Putatively, tooth agenesis was attributed to the initiation failure of tooth germs, though little is known about the histological and molecular alterations. To address if constitutively active FGF signaling is associated with tooth agenesis, we activated Fgf8 in dental mesenchyme with Osr-cre knock-in allele in mice (Osr2-creKI; Rosa26R-Fgf8) and found incisor agenesis and molar microdontia. The cell survival assay showed tremendous apoptosis in both the Osr2-creKI; Rosa26R-Fgf8 incisor epithelium and mesenchyme, which initiated incisor regression from cap stage. In situ hybridization displayed vanished Shh transcription, and immunostaining exhibited reduced Runx2 expression and enlarged mesenchymal Lef1 domain in Osr2-creKI; Rosa26R-Fgf8 incisors, both of which were suggested to enhance apoptosis. In contrast, Osr2-creKI; Rosa26R-Fgf8 molar germs displayed mildly suppressed Shh transcription, and the increased expression of Ectodin, Runx2 and Lef1. Although mildly smaller than WT controls prenatally, the Osr2-creKI; Rosa26R-Fgf8 molar germs produced a miniature tooth with impaired mineralization after a 6-week sub-renal culture. Intriguingly, the implanted Osr2-creKI; Rosa26R-Fgf8 molar germs exhibited delayed odontoblast differentiation and accelerated ameloblast maturation. Collectively, the ectopically activated Fgf8 in dental mesenchyme caused incisor agenesis by triggering incisor regression and postnatal molar microdontia. Our findings reported tooth agenesis resulting from the regression from the early bell stage and implicated a correlation between tooth agenesis and microdontia.

Focal microdontia is a dental anomaly characterized by the presence of a single abnormally small anterior or posterior tooth. The objective of this article is to provide an updated review of the literature on the advanced restorative management of focal microdontia, and to document a clinical case where the reviewed advanced restorative approaches were applied to treat a young adult presenting with a non-syndromic asymmetrical focal microdontia.We conducted a preliminary examination of the existing literature on the advanced restorative management of focal microdontia. Additionally, we presented a minimally invasive approach to the treatment of an 18-year-old female patient with non-syndromic asymmetrical focal microdontia. The primary advantage of adhesive dentistry is that it can better preserve the structure of smaller teeth. A review of literature reveals a paucity of reports on localized microdontia in the maxillary anterior region of the mouth. However, novel minimally invasive restorative procedures satisfy patients\' aesthetic and functional preferences. Well-executed additive diagnostic wax-ups and intraoral mock-ups can serve as a permanent restoration blueprint, providing predictable results for focal dental anomalies in the aesthetic zone. In conclusion, the use of minimally invasive dental approaches in young patients with focal microdontia can result in long-term satisfactory aesthetic outcomes.

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.
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.
CONCLUSIONS: 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.

Sex dimorphism has been implicated in oral health differences and the pathogenesis of oral diseases, such as tooth agenesis, periodontal disease, dental caries, and tooth loss. Tooth agenesis (TA) is one of the most common developmental anomalies in humans, and its prevalence and patterns are different across ethnic groups. The aim of this study was to investigate the phenotypes and sex-associated patterns of nonsyndromic tooth agenesis (TA) in Thai dental patients.
One thousand ninety panoramic radiographs were examined. One hundred and one subjects (37 males, 64 females, 15-20 years-old) with nonsyndromic TA were evaluated. Differences in TA prevalence between groups were analyzed using the chi-square or Fisher exact test.
The TA prevalence, excluding third molars, was 9.3% and more frequently found in the mandible compared with the maxilla. The maxilla demonstrated a higher prevalence of first premolar agenesis than the mandible (P = 0.012), while the mandible had a higher prevalence of second premolar agenesis than the maxilla (P = 0.031). There were significantly more males missing one tooth than females, however, there were more females missing two or more teeth than males (P = 0.042). A missing maxillary left lateral incisor was significantly more frequent in males (P = 0.019), while a missing mandibular right lateral incisor was more frequent in females (P = 0.025). In females, the pattern of two mandibular lateral incisors agenesis was the most common and significantly present in females more than males (P = 0.015). In contrast, the pattern of one mandibular left lateral incisor agenesis was only observed in males and significantly found in males more than females (P = 0.047).
We demonstrate sex-associated differences in nonsyndromic tooth agenesis. The prevalence of single tooth agenesis was higher in males, while that of two or more teeth agenesis was higher in females. We found different patterns of lateral incisor agenesis between males and females.

BACKGROUND:  Disturbances seen during tooth formation result in developmental dental anomalies presenting in the oral cavity. These anomalies manifest as discrepancies in the number, color, size, and shape of the teeth. These dental anomalies can either be acquired, congenital, or developmental. Their early detection and management are necessary as they affect aesthetics and occlusion. The study had the aim of gauging the prevalence of developmental anomalies in the permanent dentition of Indian subjects.
METHODS: A total of 1192 participants recruited from the institute for study purposes, comprising males and females, were examined clinically and radiographically, and their dental casts were also evaluated. These subjects were assessed for anomalies in position, structure, number, and/or shape. Anomalies in the position include transmigration, transportation, and/or ectopic position; anomalies in the structure, including dentinogenesis imperfecta or amelogenesis imperfecta; anomalies in number, including hyperdontia or hypodontia; and anomalies in shape, including peg laterals, taurodontism, fusion, dens evaginatus, talon cusp, and/or microdontia.
RESULTS: A statistically significant difference was seen in unilateral microdontia and dentinogenesis imperfecta between males and females, with attained p-values of 0.003 and 0.06, respectively. The results of the present study showed that 9.89% (n = 118) study subjects, whereas 1% (n = 12) study subjects had two dental anomalies in their permanent dentitions, with no subject presenting more than two dental anomalies, showing that various dental anomalies have a low prevalence in the Indian population.
CONCLUSIONS: The present study has led to the conclusion that the prevalence of dental anomalies is low in Indian subjects. However, these anomalies should be detected and treated early to prevent them from causing further complications.

