Table of Content

    20 February 2019, Volume 27 Issue 2
    Expert Forum
    Application of digital technology in orthodontic clinic
    LI Song,SU Rugan
    2019, 27(2):  69-73.  DOI: 10.12016/j.issn.2096-1456.2019.02.001
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    The rapid development of digital technology has made the processes of orthodontic data collection, diagnosis, design and treatment more accurate, comprehensive, convenient and safe and has improved the clinical efficiency of orthodontists. Safe, non-invasive, rapid three-dimensional facial imaging and digital dental models have enabled orthodontists to collect accurately visualized case data. In addition, during diagnosis and design, orthodontists can comprehensively analyze teeth, jaws, and cranial surfaces in 3 dimensions. Through advances that range from digitized whole-dentition information to computer-replicated design and computer-aided manufacturing, invisible orthodontic technology without brackets has become one of the best manifestations of the combination of digital technology and oral orthodontics. In addition, individualized fixed orthodontic devices have become widely used in orthodontic clinics. In this paper, the applications of digital technology in orthodontic clinics is described. It is hoped that orthodontists will be able to use digital technology rationally to benefit increasing numbers of patients with orthodontic demands.

    Application of digital technology in diagnosis and treatment of dentofacial deformities
    LI Yunfeng,ZHU Songsong
    2019, 27(2):  74-82.  DOI: 10.12016/j.issn.2096-1456.2019.02.002
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    Dento-maxillofacial deformity refers to an abnormal relationship of the volume or shape of the upper and lower jaw bones with the other bones of the craniofacial area. Its correction mainly involves hard tissues, such as the jaws and teeth. In recent years, digital techniques based on virtual surgery, real-time navigation, and 3D printing have developed rapidly in the area of craniomaxillofacial surgery. Digital technology has advantages for preoperative diagnosis, surgical plan formulation, surgical simulation, intraoperative navigation, effect prediction, doctor-patient communication, and young physician training. The Department of Orthognathic and TMJ Surgery of West China Hospital of Stomatology, Sichuan University, has conducted digitized diagnosis and treatment of dento-facial deformities since 2008 and has established a digital center for the treatment of dentofacial deformities based on equipment such as spiral CT, dental arch laser scanners, facial 3D cameras, virtual surgery software, 3D printers, and sleep-breathing monitoring. The result is a diagnostic and treatment protocol for dentofacial deformity specific to the characteristics of the population of West China. This article combines the latest domestic and foreign literature and comprehensively introduces the application of digital technology for the diagnosis and treatment of dental and maxillofacial deformities.

    Basic Study
    Effect of three kinds of medium molecular weight proteins on the corrosion resistance of Ni-Ti and stainless steel arch wires
    CUI Ye,HUANG Ziru,WANG Chunlin,LIU Conghua,ZHANG Chao
    2019, 27(2):  83-89.  DOI: 10.12016/j.issn.2096-1456.2019.02.003
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    Objective To explore the influence and mechanism of different types of proteins on the corrosion resistance of alloy to provide a reference for the safe application and surface modification of nickel-titanium (Ni-Ti) and stainless steel bow wires in the clinic.Methods The effects of fibrinogen, IgG and mucin on the electrochemical corrosion resistance of Ni-Ti and stainless steel arch wires were tested by the potentiodynamic polarization method, and the repair ability of passive films on surfaces treated with the three proteins were tested by the cyclic polarization method. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the types of corrosion products, and the surface morphology after corrosion was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM).Results The addition of fibrinogen, IgG or mucin to an alloy has different effects on its corrosion resistance. Adding protein can reduce the corrosion resistance of stainless steel alloys and slow the corrosion process of Ni-Ti alloys. The addition of mucin can improve the corrosion resistance of Ni-Ti alloy and the repair ability of passive film. Compared with mucin and IgG, fibrinogen can reduce the pitting resistance of Ni-Ti and stainless steel alloys.Conclusion Different types of proteins interact differently with the arch wire, form different deposition morphologies on the surface, and participate differently in the corrosion process of the alloy.

