Table of Content

    20 June 2020, Volume 28 Issue 6
    Expert Forum
    Clinical application and new progress of dynamic navigation system in the field of oral implantology
    MAN Yi,ZHOU Nan,YANG Xingmei
    2020, 28(6):  341-348.  DOI: 10.12016/j.issn.2096-1456.2020.06.001
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    Currently, computer-aided implant surgeries include implant placement surgery under the guidance of a dynamic navigation system. With the use of software inherent in the navigation system, doctors can make a preoperative plan including the ideal position of the implant. Then the plan can be accurately transferred to the surgery, during which the real-time condition of the drill and its relationship with the surgical region will be visualized by the surgeon and the drill can be adjusted in a timely manner. Currently the dynamic navigation system is increasingly widely utilized, especially in cases of esthetic zones or surgical sites with important anatomical structures. However, the clinical workflow of the navigation system is complicated, including CBCT taken after the registration device placement, prosthetic-driven 3D design, calibration, registration, navigated borehole preparation and implant placement surgery. Many details should be considered when the device is applied, including implant position design, fixation of the tracking device, registration, and stable borehole preparation under the guidance of dynamic navigation. Therefore, this article introduces the dynamic navigation system into the clinical workflow and evaluates, the effects of the application and the clinical features. The new progress of the navigation system in the field of implantology is demonstrated at the same time, including navigated surgery in fully edentulous arches and in the zygomatic zone. Further improvements in the navigation system in terms of the accuracy and simplification of the workflow are needed in the future.

    Basic Study
    Signal transducer and activator of transcription 3 positively modulates orthodontic tooth movement speed and alveolar bone mass
    ZHANG Cheng,TAO Guiyu,HUANG Li,LV Chunxiao,LI Tiancheng,YIN Xing,ZOU Shujuan
    2020, 28(6):  349-354.  DOI: 10.12016/j.issn.2096-1456.2020.06.002
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    Objective To elucidate the role of signal transducer and activator of transcription 3 on orthodontic tooth movement, aiming at providing evidence for improving orthodontic bone modeling and remodeling. Methods Orthodontic tooth movement (OTM) models were established in 8-week-old Wistar rats, which were divided into 2 groups: the control group (tooth movement) and the test group (tooth movement with local injection of STAT3 inhibitor stattic). Rats were sacrificed on day 7 and 14. Micro-CT scanning was conducted to measure bone volume/tissue volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and bone mineral density (BMD), and the amount of tooth movement of the specimens. The mouse preosteoblastic cell line MC3T3-e1 and mononuclear macrophagic leukemia cell line RAW264.7 were cocultured in Transwell® culture plates and divided into the control group (blank) and the test group (STAT3 inhibitor stattic was added). Alkaline phosphatase (ALP) staining and tartrate-resistant acid phosphatase (TRAP) staining were carried out to reveal osteoblastic and osteoclastic differentiation, respectively. qRT-PCR was performed to evaluate mRNA expression levels of the receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) in the MC3T3-e1 cells. Results Compared with the control group, in the test group, the alveolar bone at the OTM site showed a significant decrease in the BV/TV, Tb.N, Tb.Th, and BMD indexes and a significant increase in Tb.Sp on day 14, while there was no significant difference in the above indexes between the two groups on day 7. The amount of tooth movement was significantly smaller in the test group on day 7 but showed no difference on day 14. ALP staining and TRAP staining revealed weakened osteoblastic and osteoclastic differentiation in the test group. qRT-PCR demonstrated the inhibitor inhibited the mRNA expression of RANKL and OPG and increased the mRNA ratio of RANKL/OPG in osteogenic precursor cells. Conclusion Suppression of STAT3 activation leads to inhibition of both osteoblastic and osteoclastic differentiation, resulting in lowered tooth movement and catabolic effects on alveolar bone. STAT3 may play an important role in orthodontic bone modeling and bone remodeling.

