Role of polymorphisms of MSX1 and PAX9 genes in palatal impaction of maxillary canines

Does Current Evidence Support the Discussion Around the Guidance Theory? A Systematic Review and Meta-Analysis on the Association Between Maxillary Lateral Incisor Agenesis and Displacement or Impaction of the Permanent Canine

Palatal impaction of the maxillary canine is commonly considered as a genetic condition, while the lateral incisor root has been suggested to guide maxillary permanent canine eruption. This review assessed whether agenesis of the maxillary lateral incisor is associated with eruption disturbances of the maxillary canine (displacement or impaction). Unrestricted searches in six databases for observational case-control human studies until May 2024 assessing eruption disturbances of the permanent maxillary canine in conjunction with permanent maxillary lateral incisor agenesis were performed. Study selection, data extraction and risk-of-bias assessment with the Joanna Briggs Institute's tool were performed in duplicate. Random-effects meta-analyses of odds ratios (ORs) with their 95% confidence intervals (CIs) were performed, followed by meta-regressions and sensitivity analyses. Seventeen reports pertaining to 17 case-control studies were included covering 10,155 patients (11.6 year-old/46% male on average). Maxillary lateral incisor agenesis was associated with eruption disturbance of the maxillary canine (17 studies; OR = 3.88; 95% CI = 2.05-7.34; p < 0.001; I 2 = 58). Lateral incisor agenesis was more associated with canine displacement (7 studies; OR = 7.56; 95% CI = 2.10-27.18; p = 0.008; I 2 = 57) and to a lesser degree with canine impaction (10 studies; OR = 2.39; 95% CI = 1.28-4.48; p = 0.01). No significant effects of patient age or sex were seen, and the results were robust to study design and precision. The quality of evidence was low due to the inclusion of observational case-control studies with methodological issues and residual confounding. Evidence indicates that permanent maxillary lateral incisor agenesis is associated with eruption disturbances of the permanent maxillary canine, including mainly displacement, but also impaction. Trial Registration: PROSPERO database number: CRD42024549898.

Palatal canine impaction is not associated with third molar agenesis

BACKGROUND/OBJECTIVES

Third molar agenesis and palatally impacted canines (PICs) are two independent dental phenotypes with different developmental backgrounds. Isolated reports indicate a common genetic origin for both, however, current data is inconsistent. The aim of this study was to investigate the presence of third molar agenesis in individuals with PICs, compared to individuals without PICs.

MATERIALS/METHODS

This retrospective case-control study comprised 310 individuals (188 females and 122 males), half of whom presented with unilateral or bilateral PICs. Individuals with other dental anomalies of known genetic origin were excluded. The association between PICs and third molar agenesis was assessed using four regression models, with PIC as the dependent variable and sex, age, and third molar agenesis as predictors. One model treated PIC as a nominal variable (pattern) and the other as ordinal (severity), and both were run testing either third molar agenesis severity or third molar agenesis patterns. All statistical tests were performed assuming a type-1 error of 5%.

RESULTS

There was no significant association between canine impaction and third molar agenesis in any of the four regression models. Neither the severity nor the patterns of palatally impacted canines were associated with either the severity or the patterns of third molar agenesis (P > .05).

LIMITATIONS

Due to the common racial background of all participants, the results of this investigation might not be generalizable to the general population.

CONCLUSIONS/IMPLICATIONS

Palatal canine impaction is not associated to third molar agenesis, after accounting for age, sex, and various patterns of PICs and third molar agenesis. These results indicate that these two dental phenotypes do not share a common biological mechanism for their occurrence.

Genetic association between Class II division 1 and division 2 malocclusions with PAX9 (rs8004560) gene polymorphism in a tertiary care hospital

OBJECTIVE

To assess whether there is any difference in the genetic association between Class II division 1 (div. 1) and division 2 (div. 2) malocclusions using PAX9 (rs8004560) gene single nucleotide polymorphism (SNP).

MATERIAL AND METHODS

Sixty patients from the Orthodontics department of Subharti Dental College and Hospital (Meerut, India) were divided into two groups: Group 1 (Class II div. 1 malocclusion) and Group 2 (Class II div. 2 malocclusion). Then, 3 mL of blood was collected from each participant. DNA extraction was done, and Sanger Sequencing was performed from extracted DNA samples.

RESULTS

A statistically significant difference was found in the distribution of alleles among Class II div. 1 and Class II div. 2 malocclusions. The homozygous GG allele was the most prevalent among Class II div. 1 patients (76.7%), while the heterozygous AG allele was the most prevalent among Class II div. 2 patients (53.5%). Since GG was the most prevalent allele, it was used as a reference, and AA/AG were compared with GG to confirm the association. The results showed that individuals with the AG genotype seemed to be more susceptible to the development of skeletal Class II div. 2 malocclusion.

CONCLUSION

The homozygous GG allele was the most prevalent among Class II div. 1 patients, while the heterozygous AG allele was the most prevalent among Class II div. 2 patients, suggesting that there could be a difference between the genetic association of both malocclusions.

