of a given tooth in its natural position, in vivo, will be useful in the near future to prevent and treat teeth pathologies and malformations and for in vitro and in vivo teeth tissue regeneration.