    Effect and mechanism of allicin combined with 5-fluorouracil on proliferation and apoptosis of the MEC-1 cell line in mucoepidermoid carcinoma
    WU Fayin,XU Haili
    2020, 28(6):  355-360.  DOI: 10.12016/j.issn.2096-1456.2020.06.003
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    Objective To investigate the effect and mechanism of allicin combined with 5-FU on proliferation inhibition and apoptosis of the mucoepidermoid carcinoma MEC-1 cell line in mucoepidermoid carcinoma in order to provide the corresponding basis for subsequent clinical drug application. Methods MEC-1 cells in the logarithmic growth phase were randomly divided into control groups and experimental groups. The control groups were PBS groups containing 0.1% DMSO, while the experimental groups were the allicin group, 5-FU group and combined drug group (the allicin combined with the 5-FU group). The proliferation inhibition rates of allicin, 5-FU and allicin combined with 5-FU in MEC-1 cells were detected by the CCK8 method at different concentrations (0, 25, 50, and 75 mg/L) for 24 h, and the IC50 value of allicin and 5-FU after 24 hours was calculated. The apoptotic rate of MEC-1 cells treated with allicin, 5-FU and allicin combined with 5-FU at different concentrations (0, 25, 50, and 75 mg/L) for 24 hours was measured by flow cytometry. The expression of Bax and Bcl-2 protein was determined by Western blot analysis of the IC50 concentration of allicin and 5-FU alone and in combination with MEC-1 cells for 24 hours. Results The growth inhibition rate and apoptosis rate of MEC-1 cells in the combined drug group were higher than those in the allicin group and the 5-FU alone group (P < 0.01). Allicin and 5-FU alone and in combination downregulated Bcl-2 protein and upregulated Bax protein expression, and the combined drug group had the largest ratio of Bax/Bcl-2 (P < 0.05). Conclusion Allicin and 5-FU both alone and in combination can inhibit the proliferation of and induce apoptosis in MEC-1 cells, and allicin can enhance the apoptosis of 5-FU in MEC-1 cells, which may be related to the apoptosis of the mitochondrial pathway.

    Cinical Study
    Clinical effect of platelet-rich fibrin combined with bone substitute in alveolar ridge preservation
    ZHANG Yun,WANG Yanmei,HE Jiacai
    2020, 28(6):  361-366.  DOI: 10.12016/j.issn.2096-1456.2020.06.004
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    Objective To study the clinical outcomes of implanting platelet rich fibrinogen (PRF) mixed with Bio-Oss® in the extraction socket for alveolar ridge preservation and to provide evidence for clinical application. Methods Thirty-six patients who underwent alveolar ridge preservation were enrolled. Thirty-six extraction sites were divided into two groups: PRF mixed with Bio-Oss® group (test group) and Bio-Oss® alone (control group). Bone dimensional changes in height and width were measured by CBCT before and 6 months after surgery, and early soft tissue healing and postoperative pain sensation were evaluated clinically 1 week after surgery. Results There was no significant difference in the alveolar bone height (-1.48 ± 0.40) mm between the test group and the control group. The difference in the alveolar bone width between the test group (-1.09 ± 0.42) mm and the control group (-1.35 ± 0.22) mm was statistically significant (z=-2.63, P=0.01). The postoperative pain score of the test group was 2.39 ± 1.20, and that of the control group was 3.39 ± 1.65, the difference was statistically significant (t=-2.083, P=0.045). There was no significant difference in soft tissue healing between the test group and the control group. Conclusion The use of PRF mixed with Bio-Oss ®in the alveolar ridge preservation procedure can reduce alveolar bone absorption and postoperative pain.

    Clinical analysis of skeletal malocclusion, axial inclination in patients with short root anomaly of the maxillary central incisors
    YANG Yang,YU Zhishuang,DUAN Xiaoyuan,WU Weili,DENG Yi,YAO Ji
    2020, 28(6):  367-371.  DOI: 10.12016/j.issn.2096-1456.2020.06.005
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    Objective To investigate the prevalence and distribution of skeletal malocclusion and axial inclination of the maxillary central incisors in short root anomaly (SRA) patients in Kunming city, to provide some reference and guidance for SRA patients′ clinical diagnosis and treatment and prevention in SRA patients. Methods A total of 1 000 cases were randomly selected from the CBCT database of patients admitted to the author′s hospital from January 2011 to July 2019, and a retrospective analysis was performed. A total of 27 patients with SRA were diagnosed (SRA group).The control group, consisted of 100 randomly selected patients from non-SRA patients. According to the clinical data and cephalometric data, skeletal malocclusion was divided into three subgroups: Class I skeletal malocclusion, Class II skeletal malocclusion and Class Ⅲ skeletal malocclusion. Additionally, the axial inclination of the central incisors was divided into three subgroups: the lingual inclination group, labial inclination group and normal inclination group. The two groups each according to sex, skeletal malocclusion and types of axial inclination of the maxillary central incisors were discussed. Results The prevalence rate of SRA in the selected population was 2.7%, and the prevalence of SRA in females was 3.67% (21/572) , which was higher than that in males by 1.4% (6/428), and was significantly different between sexes (χ2=4.562, P=0.033). There was a significant difference between SRA patients and control group in terms of skeletal malocclusion (χ2=8.710, P=0.013). Class Ⅲ skeletal malocclusion was the main type of skeletal malocclusion in SRA. There was a significant difference between SRA patients and control group in terms of the axial inclination of the maxillary central incisors (χ 2=16.75,P<0.001). Lingual inclination of the maxillary central incisors was the main type of axial inclination of the maxillary central incisors in SRA. Conclusion There is a certain correlation between class Ⅲ skeletal malocclusion and lingual inclination of the maxillary central incisors and SRA, and the root-crown ratio and root shape of these patients should be evaluated before orthodontics are implemented.