Palatal canine impaction is associated with craniofacial shape in humans

BACKGROUND/OBJECTIVES

It is unclear whether palatal canine impaction is related to genetic or local/environmental factors. If a genetic origin is assumed, then it could be expected that palatal canine impaction is associated with overall craniofacial development. Within this context, the aim of this study was to evaluate the craniofacial morphology of individuals with palatal canine impaction and compare it to a matched group of normal controls.

MATERIALS/METHODS

The sample for this investigation comprised 404 individuals (232 females and 172 males). Half of these individuals presented with unilateral or bilateral palatal canine impaction confirmed clinically and radiographically. The other half were matched for sex and age with the first half and comprised individuals without tooth impaction, apart from third molars. The shape of the craniofacial structures was outlined on calibrated cephalometric images through 15 curves and 127 landmarks (11 fixed and 116 semi-landmarks). Shape configurations were superimposed using Procrustes Superimposition and the resulting shape coordinates were reduced into principal components for all subsequent analyses. The effect of palatal canine impaction on craniofacial shape was assessed with regression models, separately in females and males. All statistical tests were performed assuming a type-1 error of 5%.

RESULTS

Individuals with palatally impacted canines appear to have a less convex face, a more brachyfacial skeletal pattern, and a sagittally extended premaxilla. In females effect sizes ranged between η2 = 0.136-0.397 (P < 0.05) and in males between η2 = 0.125-0.396 (P < 0.05, apart from the entire craniofacial configuration: P = 0.259).

LIMITATIONS

Palatal canine impaction was not confirmed through cone beam computer tomography images in all patients, however, in those cases, the treatment history confirmed the diagnosis.

CONCLUSIONS/IMPLICATIONS

Palatal canine impaction is related to a distinct craniofacial shape in females and males. These findings allow for speculation that palatal canine impaction is affected by genetic pathways involved in overall craniofacial development.

"Examining the link between tooth agenesis and papillary thyroid cancer: is there a risk factor?" Observational study

BACKGROUND

Mutations in one or multiple genes can lead to hypodontia and its characteristic features. Numerous studies have shown a strong genetic influence on the occurrence of hypodontia, and identified several genes, including AXIN2, EDA, FGF3, FGFR2, FGFR10, WNT10A, MSX1, and PAX9, that are directly associated with dental agenesis and carcinogenesis. The objective of this study was to investigate the occurrence and pattern of tooth agenesis, microdontia, and palatally displaced canine (PDC) in women diagnosed with papillary thyroid cancer (PTC), compared to a control group of women without any malignancy or thyroid disease.

MATERIALS AND METHODS

This case-control study was carried at the Department of Orthodontics, School of Dental Medicine University of Zagreb, and Department of Oncology and Nuclear Medicine Sestre Milosrdnice University Hospital Centre. The study involved a clinical examination and evaluation of dental status, panoramic X-ray analysis, and assessment of medical and family history of 116 female patients aged 20-40 with PTC, as well as 424 females in the control group who were of similar age.

RESULTS

The prevalence of hypodontia, microdontia, and PDC was statistically higher in women with PTC than in the control group. The prevalence rate of hypodontia was 11.3% in the experimental group and 3.5% in the control group. The experimental group showed a higher occurrence of missing upper lateral incisors, lower left central incisors, and all the third molars (except the upper left) compared to the control group. Women with PTC showed the prevalence of PDC significantly higher than the control group (3.5%, 0.7%, p = 0.002). The probability of hypodontia as a clinical finding increases 2.6 times, and microdontia occurs 7.7 times more frequently in women with PTC.

CONCLUSION

Our study suggests a possible link between odontogenesis and PTC. The absence of permanent teeth may increase the likelihood of PTC in women. Leveraging the age-7 orthopantomogram to identify women at high risk for PTC within a critical early detection window could significantly improve oral health outcomes and PTC prognosis through proactive interventions.

Prevalence, etiology, clinical features and management associated with impacted and transmigrated mandibular canines: a systematic review

BACKGROUND

The occurrence of mandibular canine impaction and/ or transmigration is a rare clinical entity but diagnosis and treatment planning is of clinical significance. The associated etiological factors and the clinical guidelines for the management are still not clear. The aim of this systematic review was to summarize the available data to report the prevalence and identify the etiological factors, clinical features, and various treatment outcomes in patients with mandibular canine impaction and/or transmigration.

METHODS

The review protocol was registered in PROSPERO (CRD42021222566) and was conducted and reported according to the PRISMA and Cochrane Handbook / Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. A computerized search of studies published up to April 30, 2023, was conducted using the following databases: Medline, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Scopus, Web of Science, and Latin American and Caribbean Health Sciences Literature. A manual search of the reference and citation lists of eligible articles and existing systematic reviews for any additions were also conducted. The Newcastle-Ottawa Scale quality assessment tool was used to assess the studies' quality.

RESULTS

After removing 6 duplicates, 3700 articles were identified. For the final analysis, 19 studies published between 1985 and 2023 met all the eligibility criteria and were included. A total of 7 studies presented as good and 12 studies presented as satisfactory. Patients were screened in ten studies and diagnostic records from archives were retrieved in nine studies. The total number of diagnostic records screened was 138.394, and the total number of patients from the included studies was 43.127.

