Expert consensus on pediatric orthodontic therapies of malocclusions in children

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.

An overview of autophagy in the differentiation of dental stem cells

Dental stem cells(DSCs)have attracted significant interest as autologous stem cells since they are easily accessible and give a minimal immune response.These properties and their ability to both maintain self-renewal and undergo multi-lineage differentiation establish them as key players in regenerative medicine.While many regulatory factors determine the differentiation trajectory of DSCs,prior research has predominantly been based on genetic,epigenetic,and molecular aspects.Recent evidence suggests that DSC differentiation can also be influenced by autophagy,a highly conserved cellular process responsible for maintaining cellular and tissue homeostasis under various stress conditions.This comprehensive review endeavors to elucidate the intricate regulatory mechanism and relationship between autophagy and DSC differentiation.To achieve this goal,we dissect the intricacies of autophagy and its mechanisms.Subsequently,we elucidate its pivotal roles in impacting DSC differentiation,including osteo/odontogenic,neurogenic,and angiogenic trajectories.Furthermore,we reveal the regulatory factors that govern autophagy in DSC lineage commitment,including scaffold materials,pharmaceutical cues,and the extrinsic milieu.The implications of this review are far-reaching,underpinning the potential to wield autophagy as a regulatory tool to expedite DSC-directed differentiation and thereby promote the application of DSCs within the realm of regenerative medicine.

Poor oral health was associated with higher risk of gastric cancer: Evidence from 1431677 participants

BACKGROUND In recent years,the association between oral health and the risk of gastric cancer(GC)has gradually attracted increased interest.However,in terms of GC incidence,the association between oral health and GC incidence remains contro-versial.Periodontitis is reported to increase the risk of GC.However,some studies have shown that periodontitis has no effect on the risk of GC.Therefore,the present study aimed to assess whether there is a relationship between oral health and the risk of GC.AIM To assess whether there was a relationship between oral health and the risk of GC.METHODS Five databases were searched to find eligible studies from inception to April 10,2023.Newcastle-Ottawa Scale score was used to assess the quality of included studies.The quality of cohort studies and case-control studies were evaluated separately in this study.Incidence of GC were described by odds ratio(OR)and 95%confidence interval(CI).Funnel plot was used to represent the publication bias of included studies.We performed the data analysis by StataSE 16.RESULTS A total of 1431677 patients from twelve included studies were enrolled for data analysis in this study.According to our analysis,we found that the poor oral health was associated with higher risk of GC(OR=1.15,95%CI:1.02-1.29;I2=59.47%,P=0.00<0.01).Moreover,after subgroup analysis,the outcomes showed that whether tooth loss(OR=1.12,95%CI:0.94-1.29;I2=6.01%,P>0.01),gingivitis(OR=1.19,95%CI:0.71-1.67;I2=0.00%,P>0.01),dentures(OR=1.27,95%CI:0.63-1.19;I2=68.79%,P>0.01),or tooth brushing(OR=1.25,95%CI:0.78-1.71;I2=88.87%,P>0.01)had no influence on the risk of GC.However,patients with periodontitis(OR=1.13,95%CI:1.04-1.23;I2=0.00%,P<0.01)had a higher risk of GC.CONCLUSION Patients with poor oral health,especially periodontitis,had a higher risk of GC.Patients should be concerned about their oral health.Improving oral health might reduce the risk of GC.

General Considerations for the Practice of Pediatric Dentistry in the Period of COVID-19 Pandemic: A Review

Context: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2) has been identified in December 2019. Since then, it has been spreading around the world and has caused a pandemic. Strict safety protocols should be followed to resume dental treatments. Evidence Acquisition: A comprehensive search was conducted on PubMed, Scopus, Medline and google scholar databases using the MeSH words of COVID-19, SARS-COV-2, Dentistry, and Child from December 2019 until July 2020. Results: Among COVID-19 patients, asymptomatic patients still are considered to be serious carriers of the COVID-19 which can play a key role in transmission of the virus. Children are reported to be less than 2 percent of the infected population and are considered as serious potential carriers. Telemedicine can take a key part in educating parents regarding this matter. Chronic and rare diseases such as Kawasaki Disease (KD) might show acute and more frequent symptoms amongst COVID-19 patients. Salivary testing can be a convenient chairside way for COVID-19 and it has been shown to be effective in identifying critically ill patients. Dry mouth and amblygeustia have been reported to be the oral symptoms of the COVID-19. Conclusions: Dentists must make tough decisions in prioritizing patient’s needs in the period of pandemic. They should frequently get updated as the situation is fluid and the protocols might change.

