[Abstract ] PURPOSE：we study the effects of the combined application of NAF and EGCG on the growth and reproduction of Streptococcus mutans there by inhibiting the occurrence and development of dental caries. Methods: The minimum inhibitory concentration (MIC) of EGCG or NAF against Streptococcus mutans was determined by microdilution method. The potential synergistic/antagonistic effects of the NaF/EGCG combination on the growth of Streptococcus mutans was determined by checkerboard microdilution assays as described previously . Cell growth was examined by OD600 nm. The fractional inhibitory concentration (FIC) was defined as the ratio of the minimum inhibitory concentration (MIC) of an agent used in combination to the MIC of the agent used alone. Results : EGCG inhibited growth of Streptococcus mutans planktonic cells at an MIC of 100ppm and NAF inhibited growth of Streptococcus mutans planktonic cells at an MIC of 500ppm. The fraction of inhibitory concentration (ΣFIC) of the NAF/EGCG combination against Streptococcus mutans was 0.375, indicating a synergistic effect of these 2 agents against Streptococcus mutans planktonic culture. Conclusions: It is shown that the combined effect of NAF and EGCG has a synergistic inhibitory effect on Streptococcus mutans planktonic cells. EGCG can cooperate with NAF to enhance the antibacterial effect of sodium fluoride, thus reducing the toxic effect of NAF , and preventing bacteria from producing fluorine-resistant properties.

Objective　 To compare the primary stability, osseointegration and the new bone formation ability of self-tapping and non-self-tapping implants in immediate implant, and provide basis for clinical application of self-tapping implants. Methods Thirty-six healthy male adult Beagle dogs with well-developed body were selected and numbered randomly as No. 1-36. After minimally invasive tooth extraction, immediate implant placement was performed. Two self-tapping implants (BLE, TLE) and two non-self-tapping implants (BL, TL) were implanted in the mandibular of each experimental dog. Thirty-six Beagle dogs were sacrificed 4, 8, and 12 weeks after implant placement. The insertion torque analysis of all implanted implants was performed, and the primary stability and the long-term stability of the self-tapping dental implants were analyzed using the resonance Frequency Analysis. Micro-CT was used to observe and calculate the bone volume fraction (bone volume/total volume, BV/TV, %) and number of trabeculae and trabecular spacing to analyze the bone remodeling around the implant. The fluorescent marker tetracycline hydrochloride was used to trace the bone remodeling. Laser confocal microscope was used to observe, analyze and compare the new bone area of self-tapping implants and non-self-tapping implants. Results Analyzing the insertion torque and ISQ value during implant placement, the results of the self-tapping group were better than those of the non-self-tapping group (p<0.05). The ISQ values of 4 weeks, 8 weeks, and 12 weeks after implantation were significantly higher in the BLE group than in the BL group (p<0.05). The TLE group was significantly higher than the TL group 4 weeks and 8 weeks after implantation. However, 12 weeks after implantation, the TLE group was basically consistent with the TL group. Bone volume fraction and new bone area of self-tapping group were both superior to non-self-tapping group (p<0.05). Conclusion In immediate implantation, the primary stability and the osseointegration ability of self-tapping implants are better than those of non-self-tapping implants, while new bone formation ability is a little stronger .

