Dentoalveolar surgery is an important branch of oral and maxillofacial surgery. Extraction of impacted mandibular third molars is common treatment in dentoalveolar surgery. The classification of impacted mandibular third molars includes vertical impaction, horizontal impaction, mesial impaction and distal impaction. Combining preoperative imaging examination with oral inspection of the impacted third molars to make resistance analysis, we can effectively improve extraction efficiency, shorten operation time and avoid complications of extraction. This article combines clinical cases to elaborate on the new concept of standardized and minimally invasive extraction of impacted mandibular third molars in order to provide help for clinicians.

Objective To study and discuss the degradation performance of SF/PVA/n-HA and PVA/n-HA scaffolds, we used 3D printing technology to print silk fibroin/polyvinyl alcohol/nanohydroxyapatite scaffold and polyvinyl alcohol/nanohydroxyapatite scaffold with cell membrane and then replanted them in animals. Methods The SF/PVA/n-HA scaffold and PVA/n-HA scaffold were respectively implanted into the mandible of sheep. The experimental animals were sacrificed at 1, 2, and 3 months after surgery. The mandible where the stent was located was taken out, and radiographic observation, HE staining observation, and realtime quantitative PCR（RT-PCR） detection were performed to explore the difference between the degradation of the two stents in vivo and the relationship between degradation related factors. Results ①Radiographic results:the lowdensity shadows at the bone defect in the SF/PVA/n-HA stent group and PVA/n-HA stent reduced, and the lowdensity shadows in the SF/PVA/n-HA stent group were smaller. The highdensity shadow area is also more obvious in the SF/PVA/n-HA stent group than the PVA/n-HA stent group. ② HE staining results:in the SF/PVA/n-HA scaffold group, some stent remnants were still visible in the first two months, and inflammatory cells were detected around the scaffold in the first two months. The inflammation gradually subsided at the end of the third month and obvious bone lacuna was seen. ③RT-PCR:comparing different materials at the same time, the SF/PVA/n-HA stent group and PVA/n-HA stent group were compared with the patch group respectively (P<0.05). The differences were statistically significant. Comparing the SF/PVA/n-HA stent group with the PVA/n-HA scaffold group, the expression trends of the four factors IL-1, IL-6, M-CSF, and NFATc1 were similar. At 1, 2 months after surgery, the mRNA expression levels of the four factors in the SF/PVA/n-HA scaffold group were higher than those in the PVA/n-HA scaffold group; at 3 months after surgery, the mRNA expression levels of the four factors in the SF/PVA/n-HA scaffold group were lower than the PVA/n-HA stent group (P<0.05). Conclusion The SF/PVA/n-HA scaffold has certain degradation properties, and during the degradation process, it can promote the expression of osteoclastrelated factors IL-1, IL-6, M-CSF, and NFATc1.

Objective To evaluate the dimensional stability and healing of extraction sites grafted with DBBM and allografts mixed with different proportion of cancellous and cortical bone in the extraction site preservation, as well as to assess osseointegration after implantation. Methods The second, third and fourth mandible premolars of two adult male beagle dogs were extracted. A total of twelve teeth (24 extraction sockets) were randomly divided into four groups. Group A, blank group, natural healing; group B, C, D were filled with allograft 1 (cancellous bone∶cortical bone∶DBM weight ratio was 0∶9∶1), allograft 2 (cancellous bone∶cortical bone∶DBM weight ratio was 3∶6∶1) and DBBM respectively. A 2mmdiameter core biopsy was taken from the distal socket of each tooth site and implant was inserted 3 months after grafting.The changes of height and width of the alveolar ridge were compared 3 and 6 months after operation. Histomorphometric analysis was performed to determine percentage of vital bone, residual graft particles, and connective tissue (CT)/other nonbone components. Bonetoimplant contacts were measured 3 months after implantation. Results The height of the midbuccal alveolar ridge and the buccolingual width were reduced 3 and 6 months after operation. The reduction of height and width of four groups were statistically significant different through ANOVA oneway analysis(P<0.05). There was a statistically significant difference of height and width between group A and the other three groups (P<0.05). There was no signficant differencein percentage of new bone between groups was. The BIC was significant higher in group B, C, D than in group A. There was no statistically significant difference between group B,C,D. Conclusion The application of allografts and DBBM in the preservation of extraction sites has a positive effect on preserving the alveolar crest, as well as promoting the boneimplant osseointegration.

