Odontogenesis-related candidate genes involved in variations of permanent teeth size

Advance in candidate genes in mandibular retrognathism: A systematic review

OBJECTIVE

This research aims to dissect the polygenic nature of non-syndromic mandibular retrognathism (MR) and to better understand the genetic underpinnings of MR, with a particular focus on the role of ethnic diversity in influencing genetic predispositions.

METHODS

A comprehensive systematic review was conducted on MR. Electronic databases such as PubMed and Google Scholar were employed, utilizing terms like 'mandibular', 'retrognathism', 'gene', and 'genetic'. This study strictly adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework.

RESULTS

Ten genetic studies were identified that satisfied the eligibility criteria, involving 1010 participants. Variations in candidate genes were reported across different populations, including myosin 1 H (MYO1H), matrilin 1 (MATN1), a disintegrin and metalloproteinase with thrombospondin motifs 9 (ADAMTS9), bone morphogenetic protein 2 (BMP2), parathyroid hormone (PTH), the vitamin-D related genes: vitamin D receptor (VDR), cytochrome P450 family 24 subfamily A member 1 (CYP24A1), and cytochrome P450 family 27 subfamily B member 1 (CYP27B1), collagen type II alpha 1 chain (COL2A1), transforming growth factor-β (TGF-β), TGF-β receptor 2 (TGFBR2), epidermal growth factor (EGF), and EGF receptor gene (EGFR).

CONCLUSION

These findings shed light on the role of genetic factors in MR. Future studies should adopt a multicentric approach to expand sample sizes and enhance the analysis of genetic variants associated with MR.

Exploring polymorphisms in genes encoding growth factors associated with non-syndromic cleft lip with or without cleft palate and tooth agenesis

OBJECTIVE

To evaluate the association between non-syndromic cleft lip with or without cleft palate (NSCL±P) and tooth agenesis (TA), as well as the association of both conditions with polymorphisms in genes encoding growth factors.

METHODOLOGY

This cross-sectional study included children with NSCL±P and a control group of children without NSCL±P. Permanent teeth TA (excluding third molars) was evaluated using panoramic radiographs by a trained examiner. Only TA located outside the cleft was considered in the NSCL±P group. Genetic polymorphisms in Transforming Growth Factor Beta 1 (TGFB1)-rs1800470 and rs4803455-Transforming Growth Factor Beta Receptor 2 (TGFBR2)-rs3087465 and rs764522-Epidermal Growth Factor (EGF)-rs4444903 and rs2237051-and Epidermal Growth Factor Receptor (EGFR)-rs2227983- were genotyped by real-time PCR allele discrimination from buccal cell samples. Associations were tested by uni and multivariable Poisson regression models (5% significance level).

RESULTS

A total of 243 children-127 with NSCL±P (mean age = 8.80±2.14 years) and 116 without NSCL±P (mean age = 8.58±2.03 years) were included. TA was more frequent in the NSCL±P group (23.8%) than in the control group (6.2%) (p<0.01). The EGF rs2237051 was significantly associated with NSCL±P, independently of the other variables (PRa=1.41; p=0.042). Regarding TA, only the cleft presence was associated with a higher prevalence of TA regardless of different variables (PRa=3.70; p=0.001). There was no association between TA and the investigated genetic polymorphisms. When TA and NSCL±P were considered together, a borderline association was observed with rs1800470 in TGFB1 (p=0.06).

CONCLUSION

NSCL±P is associated with TA outside the cleft area. The EGF rs2237051 was associated with NSCL±P. Polymorphisms in genes encoding growth factors are not associated with TA.

Polymorphisms and dental age in non-syndromic cleft lip and palate: a cross-sectional study

BACKGROUND

Children with non-syndromic cleft lip with or without palate (CL ± P) may present alterations in dental development. The purpose of this cross-sectional study was to compare the dental age (DA) between children with and without CL ± P, and whether single nucleotide polymorphisms (SNPs) in genes encoding growth factors are associated with DA variations.

METHODS

Children aged between 5 and 14 years with and without CL ± P were recruited to participate in this study. DA was evaluated by calibrated examiners (kappa > 0.80) using the method proposed by Demirjian et al. (1973). Genomic DNA was extracted from buccal cells, and SNPs in Epidermal Growth Factor (EGF) - rs4444903 and rs2237051, Epidermal Growth Factor Receptor (EGFR) - rs2227983 -, Transforming Growth Factor Beta 1 (TGFB1) - rs1800470 and rs4803455 -, and Transforming Growth Factor Beta Receptor 2 (TGFBR2) - rs3087465 - were genotyped by real-time polymerase chain reactions using the TaqMan assay. The Student T-test was used to compare the variations in DA between the phenotypes "with CL ± P" and "without CL ± P", and the ANOVA two-way test was performed to compare the variations in DA among the genotypes (α = 0.05). A post-hoc analysis was performed using Bonferroni correction.

