Orthodontic treatment is more complicated when both soft and hard tissues must be considered because an impacted maxillary canine has important effects on function and esthetics. Compared with extraction of impacted maxillary canines, exposure followed by orthodontic traction can improve esthetics and better protect the patient's teeth and alveolar bone. Therefore, in order to achieve desirable tooth movement with minimal unexpected complications, a precise diagnosis is indispensable to establish an effective and efficient force system. In this report, we describe the case of a 31-year-old patient who had a labio-palatal horizontally impacted maxillary left canine with a severe occlusal alveolar bone defect and a missing maxillary left first premolar. Herein, with the aid of three-dimensional imaging, sequential traction was performed with a three-directional force device that finally achieved acceptable occlusion by bringing the horizontally impacted maxillary left canine into alignment. The maxillary left canine had normal gingival contours and was surrounded by a substantial amount of regenerated alveolar bone. The 1-year follow-up stability assessment demonstrated that the esthetic and functional outcomes were successful.

ObJective·To evaluate the dentofacial phenotype in non-syndromic tooth agenesis(NSTA)patients with paired box gene 9(PAX9)mutation.Methods·Patients with NSTA who visited the Department of Second Dental Center of Shanghai Ninth People's Hospital,Shanghai Jiao Tong University School of Medicine,between January 2016 and December 2023 received whole-exome sequencing to screen PAX9 mutation.The location and number of missing teeth were evaluated by oral pantomography,and dentofacial deformities were evaluated by X-ray cephalometrics.Results·Seven patients with PAX9 mutation were included in the study,including 3 males(42.9％)and 4 females(57.1％).The patients were 7-31 years old at first visit,with a mean age of(19.7±8.0)years old.All the 7 patients were PAX9 heterozygotes,of which 4 were missense and 3 were frameshift.The average number of missing teeth was 15.9±2.9.The number of missing teeth in maxilla(9.6±2.6)was slightly higher than that in mandible(6.3±2.4)(P=0.030).Maxillary second molar(100.0％),maxillary canine(85.7％)and mandibular second premolar(85.7％)were the three most common missing teeth,while mandibular lateral incisor(14.3％)and mandibular canine(14.3％)were the two least missing teeth.Patients with frameshift mutation had more missing teeth(18.3±2.1)than those with missense mutation(14.0±1.8)(P=0.032).X-ray cephalometrics analysis results showed that the angle sella-nasion-subspinale(SNA),angle nasion-subspinale-subspinale-porion(NA-Apo)and sella-nasion(S-N)in adult patients with PAX9 mutation were significantly lower than the normal reference values,suggesting a shorter anterior cranial base and maxillary length.The frankfort horizontal plane-nasion-porion(FH-NPo)was higher than the reference value,and the Y-axis was lower than the reference value,indicating a more prognathic mandible.The angle subspinale-nasion-supramental(ANB)was lower than the reference value,indicating a skeletal angle Ⅲ malocclusion.The angle upper central incisor-nasion-subspinale(angle U1-NA)was higher than the reference value,indicating a lip inclination of maxillary central incisor.The angle lower central incisor-mandibular plane(IMPA)and lower central incisor-nasion-supramental(L1-NB)were lower than the reference values,indicating a retroclination of the mandibular central incisor,and crossbite in the maxillary and mandibular anterior teeth.Conclusion·The dentofacial phenotype of PAX9-mutated patients with NSTA is reported comprehensively.It is helpful to improve the understanding of the role of PAX9 in human maxillofacial development.