CONCLUSIONS

Based on the findings from this systematic review, the prevalence of mandibular canine impaction ranged from 0.008% to 1.29% while canine transmigration from 0.12% to 0.98%. Crowding of the mandibular arch, the presence of a retained deciduous canine, and odontoma or cyst are the etiological factors more commonly associated with mandibular canine impaction and or transmigration. Surgical extraction and surgical exposure followed by orthodontic traction are the two most frequently carried out treatment modalities in the management of mandibular canine impaction and or transmigration.

Association between maxillary canine impaction and other dental anomalies: radiological study of a mixed dentition children's cohort from an orthodontic clinic

PURPOSE

To investigate the significance of association between maxillary impacted canines and various dental anomalies.

METHODS

Files of 874 orthodontic patients were evaluated for the presence of maxillary impacted canines. From this sample, a group of 97 patients (39 males and 58 females) with at least 1 impacted maxillary canine consisted the study group. This group was compared to a control group of 97 patients (42 males and 55 females) that was created by random selection from the initial sample without maxillary canine impaction. The impaction diagnosis was made from the panoramic radiographs. Chi-square test was used to perform the analysis for significant associations. Stepwise discriminant analysis, binary logistic regression and classification tree were used to identify best combinations.

RESULTS

Statistically significant difference was found for peg-shaped maxillary lateral incisors and infraoccluded deciduous molars. The presence of peg-shaped upper lateral incisors arises the probability of impacted canine to 83.3%, a distal displaced unerupted second premolar to 63.16% and the impaction of any other teeth to 80% as showed by the classification tree.

CONCLUSIONS

The presence of peg-shaped maxillary lateral incisors and infraocclusion of deciduous molars can be considered major valuable early risk indicators for maxillary canine impaction, because they manifest before the maxillary canine eruption. Special consideration should be given on distal displaced unerupted second premolar and the impaction of any other teeth. Patients with these dental anomalies are candidates for future interceptive treatment for canine eruption.

Mutation Detection and Functional Analysis of MSX1, PAX9, AXIN2, and BMP in Nonsyndromic Congenital Missing Teeth Based on Intelligent Image Detection

Due to the complexity of clinical manifestations and the lack of standardized diagnostic criteria, it is still difficult to distinguish the etiological types of congenital edentulousness corresponding to genetic defects. This paper studies the application of deep learning image processing and digital image processing in medical images in detail and analyzes the functions of congenital edentulous hotspot genes. The cases in the control group and the study group were collected, and the gene mutations of direct sequence MSX1, PAX9, AXIN2, and BMP were analyzed, and new pathogens were found. The experimental results suggest that PAX9 and MSX1 genes may have a synergistic effect in nonsyndromic congenital edentulous patients. In severely missing teeth, the role of PAX9 may be greater than that of MSX1. The experimental results will help us lay the foundation for further understanding of the disease in the future.

Association of Polymorphic and Haplotype Variants of the MSX1 Gene and the Impacted Teeth Phenomenon

It is known that genetic factors determine odontogenesis; furthermore, studies have revealed that various genes in humans can regulate the development of different types and generations of teeth. In this study it has been assumed that tooth impaction—at least to some extent—also depends on the presence of specific genetic markers, especially allelic variants of the MSX1 gene. The primary objective of the study was to evaluate the suitability of selected molecular markers located within the MSX1 gene for the determination of the risk of tooth impaction in particular patients. The study participants were divided into two groups: (1) the study group—at least one secondary tooth was impacted in the jaws; (2) the control group—no impacted tooth in the jaws. Real-Time PCR and TaqMan probes were used to detect selected polymorphisms in the analyzed genes. Two single nucleotide polymorphisms of MSX1 were analyzed. After the two subgroups of patients were distinguished in the study group based on the number of impacted teeth, statistically significant differences in the frequency of genotypes described for rs12532 in the MSX1 gene were found.

MSX1 is differentially expressed in the deepest impacted maxillary third molars

An impacted third molar is one of the most common dental abnormalities. Among the reasons for impaction the most common are: insufficient space, time of eruption, improper position of the tooth bud, and genetic disruptions. To investigate if runt-related transcription factor 2 (RUNX2), bone morphogenetic protein 2 (BMP2), and msh homeobox 1 (MSX1) are differently expressed depending on the position of the molar, we studied 32 patients who had been referred for surgical removal. An orthopantomogram was used to separate them according to Winter's, and Pell & Gregory's, classifications. Bone samples were harvested during the operation for gene expression assay. The Kruskal-Wallis, Dunn's post hoc, and Spearman's correlation, tests were used to assess the significance of differences. No correlations were found in expression of the genes, and no differences between expression in maxillary and mandibular third molars, nor were they expressed differently according to Winter's or Pell and Gregory's classifications or in relation to impaction of the mandibular ramus. However, MSX1 was expressed differently when account was taken of the depth of impaction in maxillary third molars (p = 0.029), but there was no difference in expression of RUNX2, BMP2, and MSX1 for the Pell and Gregory classification of depth of impaction (p > 0.05). We conclude that MSX1 is expressed differently depending on the depth of maxillary impaction phenotypes.