RESULTS

Two hundred and nine (n = 209) children (100 with CL ± P and 109 without CL ± P) with a mean chronological age of 8.66 years - standard deviation (SD) = 1.92 - were included. The group with CL ± P demonstrated a significantly delayed DA (mean=-0.23; SD = 0.71) compared to the group without CL ± P (mean=-0.01; SD = 0.88) (p = 0.049). Genotype distributions were in Hardy-Weinberg equilibrium. The SNP rs4803455 in TGFB1 was significantly associated with DA variations in children without CL ± P (p < 0.01). In the group with CL ± P, no significant differences in DA were observed among the genotypes.

CONCLUSION

Children with CL ± P presented delayed DA compared with children without CL ± P. The SNP rs4803455 in TGFB1 is associated with variations in DA in children without CL ± P.

Impact of FokI (rs2228570) and BglI (rs739837) polymorphisms in VDR gene on permanent tooth eruption: A cross-sectional study

Introduction

Genetic polymorphisms who disturb the mineral homeostasis during tooth development and eruption are candidate to clarify the molecular mechanisms involved in changes in the tooth eruption chronology. In this study, we evaluate whether the FokI (rs2228570) and BglI (rs739837) polymorphisms in the Vitamin D receptor (VDR) gene are associated with changes in the chronology of eruption of permanent teeth.

Material & method

This cross-sectional study randomly included 353 biologically unrelated children, both sexes, without systemic impairment or syndromes and history of trauma during the primary dentition. One operator perform the oral clinical examination. The tooth was considered erupted if there was a visible minimum of any tooth surface emerging from the mucosa. Genomic DNA was extracted from buccal epithelial cells from saliva samples. Genotyping was performed by Real-Time Polymerase Chain Reactions using TaqMan® technology. The average of the total number of erupted permanent teeth between the genotypes was compared by the Mann-Whitney test and multivariate Generalized Linear Models (GLM) (α = 5 %). β values with Confidence Interval (CI) 95 % were calculated.

Results

The heterozygous adenine-guanine genotype of the FokI significantly decreases the number of erupted permanent teeth (β = -1.15; CI 95 % = -2.22 to -0.07; p = 0.036). In the stratified analysis for maxillary and mandibular teeth, this genotype was associated with a decrease in the number of erupted maxillary permanent teeth (β = -0.65; CI 95 % = -1.22 to -0.09; p = 0.023). BglI was not associated with permanent teeth eruption.

Conclusion

The FokI, but not BglI, in the VDR may delay the eruption of permanent teeth.

Single Nucleotide Polymorphisms in RUNX2 and BMP2 contributes to different vertical facial profile

The vertical facial profile is a crucial factor for facial harmony with significant implications for both aesthetic satisfaction and orthodontic treatment planning. However, the role of single nucleotide polymorphisms (SNPs) in the development of vertical facial proportions is still poorly understood. This study aimed to investigate the potential impact of some SNPs in genes associated with craniofacial bone development on the establishment of different vertical facial profiles. Vertical facial profiles were assessed by two senior orthodontists through pre-treatment digital lateral cephalograms. The vertical facial profile type was determined by recommended measurement according to the American Board of Orthodontics. Healthy orthodontic patients were divided into the following groups: "Normodivergent" (control group), "Hyperdivergent" and "Hypodivergent". Patients with a history of orthodontic or facial surgical intervention were excluded. Genomic DNA extracted from saliva samples was used for the genotyping of 7 SNPs in RUNX2, BMP2, BMP4 and SMAD6 genes using real-time polymerase chain reactions (PCR). The genotype distribution between groups was evaluated by uni- and multivariate analysis adjusted by age (alpha = 5%). A total of 272 patients were included, 158 (58.1%) were "Normodivergent", 68 (25.0%) were "Hyperdivergent", and 46 (16.9%) were "Hypodivergent". The SNPs rs1200425 (RUNX2) and rs1005464 (BMP2) were associated with a hyperdivergent vertical profile in uni- and multivariate analysis (p-value < 0.05). Synergistic effect was observed when evaluating both SNPs rs1200425- rs1005464 simultaneously (Prevalence Ratio = 4.0; 95% Confidence Interval = 1.2-13.4; p-value = 0.022). In conclusion, this study supports a link between genetic factors and the establishment of vertical facial profiles. SNPs in RUNX2 and BMP2 genes were identified as potential contributors to hyperdivergent facial profiles.

