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28 January 2023, Volume 43 Issue 1
Academician Column
Molecular mechanisms of tooth, maxilla and mandible development
ZHANG Ran,SHEN Zongshan,WU Xiaoshan,WANG Songling
2023, 43(1):  1-10.  doi:10.13591/j.cnki.kqyx.2023.01.001
Abstract ( 350 )   HTML ( 36)   PDF (1940KB) ( 228 )  
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Understanding the pattern and molecular mechanisms of tooth, maxilla and mandible development is the prerequisite for studying their regeneration. Tooth development can be divided into three stages: bud-bell stage, tooth crown development stage and tooth root development stage. During these processes, key genes show spatial and temporal expression pattern. Tooth development is a complex process involving interactions between dental epithelium and mesenchyme, precise regulations of enamel knots in cusp patterning, as well as successful eruption into the oral cavity under proper biomechanical stress and signaling transductions. The development of tooth, maxilla and mandible, all of which originate from the first branchial arch, is independent and regulates each other to form a whole during development. Any developmental defects of them will ultimately cause defects to the others. In this paper, we briefly reviewed the development of tooth, maxilla and mandible, proposed that the homeostasis of microenvironment is critical for their development. Moreover, we reviewed the role of Meckel’s cartilage, a special structure and signaling mechanism during mandible development. At last, we proposed an integrated development model of tooth, maxilla and mandible. We also hope that the regeneration of fully functional tooth, maxilla and mandible in human can be achieved based on fundamental knowledge we have gained so far.

Complications of implantation
Progress of research on bone grafts for implant dentistry
NIU Lina,SHEN Minjuan,FANG Ming
2023, 43(1):  11-17.  doi:10.13591/j.cnki.kqyx.2023.01.002
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With the development of dental implant techniques, dental rehabilitation of partially or totally edentulous patients with oral implants has become a common practice. Adequate bone volume in the implant area is a key factor for the success of implant restoration. However, insufficient bone volume in the implant area is very common in clinical practice, which jeopardizes the structural, functional, and esthetic outcomes of implant treatment. Bone augmentation with bone grafts is one of the methods commonly used in clinical practice to meet the requirements of implantation. Properties of bone grafts, such as biocompatibility,osteoconduction, osteoinduction and osteogenesis, are important to the success of bone augmentation. This paper reviews current research on dental bone grafts about their clinically relevant capabilities, classification and their potential development in the future, in order to provide theoretical reference for clinical application of bone grafts and successful implant restoration.

Analysis of causes for dental implant failure
LIN Guofen,XU Yangbo,WANG Siyuan,LIN Mengna,HE Fuming
2023, 43(1):  18-23.  doi:10.13591/j.cnki.kqyx.2023.01.003
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The implant-supported prosthesis has gradually become the preferred treatment for patients with partial edentulous or complete edentulous. Causes for the implant failure have been discussed in the majority of studies conducted in recent years, while their risk factors are still controversial. Patient factors (gender, age, smoking, osteoporosis, diabetes, medication, periodontitis and bruxism), clinical parameters (implant area, bone quality, implant size) and doctor factors (surgical-related factors, prosthesis-related factors) will all affect implant failure. This article presents typical clinical cases and reviews the potential risk factors for dental implant failure, in order to provide guidance for clinical practice.

Risk prevention and treatment of implant-supported central screw fracture
CAO Cong, MAN Yi
2023, 43(1):  24-27.  doi:10.13591/j.cnki.kqyx.2023.01.004
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In the complications of dental implant treatment, the mechanical complications, such as central screw breakage, are often complex and serious. This article analyzes factors that affect the loosening of the central screw. Understanding relevant risk factors can prompt doctors to take corresponding strategies to reduce the possibility of complications in clinical operations. After encountering broken cases, this paper also gives some ideas and methods of treatment, and finally summarizes clinical suggestions for preventing the central screw fracture.