Objective To study the effect of necroptosis on the expression of IL-1β and IL-17 in periodontal membrane during orthodontic tooth movement in rats. Methods Eighty male SD rats were randomly divided into four groups:control group, inhibitor group, force group and force+inhibitor group. Rats in each group were randomly divided into 1, 3, 5, 7 and 14 d five subgroups according to the modeling time. Rats were used to establish models for orthodontic force applied on the left side of the maxillary first molars. The moving distance of the maxillary first molar was measured with a vernier caliper. HE staining was used to observe the pathological changes of periodontal tissue on the pressure side. The periodontal tissues on the pressure side of the rats were collected and the expression of IL-1β and IL-17 was detected by immunohistochemical staining. Results The expressions of IL-1β and IL-17 in the pressure side of periodontal tissue were firstly increased and then decreased as the time of stress treatment increased (P<0.05). Compared with the force group at the same time point, the positive expression of IL-1β and IL-17 in the periodontal tissues of the force+inhibitor group was downregulated (P<0.05). Conclusion Inhibition of necroptosis can downregulate the secretion of inflammatory factors. Necroptosis may be involved in the death of periodontal cells in the pressure side of tooth movement and affect the differentiation of osteoclasts and orthodontic tooth movement.

Objective To compare the central positioning ability of three kinds of NiTi rotary files, ORODEKA PLEX 2.0, ProTaper and WaveOne Gold，when preparing curved resin to simulate root canals. Methods Thirty singlecurved clear resin canal blocks were divided into 3 groups with 10 in each group randomly. Three kinds of NiTi rotary files were used to prepare the canal blocks according to instructions given by manufacturers. After filling with black and red ink before and after preparation, the root canal images were obtained under stereoscopic microscope, and the overlapping images were obtained by Adobe Photoshop CC 2018 and ImageView. Taking the apical foramen as the center, 10 measuring points were set up, and the difference of resin removal from the inner and outer walls of the root canal at each point were recorded. The central positioning ability of the three kinds of NiTi rotary files was measured. Oneway analysis of variance, SNK test and KruskalWallis test were used to do data analysis. Results Center positioning ability：there was no significant difference between the three groups at 1 mm and 9 mm（P＞0.05）. The center positioning ability of ORODEKA PLEX2.0 group and WaveOne Gold group was better than that of ProTaper group at 2 mm（P<0.05）. At 3 mm, 5-7 mm, ORODEKA PLEX2.0 group was better than WaveOne Gold group and ProTaper group（P<0.05）. WaveOne Gold group had the worst center positioning ability at 4 mm and 10 mm（P<0.05）. ORODEKA PLEX2.0 group had better center positioning ability at 8 mm. Conclusion The experimental results show that ORODEKA PLEX 2.0 group has better central positioning ability than the other two nickeltitanium instruments. The three groups can conform to the original shape of the root canal when preparing the curved canal with nickeltitanium instrument, and all can maintain good shape of the root canal.