Objective: To compare the stress of implant and cortical bone and the deformation of titanium framework, using different design of All-on-Four and zygomatic implants with various thickness of cortical bone , via finite element analysis in the maxillary edentulous with severe insufficient vertical bone in the posterior region. Methods: An CBCT data of an maxillary edentulous was selected to establish four different cortical bone thickness models. The model also included implant, abutment and titanium framework. The stress of the implant and cortical bone and the deformation of the titanium framework were calculated with a vertical load of 200N bilaterally in the posterior region. Results: With the increase of cortical bone thickness, the stress of implant and cortical bone and the deformation of the titanium framework gradually decreased. In the All-on-Four model. When the thickness of cortical bone increased from 0.5mm to 1.5mm, the stress and the deformation decreased significantly while the thickness of cortical bone increased from 1.5mm to 2.0mm, the decrease tended to level off. Both of the stress and the deformation had reached a very low level at 1.5mm cortical thickness point.However, in zygomatic implant model ,the change appeared slightly from various cortical bone thickness. Being compared with each other, the stress of implant and cortical bone and the deformation of titanium framework in the zygomatic implant model are smaller than those in the All-on-Four model, and there was a statistical difference in the stress of cortical bone and the deformation of titanium framework at the sites of second premolar and lateral incisor (P<0.05). Conclusion: For maxillary edentulous with insufficient vertical bone in the posterior region, the increase in the thickness of cortical bone is beneficial to reduce the stress distribution of implant and cortical bone and deformation of titanium framework. The zygomatic implant is a more suitable design in the thin cortical bone(<1.5mm). If the cortical bone is thick（≥1.5mm）, though the zygomatic implant model is better than the All-on-Four model, the distribution of the stress and deformation decrease significantly in the All-on-Four model. Thus, we can take the All-on-Four into consideration for patients in this condition.

Objective　 To establish a three-dimensional (3D) model of maxillary molar distalization with clear aligners, analyze the initial displacement and stress distribution of the orthodontic system and find the optimal force for anterior anchorage. Methods A 3D Finite Element (FE) model of maxillary molars distalization including the teeth, periodontal ligament (PDL), alveolar bone and clear aligners were conducted to analyze the effects of molar distalization and different forces on Class II elastics. Results The distal movement of the second molar was accompanied by distal inclination, distal rotation, extrusion and lingual inclination. The anterior teeth showed labial inclination and depression, and the displacement was inversely proportional to the distance from the abutment teeth. All the anterior teeth moved backward in every group of Class II elastic. Except for applying a force of 300g on the aligner, all stress didn’t exceed the maximum magnitude for the periodontal tissue. In addition, the stress concentration in the second molar and the displacement peak was less than the elastic and tensile limit of the aligner material. Conclusion Molar distalization with clear aligners can’t completely induce bodily movement, and the anterior teeth require additional anchorage control. A Class II elastic of 100g is sufficient to enhance anterior anchorage, while applying a force of 300g on the aligner should be avoided for the health of periodontal tissues.

Objective To observe and study the clinical effect of Pingyangmycin injection under robot assisted localization in the treatment of vascular malformations in oral and maxillofacial region. Methods A total of 20 patients with vascular malformations in oral, maxillofacial and cervical region who had complete clinical data in our hospital from 2017 to 2021 were collected and analyzed retrospectively. All patients were treated with Pingyangmycin injection assisted by robot localization. The prognosis of patients was observed and recorded. The changes of tumor size were evaluated by maxillofacial enhanced CT or MRI as the evaluation index of curative effect. Results All the 20 patients successfully completed the operation with the assistance of robot. The clinical effective rate was 95%, and there was no adverse drug reaction after the operation. This technique has good safety, gives full play to the advantages of accurate robot positioning, enhances the interaction area between drugs and vascular malformation endothelial cells by using the method of needle withdrawal administration, gives full play to the role of drug therapy, and shortens the interval time of Pingyangmycin drug injection. Conclusion Robot assisted localization and Pingyangmycin drug injection in the treatment of vascular malformation is safe and effective, with small trauma and high precision, which can accept repeatable injection treatment and achieve the maximum preservation of the original organ shape and function, and has high clinical application value.