Exploring complications related to abnormal implant position and their management
TANG Chunbo,CHU Zhuangzhuang
2023, 43(1):  28-34.  doi:10.13591/j.cnki.kqyx.2023.01.005
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Abnormal implant placement is a common challenge in clinical work, including root direction, occlusion direction, mesial direction, distal direction, buccal (lip) direction, tongue (palate) direction, a total of 6 directions. Clinicians should pay great attention to the risk of many complications due to improper placement of implants. Understanding the etiology is the premise to effectively prevent the complications of implant restoration, and this article will discuss the causes, the classification of complications and related treatment principles and treatment plans from 6 different directions of abnormal implant positions.

Re-osseointegration of peri-implantitis affected and failed implants
ZHOU Yi,CHEN Jiajie
2023, 43(1):  35-38.  doi:10.13591/j.cnki.kqyx.2023.01.006
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Peri-implantitis and implant failure are common issues in the implant dentistry. The contaminated implant can be treated with mechanical, chemical and assisted methods for the formation of re-osseointegration. Re-osseointegration is achievable with valid bone regeneration strategies. The survival rate of implant into the site of previous failure is lower than that of the initial implant. For the hopeless and failed implant, it is necessary to remove the implant with corresponding technique.

Basic Research
Effect of calcium on biological properties of the ameloblast ALC
GAO Zhen,HOU Ruikai,SONG Suocheng,RUAN Jianping
2023, 43(1):  39-45.  doi:10.13591/j.cnki.kqyx.2023.01.007
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Objective To observe the effect of calcium on biological characteristics (proliferation, apoptosis and cell cycle) of ALC ameloblasts. Methods ALC cell lines were cultured in vitro in DMEM medium with high glucose at different concentrations (0, 2.0, 2.5, 3.0 and 3.5 mmol/L CaCl2 aqueous solution) for 24 h and 48 h, respectively. Changes of ALC cells under two kinds of incubation time were observed with an inverted microscope. CCK-8 method was used to analyze the effect of calcium ion on ALC cell proliferation. Hoechst staining was used to observe the effect of calcium ion on ALC cell apoptosis. PI staining and FCM method were used to analyze the effect of calcium ions on the growth cycle of ALC cells. Western blot was used to detect the effect of calcium ions on the expression of Cyclin A, Cyclin B and Cyclin D in ALC cells. Results In the 0 mmol/L CaCl2 group, ALC cells were oval or polygonal in shape, and the cells were closely connected and grew like paving stones. In other concentration groups, the morphology of ALC cells did not change significantly after calcium intervention for 24 h and 48 h. Results of CCK-8 method showed that the survival rate of ALC cells slightly decreased with increasing calcium ions concentration after calcium intervention for 24 h and 48 h. However, there was no significant differences in this trend. Results of Hoechst staining showed that the number of ALC cell apoptosis did not increase significantly after different concentrations of calcium intervention for 24 h and 48 h. With the increase of calcium ion concentration, results of PI staining and FCM method showed that the cell cycle of ALC cells gradually increased in S phase and decreased in G1 and G2 phase gradually. Western blot results showed that the expression of Cyclin A and Cyclin B in ALC cells decreased and the expression of Cyclin D increased after different concentrations of calcium intervention for 24 h and 48 h. Conclusion In this study, calcium has no significant effect on the proliferation and apoptosis of ALC cells. Calcium, however, has an effect on the ALC cell cycle. Results of this study show that calcium ions has no obvious toxic or side effects on the ameloblasts, which could be used to explore the possible mechanism and effect of calcium on dental fluorosis.
