Table of Content

20 October 2020, Volume 28 Issue 10

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Expert Forum

Epigenetic and oral squamous cell carcinoma

WANG Anxun

2020, 28(10):  613-622.  DOI: 10.12016/j.issn.2096-1456.2020.10.001

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In recent decades, although great progress has been made on the diagnosis and treatment of oral squamous cell carcinoma (OSCC), its 5-year survival rate has not been significantly improved. The basic reason is the unclear pathogenesis, lack of effective molecular markers for assessing invasion, metastasis, and recurrence as well as therapeutic targets. The present view is that genetic and epigenetic abnormalities are related to the occurrence and development of OSCC. Epigenetic inheritance is a biological behavior that can be regulated and reversed, and it plays an important role in the occurrence and development of malignant tumors. First, this review will describe the role of epigenetic modifications in the development of OSCC in combination with our research and the latest research progress of epigenetics, including DNA methylation, RNA methylation, short noncoding RNAs (miRNAs, etc.), long noncoding RNAs, circular RNAs, histone modifications (acetylation and methylation), chromatin remodeling and genomic imprinting. Then, we will analyze the value of epigenetic studies in the prevention, diagnosis, and targeted therapy of OSCC.

Study and application of an eye tracking technique in dental aesthetics

BAO Baicheng,WANG Xi

2020, 28(10):  623-629.  DOI: 10.12016/j.issn.2096-1456.2020.10.002

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Eye tracker is an instrument that can record the characteristics of eye movement when people process visual information. This instrument is important for basic psychological research. In the study of dental aesthetics, an eye tracker reflects the observer′s objective eye movement pattern and reveals the underlying aesthetic psychology. This paper summarizes the major research methods of dental aesthetics while focusing on eye-tracking studies in oral aesthetics. Eye tracking studies show that different population has different eye movement patterns when observing the same faces, while the same population can have different eye movement patterns when observing the faces of dental patients and normal people. This finding reveals that the personal characteristics and experience, the social environment and the featured facial structure of the observed individuals can influence eye movement patterns. This study also shows the factors that cause the aesthetic differences among different individuals and groups, as well as the psychological mechanisms.

Basic Study

Study of root canal isthmus dentin structure and mineral content and microhardness

YAO Qingting,LI Jun,LI Shuhui

2020, 28(10):  630-634.  DOI: 10.12016/j.issn.2096-1456.2020.10.003

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Objective To investigate the differences in dentin structure, mineral content and microhardness of single premolar roots with or without an isthmus. Methods Thirty single-root premolars with a canal isthmus (experimental group) and thirty single-root premolars without a canal isthmus (control group) were collected and analyzed by scanning electron microscopy, X-ray energy spectrometry and a Vickers microhardness tester. Structure, mineral content and microhardness were compared. Results In the experimental group, the dentinal tubules were not obvious, and the structure was disordered. In the control group, the dentin tubules of the root canal wall were arranged regularly, and the lumen opening was clear. The Ca and P contents and Ca/P ratio of the experimental group were lower than those of the control group (P < 0.05). The microhardness of the experimental group was less than that of the control group (P < 0.05). Conclusion The dentin structure of the root canal isthmus was changed, and the Ca, P contents and microhardness were low. The root canal isthmus was a weak link in the root, which could weaken the resistance of the hard tissue of the root tooth, which may be one of the important factors that could cause vertical root fracture.

Typodont model study on double keyhole loop in mandibular extraction space closure

CAI Senxin,LIU Jiali,CHEN Zexing,XU Linyu,SU Jiehua

2020, 28(10):  635-640.  DOI: 10.12016/j.issn.2096-1456.2020.10.004

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Objective To analyze the impact of the activation mode on the results of space closure in the mandibular arch using a double keyhole loop (DKHL) with a typodont model and reverse engineering technique to provide guidance for clinical treatment. Methods Nine normal mandibular typodont models after leveling were randomly divided into 3 groups, which then underwent three types of DKHL activation for space closure. Each model was assessed at the initial stage and after the warm water bath, and the images were superimposed to measure the displacement of special crown and root mark points. All statistical analysis of the data was performed using SPSS 19.0. Results After equal activation times, the root retraction of anterior teeth and the crown forward position of posterior teeth in groups activated at the distal loop (conditions 2 and 3) were much greater than those in the group activated horizontally (condition 1). Activation between mesial and distal loops (condition 3) induced significant anterior tooth intrusion, together with elongation and buccal inclination of posterior teeth. The displacement of mark points among the three conditions showed a statistically significant difference. Conclusion The movement of mandibular anterior and posterior teeth could be flexibly controlled through different DKHL activation modes, which should be chosen carefully according to individual conditions.