Mandibular and dental measurements for sex determination using machine learning

The present study tested the combination of mandibular and dental dimensions for sex determination using machine learning. Lateral cephalograms and dental casts were used to obtain mandibular and mesio-distal permanent teeth dimensions, respectively. Univariate statistics was used for variables selection for the supervised machine learning model (alpha = 0.05). The following algorithms were trained: logistic regression, gradient boosting classifier, k-nearest neighbors, support vector machine, multilayer perceptron classifier, decision tree, and random forest classifier. A threefold cross-validation approach was adopted to validate each model. The areas under the curve (AUC) were computed, and ROC curves were constructed. Three mandibular-related measurements and eight dental size-related dimensions were used to train the machine learning models using data from 108 individuals. The mandibular ramus height and the lower first molar mesio-distal size exhibited the greatest predictive capability in most of the evaluated models. The accuracy of the models varied from 0.64 to 0.74 in the cross-validation stage, and from 0.58 to 0.79 when testing the data. The logistic regression model exhibited the highest performance (AUC = 0.84). Despite the limitations of this study, the results seem to show that the integration of mandibular and dental dimensions for sex prediction would be a promising approach, emphasizing the potential of machine learning techniques as valuable tools for this purpose.

BMP2 rs1005464 is associated with mandibular condyle size variation

This study aimed to evaluate the association between single nucleotide polymorphisms (SNPs) in endochondral development-related genes and mandibular condyle shape, size, volume, and symmetry traits. Cone-beam Computed Tomographies and genomic DNA from 118 individuals were evaluated (age range: 15-66 years). Data from twelve 3D landmarks on mandibular condyles were submitted to morphometric analyses including Procrustes fit, principal component analysis, and estimation of centroid sizes and fluctuating asymmetry scores. Condylar volumes were additionally measured. Seven SNPs across BMP2, BMP4, RUNX2 and SMAD6 were genotyped. Linear models were fit to evaluate the effect of the SNPs on the mandibular condyles' quantitative traits. Only the association between BMP2 rs1005464 and centroid size remained significant after adjusting to account for the false discovery rate due to multiple testing. Individuals carrying at least one A allele for this SNP showed larger condylar size than common homozygotes GG (β = 0.043; 95% CI: 0.014-0.071; P value = 0.028). The model including BMP2 rs1005464, age and sex of the participants explained 17% of the variation in condylar size. Shape, volume, and symmetry were not associated with the evaluated SNPs. These results suggest that BMP2 rs1005464 might be associated with variation in the mandibular condyles size.

Polymorphisms in hormonal-related genes might be associated with variations in permanent tooth crown size

BACKGROUND

The variability in tooth crown size (TCS) is influenced by genetic factors and might be regulated by the difference in hormonal response.

MATERIALS AND METHODS

This study aimed to evaluate the association between variations in TCS of permanent teeth with associated factors and genetic polymorphisms in hormonal-related genes (ESR1, ESR2 and PTH). This cross-sectional study involved dental casts from 86 individuals of both sexes. Dental casts were used to determine the maximum TCS of all fully erupted permanent teeth (except third molars) in the mesiodistal (MD) and buccolingual (BL) dimensions. Data such as sex, ethnicity, dental group (incisor, canine, premolar and molar), dental arch (upper and lower) and genetic polymorphisms of hormonal-related genes were used. The DNA from each patient was collected to evaluate the genetic polymorphisms in ESR1 (rs2234693 and rs9340799), ESR2 (rs1256049 and rs4986938) and PTH (rs694, rs6256 and rs307247) through real-time PCR. The data were submitted to statistical analysis with a significance level of 0.05.

RESULTS

In the MD dimension, the sex, dental group and dental arch were associated with variation in TCS (P < .05). In the BL dimension, the sex, dental group, dental arch and polymorphism in rs694 and rs307247 were associated with variation in TCS.

CONCLUSIONS

In short, this study suggests that genetic polymorphisms of PTH are associated with variations in the BL TCS of permanent human teeth.