The effect of sonic activated device used for different time on intracanal smear layer removal: An SEM analysis
XIAO Min, LIU Jin, FAN Xiaomin, WU Haoze, WANG Jueyu, WANG Kejing, LI Na, JIANG Wenkai, MEI Xiaohan
2023, 43(1):  46-51.  doi:10.13591/j.cnki.kqyx.2023.01.008
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Objective To observe the clearance of smear layer on the root canal wall in different action time by scanning electron microscope (SEM), and to determine the optimal amount of time using sonically activated irrigation to wash root canal in clinic. Methods Fifty-six ex vivo human anterior teeth with single straight root canal were selected. After routine mechanical preparation, they were divided into two experimental groups according to different irrigating agents: saline group and EDTA group. Each group was assisted by VDW sonic activation EDDY. The saline group was divided into three subgroups according to the irrigating time: 5 s, 30 s and 50 s; EDTA group was divided into six subgroups according to the irrigating time: 5 s, 10 s, 20 s, 30 s, 40 s and 50 s. The control group did not undergo root canal irrigation. After irrigation, the root was cut longitudinally. The smear layer of crown, middle and apical of root canal wall was observed by SEM. Results After irrigating for 30 seconds, there was a significant difference between the normal saline group and the control group and the 5 second group (P<0.05), and there was no difference in the middle and apical part (P>0.05). After 50 seconds, there was a significant difference in the score of the smear layer between the apical area and the other groups (P<0.05). After irrigating for 5 seconds or 10 seconds in EDTA group, there was a significant difference between the scores of the crown and middle area of the root canal and the control group (P<0.05), and there was no significant difference in the apical area (P>0.05). There was a significant difference between the 20-40 second group and the first two groups (P<0.05). There was a significant difference between the 50 second group and the other groups (P<0.05). Comparing the cleaning effect on the smear layer after 50 seconds of irrigating between the two experimental groups, the whole root canal showed significant statistical difference (P<0.05). Conclusion The EDTA-assisted sonic activated device used for 50 seconds has the best cleaning effect.
Studies on the effect of ultrasound on properties and bonding strength of dentin smear layer
WANG Ruyu, PAN Yahui, NIE Rongrong, MENG Xiangfeng
2023, 43(1):  52-56.  doi:10.13591/j.cnki.kqyx.2023.01.009
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Objective To explore the effect of ultrasound on dentin smear layer's surface and bonding strength of the universal resin adhesive under self-etching mode. Methods Forty mandibular third molars without caries were randomly divided into two groups; one was polished with silicon carbide sandpaper; the other was polished with silicon carbide sandpaper followed by ultrasonic treatment. Scanning electron microscope (SEM) was used to observe surface of the dentin. Treated teeth were bonded with two universal resin adhesives, Clearfil Universal Bond (pH=2.3) and All-Bond Universal (pH=3.1), and the penetration of the bonding interface was observed with a confocal laser scanning microscope (CLSM) after Rhodamine B staining. Finally, the micro tensile bond strength test was conducted to test the adhesion. Results The SEM showed that after polishing with silicon carbide sandpaper, the smear layer of the dentin surface was scratched, and dentin tubules were almost completely blocked, with no obvious dentin tubules exposed. After ultrasonic treatment, the scratches were reduced, and a large number of dentin tubules were exposed. CLSM showed that both adhesives could penetrate the dentin along the dentin tubules more deeply after ultrasound treatment. Micro tensile bond strength tests showed that ultrasonic treatment could enhance the bonding strength of two universal resin adhesives. However, there was no statistical difference in bonding strength between these two universal resin adhesives under the same treatment. Conclusion Ultrasound can partially remove the smear layer on dentin's surface, expose dentin tubules, and increase universal resin adhesives' penetration depth and bonding strength under self-etching mode.
Clinical Research
Relationship between congenital absence of third molars and craniomaxillofacial structure
WU Lina, XIONG Xin, WU Yange, ZHANG Qinlanhui, WANG Jun
2023, 43(1):  57-61.  doi:10.13591/j.cnki.kqyx.2023.01.010
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Objective To analyze the correlation between third molar agenesis and craniofacial morphology by studying the location and number of congenital missing third molars and results of craniofacial cephalometric measurement. Methods A total of 123 patients were included, including 64 patients in the control group without congenital third molar absence and 59 patients in the absence group with at least one third molar absent. Cephalometric measurements included FMA, IMPA, AR-Go, GoGn-Sn, Co-A, Co-Gn, ANS-Me, Go-Me, SN-MP, Ar-Go-Me, SNA, SNB, ANB, Y-axis angle, Y-axis length, Ar-Go, Go-Me, MP-OP, FH-PP, FH-OP, a total of 18 bone tissue indicators, U1-SN, U1-L1, U1-NA, L1-NB, U1-APo and L1-APo, a total of 6 dental indicators, and UL-EP, LL-EP and nasolabial angle, a total of 3 soft tissue indicators. The correlation between congenital agenesis of third molars and craniofacial morphology was analyzed. Results The most common missing location of the third molar occured in the upper jaw and the most common number of missing teeth was one. In control group, Ar-Go-Me and SN-MP were larger (P<0.05), U1-SN, U1-NA, L1-NB, UL-EP and LL-EP were larger (P<0.05), and U1-L1 was smaller (P<0.01). There were no significant differences in Ar-Go and Go-Me between the two groups(P>0.05). Conclusion Patients with four third molars are more likely to have backward and downward rotation of the mandible and are more likely to develop into a convex facial type than patients with missing third molars, which has a higher correlation with hyperdivergent growth pattern and convex facial type.