    Analysis of crown-root morphology in canines based on cone-beam computed tomography
    AI Yilong,WU Siyuan,ZOU Chen
    2020, 28(6):  372-376.  DOI: 10.12016/j.issn.2096-1456.2020.06.006
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    Objective To compare the morphology of the crown roots of upper and lower canines in patients with skeletal Class Ⅰ, Ⅱ, and Ⅲ malocclusions by CBCT and to provide guidance for the clinical treatment of orthodontics. Methods Randomly selected patients with permanent occlusal malocclusion who had undergone CBCT and X-ray skull lateral radiographs were Classified according to the ANB angle size: group Ⅰ, group Ⅱ, and group Ⅲ. Three-dimensional reconstruction was used to obtain the median sagittal section images of the right upper and lower canines. The crown root angle, crown root deflection distance, and lip tangent angle at the center of the clinical crown were used as indicators for measurement and analysis with the use of AutoCAD software. Results The difference in the crown-root skew distance between different sagittal face types, including upper canines (F=3.335, P=0.042), lower canines (F=3.745, P=0.029) crown root angles and upper canines (F=3.312, P=0.043), and lower canines (F=3.641, P= 0.032), was statistically significant (P < 0.05). The crown root angle of the maxillary canine in group Ⅰ was larger than that in group Ⅱ, and the deflection distance of the crown root was negative and the absolute value was lager in group Ⅰ than in group Ⅱ (P < 0.05). The deflection distance was positive and greater in group Ⅲ than in groups Ⅰ and Ⅱ (P < 0.05). There was no significant difference in the maxillary canine crown-labial tangent angle between the different sagittal facial misalignment groups (P > 0.05). Conclusion Differences in the morphology of canines were found among subjects with skeletal Class Ⅰ, Ⅱ, and Ⅲ malocclusions. The root of the upper canine in Class Ⅰ malocclusions was relatively closer to the labial side of the crown than that in Class Ⅱ malocclusions. The root of the lower canine in Class Ⅲ malocclusions was the closest to the lingual side of the crown among the three Classes.

    Prevention and Treatment Practice
    Idiopathic gingival fibromatosis: a case report and literature review
    ZHANG Limu,LIN Xiaoping
    2020, 28(6):  377-382.  DOI: 10.12016/j.issn.2096-1456.2020.06.007
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    Objective To explore the etiology, clinical manifestations, diagnosis, differential diagnosis and treatment of idiopathic gingival fibromatosis, and to provide references for clinical diagnosis and treatment. Methods The clinical data and related literatures of a case of idiopathicgingival fibroma that occurred in the oral cavity were retrospectively analyzed. Results Total periodontal treatment was performed for the patient, and the gingival morphology was improved after periodontal surgery in the anterior region. Idiopathic gingival fibromatosis is a rare disease characterized by gingival tissue hyperplasia. The etiology and pathogenesis are unknown. The disease can occur in young children. Generally, it occurs after the permanent teeth erupt, and it manifests as extensive gingival hyperplasia, which can affect the entire gingival margin, gingival papilla and attached gingival, and can even reach the membrane-gingival junction. The pathological changes include thickening of the spinous layer of the gingival epithelium, significant increases in the epithelial styloid process, increases in the connective tissue volume, and filling with large collagen fiber bundles and a large number of fibroblasts. The blood vessels are relatively small, and inflammation is not obvious. Clinically, this disease needs to be distinguished from drug-induced gingival hyperplasia and chronic gingivitis with hyperplasia as the main manifestation. At present, the treatment of idiopathic gingival fibromatosis is mainly gingival angioplasty. The disease easily relapses after surgery. The recurrence rate is related to the quality of oral hygiene. After recurrence, it can be treated again. Conclusion Idiopathic gingival fibromatosis is relatively rare, and the diagnosis mainly depends on the history of inquiry, clinical manifestations and pathological examination. The treatment is mainly surgical resection, and future research should focus on finding a more effective treatment.