Objective·To explore EDAR(ectodysplasin A receptor)gene variants that lead to congenital tooth agenesis,and preliminarily analyze the reasons why variants in EDAR can cause both syndromic and non-syndromic tooth agenesis.Methods·Patients with congenital tooth agenesis admitted to the Department of 2nd Dental Center,Shanghai Ninth People's Hospital,Shanghai Jiao Tong University School of Medicine and their family members were included,and genomic DNA from their peripheral blood was extracted for whole exome sequencing(WES).After preliminary screening,PolyPhen-2,Mutation Taster,and Provean were used to predict the harmfulness of potential variants.The screened variants in patients and their families were verified by Sanger sequencing.Conservation analysis of variants was performed,and Swiss-Model was used to analyze the changes in the three-dimensional structure of EDAR.The teeth and syndromic phenotype of the patients and their family members were investigated.Results·Among the included congenital tooth agenesis patients,five patients with EDAR mutations were found,one with EDAR frameshift mutation c.368_369insC(p.L123fs)and the other four with EDAR missense mutations.Two of these four patients were diagnosed as non-syndromic tooth agenesis(NSTA),resulted from c.77C＞A(p.A26E)homozygous mutation and c.380C＞T(p.P127L)heterozygous mutation,respectively.The other two patients with two variants were diagnosed as hypohidrotic ectodermal dysplasia(HED).One compound heterozygous missense mutation patient carried EDAR c.77C＞T(p.A26V)from her father andEDAR c.1281G＞C(p.L427F)from her mother;the other patient with both EDAR and EDA mutations carried EDAR c.1138A＞C(p.S380R)heterozygous mutation and EDA c.1013C＞T(p.T338M)hemizygous mutation.Both variants were from his mother and were reported to be related with NSTA.Two of these missense mutations,EDAR c.1281G＞C(p.L427F)and EDAR c.77C＞A(p.A26E),had not been reported before.The missense mutations affected the protein's spatial conformation by altering the polarity,charge,or volume of the amino acid residues.The frameshift mutation caused a non-triplet base addition,which probably led to protein truncation or degradation.Conclusion·Two new EDAR missense mutations are discovered.An NSTA patients with EDAR homozygous mutations and an HED patient with both EDA and EDAR mutations are reported.It expands the understanding of pathogenic mechanisms of EDAR mutations causing HED and NSTA.

The temporomandibular joint is the only joint structure within the craniofacial skeletal system,responsible for performing functions related to opening and closing mouth movements,such as chewing,speaking,and facial expression in daily life.The condyle of the mandible,as a vital component of the temporomandibular joint,originates from the mandibular process formed by the first gill arch and is the key growth center at the end of the mandibular ramus.Condyle is composed of a layer of cartilage as its surface and subchondral bone below,exhibiting unique biological processes during its growth and development.In the articular fossa,the functional movement of the condyle depends on its normal physiological and anatomical structure,which plays a crucial role in establishing occlusion and shaping facial features.Abnormal growth and development can lead to the occurrence of condylar deformities,which affect the vertical height of the patient's maxillofacial region and ultimately lead to secondary skeletal class Ⅱ or Ⅲ craniofacial deformities.During the process of growth and development,the condyle is subject to complex signal regulation.In recent years,with in-depth research on the temporomandibular joint,researchers have begun to discuss the regulatory mechanisms of condyle growth and development from the perspectives of gene expression and molecular level,in order to explain the causes of temporomandibular joint diseases and condylar deformities.This article provides a review on the growth process and structure of condyle,classification and pathological manifestations of condylar deformities,and related regulatory mechanisms of the growth and development of condyle,as well as pathogenesis of condylar deformities.The aim of this article is to provide research ideas for temporomandibular joint diseases and craniofacial malformations caused by abnormal development of the mandibular condyle in clinical practice.

Objective·To construct and verify the mouse model that can mimic the vitamin A deficiency(VAD)-like craniofacial skeletal deformity and do not cause embryonic death.Methods·Based on the Cre-LoxP system,the OsxCre;Rosa26dn/dn mice expressing osteoblast-specific dominant-negative retinoid acid receptor α(dnRARα)mutation were obtained by hybridization through OsxCre and Rosa26dnRARa/ddnRARa mice,to achieve the conditional inhibition of retinoic acid signaling to simulate VAD disease.Femur bone mesenchymal stem cells(BMSCs)and parietal bone cells of OsxCre;Rosa26dn/dn mice and their control littermates were isolated and underwent osteogenic induction,to assess the expression of retinoid acid receptor α(RARα)protein through Western blotting.Osteoblasts induced from parietal bone cells of OsxCre;Rosa26dn/dn mice and their control littermates were isolated and the effect of retinoic acid signaling inhibition was verified through dual luciferase gene reporter assay.Meanwhile,Ad-eGFP or Ad-Cre adenovirus-infected femur BMSCs and parietal bone cells of Rosa26dn/dnmice underwent osteogenic induction to assess the expression of dominant-negative mutant protein and the inhibition of the retinoic acid signaling pathway in vitro by Western blotting and dual luciferase gene reporter assay.Moreover,the skulls of 6-week-old OsxCre;Rosa26dn/dn mice were collected,and Micro-CT scanning and three-dimensional(3D)reconstruction were performed to verify the craniofacial skeletal deformities of the mouse model.Results·Western blotting results demonstrated that the level of RARα protein increased in the femur and parietal osteoblasts of OsxCre;Rosa26dn/dn mice compared to that of their control littermates,and also increased in the Ad-Cre-infected femur and parietal osteoblasts of Rosa26dn/dn mice compared to that in the Ad-eGFP-infected group(P＜0.05).Dualluciferase gene reporter assay results indicated that the activity of retinoid acid response element(RARE)was inhibited in the osteoblasts of OsxCre;Rosa26dn/dn mice compared to their control littermates,and was also inhibited in the Ad-Cre-infected group compared to the Ad-eGFP-infected group(P＜0.05).Micro-CT and 3D reconstruction suggested that the skull of 6-week-old OsxCre;Rosa26dn/dn mice exhibited VAD-like craniofacial skeletal deformities,including smaller size of the skull and osteogenesis imperfecta compared to their control littermates.Conclusion·An osteoblast-specific dnRARα expressing mouse model that can mimic VAD-like craniofacial skeletal deformity is successfully constructed,therefore providing a new model for exploring the pathogenesis and therapeutic targets of VAD-like craniofacial skeletal deformity in the future.