Application of computer-assisted navigation technology in the resection and reconstruction of mandibular ameloblastoma
LIU Min, TANG Enyi, LIU Zhe, GE Sumeng, WU Zhuhao, ZHANG Xingwei, SUN Guowen
2023, 43(1):  62-69.  doi:10.13591/j.cnki.kqyx.2023.01.011
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Objective Using computer-assisted navigation technology to guide the resection and reconstruction of mandibular ameloblastoma, evaluating its treatment effect. Methods Twelve patients were selected from the Affiliated Stomatological Hospital of Nanjing University from January 2017 to May 2022. All 12 patients accepted same surgery which included resection of mandibular ameloblastoma and reconstruction by fibula musculocutaneous flap. Among them, 6 cases were included in the navigation group; 6 cases were in the non-navigation group. Advantages and disadvantages of computer-assisted navigation technology in this operation were evaluated with these cases. Results The 12 operations were performed by the same operator. The average time for fixing the navigation bracket and performing navigation in the navigation group was about 15 minutes. Compared with the non-navigation group, the average operation time in the navigation group was shortened by about 10 minutes. In the navigation group, the mandible resection range matched the fibula musculocutaneous flap well, and the occlusal relationship recovered well. Conclusion Using the mandibular reference frame, under the guidance of computer-assisted navigation technology, the resection and reconstruction of mandibular ameloblastoma can be performed quickly and accurately.
Comparison of panoramic radiography and cone-beam computed tomography images for detecting external root resorption of mandibular second molar associated with third molar impaction
SONG Hongcheng, HUANG Hong, WANG Zhifan, JING Qiuping, WANG Dongmiao
2023, 43(1):  70-74.  doi:10.13591/j.cnki.kqyx.2023.01.012
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Objective To compare the diagnostic performance between panoramic radiography(PR)and cone beam computed tomography(CBCT)in the assessment of external root resorption(ERR)of mandibular second molars associated with impacted third molars. Methods A total number of 832 patients with 1 074 mesially and horizontally impacted mandibular third molars treated at our institution from January 2019 to December 2020 were retrospectively analyzed. Presence of ERR on the adjacent second molar was investigated with PR and CBCT. Factors affecting the diagnostic accuracy of PR were determined. Results The overall incidence of ERR in second molars was 33.15%(356/1 074)as detected by CBCT images. The accuracy of PR was 66.39%. Multivariate Logistic regression analyses further revealed that middle and Class Ⅲ impaction, crown contact or overlap with the root of adjacent tooth were risk factors for inaccurate diagnosis of PR(P<0.05). Conclusion The accuracy of detection on ERR of mandibular second molar associated with impacted third molar using panoramic radiography is lower. CBCT is recommended for this clinical scenario.
