Objective This study investigates the force distributions and movement patterns of the maxillary dentition during molar intrusion with clear aligners,aiming to provide a theoretical basis for optimizing clinical orthodontic treatment strategies.Methods A three-dimensional(3D)finite element model of the periodontal ligament-teeth-clear aligners complex was established to simulate different intrusion modes,including bilateral first molar intrusion,bilateral second molar intrusion,and simultaneous intrusion of bilateral first and second molars.The von Mises stress distribution characteristics and displacement patterns of each tooth under different intrusion conditions were systematically analyzed.Results Compared with simultaneous molar intrusion,the individual intrusion design resulted in greater intrusive movement(4.260-10.500 μm)accompanied by distal-lingual crown inclination(distal displacement:-7.690--5.100 μm;buccal displacement:-20.500--6.750 μm).Anchorage teeth displayed a displacement trend opposite to that of the intruded molars.The anterior teeth demonstrated minimal displacement and low stress levels.During maxillary molar intrusion with clear aligners,the maximum equivalent stress in the periodontal ligaments occurred at the anchorage teeth mesial to the intruded molars,primarily concentrated in the apical region and the mesial aspect of the buccal cervical area.Conclusions A sequential intrusion strategy enhances vertical control efficiency compared to simultaneous intrusion.Unanticipated mesiodistal and buccolingual displacements in the posterior region necessitate the implementation of counteracting mechanisms in aligner design.In clinical practice,priority should be given to monitoring the risks of root resorption and bone remodeling effects in stress-concentrated zones(apical and buccal cervical regions)of anchorage teeth.

Objective·To investigate the regulatory effects and underlying mechanisms of mouse mandibular osteoblasts on B cell differentiation and development.Methods·Single-cell suspensions from mouse mandibular bone were prepared using an optimized enzymatic digestion method and induced to differentiate into osteoblasts in vitro.Osteogenic potential was validated by real-time quantitative PCR(RT-qPCR),alkaline phosphatase(ALP)staining,and alizarin red S(ARS)staining.The spatial localization relationship between osteoblasts and B cells in mandibular tissues was examined via immunofluorescence staining.High-purity hematopoietic progenitor cells were isolated using fluorescence-activated cell sorting.A Transwell co-culture system was established to assess the regulatory effects of different osteoblast concentrations(5×104,2.5×105,and 5×105 cells/well)on B cell differentiation(5×104 cells/well).Flow cytometry and RT-qPCR were employed to evaluate B cell viability and differentiation.Additionally,RT-qPCR was used to analyze the expression of osteoblast-secreted factors associated with B cell development during osteogenic differentiation.Results·Mandibular osteoblasts exhibited robust osteogenic potential,as confirmed by ALP/ARS staining and high expression of osteogenic markers(Runx2,Osx,Ocn,and Alp)via RT-qPCR.Immunofluorescence revealed close spatial proximity between osteoblasts and B cells in mandibular tissues.In the co-culture system,osteoblasts promoted B cell differentiation in a concentration-dependent manner.RT-qPCR and immunofluorescence demonstrated that osteoblasts significantly upregulated key genes involved in B cell development(Ebf1,Rag1,Il7r,and Pax5;all P<0.001).Furthermore,osteoblast-derived factors(Il7,Baff,and Flt3l)were markedly elevated during osteogenic differentiation(all P<0.05).Conclusion·Mandibular osteoblasts enhance B cell differentiation and development in a concentration-dependent manner,likely through secreting growth factors that upregulate critical B cell differentiation genes.