Objective　 To investigate the clinical features, diagnosis, surgical management as well as the prognosis of intraparotid facial nerve schwannoma. Methods 17 cases of intraparotid facial nerve schwannoma from June 1994 to June 2019 were collected from the First People's Hospital of Changzhou (the Third Affiliated Hospital of Soochow University) in oral and maxillofacial surgery department, Information on their age, sex, imaging examination, treatment, relationship between tumor and facial nerve, and impairment of facial nerve function was included. SPASS17.0 software package was used for Fisher's exact test. Results 3 patients (17.6%) had facial paralysis or other neural symptoms and 6 patients (35.29%) were diagnosed by B ultrasound, CT, MRI or FNAC (fine needle aspiration cytology examination) before operation. In one case, nerve grafting was performed after nerve transection because it was impossible to separate the facial nerve from the tumor during the operation. In other 16 cases, stripping surgery and intracapsular enucleation surgery were performed respectively. 10 cases (58.82%) had symptoms of facial nerve impairment postoperatively. Symptoms of nerve injury disappeared in 3 patients, and improved in 7 patients after follow-up for more than one year. The effective rate of preserving facial function was 28.57% (2/7) in stripping surgery group, and the rate was 88.89%（8/9) in Intracapsular enucleation surgery group. All patients were followed up for 12 months to 220 months, and no recurrence and malignant transformation were found. Conclusion Intraparotid facial nerve schwannoma is rare. The diagnosis of schwannoma in parotid region is difficult and needs to be confirmed by pathology. Intracapsular enucleation surgery can protect facial nerve to the greatest extent and is the best surgical scheme for intraparotid facial nerve schwannoma.

Objective　 To investigate the clinical application of multimodal mixed reality technology in the treatment of craniofacial, head and neck tumor, thus providing a reference for the treatment of tumor, enhancing the treatment efficiency of the disease, and improving the prognosis of patients. Methods Forty-six cases of craniofacial head and neck tumor treated in our hospital were analyzed retrospectively, who were divided into two groups. The patients in the control group accepted the examination of magnetic resonance imaging, computed tomography, and then they underwent surgery based on these traditional two-dimensional imaging data. Patients in the observation group used Mimics software for data processing and fusion, and the three-dimensional model was constructed by mixed reality (MR) technology, which assisted preoperative analysis and intraoperative guidance. The communication time, satisfaction, and anxiety of the patients in each group before operation were collected. The operation time, amount of bleeding during operation, postoperative complications and recovery were recorded. Results Compared with the control group, there was less preoperative communication time, higher level of satisfaction, less anxiety, shorter operation duration, and less intraoperative blood loss in the observation group. The differences were statistically significant (P<0.05). In addition, 11 patients in the control group had postoperative complications, while only 4 patients in the observation group occurred. As for rehabilitation, there were obvious differences in language communication ability, activity of daily living and prognostic scores between two groups (P<0.05). All rehabilitation scores in the observation group were better than the control group. Conclusion The status of craniofacial head, and neck tumors can be fully demonstrated by multimodal MR imaging technology, which helps to reduce the time of preoperative communication and relieve anxiety, reduce the occurrence of postoperative complications, improve patient prognosis and promote patient recovery. The new technology can be further promoted in clinic.

[Objective]The aims of this study were to measure the buccolingual alveolar bone thickness between the maxillary central incisors by using cone beam computed tomography and to explore the optimal insertion height and angle for orthodontic mini-implant placement. [Material and Methods] Three-dimensional reconstruction was performed on CBCT images of 80 normal persons aged 12-25 years .For each subject ,the buccolingual alveolar bone thickness of 12 insertion paths on the median sagittal plane was measured at four different levels of 14.0,16.0,18.0 and 20.0mm from the reference plane and three angles of 60°,75°, and 90° with the surface of the cortical bone. [Result]Mean buccolingual alveolar bone thickness of every site was greater than 7 mm. At the same height level, the bone thickness is the largest at the angle of 60°, the difference was statistically significant. Male has greater bone thickness than female at most sites. [Conclusion]The orthodontic mini-implant with 6mm length in the bone can be placed between the maxillary central incisors. In clinical application, there was more alveolar bone with the insertion angle of 60°.The insertion height is recommended according to clinical needs and the patient's soft tissue condition.