Objective To evaluate the application value of periodontal endoscopy in the diagnosis of vertical root fracture (VRF) by comparing the accuracy of periodontal endoscopy and CBCT in the diagnosis of VRF with deep periodontal pocket. Methods Fiftysix teeth with high suspicion of VRF based on clinical symptoms but undiagnosed by periapical film were included. CBCT and periodontal endoscopy were performed respectively to evaluate the diagnostic effects on VRF. Results In the diagnosis of the 56 suspected VRF teeth, the correct index of periodontal endoscopy was 83.7%, and the correct index of CBCT was 53.1%. Among them, in the diagnosis of 43 suspected VRF teeth after root canal treatment, the correct index of periodontal endoscopy was 92.3%, while that of CBCT was only 41.0%. There was significant difference between the two methods in the diagnosis of VRF(P<0.05). Conclusion Periodontal endoscopy is more accurate than CBCT in diagnosing concealed VRF with deep periodontal pocket, especially for VRF teeth after root canal treatment, which provides a reliable examination method for clinicians.

Objective To compare the application of attachments made of traditional resin and flowable resin in invisalign treatment without brackets. Methods Twentytwo patients, 232 attachments in total were selected from the Stomatology Hospital of Lianyungang from 2019 to 2020. Operation time was compared; defect, shedding rate of two kinds of attachments, differences in different shapes of attachments and different positions of the tooth were compared at the time of bonding and one year after the bonding. Results The operation time of attachments made of flowable resin was shorter than traditional resin; the difference was statistically significant (P<0.05). At the time of bonding and one year after bonding, the shedding rate of the optimized attachment was lower than that of the traditional attachment; difference was statistically significant (P<0.05). At the time of bonding, the shedding rate of the anterior attachment was lower than that of the posterior attachment; difference was statistically significant (P<0.05). Conclusion In invisalign treatment without brackets, attachments made of flowable resins are suitable for the clinic; the optimized attachment is more suitable for the clinic than the traditional attachment; when the attachments are bonded, the template for posterior area can be cut to reduce the loss of the attachment.

Objective To explore clinical effect of moving the third permanent molar to replace the damaged first or second permanent molar, and to investigate the health of the pulp, root and periodontal and compare the difference among three treatment methods, in order to provide important clinical reference. Methods A total of 36 patients and 48 impacted third molars were included. All the teeth were randomly divided into three groups with sixteen in each group, group A:implant anchorage assisted cantilever, group B:implant in the retromolar area and group C:fishhook wire. Changes of the pulp, root and alveolar bone and three different orthodontic methods were compared and analyzed. Results The results showed that the root length of the third permanent molar was absorbed, and the difference was statistically significant (P<0.05). The resorption degree of the distal roots was slightly higher than that of the mesial roots, but the difference was not statistically significant (P＞0.05). The height of alveolar bone increased significantly after treatment, and the difference was statistically significant (P<0.05). No periodontal pocket was found in the periodontal exploration after treatment, and the depth of gingival crevicular was statistically significant compared with that of the contralateral teeth (P<0.05). Vitality test was performed to all teeth after treatment and they all gave response of being vital. The results of pairwise comparison between the three groups showed that the reduction of root length and the increase of alveolar bone height had no significant difference (P＞0.05). The treatment time of the implants in the retromolar area was the shortest, and the difference was statistically significant (P<0.05). Conclusion It is practicable to move the mandibular third molar to close the missing gap of the first or second molar. It is necessary to pay attention to the root absorption and periodontal health during clinical treatment. The occlusal trauma should be checked in time.

Objective To explore the understanding of conservative treatment and the choice of treatment strategies of acute anterior disc displacement without reduction. Methods Twenty patients of acute anterior disc displacement without reduction with limited opening from May, 2018 to May, 2020 in the Department of Temporomandibular Joint, Nanjing Stomatological Hospital Medical School of Nanjing University, were included in the study. All patients received mandibular manipulation followed by occlusal splint therapy. After 3 months, the joint disc reduction and maximum active mouth opening of all patients were evaluated. SPSS 24.0 was used to test and analyze the data. Results The maximum active mouth opening of 20 patients was significantly improved, increasing from (27.15±5.91) mm to (41.35±4.82) mm; after treatment, MRI showed 13 cases (65%) of joint disc reduction in 20 patients, and 7 cases (35%) still had displacement without reduction. The difference between the maximum active mouth opening and the reduction of the joint disc after 3 months of treatment was statistically significant. Conclusion Mandibular manipulation combined with stabilization splint treatment of acute anterior disc displacement without reduction can effectively restore patients' mouth opening, improve joint function, and have a significant effect on the restoration of disccondyle relationship.