    Review Articles
    Biomimetic remineralization of dentin
    SONG Qun,LIU Xiaochen,MA Yuxuan,WANG Chenyu,JIAO Kai,NIU Lina
    2020, 28(6):  383-389.  DOI: 10.12016/j.issn.2096-1456.2020.06.008
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    In recent years, due to precise control of the amorphous mineral precursor in the demineralization of dentine collagen fibers in orderly deposition, forming apatite crystals similar to the natural mineralized dentin, the bottom-up remineralization approach which does not depend on the existence of seed crystallites, dentin biomimetic mineralization techniques gradually become a hotspot in the research field of restoration of demineralized dentin caused by dental caries. This paper reviews the changing concepts and practices of the remineralization of demineralized dentin, emphasizing biomimetic remineralization studies. The results of the literature review show that the traditional dentin remineralization method is usually a disordered mixture of demineralized dentin and minerals, so mineralized dentin is not comparable to natural mineralized dentin in terms of the morphological characteristics and mechanical properties. With its gradual increase in recent years, dentine biomimetic mineralization technology perfectly resembles the minerals in the dentin overlapping sequence arranged with the dentine collagen fiber structure characteristics, leading to greatly improved microstructural, physical and chemical properties. As a result, dentine biomimetic mineralization technology is expected to achieve new breakthroughs in the fields of resin-dentin bonding mixing layers and the decay of dentin. At present, the technical obstacles that need to be overcome in the clinical application of the biomimetic remineralization of dentin are how to continuously supplement all the active ingredients needed for mineralization in the process of remineralization and how to keep the mechanical properties of the parent material unchanged while slowly releasing all ingredients. Researchers have successively proposed three-step transportation of the biomimetic remineralization of raw materials, as well as the preparation of mineralization precursors stabilized by polymers in advance and the reuse of mesoporous silicon nanomaterials for the transportation of the mineralized ingredient system. The concept described above provides the preliminary in vitro experimental basis for the transformation of the biomimetic remineralization strategy of dentin in clinical applications.

    Factors influencing the structure of the oral microbiome
    TANG Can,LIU Shiyu,CHENG Lei
    2020, 28(6):  390-393.  DOI: 10.12016/j.issn.2096-1456.2020.06.009
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    The oral microbiome has been identified as one of the most diverse microbial communities in the human body, and the ecological imbalance of the oral microbiome can not only induce a variety of oral diseases, such as dental caries, pulpitis, apical periodontitis, and periodontal diseases, but also is closely related to cardiovascular diseases, diabetes and other systemic diseases. The structure of the oral microbiome is affected by multiple factors. This paper reviews and summarizes the effects of genetics, the environment, diet and systemic diseases. Literature reviews have shown that environmental factors play an important role in the structure of the oral microbiome, while the influence of genetic and dietary factors is still controversial. In addition, systemic diseases may also affect the oral microbial community. High-throughput sequencing studies have identified some “core microbiota”, and “core microbiota” in different environments and in different genetic backgrounds will be the next research direction.