Porphyromonas gingivalis bacteremia increases the permeability of the blood-brain barrier via the Mfsd2a/Caveolin-1 mediated transcytosis pathway

Bacteremia induced by periodontal infection is an important factor for periodontitis to threaten general health. P. gingivalis DNA/virulence factors have been found in the brain tissues from patients with Alzheimer’s disease(AD). The blood-brain barrier(BBB) is essential for keeping toxic substances from entering brain tissues. However, the effect of P. gingivalis bacteremia on BBB permeability and its underlying mechanism remains unclear. In the present study, rats were injected by tail vein with P. gingivalis three times a week for eight weeks to induce bacteremia. An in vitro BBB model infected with P. gingivalis was also established. We found that the infiltration of Evans blue dye and Albumin protein deposition in the rat brain tissues were increased in the rat brain tissues with P. gingivalis bacteremia and P. gingivalis could pass through the in vitro BBB model. Caveolae were detected after P. gingivalis infection in BMECs both in vivo and in vitro. Caveolin-1(Cav-1) expression was enhanced after P. gingivalis infection.Downregulation of Cav-1 rescued P. gingivalis-enhanced BMECs permeability. We further found P. gingivalis-gingipain could be colocalized with Cav-1 and the strong hydrogen bonding between Cav-1 and arg-specific-gingipain(RgpA) were detected.Moreover, P. gingivalis significantly inhibited the major facilitator superfamily domain containing 2a(Mfsd2a) expression. Mfsd2a overexpression reversed P. gingivalis-increased BMECs permeability and Cav-1 expression. These results revealed that Mfsd2a/Cav-1 mediated transcytosis is a key pathway governing BBB BMECs permeability induced by P. gingivalis, which may contribute to P. gingivalis/virulence factors entrance and the subsequent neurological impairments.

Oral Health Management of Three Head and Neck Cancer Patients Performed by Dental Hygienists

Introduction: Oral health management is often difficult in patients after surgical tumor resection and/or radiotherapy due to defects, bulky flaps, limitation of tongue movement, and trismus. In addition, patients who have undergone radiotherapy have serious disabilities such as oral mucositis, mucosal weakening, soft tissue fibrosis, salivary gland disorder, and osteoradionecrosis. Dental hygienists must understand the characteristics of patients after surgical tumor resection and/or radiotherapy. In this report, the oral health management of three patients after maxillectomy, mandibulectomy, and radiotherapy was shown. Case Description: Case 1: A 53-year-old male patient visited our clinic after chemotherapy, radiotherapy, and partial maxillectomy for cancer of the right maxillary gingiva. Case 2: A 65-year-old male patient visited our clinic after radiotherapy for a right-sided tongue cancer, partial mandibulectomy of the right tongue to the oropharynx, a right-sided segmental mandibulectomy and a speech aid and a mandibular prosthesis were provided. Case 3: A 36-year-old female visited our clinic for radiotherapy for left-sided tongue cancer. Dental hygienists provided oral health management to the patients. In oral health management, it was suggested that intervention before cancer treatment, oral hygiene instructions tailored to patients’ symptoms, and frequent professional care are important. Conclusion: Oral health management by dental hygienists is extremely important for patients undergoing maxillofacial cancer treatment to maintain their quality of life in the long term.