Objective To investigate the clinical effect of transalveolar maxillary sinus floor elevation and simultaneous implant implantation with different residual bone height(RBH) in maxillary posterior region using concentrated growth factors (CGF). Methods From January 2014 to December 2017, 38 patients with insufficient height of residual alveolar bone in maxillary posterior region were included and divided into four groups according to different RBH and whether CGF was used during operation. Group A:3 mm ≤ RBH < 5 mm, 7 cases were implanted with implants after maxillary sinus elevation. Group B:3 mm ≤ RBH < 5 mm, 9 cases were implanted with implants after maxillary sinus elevation + CGF. Group C:5 mm ≤ RBH < 8 mm, 12 cases were implanted with implants after maxillary sinus elevation. Group D:5 mm ≤ RBH < 8 mm, 10 cases were implanted with implants after maxillary sinus elevation + CGF. CBCT was reexamined immediately after implantation, 6 months, 12 months and 24 months after implantation to check changes of bone level of implant neck margin, bone height after sinus floor elevation, osseointegration and new bone formation of implant, peri implant inflammation, stability of implant and prosthesis, and complications of implant denture. Results There was no inflammatory reaction or perforation of maxillary sinus mucosa in 38 cases. The implant bone union was good. The implant and prosthesis were stable after permanent restoration, and the level of implant neck bone was stable one year after operation. There were significant differences in ISQ between group A and group B, group C and group D at 4 and 6 months after operation (P<0.05). There was significant difference in the amount of maxillary sinus floor bone lifting between group A and group B, group C and group D during postoperative and 24 months of followup (P<0.05), and the amount of maxillary sinus floor bone lifting in group B and group D was higher than that in group A and group C respectively. Conclusion When 3 mm ≤ RBH < 8 mm, good osseointegration can be obtained after maxillary sinus lifting and simultaneous implantation. The application of CGF during operation can promote the formation of new bone, accelerate osseointegration, effectively increase the height of sinus floor bone and enhance the stability of implant.

Objective To explore the association between periodontitis and inflammatory bowel diseases. Methods Chinese and English journal databases such as Medline, Pubmed, EMBASE, CBM, CNKI and VIP were searched electronically and examined by hand. The literatures on the association between periodontitis and inflammatory bowel diseases were collected through systematic literature screening and data extraction. Metaanalysis was performed by Revman 5.3.3. Results Nine English trials met the inclusion criteria, including 35 129 participants, 7 676 of whom with inflammatory bowel diseases. The result of Metaanalysis showed that patients with inflammatory bowel diseases（OR=1.66，Z=13.21，P<0.000 01）, Crohn's disease（OR=1.60，Z=11.92，P<0.000 01）or ulcerative colitis（OR=3.33，Z=7.58，P<0.000 01） were more likely to develop chronic periodontitis. Conclusion There is a significant correlation between periodontitis and inflammatory bowel diseases such as Crohn's disease and ulcerative colitis.

Radicular cysts are one of the most common odontogenic cysts of jaws. However, those arising from primary teeth are rare. The case of an 8yearold patient with a massive mandibular radicular cyst involving several primary teeth and permanent embryos is reported in this paper. In addition, we also discuss its pathogenesis, treatment and prevention.

The degree of midpalatal suture calcification varies greatly with age. The clinical use of physiological age as the basis for arch expansion decision is often inaccurate. Angelieri proposed a personalized midpalatal suture maturity grading system based on CBCT, which is conducive to accurately obtaining the degree of midpalatal suture calcification, choosing the most suitable and effective personalized treatment method for the patient, improving the success rate of arch expansion and avoiding unnecessary surgical operations. Its application also has certain limitations. This article discusses Angelieri staging in clinical orthodontic expansion. The domestic and foreign research and application of arch expansion decisionmaking are reviewed.