Objective This study investigates the force distributions and movement patterns of the maxillary dentition during molar intrusion with clear aligners,aiming to provide a theoretical basis for optimizing clinical orthodontic treatment strategies.Methods A three-dimensional(3D)finite element model of the periodontal ligament-teeth-clear aligners complex was established to simulate different intrusion modes,including bilateral first molar intrusion,bilateral second molar intrusion,and simultaneous intrusion of bilateral first and second molars.The von Mises stress distribution characteristics and displacement patterns of each tooth under different intrusion conditions were systematically analyzed.Results Compared with simultaneous molar intrusion,the individual intrusion design resulted in greater intrusive movement(4.260-10.500 μm)accompanied by distal-lingual crown inclination(distal displacement:-7.690--5.100 μm;buccal displacement:-20.500--6.750 μm).Anchorage teeth displayed a displacement trend opposite to that of the intruded molars.The anterior teeth demonstrated minimal displacement and low stress levels.During maxillary molar intrusion with clear aligners,the maximum equivalent stress in the periodontal ligaments occurred at the anchorage teeth mesial to the intruded molars,primarily concentrated in the apical region and the mesial aspect of the buccal cervical area.Conclusions A sequential intrusion strategy enhances vertical control efficiency compared to simultaneous intrusion.Unanticipated mesiodistal and buccolingual displacements in the posterior region necessitate the implementation of counteracting mechanisms in aligner design.In clinical practice,priority should be given to monitoring the risks of root resorption and bone remodeling effects in stress-concentrated zones(apical and buccal cervical regions)of anchorage teeth.

Objective·To investigate the regulatory effects and underlying mechanisms of mouse mandibular osteoblasts on B cell differentiation and development.Methods·Single-cell suspensions from mouse mandibular bone were prepared using an optimized enzymatic digestion method and induced to differentiate into osteoblasts in vitro.Osteogenic potential was validated by real-time quantitative PCR(RT-qPCR),alkaline phosphatase(ALP)staining,and alizarin red S(ARS)staining.The spatial localization relationship between osteoblasts and B cells in mandibular tissues was examined via immunofluorescence staining.High-purity hematopoietic progenitor cells were isolated using fluorescence-activated cell sorting.A Transwell co-culture system was established to assess the regulatory effects of different osteoblast concentrations(5×104,2.5×105,and 5×105 cells/well)on B cell differentiation(5×104 cells/well).Flow cytometry and RT-qPCR were employed to evaluate B cell viability and differentiation.Additionally,RT-qPCR was used to analyze the expression of osteoblast-secreted factors associated with B cell development during osteogenic differentiation.Results·Mandibular osteoblasts exhibited robust osteogenic potential,as confirmed by ALP/ARS staining and high expression of osteogenic markers(Runx2,Osx,Ocn,and Alp)via RT-qPCR.Immunofluorescence revealed close spatial proximity between osteoblasts and B cells in mandibular tissues.In the co-culture system,osteoblasts promoted B cell differentiation in a concentration-dependent manner.RT-qPCR and immunofluorescence demonstrated that osteoblasts significantly upregulated key genes involved in B cell development(Ebf1,Rag1,Il7r,and Pax5;all P<0.001).Furthermore,osteoblast-derived factors(Il7,Baff,and Flt3l)were markedly elevated during osteogenic differentiation(all P<0.05).Conclusion·Mandibular osteoblasts enhance B cell differentiation and development in a concentration-dependent manner,likely through secreting growth factors that upregulate critical B cell differentiation genes.

Dento-maxillofacial skeletal abnormalities exhibit high incidence rate,complex etiology,severe symptoms,difficult diagnosis and treatment,and lack of early intervention strategies,which is mainly due to insufficient exploration of mechanism research.These diseases are characterized by abnormal morphology,disordered mutual location and impaired function of bones and teeth,including skeletal abnormalities and malocclusion.Among them,maxillofacial bone and dento-periodontal complex are the two core structures,which respectively determine facial aesthetics and occlusal function.As for maxillofacial skeletal abnormalities,mechanism studies on skeletal development and pathogenesis are required for precise prevention and treatment.As for malocclusion,mechanism studies on homeostasis and stress remodeling are required from the perspective of orthodontics.Both mechanism studies can provide basic support for the diagnosis and treatment of dento-maxillofacial skeletal deformities.In this regard,previous studies usually focused on the expression maps of mutated genes and differential factors.In recent years,the development of conditional gene editing techniques,such as Cre-LoxP system,has enabled researchers to intuitively evaluate the function of key genes in a single cell lineage in vivo,helping to advance research on dento-maxillofacial skeletal abnormalities from phenotype level to molecular mechanism level.This review summarizes recent domestic and foreign researches on dento-maxillofacial skeletal abnormalities,as well as recent achievements of the author's team,and systematically proposes a research mode concluded as"One Centre,Two Motives".The centre is dento-maxillofacial skeletal abnormalities.One motive is the development and pathogenic mechanisms of maxillofacial bone,and the other is the homeostasis and remodeling mechanisms of dento-periodontal complex.The research mode aims at systematical study of the pathogenesis and prognosis of diseases to explore potential therapies.Many advanced technologies have contributed to the exploration of"One Centre"through"Two Motives":on the one hand,conditional gene editing models have provided a new strategy for studying the function of key factors in key cells in vivo;on the other hand,inducible conditional gene editing models have supported the precise control of the timeline for interventions after birth.Furthermore,with the help of single-cell sequencing and lineage tracing techniques,researchers have been focusing on tissue-specific stem cells,due to their in situ and characteristic functions.This situation is highly in line with the"One Centre,Two Motives"mode,and is benefit to shed a new insight on the theoretical researches and clinical applications of dento-maxillofacial skeletal abnormalities.The article reviews the"One Centre,Two Motives"mechanism research mode of dento-maxillofacial skeletal abnormalities.