    Clinical application of autogenous dentin as a bone graft material
    XIAO Wenlan,HU Chen,RONG Sheng′an,QU Yili
    2020, 28(6):  394-398.  DOI: 10.12016/j.issn.2096-1456.2020.06.010
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    Autogenous dentin is a promising biological material that can be used as a substitute for autologous bone. It has been used in postextraction site preservation, maxillary sinus floor elevation, and alveolar ridge augmentation. The clinical application methods of autologous dentin have showed great diversity without uniform standard. The present article reviewed the clinical application of autogenous dentin to provide new ideas for its future development. The literature review results show that dentin materials require several preparations before transplantation, among which the demineralization is a common chemical processing method. Demineralization can enhance the osteoconductive and osteoinductive properties of dentin, but the complex and time-consuming operation process has limited its application to a certain extent. Partial demineralization may be a more appropriate choice. During transplantation, the morphology of dentin depends on the condition of the bone defect and the surgical method. Granular materials with different diameters are convenient for filling irregular defects. Block materials are conducive to maintaining the space of the reconstruction site. Hollow frame materials are slightly more complicated to process but can combine the advantages of granular and block grafts. In addition to being used alone, dentin can also be transplanted in combination with multiple biological materials. Platelet-rich plasma combined with dentin materials has shown ideal results in clinical studies. Plaster of paris and calcium phosphate ceramics have also been combined with dentin materials in animal experiments. But since they have not been applied in humans, their clinical effects require further research.

    Different jaw positions and condylar positions in oral therapy
    ZHANG Hongqi,LI Xiaojing,MENG Yukun
    2020, 28(6):  399-403.  DOI: 10.12016/j.issn.2096-1456.2020.06.011
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    In the stomatognathic system, a stable jaw position is influenced by occlusion, the temporomandibular joint and neuromuscular stability. The condylar position in the glenoid fossa is closely related to the jaw position, while no consensus has been reached on the optimum jaw position and its corresponding condylar position in oral therapy. This paper summarizes the controversial opinions regarding the selection of jaw position and the corresponding condylar position in prosthetics and orthodontics, including antero-superior, antero-inferior, and therapeutic positions. Their indications, theoretical bases and clinical applications are also included. The literature review results suggest that, the antero-superior position, in other words, centric relation, should be chosen when the patient has a stable jaw position without TMD. In cases where finding an ideal antero-superior position is difficult due to hyperplasia or deformation or disarrangement of the articular disc, the antero-inferior position is recommended to alleviate symptoms and facilitate reconstruction of the TMJ to obtain good stability. Moreover, for high-angle patients with Class Ⅱ malocclusion or for patients with mild skeletal malocclusion, camouflaged orthodontic treatment combined with antero-inferior jaw repositioning through the potential of condyle remodeling can be an alternative to orthognathic surgery and can simplify the treatment plan. While the therapeutic position is specifically proposed for coping with complicated situations related to cranio-mandibular dysfunction, such as maximal intercuspal position abnormalities or deflection, muscle and TMJ dysfunction, unstable jaw position, in which changes in the original occlusion or abnormal TMJ guidance are induced, and a new intercuspal position can be established and stabilized on the basis of occlusal support and modified guidance. The therapeutic position put aside the debate regarding condylar position, however, the specific position of the condyle has not been reported in this case. This review suggests that different jaw positions and condylar positions have different scopes of application, and their clinical selection should be based on based on whether the patient′s joints have organic changes and the stability of the jaw positions should be comprehensively considered. However, the long-term effects of oral therapy based on different jaw positions need to be further verified by controlled clinical trials in the future.

    New progress in the clinical application of GBR membrane materials
    REN Lizhi,SUN Rui
    2020, 28(6):  404-408.  DOI: 10.12016/j.issn.2096-1456.2020.06.012
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    Guided bone regeneration (GBR) barrier membranes are of great significance for the reconstruction of the health and function of different periodontal tissues. Biocompatibility, spatial maintenance, closure, controllability and biological activation are the main criteria that should be met by these membranes. Artificial barrier membrane biomaterials can be divided into synthetic polymer materials, natural polymer materials and metals. According to their degradation characteristics, these membranes can be divided into two categories, absorbable and nonabsorbable membranes. GBR used for horizontal bone increments can be used to treat various types of bone defects, including the treatment of bone fenestration and bone cracking. The use of a non-absorbable e-PTFE membrane or absorbable collagen membrane can achieve the expected effect. However, for incremental or vertical bone growth at the alveolar crest, the use of this membrane is very challenging and requires good strength to maintain the osteogenic space. This space can be enhanced with e-PTFE or d-PTFE membranes with stable morphology, or absorbable membranes can be covered with titanium plates or meshes to achieve vertical bone increments. Currently, bioactive membranes, digital 3D-printed titanium membranes and piezoelectric active biological membranes are research hotspots. In future research, the biological activation of these membranes will be further improved, which will promote the development of artificial membranes in the next stage.