Oxidative stress is considered to be related to the pathogenesis and malignant transformation of oral potential malignant diseases (OPMD). Antioxidant micronutrients are potential in preventing, inhibiting and reversing the occurrence of oral cancer.Therefore, maintaining an appropriate range of antioxidant micronutrient concentrations is of important significance for the treatment of related diseases. This article reviewed the research progress on the antioxidant mechanism of micronutrients and the occurrence, development and treatment of OPMD.

Neural cell adhesion molecule l（NCAM1） is a calcium independent intercellular adhesion molecule, which can mediate the interaction of celltocell and celltomatrix. Moreover, it plays an important role in the development of nervous system, the regulation of immune cell function, the recognition and metastasis of cells, and the invasion and growth of tumor. In recent years, studies have shown that NCAM1 may have being involved in the pathogenesis and cancerization of oral lichen planus(OLP).This article will review the research progress on NCAM1 in the following aspects:the structure, function, and regulation of NCAM1, the abnormal expression of NCAM1 in OLP, the possible role of NCAM1 in the occurrence and development of OLP, and NCAM1 and cancerization of OLP.

Exosomes are small membranous vesicles that contain large amounts of proteins, lipids, genetic materials and metabolites from parent cells. They can transmit biologically active ingredients to achieve celltocell communication and signal transduction, thereby regulating the function of recipient cells. Oral squamous carcinoma cancer (OSCC) is the most common malignant tumor in the oral and maxillofacial region. Current studies have confirmed that exosomes are involved in the occurrence, development, invasion, metastasis, and chemical resistance of OSCC, and play an important role in the diagnosis, treatment, and prognosis evaluation of OSCC. Therefore, understanding the internal mechanism of exosomes promoting the occurrence, development and metastasis of cancer in OSCC is particularly important for improving the treatment effect of the disease and increasing survival rate. This article reviews the research progress of the role of exosomes in promoting the occurrence, development, invasion, metastasis and chemotherapy resistance of OSCC.

As one of the targets of orthodontic treatment, orthodontists need to pay close attention to the tooth mesiodistal angulation which refers to the angulation between the long axis of the tooth and the vertical line of the occlusal plane before or after treatment. Nowadays, major clinical methods of measuring mesiodistal angulation include panoramic radiography and conebeam computed tomography (CBCT), which have different characteristics. This article is to review the progress of these two methods of evaluating tooth mesiodistal angulation and their accuracy.

Runt-related transcription factor 2 (Runx2) is a protein transcription factor, which is involved in a variety of biological processes. In recent years, studies have shown that Runx2 is a key regulator of condylar cartilage development, involving in the process of condylar cartilage proliferation and differentiation, functional remodeling and pathological changes. This article reviews the effects of Runx2 on the development, remodeling and joint diseases of mandibular condylar cartilage.

Skeletal Class Ⅱ malocclusion is common in children and adolescents in our country, mainly for the mandibular retrusion, which affects both function and appearance. Functional orthodontics is an important means of treating skeletal Class Ⅱ malocclusion at growth and development stages, improving the occlusal relationship and appearance, meanwhile avoiding inferiority complex among teenagers. This review summarized the anatomical structure changes of the temporomandibular joint through imaging analysis, believing that the improvement of occlusal relationship was due to the adaptive remodeling of the temporomandibular joint, and functional orthodontics was not a risk factor of temporomandibular joint disorders.

Regenerative endodontic therapy is widely used in the treatment of pulp necrosis and periapical periodontitis of young permanent teeth, and the overall success rate is high. However, with the extension of observation time, more and more failed cases gradually appear. Regenerative endodontic therapy is a technically sensitive treatment method. This paper aims to probe into the common factors affecting the prognosis of regenerative endodontic therapy and provide suggestions for operators to avoid adverse factors in future treatment.