Objective·To explore the effect of all-trans retinoic acid(ATRA)of different concentrations on osteogenic differentiation of jaw bone mesenchymal stem cells(jBMSCs)in rats.Methods·jBMSCs from 4-week-old Sprague-Dawley(SD)rats were isolated and cultured with whole bone marrow adherence method.The surface antigens were identified by using flow cytometry.Alkaline phosphatase(ALP)staining/alizarin red staining,oil red O staining and alcian blue staining were used to prove the multilineage differentiation potential of jBMSCs after osteogenic,adipogenic and chondrogenic induction respectively.jBMSCs were induced in osteogenic medium with ATRA of concentration of 0.01,0.1,1,5,10,20 μmol/L in vitro,and dimethyl sulfoxide(DMSO)was used as control group.Cell viability of jBMSCs in different groups were determined by CCK8.ALP staining and alizarin red staining were used to investigate the osteogenic ability of jBMSCs in each group and screened the concentrations for subsequent experiments.Quantitative real-time polymerase chain reaction(qPCR)and immunofluorescence staining were used to analyze the expressions of osteogenesis-related genes and proteins in jBMSCs of different concentrations.Results·The flow cytometry analysis showed that more than 98%of P1 jBMSCs were positive for CD29+CD90+CD31-CD45-,which was congruent with the characteristics of bone mesenchymal stem cells.The results of ALP staining/alizarin red staining,oil red O staining and alcian blue staining indicated that the P1 jBMSCs had the multilineage differentiation potential of osteogenesis,adipogenesis and chondrogenesis.The results of ALP staining/alizarin red staining showed that the osteogenic activity and mineralization ability of jBMSCs in 0.01,0.1 and 1 μmol/L ATRA groups were increased compared with those in the control group,while the osteogenic activity and mineralization ability were decreased when the concentration of ATRA increased,especially higher than 5 μmol/L(all P<0.05).qPCR analysis showed that the mRNA expression levels of osteogenesis-related genes such as Alp,bone sialoprotein(Bsp),collagen type Ⅰ α1(Col1a1)and osteocalcin(Ocn)were higher in the 0.1 and 1 μmol/L ATRA groups compared to the control group.However,further increasing the concentration of ATRA led to a decrease in gene expression levels,and when the concentration exceeded 5 μmol/L,it began to be lower than the control group level(all P<0.05).The immunofluorescence staining showed that the expression of osteogenic related proteins SP7,ALP and OCN in the 0.1 and 1 μmol/L ATRA groups were increased compared to the control group,while further increasing the concentration of ATRA led to a decrease in protein expression.When the concentration was higher than 5 μmol/L,it began to be lower than the control group level(all P<0.05).Conclusion·Lower concentrations(0.1,1 μmol/L)of ATRA can promote the osteogenic differentiation of rat jBMSCs,and the promoting effect reaches its peak at 0.1 μmol/L,while the effect can be weakened by further increasing the concentration.Higher concentrations(5,10,20 μmol/L)of ATRA could inhibit the osteogenic differentiation of rat jBMSCs,showing an inhibitory effect.In this study,the dual-directional effect of retinoic acid on osteogenic differentiation of jBMSCs was demonstrated in vitro,and 0.1 μmol/L ATRA was identified as the optimal concentration for osteogenic differentiation of jBMSCs in rats,which provided a reference basis for the development of in vivo studies and clinical application of ATRA.