Loss of epithelial FAM20A in mice causes amelogenesis imperfecta, tooth eruption delay and gingival overgrowth

FAM20A has been studied to a very limited extent. Mutations in human FAM20A cause amelogenesis imperfecta, gingival fibromatosis and kidney problems. It would be desirable to systemically analyse the expression of FAM20A in dental tissues and to assess the pathological changes when this molecule is specifically nullified in individual tissues. Recently, we generated mice with a Fam2OA-floxed allele containing the beta-galactosidase reporter gene. We analysed FAM20A expression in dental tissues using X-Gal staining, immunohistochemistry and in situ hybridization, which showed that the ameloblasts in the mouse mandibular first molar began to express FAM20A at 1 day after birth, and the reduced enamel epithelium in erupting molars expressed a significant level of FAM2OA. By breeding K14-Cre mice with Fam20An^x/fl^x mice, we created K14-Cre;Fam20Af/flox/flox （conditional knock out, cKO） mice, in which Fam20A was inactivated in the epithelium. We analysed the dental tissues of cKO mice using X-ray radiography： histology and immunohistochemistry. The molar enamel matrix in cKO mice was much thinner than normal and was often separated from the dentinoenamel junction. The Fam2OA-deficient ameloblasts were non-polarized and disorganized and were detached from the enamel matrix. The enamel abnormality in cKO mice was consistent with the diagnosis of amelogenesis imperfecta. The levels of enamelin and matrix metalloproteinase 20 were lower in the ameloblasts and enamel of cKO mice than the normal mice, The cKO mice had remarkable delays in the eruption of molars and hyperplasia of the gingival epithelium. The findings emphasize the essential roles of FAM20A in the development of dental and oral tissues.

Dental management of a patient with Moebius syndrome:A case report

BACKGROUND Moebius syndrome(MBS)is a nonprogressive and rare congenital neuromuscular disorder involving the facial nerve and abductor nerve;it mainly manifests as facial paralysis and eye strabismus paralytic symptoms.Tissues in the oral cavity are also compromised,characterized by microstomia,micrognathia,tongue malformation,cleft lip,high arched palate or cleft palate,bifid uvula,and dental malocclusion.Therefore,dentistry plays a fundamental and crucial role in caring for these individuals.However,there is limited available data on MBS treatment,particularly regarding dental management.CASE SUMMARY This case report presents dental treatment of a 21-year-old man with MBS and discusses crucial interactions among oral complications of MBS.In this case,the patient was clinically characterized by congenital neuromuscular disorder,occlusal disorders,and tooth and gum problems.It is noteworthy that the patient presented early eruption of deciduous teeth 2 mo after birth,which has not been reported in other MBS cases and suggests a potentially new clinical manifestation of this syndrome.It is important to note that MBS cannot be cured,and oral manifestations of this syndrome can be managed by a multidisciplinary health care team that helps the patient maintain oral hygiene and dental health.After a series of oral treatments,no obvious poor oral hygiene,swollen gums,or abnormal imaging results were observed after 2 years of follow-up.CONCLUSION This case addressed the oral clinical manifestations of MBS and difficulties experienced during dental management,and suggested early tooth eruption as a potentially new clinical manifestation of this syndrome.Knowledge of the loopmediated association among oral complications of this syndrome is essential to perfecting treatments.

Dental anomalies in first-degree relatives of transposed canine probands

The aim of this study was to investigate and compare the inheritance pattern and prevalence of inheritable dental anomalies in a sample of patients with maxillary canine—first premolar transposition and their first-degree relatives with a sample of palatally displaced canine families. Thirty-five consecutive maxillary canine—first premolar transposition probands and 111 first-degree relatives were matched to 35 consecutive palatally displaced canine probands and 115 first-degree relatives. These were assessed for palatally displaced canines and incisor-premolar hypodontia. Parental age at birth of the proband was also noted. The results revealed that（i） there is no difference in the overall prevalence of palatally displaced canine or incisor-premolar hypodontia between the groups of relatives;（ii） first-degree relatives of bilateral palatally displaced canine probands have a higher prevalence of palatally displaced canine and incisor-premolar hypodontia than those with unilateral palatally displaced canine; and（iii） maternal age at birth of the maxillary canine—first premolar transposition probands was significantly higher than that of the palatally displaced canine probands.The results suggest that maxillary canine—first premolar transposition and palatally displaced canine are unlikely to be different genetic entities and also indicate environmental or epigenetic influences on dental development.

Age estimation of individuals aged 5-23 years based on dental development of the Indonesian population

Dental development can be used to estimate age for forensic purposes.However,most of the currently available methods are less reliable for the Indonesian population due to population variability.This study presents a new method and evaluates other methods that utilize dental development to estimate the age of Indonesian people.Panoramic radiographs of 304 young Indonesian people aged 5–23 years old were analysed for deciduous tooth root resorption,permanent tooth calcification,and eruption.The extent of tooth root resorption was determined based on AlQahtani’s modified Moorrees et al.method.Tooth calcification was classified based on a modified Demirjian et al.method.Tooth eruption was evaluated based on AlQahtani’s modified Bengston system.The sequence of tooth root resorption,and permanent tooth calcification and eruption were grouped into 19 age categories(from 5–23 years old)in an atlas.The differences between males and females,between maxillary and mandibular teeth,and between right and left teeth were also analysed.There were minimal significant differences of tooth development between males and females,and between the right and left teeth(P>0.05),while the maxillary and mandibular dental development was significantly different(P<0.05).The newly developed atlas showed the development of the right side of maxillary and mandibular tooth of combined sex of Indonesian population.Another 34 panoramic radiographs of known-age and sex individuals from Indonesia were assessed using the newly developed Atlas of Dental Development in the Indonesian Population,Ubelaker’s Dental Development Chart,The London Atlas of Human Tooth Development and Eruption by AlQahtani,and the Age Estimation Guide-Modern Australia population by Blenkin-Taylor.Accuracy was assessed by comparing estimated age to actual chronological age using the Bland-Altmand test.Results show that the smallest range of error was found in the Atlas of Dental Development in the Indonesian Population(−0.969 to 1.210 years),followed by The London Atlas of Human Tooth Development and Eruption by AlQahtani(−2.013 to 1.990 years),the Age Estimation Guide-Modern Australia population by Blenkin-Taylor(−2.495 to 2.598 years),and the Dental Development Chart by Ubelaker(−2.960 to 3.289 years).These findings show that the Atlas of Dental Development constructed in this study performs better than the other three methods and presents greater accuracy of age estimation in the Indonesian population.