    Effect of dentin exposure on the shear bond strength of cast porcelain veneers
    LI Shanshan,CHU Fuhang,MO Hongbing
    2019, 27(2):  90-94.  DOI: 10.12016/j.issn.2096-1456.2019.02.004
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    Objective To explore the best indication for veneers and to improve the repair success rate by investigating the effects of different types of dentin exposure on the shear bond strength of cast porcelain veneers with two new veneer bonding systems.Methods Bonding interfaces with 0%, 25%, 50%, 75% and 100% dentin exposure were designed and fabricated. The bonding interfaces were divided into groups A, B, C, D and E. Sixty 4-mm x 4-mm x 2-mm (length x width x thickness) ceramic specimens were bonded by using two bonding systems, The VN-A, VN-B, VN-C, VN-D and VN-E groups were bonded with Variolink bonding system, and the PF-A, PF-B, PF-C, PF-D and PF-E were bonded with Panavia F bonding system (six specimens per group). The bonded specimens were stored in a distilled water bath at (37 + 1)℃ for 24 hours. The fracture load was tested by a universal testing machine, and the fracture type was observed by scanning electron microscopy.Results The VN-A (25.14 ± 3.40 MPa), VN-B (22.54 ± 4.48 MPa), VN-C (19.59 ± 2.21 MPa), PF-A (20.61 ± 2.42 MPa), PF-B (18.08 ± 4.11 MPa), PF-C (17.06 ± 2.29 MPa) groups’ shear bond strengths were above 17 MPa. The VN-A group had the highest shear bond strength value. There was no statistically significant difference in bond strength between the VN-A group and the VN-B and VN-C groups (P > 0.05) or the PF-A and PF-B groups (P > 0.05); however, the differences between VN-A and the VN-D and VN-E groups (P < 0.05) and between PF-A and the PF-C and PF-D and PF-E groups (P < 0.05) were statistically significant. The differences between the VN-A group and PF-A group (P < 0.05) were statistically significant. The fracture modes of the VN-A, PF-A, VN-B, PF-B, and VN-C groups mainly included resin cement cohesive failure and mixed failure; the VN-D, VN-E, PF-C, PF-D and PF-E groups were dominated by interface failure and mixed failure.Conclusion When the dentin exposure is greater than 50%, the shear bond strength value of the veneer was significantly affected. To obtain a better clinical effect, the dentin exposure rate should be less than 25%.

    Cinical Study
    Comparison of the shaping ability of different nickel-titanium instruments in simulated root canals in resin
    ZHANG Xiaowei,LIANG Jingping,SUN Zhe
    2019, 27(2):  95-99.  DOI: 10.12016/j.issn.2096-1456.2019.02.005
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    Objective To compare the shaping ability of 3 different nickel (Ni)-titanium (Ti) systems in simulated root canals in resin and to provide a reference for clinicians.Methods Forty-eight resin blocks were prepared using the F360 (Komet, Brasseler GmbH & Co., Lemgo, Germany) (Group 1), F6 SkyTaper (20/06) (Komet, Brasseler GmbH & Co., Lemgo, Germany) (Group 2), F6 SkyTaper (25/06) (Komet, Brasseler GmbH & Co., Lemgo, Germany) (Group 3) and Reciproc R25 systems (VDW, Munich, Germany) (Group 4) (n=12 canals/group). The images taken before and after preparation were superimposed and analyzed by Adobe Photoshop v7.0. The amount of resin removed by each system was measured, and the centering ability was assessed. The data were statistically analyzed using SPSS 20.0.Results At the 1 mm point, the transportation in Group 4 [(0.10 ± 0.03) mm] was significantly greater than that in Groups 2 [(0.05 ± 0.03) mm] and 3 [(0.05 ± 0.03) mm] (P < 0.05). At the 8 mm and 9 mm points, the transportation values in Group 4 [(0.12 ± 0.06) mm and (0.13 ± 0.05) mm] were significantly higher than those in Groups 2 [(0.05 ± 0.05) mm and (0.05 ± 0.05) mm] and 3 [(0.05 ± 0.04) mm and (0.06 ± 0.05) mm] (P < 0.05). At the 10 mm point, the transportation was significantly greater in Group 4 [(0.13 ± 0.06) mm] than in Group 2 [(0.06 ± 0.06) mm].Conclusion F6 SkyTaper exhibits better centering ability than Reciproc.