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 analyze the anatomical and macroscopic characteristics of the pterygopalatine suture(PPS)in Chinese population using cone-beam computed tomography(CBCT)technology,and to preliminarily investigate its developmental pattern and its association with the correction of maxillary underdevelopment.Methods·A total of 134 CBCT images,taken from July to August 2023 at Shanghai Ninth People's Hospital,Shanghai Jiao Tong University School of Medicine,were categorized into six age groups.The PPS landmarks were utilized to determine the overall transverse position(XPPS),sagittal position(YPPS),insertion angle(IAP),insertion width of the pyramidal process(IWP),and insertion depth of the pyramidal process(IDP).The pterygomaxillary junction was identified through multiplanar observations.Regression analysis was performed to assess the correlation of these parameters with age and gender,and pairwise comparisons were made to determine the stable age range for parameter changes.Paired t-tests and paired chi-squared tests were conducted to analyze the bilateral parameter differences.Results·Results showed that YPPS and IDP did not exhibit significant correlation with age,whereas XPPS,IAP,IWP,and the incidence of pterygomaxillary fusion were significantly positively correlated with age(P<0.01).Gender differences were only significant for XPPS,with males demonstrating greater values than females(P<0.01).Analysis of age-related trends indicated significant differences in XPPS between group 1(6 years≤age<9 years)and group 2(9 years≤age<12 years)(female:P=0.006,male:P=0.004);significant differences in IAP were observed between group 2 and group 3(12 years≤age<15 years)(P=0.042),with 98.5%of samples having an IAP greater than 45 degrees;IWP differences were significant between group 1 and group 3(P=0.016),and the pterygomaxillary fusion incidence was significantly different among group 1,2,and 3(group 1 vs.2:P<0.001,group 2 vs 3:P=0.037,group 1 vs 3:P<0.001),with an incidence rate exceeding 90%in adults.No significant bilateral differences were found for all parameters.Conclusion·No significant changes were observed in YPPS and IDP after the age of 6,indicating a trend towards fusion of the maxilla with the pterygoid process.The overall transverse position of the PPS tends to stabilize around 12 years of age,while the IAP and IWP continue to increase and reach stability around 15 years of age,with a sagittal insertion orientation of the pyramidal process into the pterygoid notch.

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 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.

Malocclusion,identified by the World Health Organization(WHO)as one of three major oral diseases,profoundly impacts the dental-maxillofacial functions,facial esthetics,and long-term development of～260 million children in China.Beyond its physical manifestations,malocclusion also significantly influences the psycho-social well-being of these children.Timely intervention in malocclusion can foster an environment conducive to dental-maxillofacial development and substantially decrease the incidence of malocclusion or reduce the severity and complexity of malocclusion in the permanent dentition,by mitigating the negative impact of abnormal environmental influences on the growth.Early orthodontic treatment encompasses accurate identification and treatment of dental and maxillofacial morphological and functional abnormalities during various stages of dental-maxillofacial development,ranging from fetal stages to the early permanent dentition phase.From an economic and societal standpoint,the urgency for effective early orthodontic treatments for malocclusions in childhood cannot be overstated,underlining its profound practical and social importance.This consensus paper discusses the characteristics and the detrimental effects of malocclusion in children,emphasizing critical need for early treatment.It elaborates on corresponding core principles and fundamental approaches in early orthodontics,proposing comprehensive guidance for preventive and interceptive orthodontic treatment,serving as a reference for clinicians engaged in early orthodontic treatment.