Autophagy and circadian rhythms:interactions and clinical implications

Autophagy is a widespread biological process that controls cellular growth,survival,development,and death.Circadian rhythm is a recurring reaction of living organisms and behaviors to variations in surrounding brightness and obscurity.Most of the fundamental physiological processes in mammals,such as the sleep-wake pattern and the rhythm of nutrition and energy metabolism,are governed by circadian rhythms.Research has indicated that autophagy exhibits a specific circadian pattern in both normal and abnormal conditions.Autophagy can modulate circadian rhythms by breaking down proteins that regulate the circadian clock.The potential regulatory connection between the two has been a popular subject of clinical and fundamental research.Understanding the interaction between circadian rhythm and autophagy could potentially lead to the development of novel approaches for disease treatment in the future.The present analysis presented a summary of the molecular processes implicated in the interplay between autophagy and circadian rhythm,as well as the pathological importance of the disrupted regulatory association between these two phenomena.

Cell membrane vesicles derived from hBMSCs and hUVECs enhance bone regeneration

Bone tissue renewal can be enhanced through co-transplantation of bone mesenchymal stem cells(BMSCs)and vascular endothelial cells(ECs).However,there are apparent limitations in stem cell-based therapy which hinder its clinic translation.Hence,we investigated the potential of alternative stem cell substitutes for facilitating bone regeneration.In this study,we successfully prepared cell membrane vesicles(CMVs)from BMSCs and ECs.The results showed that BMSC-derived cell membrane vesicles(BMSC-CMVs)possessed membrane receptors involved in juxtacrine signaling and growth factors derived from their parental cells.EC-derived cell membrane vesicles(EC-CMVs)also contained BMP2 and VEGF derived from their parental cells.BMSC-CMVs enhanced tube formation and migration ability of hUVECs,while EC-CMVs promoted the osteogenic differentiation of hBMSCs in vitro.Using a rat skull defect model,we found that co-transplantation of BMSC-CMVs and EC-CMVs could stimulate angiogenesis and bone formation in vivo.Therefore,our research might provide an innovative and feasible approach for cell-free therapy in bone tissue regeneration.

Glanzmann Thrombasthenia: Managing Gingival Bleeding Triggered by Tooth Eruption—A Rare Case Report

Glanzmann thrombasthenia (GT) is a rare and often underdiagnosed congenital bleeding disorder caused by mutations in the genes encoding glycoproteins GPIIb or GPIIIa, resulting in platelet dysfunction. Inherited in an autosomal recessive manner, GT is characterized by the inability of platelets to aggregate. Clinically, it presents with mucocutaneous bleeding, such as easy and extensive bruising, severe epistaxis, menorrhagia, gingival bleeding, postpartum hemorrhage, and unexpected bleeding following procedures, despite a normal platelet count. We present a case involving a 6-year-old male patient who experienced spontaneous gingival bleeding for the past 4 weeks due to the eruption of his first permanent molars. The bleeding was particularly severe at night, disrupting the child’s sleep. The patient had been diagnosed with GT at the age of 16 months. Dental management was pursued, and the use of tranexamic acid mouthwash, combined with meticulous oral hygiene, resulted in an excellent response.

Epigenetic regulation of dental pulp stem cells and its potential in regenerative endodontics

Regenerative endodontics(RE)therapy means physiologically replacing damaged pulp tissue and regaining functional dentin–pulp complex.Current clinical RE procedures recruit endogenous stem cells from the apical papilla,periodontal tissue,bone marrow and peripheral blood,with or without application of scaffolds and growth factors in the root canal space,resulting in cementum-like and bone-like tissue formation.Without the involvement of dental pulp stem cells(DPSCs),it is unlikely that functional pulp regeneration can be achieved,even though acceptable repair can be acquired.DPSCs,due to their specific odontogenic potential,high proliferation,neurovascular property,and easy accessibility,are considered as the most eligible cell source for dentin–pulp regeneration.The regenerative potential of DPSCs has been demonstrated by recent clinical progress.DPSC transplantation following pulpectomy has successfully reconstructed neurovascularized pulp that simulates the physiological structure of natural pulp.The self-renewal,proliferation,and odontogenic differentiation of DPSCs are under the control of a cascade of transcription factors.Over recent decades,epigenetic modulations implicating histone modifications,DNA methylation,and noncoding(nc)RNAs have manifested as a new layer of gene regulation.These modulations exhibit a profound effect on the cellular activities of DPSCs.In this review,we offer an overview about epigenetic regulation of the fate of DPSCs;in particular,on the proliferation,odontogenic differentiation,angiogenesis,and neurogenesis.We emphasize recent discoveries of epigenetic molecules that can alter DPSC status and promote pulp regeneration through manipulation over epigenetic profiles.