Objective: To study the relevance of the results of the commonly used indicators of the cephalometric measurement obtained from the three-dimensional (3D) transformation lateral cephalometric radiograph and the three-dimensional cone-beam computed tomography (3D CBCT). Methods: To choose 100 malocclusion patients who fit the inclusion criteria, to do the cephalometric analysis with 2D and 3D methods, and to analyze the difference and the fitting degree between the two methods. Results: The differences between the two cephalometric analysis measurements were statistically significant (P <0.05), 7 indexes had the good fitting and 1 index had the moderate fitting. Objective: To explore preliminarily the application of three-dimensional cephalometric measurement of CBCT by studying the relevance ofthe results of the commonly used indicators of the cephalometric measurement obtained from the three-dimensional (3D) transformation lateral cephalometric radiograph and the three-dimensional cone-beam computed tomography (3D CBCT).Methods: To choose 100 malocclusion patients who fit the inclusion criteria, to do the cephalometric analysis with 2D and 3D methods, and to analyze the difference and the fitting degree between the two methods.Results: The differences between the two cephalometric analysis measurements were statistically significant (P <0.05), 7 indexes had the good fitting and 1 index had the moderate fitting. There was the correlation between the two cephalometric analysis measurements. Conclusion:The results of the commonly used indicators of the cephalometric measurement obtained from the 3D CBCT can reflect the maxillofacial morphology in patients with malocclusion.The establishment of standardized fixed-point and normal value database of three-dimensional cephalometric measurement needs to be further studied and established.

Abstract：　Objective　To analyze the accuracy of superimposition technique of common cephalometric software Methods　A total of 80 patients treated in the Department of Orthodontics in Harbin Medical University from 2010 to 2018 were selected and divided into adolescent group and adult group, each with 40 cases. Cephalograms were taken from each sample before and after treatment. The maxillary and mandibular superimposition was analyzed by Bj?rk structural superimposition method and cephalometric software superimposition method, and the vertical and horizontal displacement and axis rotation of the landmarks of the upper and lower central incisors and the upper and lower first molars were calculated before and after orthodontic treatment. Using SPSS23.0 software, Wilcoxon signed-rank test were used to calculate whether there were differences between the two superimposition methods. Results　There were significant differences between the two methods in the vertical displacement of the upper incisors and molars in the adolescent group (P<0.05), and there was no significant difference between the two methods in the mandibular superimposition(P>0.05). There was no significant difference in the measured values of the two methods in the adult group (P>0.05). Conclusion　The analysis of the superimposition method in the cephalometric software for adolescent patients may result in inaccurate tooth movement information, so it is recommended to use the accurate Bj?rk structural superimposition method. Adult patients can use cephalometric software superimposition technique.

Objective To study the risk factors of wedge-shaped defects. Methods Thirty patients with total 420 maxillary teeth were selected. And the Teetester occlusal analysis system was employed to record premature contact teeth, disocclusion time (DT) and occlusal force through which the risk factors were thus statistically revealed. Results Among the maxillary teeth, premolars occupied 46.49%, which illustrates that the maxillary premolar region is the susceptible area of wedge-shaped defects. Among 64 premature contact teeth, 42 were defected teeth, according to Chi-square statistics, Pearsonχ2=25.732, P<0.001, OR=4.0, 95% Confidence interval (2.282~7.015), which illustrates that premature contact is a risk factor. Moreover, among 26 over disocclusion time teeth, 17 were defected teeth, according to Chi-square statistics, Pearsonχ2=9.285, P<0.05, OR=3.427, 95% Confidence interval (1.489~7.890), which illustrates that disocclusion time is another risk factor. The difference of occlusal force between 41 defected teeth and normal teeth were obvious (P<0.05). And the difference of occlusal force between 43 pairs of deeper defected teeth and lighter defected teeth were obvious (P<0.05) too. Conclusion The maxillary premolar region is the susceptible area of wedge-shaped defects. Premature contact teeth, disocclusion time, and occlusal force are risk factors.

