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Molecular mechanisms of tooth, maxilla and mandible development

Ran ZHANG ; Zongshan SHEN ; Xiaoshan WU ; Songling WANG

STOMATOLOGY.2023;43(1):1-10. doi:10.13591/j.cnki.kqyx.2023.01.001

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.

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Progress of research on bone grafts for implant dentistry

Lina NIU ; Minjuan SHEN ; Ming FANG

STOMATOLOGY.2023;43(1):11-17. doi:10.13591/j.cnki.kqyx.2023.01.002

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.

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Analysis of causes for dental implant failure

Guofen LIN ; Yangbo XU ; Siyuan WANG ; Mengna LIN ; Fuming HE

STOMATOLOGY.2023;43(1):18-23. doi:10.13591/j.cnki.kqyx.2023.01.003

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.

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Risk prevention and treatment of implant-supported central screw fracture

Cong CAO ; Yi MAN

STOMATOLOGY.2023;43(1):24-27. doi:10.13591/j.cnki.kqyx.2023.01.004

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.

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Exploring complications related to abnormal implant position and their management

Chunbo TANG ; Zhuangzhuang CHU

STOMATOLOGY.2023;43(1):28-34. doi:10.13591/j.cnki.kqyx.2023.01.005

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.

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Re-osseointegration of peri-implantitis affected and failed implants

Yi ZHOU ; Jiajie CHEN

STOMATOLOGY.2023;43(1):35-38. doi:10.13591/j.cnki.kqyx.2023.01.006

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.

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Effect of calcium on biological properties of the ameloblast ALC

Zhen GAO ; Ruikai HOU ; Suocheng SONG ; Jianping RUAN

STOMATOLOGY.2023;43(1):39-45. doi:10.13591/j.cnki.kqyx.2023.01.007

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.

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The effect of sonic activated device used for different time on intracanal smear layer removal: An SEM analysis

Min XIAO ; Jin LIU ; Xiaomin FAN ; Haoze WU ; Jueyu WANG ; Kejing WANG ; Na LI ; Wenkai JIANG ; Xiaohan MEI

STOMATOLOGY.2023;43(1):46-51. doi:10.13591/j.cnki.kqyx.2023.01.008

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.

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Studies on the effect of ultrasound on properties and bonding strength of dentin smear layer

Ruyu WANG ; Yahui PAN ; Rongrong NIE ; Xiangfeng MENG

STOMATOLOGY.2023;43(1):52-56. doi: 10.13591/j.cnki.kqyx.2023.01.009

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

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Relationship between congenital absence of third molars and craniomaxillofacial structure

Lina WU ; Xin XIONG ; Yange WU ; Qinlanhui ZHANG ; Jun WANG

STOMATOLOGY.2023;43(1):57-61. doi:10.13591/j.cnki.kqyx.2023.01.010

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.

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