Transplantation of stem cells from human exfoliated deciduous teeth for bone regeneration in the dog mandibular defect

AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-andthrough defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P < 0.05 was considered as significant level.RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue(P = 0.248), woven bone(P = 0.248) and compact bone(P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs.

The photodynamic therapy on Streptococcus mutans biofilms using erythrosine and dental halogen curing unit

The purpose of our study was to evaluate the effect of photodynamic therapy （PDT）, using erythrosine as a photosensitizing agent and a dental halogen curing unit as a light source, on Streptococcus mutans in a biofilm phase. The S. mutans biofilms were formed in a 24-well cell culture cluster. Test groups consisted of biofilms divided into four groups： group 1： no photosensitizer or light irradiation treatment （control group）; group 2： photosensitizer treatment alone; group 3： light irradiation alone; group 4： photosensitizer treatment and light irradiation. After treatments, the numbers of colony-forming unit （CFU） were counted and samples were examined by confocal laser scanning fluorescence microscopy （CLSM）. Only group 4 （combined treatment） resulted in significant increases in cell death, with rates of 75% and 55% after 8 h of incubation, and 74% and 42% at 12 h, for biofilms formed in brain-heart infusion （BHI） broth supplemented with 0% or O. 1% sucrose, respectively. Therefore, PDT of S. mutans biofilms using a combination of erythrosine and a dental halogen curing unit, both widely used in dental clinics, resulted in a significant increase in cell death. The PDT effects are decreased in biofilms that form in the presence of sucrose.

Activation of β-catenin signaling in aggrecan-expressing cells in temporomandibular joint causes osteoarthritis-like defects

β-Catenin plays a critical role in cartilage formation and development. To further understand the role of β-catenin in osteoarthritis（OA） development in temporomandibular joint（TMJ）, we have generated β-catenin conditional activation mice（β-cat（ex3）^Agc1CreER）by breeding Agc1-CreER mice with β-catenin^flox（ex3/＋）mice. Results of histologic analysis showed the progressive TMJ defects in 3-and 6-month-old β-cat（ex3）^Agc1CreERmice（tamoxifen induction was performed at 2 weeks of age）, including decreased chondrocyte numbers in the superficial layer associated with less Alcian blue staining, increased numbers of hypertrophic chondrocytes in deep layers, and rough articular surface. Compared to the TMJ phenotype of β-cat（ex3）^（Col2CreER）mice, β-cat（ex3）^（Agc1CreER）mice showed much severe morphological defects in the superficial layer of TMJ. This may reflect that Agc1-CreER mice could efficiently target cells in the superficial layer of TMJ. Results of immunostaining showed significantly increased expression of MMP13, Col-X, Adamts4,and Adamts5 in TMJ of β-cat（ex3）^（Agc1CreER）mice. Results of proliferating cell nuclear antigen（PCNA）, Ki67, and terminal deoxinucleotidyl transferase-mediated d UTP-fluorescein nick end labeling（TUNEL） staining further demonstrated that cell proliferation was decreased and cell apoptosis was increased in condylar cartilage of β-cat（ex3）^Agc1CreERmice. Our findings indicate that abnormal upregulation of β-catenin in TMJ leads to defects assembling to OA-like phenotype, further demonstrating that β-catenin plays a critical role in TMJ pathogenesis.