Magnetic nanomaterials have a variety of excellent properties, making it a research hotspot in the field of biomedicine. At present, magnetic nanomaterials have been studied in the diagnosis and treatment of some common oral diseases, including the early diagnosis of oral mucosal disease realized by electrochemical immunization based on magnetic nanomaterials；magnetic nanomaterials added to fiber scaffolds to induce directional differentiation of oral cells so as to achieve bone and tooth regeneration；magnetic nanoparticles used to prevent and cure oral infectious diseases by modifying antibacterial dental materials. This paper reviews the recent progress of magnetic nanomaterials in the diagnosis and treatment of common oral diseases.

In orthodontic clinics, more and more patients have sought orthodontic treatment with the chief complaint of improving facial appearance, but the changes of soft tissue are exactly the most uncertain and difficult to predict compared with dental tissue and bone tissue. The implementation of Visual Treatment Objective (VTO) enables patients to have a more intuitive understanding of the treatment objective, and at the same time improves the predictability and scientificity of the treatment process. In this article, based on Visual Treatment Objective, we review the goal, principle and accuracy of soft tissue prediction in orthodontic treatment.

Missing teeth may result in a functional and aesthetic deficit and have traditionally been replaced with dentures or bridges. Dental implants offer an alternative. They are inserted into the jawbones and used to support dental prostheses. Although dental implants show high survival rates, complications occasionally lead to marginal bone loss which could result in implant failure. So as to facilitate obtaining adequate osseointegration and stability, a large number of implant neck surface characteristics were designed for different bone types and clinical situations. There is, however, a paucity of well-presented reviews addressing the influence of the implant neck design on bone and soft tissue parameters. Thus, in this review, we made a detailed discussion about

Titanium implant is widely used in dental restorations due to its good biocompatibility. It is known to all that implant surface morphology and physicochemical properties have positive effects on the integration of hard and soft tissues which surround implant, and the relevant physicochemical properties will change with surface morphology changing. Through the preparation of bionic nanostructures to perform implant surface modification, peri-implant connective tissue adhesion can be improved, and a specific fiber direction can be formed and so on, which is one of the ways to extend the longevity of implant. In this paper, the effects of titanium surface nanostructures on the fibroblasts biological behavior are reviewed, and the physicochemical characteristics with the change of surface morphology are briefly introduced.

Stabilizing the gingiva margin of the fixed dentures and the implant dentures to avoid gingiva recession is one of the keys to maintaining the long-term effect of aesthetic restoration. Loi proposed the biologically oriented preparation technology (BOPT) in 2008, which can be applied to both fixed dentures and implant dentures in order to thicken the gingiva tissue around the prosthesis, playing an important role in the stability of the gingiva margin. This paper reviews the application and efficacy evaluation of BOPT in both fixed dentures and implant dentures.

A Temporomandibular disorders (TMD) is a general term for a group of musculoskeletal diseases. The main clinical features of TMD are joint pain, articular noise and limited mouth opening. At present, the etiology of TMD is not clear, and it is generally considered as multifactorial. A number of published clinical studies have proved that TMD patients often suffer from sleep disorders, in which the most prevalent manifestation includes sleep-related movement disorders, sleep-related breathing disorders and sleep quality. To further verify the relationship between TMD and sleep disorders, a large number of studies have been carried out. The aim of this study is to analyze the relationships between TMD and sleep disorders by presenting relevant lastest findings. In this paper, the epidemiology, clinical manifestation and treatment of TMD are reviewed to provide new ideas for the etiological analysis and treatment of TMD.

With the aging of the society, the number of edentulous patients is increasing. Currently, fixed implant-supported prostheses have been widely used in the clinic. Previous literatures have compared the occlusion of natural teeth with traditional complete denture. However, the occlusion design of All-on-4 implant prosthesis has been rarely discussed. The occlusion design of All-on-4 was reviewed in this paper, in order to provide references for long-term and stable treatment.