    Application of digital 3D printing technology in repairing mandibular defects with a fibular flap
    LI Jin,CHEN Jufeng,LIU Shiwei,LI Jiapeng
    2019, 27(2):  100-103.  DOI: 10.12016/j.issn.2096-1456.2019.02.006
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    Objective To explore the application value of digital 3D printing technology for repairing mandibular defects with fibular flaps and to provide a basis for accurate repair mandibular defects.Methods Nine cases of mandibular defects were selected, and spiral CT and CTA of the lower limbs were performed before the operation. The osteotomy guide plate and plastic guide plate were created using computer software, and the titanium plate was rebuilt according to the printed mandibular model. During the operation, an osteotomy guide plate was used for mandibular resection; a fibula bone plastic guide plate was used to reconstruct the fibular flap and reconstruct the mandibular defects.Results The entire fibula flap survived, and the occlusal relationship was good. There was no complications in the donor site. The patients were satisfied with the appearance of the repair. All patients were followed up for 3 to 6 months, at which point the bone was basically healed.Conclusion Using a digital 3D printing technique to repair mandible defects with a fibular flap can shorten the operation time, reduce the risks of operation, and better restore the maxillofacial shape and the function of the jaw, which is consistent with the concept of appropriate medical treatment. Additionally, this process provides a better method for the treatment of mandibular defects.

    Prevention and Treatment Practice
    The management of dental fear symptoms in children in a coparticipation model
    ZHANG Fan,REN Weiwei,GUAN Qin,ZHAO Hui,LI Shouhong
    2019, 27(2):  104-106.  DOI: 10.12016/j.issn.2096-1456.2019.02.007
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    Objective To explore the impact of procedural behavior management on children with dental fear (DF) using the interactive mode of coparticipative doctor-patient interactions.Methods Ninety-eight children with dental fear and aged 3-6 years were randomly divided into an observation group and a control group. Dental treatment was performed on the observation group under the coparticipation model, while the control group adopted the traditional tell-show-do (TSD) operation. The entire process of diagnosing and treating each child was recorded, and the degree of dental fear was assessed using a behavioral grading method as the standard.Results The degrees of fear in the children in the observation group and the control group were 3.571 ± 0.913 and 3.857 ± 1.000. The two groups showed no significant difference in the degree of fear (t=1.477, P > 0.05). During the treatment, the fear scores of the children in the observation group and the control group were 1.428 ± 1.061 and 3.286 ± 0.707. The two groups showed statistically significant differences in fear scores (t=10.198, P < 0.001).Conclusion In the coparticipative model, the fear level of DF children was significantly reduced by process-based behavior management, which helped to improve the dental fear of the children.

    A case of maxillary second premolar with 3 teeth and 4 root canals and a literature review
    LI Hong,XIN Bingchang,TENG Qi
    2019, 27(2):  107-109.  DOI: 10.12016/j.issn.2096-1456.2019.02.008
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    Objective To explore the discovery and treatment of multiple root canals in the maxillary second premolar to provide a reference for root canal therapy.Methods A case of maxillary second premolar occlusal discomfort accompanied by cold and heat stimulation pain and spontaneous pain was analyzed retrospectively.Results In this case, the number of roots and root canals in the tooth was determined by CBCT to be three roots with four canals. Root canal therapy was performed with Ni-Ti endodontic files and thermoplastic gutta-percha via root optical microscopy. The clinical symptoms disappeared after the operation.Conclusion The maxillary second premolar root canal system is complex, and additional root canals can be found and located with CBCT and optical microscopy. High-quality root canal therapy was completed.

    Review Articles
    Research progress on extracellular vesicles and bone regeneration
    WEI Shimin,WANG Yuanjing,HUANG Wen,QU Yili
    2019, 27(2):  110-114.  DOI: 10.12016/j.issn.2096-1456.2019.02.009
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    Extracellular vesicles (EVs) are lipid bilayers secreted by a variety of cells that contain nucleic acids, proteins, etc. They can be used as a carrier for cell-to-cell communication. In related research on bone regeneration, mechanisms for transmitting regeneration signals to target cells to achieve the desired goal of osteogenesis have become one of the most important and unsolved topics. Therefore, this review aims to explore the role of mesenchymal stem cells and EVs derived from osteoblasts in bone regeneration in four processes, immunity, angiogenesis, osteogenesis and mineralization, and to provide new ideas for basic and clinical research.

    Research progress on the CD4 +T cell balance in oral cancer and precancerous diseases
    TIAN Yuanye,TANG Zhangui
    2019, 27(2):  115-121.  DOI: 10.12016/j.issn.2096-1456.2019.02.010
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    CD4 +T cells play an important role in regulating adaptive immune responses to various inflammatory responses. Parental T cell populations can differentiate in response to different cytokines into at least four subpopulations: Th1, Th2, Th17, and Treg cells. These differentiated T cells participate in various immune responses and have different roles and functions in oral cancer and precancerous diseases. The Th1/Th2 balance, the Th17/Treg balance and the occurrence and development of oral cancer and precancerous diseases are related to immune imbalances. Reversing these T cell imbalances and strengthening the patient’s autoimmune function may prevent or even reverse the progression of oral and precancerous diseases. This paper reviews the research advances on the CD4 +T cell balance in oral cancer and precancerous lesions.