To investigate the distribution of dental anomalies between non-syndromic orofacial cleft patients and their association with the cleft type and gender.
Retrospective cross-sectional study involving examination of intraoral dental records and radiographs.
300 non-syndromic orofacial cleft patients included (161 males and 139 females, mean age: 10.23 ± 2.3 years).
Variables analyzed: tooth agenesis, microdontia, and supernumerary teeth. Data analysis: Chi-square and Fisher\'s exact tests to investigate the correlation between dental anomalies, cleft type, and gender.
Agenesis occurred in 66% of the subjects, supernumerary teeth in 19.6%, and microdontia in 18.3%. In females with unilateral left cleft lip and palate (CLP), agenesis was significantly higher compared to males. Both genders presented significant agenesis of maxillary lateral incisors and right central incisor. Significant agenesis of central incisor, canine and second premolar on the upper left side and lower second premolars were observed only in males, with significant microdontia for maxillary lateral incisors and left central incisor. Significant agenesis of maxillary first premolars was seen only in females. Agenesis in maxillary quadrants was significant for patients with unilateral right and left CLP, and bilateral CLP. In mandibular quadrants, agenesis was substantially higher for patients with isolated CP.
Results suggest that tooth agenesis and microdontia might not be directly associated with the cleft area\'s anatomical irregularity but are affected by gender and other genetic factors that regulate the development of the anomaly and the orofacial clefting mutually.

暂无摘要。

The present study aimed to evaluate if functional genetic polymorphisms in vitamin-D-related genes are associated with third molar agenesis and third molar microdontia in German orthodontic patients. Pre-orthodontic and follow-up treatment records were evaluated for phenotype definition. Saliva samples were collected for DNA extraction. Eight potential functional genetic polymorphisms in VDR [rs731236 (TaqI), rs7975232 (ApaI), rs2228570 (FokI), and rs1544410 (BsmI)], CYP27B1 (rs4646536), CYP24A1 (rs927650), GC (rs4588), and SEC23A (rs8018720) were evaluated using real-time PCR. Comparison among the groups were performed (third molar anomaly vs. control; third molar agenesis vs. control; and third molar microdontia vs. control) with an alpha of 5%. A total of 164 patients were analyzed. Forty-nine (29.9%) patients had at least one third molar anomaly. In the haplotype analysis, genetic polymorphisms in VDR and CYP27B1 were associated with third molar anomalies (p < 0.05). The G allele in rs8018720 (SEC23A) was more frequent in microdontia cases. In the genotype distribution analysis, rs8018720 in SEC23A was associated with third molar microdontia in the co-dominant (p = 0.034; Prevalence Ratio [PR]=5.91, 95% Confidence Interval [CI]= 1.14-30.66) and in the recessive (p = 0.038; PR=5.29; 95% CI= 1.09-25.65) models. In conclusion, vitamin D-related genes could be involved in third molar anomalies.

Nonsyndromic tooth agenesis is associated with variants in several genes. There are numerous genotype-phenotype publications involving many patients and kindreds. Here, we identified six Thai individuals in two families with nonsyndromic tooth agenesis, performed exome sequencing, and conducted functional experiments. Family 1 had four affected members carrying the heterozygous PAX9 variant, c.59C>T (p.Pro20Leu). The p.Pro20Leu was previously reported in two families having four and three affected members. These seven cases and Proband-1 had agenesis of at least three third molars. Family 2 comprised two affected members with agenesis of all 12 molars. Both individuals were heterozygous for c.230G>A (p.Arg77Gln) in PAX9, which has not been reported previously. This variant is predicted to be damaging, evolutionarily conserved, and resides in the PAX9 linking peptide. The BMP4 RNA levels in Proband-1\'s leukocytes were not significantly different from those in the controls, whereas BMP4 levels observed in Proband-2 were significantly increased. Moreover, the p.Arg77Gln variant demonstrated nuclear localization similar to the wild-type but resulted in significantly impaired transactivation of BMP4, a PAX9 downstream gene. In conclusion, we demonstrate that the PAX9 p.Pro20Leu is highly associated with absent third molars, while the novel PAX9 p.Arg77Gln impairs BMP4 transactivation and is associated with total molar agenesis.

OBJECTIVE: The purpose of this study was to determine the prevalence of developmental dental anomalies in the East Indian subpopulation.
METHODS: The study was based on clinical examination, evaluation of dental casts, and radiographs of 2385 Indian patients (1169 males and 1216 females), who visited Dental Institute, Rajendra Institute of Medical Sciences, Ranchi. These patients were examined for shape anomalies, number anomalies, structural anomalies, and positional anomalies.
RESULTS: It was observed that 5.83% of patients reported with a dental anomaly. Males reported with higher incidence with a male-to-female ratio of 1: 0.96. Microdontia was the most common anomaly. Unilateral microdontia was more common than bilateral and was more prominent in males (9.05%). It was observed that peg laterals were frequently encountered developmental anomaly at 1.34%, while the incidence of amelogenesis imperfecta and dentinogenesis imperfecta was 0.29% and 0.33%, respectively. The present demography reported a very low incidence of dens, fusion, hyperdontia, hypodontia, and macrodontia at <0.01%, whereas anomalies such as transportation, transmigration, and hypodontia of the maxillary molar reported no prevalence.
CONCLUSIONS: The percentage of dental anomalies although low should be treated as soon as possible to avoid further complications. The results of our study can serve as an indicator to ascertain the pattern of dental anomalies in Jharkhand. This might help to plan the dental treatment of the community.