Developmental enamel defects and dental anomalies of number and size in children with growth hormone deficiency

Growth hormone is meaningfully involved in the processes of tooth cells differentiation and tissue formation. The aim of the study was to evaluate the occurrence of dental anomalies: microdontia, macrodontia, hypodontia and developmental defects of enamel (DDE) amongst a group of isolated growth hormone deficient (GHD) patients and healthy children. This cross-sectional study was based on a group of 101 Caucasian children: 33 with GHD (mean age 10.94, SD 2.51) and 68 being healthy, normal height subjects (mean age 10.4, SD 2.38). The dental examination in primary and permanent teeth was carried out by one trained and calibrated dentist, in accordance with the WHO guidelines. It was observed that 33% of GHD patients suffer from dental anomalies (hypodontia, microdontia or macrodontia), the difference between the study group and the control group was statistically significant (33% vs 4%, p < 0.001). Hypodontia and microdontia/macrodontia were the most common problems affecting 18% and 21% of the GHD individuals, respectively. The prevalence of DDE did not differ significantly between GHD group and the control group (58% vs 48%, p > 0.05). As children with GHD present more dental anomalies than their healthy coevals, clinicians should be aware of the possible oral health problems associated with GHD and consider dental screening and management as part of the patient's overall health care plan.

Single nucleotide polymorphisms in odontogenesis-related genes associated with tooth-size discrepancy

Introduction: The present study aimed to determine the association between single nucleotide polymorphisms (SNPs) in RUNX2, SMAD6, BMP2, and BMP4 genes in relation to tooth-size discrepancy (TSD).

Methods: A cross-sectional study of patients undergoing orthodontic treatment measured the mesiodistal width of permanent teeth from pretreatment dental casts. Sixty-two patients were included in the study and TSD was assessed according to the Bolton analysis. The patients were allocated into a control group (without a TSD), an anterior excess group and an overall excess group. Genomic DNA was extracted from saliva samples, and SNPs previously associated with tooth size were evaluated using a real-time polymerase chain reaction (PCR) system. The Fisher exact test was performed to compare genotype and allele frequencies at an α = 0.05. An Odds Ratio (OR) and 95% Confidence Interval (95% CI) were calculated.

Results: The rs59983488 SNP in the RUNX2 gene was significantly related to the presence of anterior mandibular tooth-size excess in allele (T allele: p<0.001; OR = 11.74; 95% CI =2.61–55.80), and genotype models (GT genotype: p = 0.002; OR = 12.69; 95% CI = 2.47–64.83). The rs3934908 SNP in the SMAD6 gene was significantly associated with the presence of an overall maxillary tooth-size excess in allele (T allele: p < 0.001) and genotype models (TT genotype: p = 0.010).

Conclusion: The present results suggest that SNPs in RUNX2 (rs59983488) and SMAD6 (rs3934908) genes may be associated with the presence of tooth-size excess.

Assessing the prevalence of S-shaped root canal and associated genes in humans

BACKGROUND

Multiple signaling molecules have been shown to play crucial roles in dental root development. Therefore, we aimed to investigate the prevalence of S-shaped roots and also to investigate, if single nucleotide polymorphisms (SNPs) in BMP2, BMP4 and SMAD6 are associated with this phenotype in humans.

METHODS

This is a cross-sectional phenotype-genotype association study that used radiographs to determine the phenotypes and DNA to investigate SNPs in candidate genes. During the radiographic exam, teeth presenting root canal(s) doubly curved were considered S-shaped roots. SNPs in BMP2 (rs1005464 and rs235768), BMP4 (rs17563) and SMAD6 (rs2119261 and rs3934908) were blindly genotyped by real-time PCR using TaqMan assay. The relative and absolute frequency of S-shaped roots were calculated. Chi-square test was used to compare the genotype distributions between control and S-shaped groups.

RESULTS

Among the 578 subjects, 61 (10.6%) presented at least one tooth with an S-shaped root. The most commonly affected type of tooth was the premolar. rs1005464 in BMP2 was statistically associated with an S-shaped root (p=0.036). rs235768 in BMP2 was associated with an S-shaped root also in mandibular teeth (p=0.017). A statistical significance was observed for the rs3934908 in SMAD6 (p=0.049) for S-shaped root in the mandible. In the analysis stratified according to the type of tooth, rs235768 in BMP2 was associated with S-shaped roots in premolars (p=0.029).

CONCLUSION

The prevalence of S-shaped roots is 10.6% in permanent teeth. SNPs in BMP2 and SMAD6 could be involved in a higher chance to present S-shaped roots.