Molecular mechanisms of inhibiting glucosyltransferases for biofilm formation in Streptococcus mutans

Glucosyltransferases(Gtfs)play critical roles in the etiology and pathogenesis of Streptococcus mutans(S.mutans)-mediated dental caries including early childhood caries.Gtfs enhance the biofilm formation and promotes colonization of cariogenic bacteria by generating biofilm extracellular polysaccharides(EPSs),the key virulence property in the cariogenic process.Therefore,Gtfs have become an appealing target for effective therapeutic interventions that inhibit cariogenic biofilms.Importantly,targeting Gtfs selectively impairs the S.mutans virulence without affecting S.mutans existence or the existence of other species in the oral cavity.Over the past decade,numerous Gtfs inhibitory molecules have been identified,mainly including natural and synthetic compounds and their derivatives,antibodies,and metal ions.These therapeutic agents exert their inhibitory role in inhibiting the expression gtf genes and the activities and secretion of Gtfs enzymes with a wide range of sensitivity and effectiveness.Understanding molecular mechanisms of inhibiting Gtfs will contribute to instructing drug combination strategies,which is more effective for inhibiting Gtfs than one drug or class of drugs.This review highlights our current understanding of Gtfs activities and their potential utility,and discusses challenges and opportunities for future exploration of Gtfs as a therapeutic target.

Runxl protects against the pathological progression of osteoarthritis

Runt-related transcription factor-1(Runxl)is required for chondrocyte-to-osteoblast lineage commitment by enhancing both chondrogenesis and osteogenesis during vertebrate development.However,the potential role of Runxl in joint diseases is not well known.In the current study,we aimed to explore the role of Runxl in osteoarthritis induced by anterior cruciate ligament transaction(ACLT)surgery.We showed that chondrocyte-specific Runxl knockout(Runx1f/fCol2a1-Cre)aggravated cartilage destruction by accelerating the loss of proteoglycan and collagen II in early osteoarthritis.Moreover,we observed thinning and ossification of the growth plate,a decrease in chondrocyte proliferative capacity and the loss of bone matrix around the growth plate in late osteoarthritis.We overexpressed Runxl by adeno-associated virus(AAV)in articular cartilage and identified its protective effect by slowing the destruction of osteoarthritis in cartilage in early osteoarthritis and alleviating the pathological progression of growth plate cartilage in late osteoarthritis.ChIP-seq analysis identified new targets that interacted with Runxl in cartilage pathology,and we confirmed the direct interactions of these factors with Runxl by ChIP-qPCR.This study helps us to understand the function of Runxl in osteoarthritis and provides new clues for targeted osteoarthritis therapy.

In vitro study of nonthermal atmospheric pressure plasma in improving the durability of the dentin–adhesive interface with an etch-and-rinse system

In this study, we employed a nonthermal atmospheric pressure plasma(NTAPP) jet to evaluate the effect of plasma treatment on the durability of resin–dentin bonding under a thermocycling challenge. Furthermore, we assessed the degradation resistance of plasma-treated collagen under a sodium hypochlorite(NaClO) challenge. We assessed the beneficial effect of NTAPP treatment on the acid-etched dentin–bonding interface by testing the micro-tensile bond strength and examining the morphology. We found that the immediate bonding strength of the dentin significantly increased after NTAPP treatment. Compared with the control group, NTAPP resulted in a more prominent effect on the bonding durability of the dentin–adhesive interface after treatment for 5 or 10 s. Simultaneously, the mechanical strength of dentin collagen under the NaClO challenge was improved. Our results indicate that, in optimal conditions, NTAPP could be a promising method to protect dentin collagen and to improve the bonding durability between dentin and etch-and-rinse adhesives.

Automated classification of dual channel dental imaging of auto-fluorescence and white lightby convolutional neural networks

Prevention is the most effective way to reduce dental caries.In order to provide a simple way to achieve oral healthcare direction in daily life,dual Channel,portable dental Imaging system that combine white light with autofluorescence techniques was established,and then,a group of volunteers were recruited,7200 tooth pictures of different dental caries stage and dental plaque were taken and collected.In this work,a customized Convolutional Neural Networks(CNNs)have been designed to classify dental image with early stage caries and dental plaque.Eighty percentage(n=6000)of the pictures taken were used to supervised training of the CNNs based on the experienced dentists'advice and the rest 20%(n=1200)were used to a test dataset to test the trained CNNs.The accuracy,sensitivity and specificity were calculated to evaluate perfor-mance of the CNNs.The accuracy for the early stage caries and dental plaque were 95.3%and 95.9%,respectively.These results shown that the designed image system combined the cus-tomized CNNs that could automatically and efficiently find early caries and dental plaque on occlusal,lingual and buccal surfaces.Therefore,this will provide a novel approach to dental caries prevention for everyone in daily life.