    Research Progress on regarding the torque control of upper anterior teeth with a lip appliance
    YANG Pingzhu,WEN Xiujie
    2019, 27(2):  122-126.  DOI: 10.12016/j.issn.2096-1456.2019.02.011
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    The normal torque angle of the maxillary anterior teeth is an important factor in the aesthetics and function of the anterior teeth, and torque control of the front teeth is an extremely important aspect of the correction process. At present, the normal torque angle of the front teeth is among the phase Ⅲ clinical test items recognized by the American orthodontic professional committee; consequently, good control of front teeth torque is of great significance to the aesthetics of the upper anterior teeth. In this paper, the influence of a lip appliance on the bad torque of upper anterior teeth and the associated methods of control are reviewed in detail. The advantages and disadvantages of various control methods for the anterior teeth and the significance of correct anterior teeth torque angle are summarized. The existing research results indicate that the torsion of a straight arch wire applied directly to individual teeth is too great, making it difficult to enter the groove. Although the bending of the arch wire overcomes these shortcomings, the procedure is cumbersome; it stimulates the soft tissue of the vestibular groove and increases the patient’s discomfort. The bending mechanism of the rocking chair is more complicated; it is greatly affected by the friction between the arch wire and the bracket and is not conducive to closing the tooth extraction gap using the sliding method. The portal auxiliary arch and the single bending torque are suitable for correcting the torque angle of a single tooth. Auxiliary arch torque can be used to correct the upright upper anterior teeth during the process of closing the extraction space and after adduction; therefore, this procedure is worth popularizing. However, the accuracy of orthodontic control of anterior teeth torque requires further study.

    Research progress on regarding brain-derived neurotrophic factors in chronic pain
    LIU Lijuan,GAO Yun,XIONG Wei
    2019, 27(2):  127-131.  DOI: 10.12016/j.issn.2096-1456.2019.02.012
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    Chronic pain is a disease that seriously affects people's physical and mental health and affects the quality of life of millions of people worldwide. It can have multiple etiologies and a complex pathogenesis, and it generally requires a combination approach. Current clinical treatments and drugs address only a limited number of these pathways or only provide symptomatic treatment, which presents some drawbacks and cannot achieve the ideal therapeutic effect. Thus, research on the pathogenesis of chronic pain is especially important. Recent studies have found that brain-derived neurotrophic factor (BDNF) is involved in the pathogenesis of various chronic pain pathways that play a role in promoting pain transmission in chronic pain. Therefore, BDNF and its receptors may become important targets in the treatment of chronic pain. This paper reviews the research progress regarding the molecular mechanism of BDNF in chronic neuropathic pain, inflammatory pain, cancer pain and oral and maxillofacial pain and aims to provide a theoretical basis for further research into and prevention methods for chronic pain. The literature review showed that in chronic pain, the expression of BDNF in the primary sensory ganglia and spinal dorsal horn was significantly increased, revealing that BDNF may be closely related to the mechanism of chronic pain and may represent a new treatment direction.

    Application of an individualized appliance in orthodontic treatment
    WU Kunji,KONG Weidong
    2019, 27(2):  132-144.  DOI: 10.12016/j.issn.2096-1456.2019.02.013
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    More than 20 years have passed since the advent of individualized appliances, which are designed according to the corrective target position. Through a series of digital technology-aided design and production processes, individual appliances have been increasingly recognized and accepted by the public. At present, there are three types of individualized orthodontic appliances: individualized lingual orthodontic appliances, non-bracket invisible appliances and individualized labial appliances. Because of their good effects in orthodontics, these appliances have gradually become mainstream orthodontic treatment tools. However, many doubts persist regarding their use in clinical treatment. This article reviews the development history, design principles and characteristics of the three types of individualized appliances. The results of a literature review showed that CAD/CAM and CBCT provide a hardware foundation for personalized orthodontic appliances that simplifies the therapeutic process. Additionally, individualized appliances also place higher demands on orthodontists. This article could provide references for and help with the clinical selection and use of individualized appliances.