Correction of hemifacial microsomia using preformed titanium mesh combined with contralateral mandibular angle bone graft with CAD/CAM assistance
SONG Libin,Mohammed Qasem AlWatary,HE Yingyou,BI Dandan,LI Jihua
2023, 43(1):  75-81.  doi:10.13591/j.cnki.kqyx.2023.01.013
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Objective To explore the indications and clinical effects of simultaneous mandibular angleplasty on the unaffected side, performed using preformed titanium mesh combined with mandibular angle bone graft, for the treatment of hemifacial microsomia (HFM). Methods The study group included 11 patients between 2013 and 2021 with HFM who underwent simultaneous mandibular angle reduction of the unaffected side and augmentation of the affected side using resected bone scaffolds within the titanium mesh. A series of mandibular linear measurements such as ramus height(RH)and mandibular body length(BL), angular measurements, and asymmetry index combined with clinical photographs and postoperative complications were used to assess the therapeutic effect. Results Postoperatively, all patients were satisfied. Significant improvement in mandibular contour was shown, with no obvious complications. Postoperative data, such as BL and angular measurements, showed no statistically significant differences(P>0.05) between the affected and unaffected sides with improvement in symmetry, except for RH(P<0.05). The preoperative and postoperative asymmetry index were (17.11±4.56)% and (4.81±1.73)%, respectively, with significant improvement(P=0.002). Conclusion This approach provides satisfactory results and significantly improves facial asymmetries for unilateral HFM with hypertrophy of the contralateral mandibular angle.
Summary
Research advances of 3D printing in vascularization
CHEN Yifei,ZHANG Chenyue,ZHANG Jinglan,ZHANG Binjing,RONG Xin,HU Zhiai
2023, 43(1):  82-87.  doi:10.13591/j.cnki.kqyx.2023.01.014
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As the key to regeneration of oral and maxillofacial tissues such as bone, dental pulp and skin, vascularization has always been the focus of tissue engineering. With the development of three-dimensional (3D) printing in tissue engineering, there are increasing ways to construct vascular structures. However, to achieve the objective of highly simulating vascular structure in morphology and function and promote tissue repair, it is still a major difficulty for 3D bioprinting to construct highly precise and biologically functional simulated vascular structures. This paper summarizes new progress of 3D printing vascular structure, expounds frontier biological manufacturing technologies of vascular and vascularized structure such as suspension printing, coaxial printing, 4D printing, and so on, analyzes its advantages and disadvantages, and discusses its development prospect, in order to provide reference for the application of 3D printing blood vessels in regeneration and repair of oral and maxillofacial tissues.

Progress of research on application of chondroitin sulfate in osteogenic repair materials
ZHANG Qian, WANG Chang, LIANG Chen, QU Xingyuan, LIU Yue, YAN Baojun, WANG Lei
2023, 43(1):  88-91.  doi:10.13591/j.cnki.kqyx.2023.01.015
Abstract ( 144 )   HTML ( 5)   PDF (733KB) ( 25 )  
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Chondroitin sulfate is an important component of extracellular matrix (ECM) in animal and human body. In recent years, chondroitin sulfate has been proven to have potential efficacy in biomedical application and has been widely used in bone regeneration and osteogenesis, especially in craniofacial reconstruction and dental medicine. Research shows that chondroitin sulfate derivatives and chondroitin sulfate composite scaffolds have great potential in promoting osteogenesis and biomineralization. However, due to the variety of chondroitin sulfate and various application forms, study on its mechanism of osteogenic repair is still insufficient. In this paper, biological characteristics, bone regeneration and osteogenesis of chondroitin sulfate, its application in different biomaterial design and future prospect are discussed.

Progress of research on chitosan-based microspheres in oral tissue lesions
ZHOU Huajun,DING Yude,YANG Fan
2023, 43(1):  92-96.  doi:10.13591/j.cnki.kqyx.2023.01.016
Abstract ( 162 )   HTML ( 7)   PDF (1155KB) ( 25 )  
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Chitosan-based microspheres use chitosan as the main material to obtain particles with special structures through microsphere processing technology. They have the ability of slow and controlled release of drugs and the role of scaffolding, which have great application prospect in stomatology, but the application of chitosan-based microspheres is still in the research stage and has not yet been applied in clinical practice. This article reviews progress of domestic and foreign research on chitosan-based microspheres, in aspects of treatment of oral and jawbone tissue defects, periodontal diseases, dental pulp diseases and nerve tissue injury, in order to provide reference for follow-up research.