Efficacy of two calcium phosphate pastes on the remineralization of artificial caries: a randomized controlled double-blind in situ study

To test the efficacy of two calcium phosphate pastes compared to that of fluoride toothpaste on remineralizing artificial caries in situ, this study had a double-blind crossover in situ design, involving three experimental phases of 14 days each, with an 8-day washout period between phases. Nine healthy subjects participated in the study. The subjects wore removable palatal appliances mounted with six human enamel slabs with artificial caries lesions, and in each of the experimental phases, used one of the following methods two times/day： group A, brushing with 1.0 g of Colgate Regular Flavor, followed by applying 0.25 g of Tooth Mousse Plus; group B, brushing with 0.25 g of Clinpro Tooth Crbme; and group C, brushing with 1.0 g of Colgate Regular Flavor. After 14 days, the enamel slabs （54 slabs/ group） were embedded in resin, sectioned and examined with a polarized-light microscope, and the lesion areas were quantified using Image-Pro Plus. All experimental groups showed a significant reduction in lesion area compared to the initial lesion area （paired t-test, P〈O.O01）. The mean reduction in lesion area of Groups A, B and C were （0.029__.0.010）, （0.030_＋0.009） and （0.027_＋0.009） mm2, respectively. There were no statistical differences between groups （KruskaI-Wallis test, P〉0.05）. All three groups remineralized the enamel slab lesions, indicating model sensitivity to fluoride. Given the differences in usage amounts and treated regimens, Clinpro Tooth Crbme provided similar benefits to the fluoride toothpaste; however, no additional benefit of Tooth Mousse Plus was observed when used in conjunction with the fluoride toothpaste.

Meeting report:a hard look at the state of enamel research

The Encouraging Novel Amelogenesis Models and Ex vivo cell Lines （ENAMEL） Development workshop was held on 23 June 2017 at the Bethesda headquarters of the National institute of Dental and Craniofacial Research （NIDCR）. Discussion topics included model organisms, stem cells/cell lines, and tissues/3D cell culture/organoids. Scientists from a number of disciplines, representing institutions from across the United States, gathered to discuss advances in our understanding of enamel, as well as future directions for the field.

Non-surgical management of dens invaginatus type IIIB in maxillary lateral incisor with three root canals and 6-year follow-up:A case report and review of literature

BACKGROUND The presence of dens invaginatus(DI)complicates treatment of any tooth,from diagnosis to access cavity and biomechanical preparation and obturation.Reports of successful non-surgical management of DI type IIIB in maxillary lateral incisor are rare.Here,we report such a case,with three root canals and a long follow-up.CASE SUMMARY A 13-year-old female patient presented with mild pain in the maxillary right lateral incisor(#7)for 10-15 d.On examination,the tooth was slightly rotated,with slight tenderness on percussion and grade I mobility but with no caries,pockets or restorations and non-vital pulp(via vitality tests).Radiographic examination revealed unusual configuration of the tooth’s root canals,with an enamel-lined invagination extending to the apex,suggesting the possibility of DI Oehler’s type IIIB and a periapical radiolucency.Widening the access cavity lingually revealed one distinct buccal orifice and two distinct palatal orifices;under higher magnification of a dental operating microscope(DOM),the mesio palatal and disto-palatal orifices were observed as connected by a C-shaped groove.The root canals were prepared with hand K-files following a step-back technique,and obturated using a combination technique of lateral condensation and vertical compaction.At the 6-year follow-up,the patient was asymptomatic,and the periapical radiography displayed significant healing around the apical end of the root.CONCLUSION Proper knowledge of unusual root canal anatomy is required in treating DI.Conventional methods of root canal treatment can successfully resolve such complex cases,facilitated by DOM and cone-beam computed tomography.