Cinical Study

Clinical application of molar uprighting for impacted mandibular second molars

LI Ning,YANG Liu,WANG Hongning,WANG Tiejun

2020, 28(10):  641-645.  DOI: 10.12016/j.issn.2096-1456.2020.10.005

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Objective To investigate the effect of the clinical application of molar uprighting in the treatment of impacted mandibular second molars. Methods A total of 16 cases of impacted mandibular second molars were chosen, and the impacted molars were treated with straight wire appliances and molar uprighting. Before and after treatment, the vertical angle of the molar, the height of the distal buccal tip, the height of the distal buccal tip of the anchorage molar, the depth of the periodontal pocket and the height of the alveolar bone were measured. Moreover, the treatment cycles of the third molar extraction group, the premolar group and the nonextraction group were compared. Results All impacted molars responded well to treatment. The vertical time of impacted molars was (1.34 ± 0.45) months, (2.20 ± 0.57) months, and (2.30 ± 0.45) months in the third molar extraction group, the premolar extraction group and the nonextraction group, respectively. The treatment time of the third molar extraction group was shorter than that of the other two groups, and the difference was statistically significant (P < 0.05). After treatment, the inclination of impacted second molars increased by (25.94 ± 8.85)°, the elongated distal buccal tip was depressed by (1.00 ± 1.48) mm, the depth of the proximal and middle periodontal pocket of impacted molars decreased by (1.21 ± 1.03) mm, and the height of the alveolar bone of the proximal and middle adjacent surfaces of impacted second molars increased by (4.57 ± 1.45) mm; these differences were statistically significant (P < 0.05). There was no significant difference in the height of the distal buccal tip of the first molar before and after treatment (P > 0.05). Conclusion Molar uprighting is an efficient, reliable, and convenient method that can shorten the treatment period. Extraction of crowded third molars is beneficial for the vertical and periodontal health of impacted second molars.

Study of mandibular buccal gingival mucosa pain sensitivity

BAI Zhongcheng,WANG Yayu,LI Xiaoling,LI Xiaoning,NIU Zhongying

2020, 28(10):  646-650.  DOI: 10.12016/j.issn.2096-1456.2020.10.006

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Objective Through a pain study of buccal gingival mucosa sensitivity of the mandible, the corresponding sensitive area of pain was determined, which provided the basis for reducing the pain and discomfort of oral diagnosis and treatment. Methods 400 patients with mandibular tooth extraction in the outpatient department of stomatology were selected. During tooth extraction, articaine epinephrine injection was used for infiltration anesthesia. The injection needle size was 0.3 mm × 21 mm, and the injection site was about 5 mm away from the buccal gingival margin. The pain degree of the patients was recorded. The data were statistically analyzed using the modified International pain classification method. Results Among the 400 patients who underwent mandible extraction, 75% (300 patients) graded their pain from painless to moderate, and 25% (100 patients) reported moderate to severe and severe pain. Of those in the moderate to severe and severe groups, 50% and 42% reported pain in the central and lateral incisors, respectively, and 38% were in the canine group. When comparing the moderate to severe and the severe groups, 16% and 10% were in the bicuspid group, 16% and 12% and 16% were in the molar group, respectively . There were significant differences in the pain sensitivity of different teeth positions (χ²=54.203, P < 0.001). The proportion of moderate to severe and severe pain in the anterior teeth group was higher than it was in the posterior teeth group (χ²=55.555, P < 0.001). There were significant differences in the pain sensitivity of different ages (χ²=96.501, P=0.000), and there was a positive correlation between pain and age (r=0.465, P < 0.001). The proportion of women with at least a moderate degree of pain was higher than that of men (χ²=12.298, P=0.031). Conclusion The sensitivity of the buccal gingival mucosa to pain is different in different positions of the mandible. The sensitivity of the anterior gingiva is higher than that of the posterior gingiva. Age is positively correlated with the degree of pain. Further, compared with men, women are more sensitive to pain.

Prevention and Treatment Practice

Application of digital technology in the restoration of partial edentulous dentition with microstomia

WU Yuqiong,RUAN Yaye,MING Jiajun,CHENG Huijuan,JIAO Ting

2020, 28(10):  651-656.  DOI: 10.12016/j.issn.2096-1456.2020.10.007

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Objective To explore the application of digital technology in the restoration of partial edentulous patients with microstomia. Methods A patient with microstomia was presented and seeking for the restoration of her full edentulous in the upper jaw and partial edentulous in the lower jaw (Kennedy Ⅲ). A digital intraoral scanning was used to obtain digital impressions of soft and hard tissues in the oral cavity. Computer aided design and 3D printing technology were used to design and fabricate the metal framework. Results The patient had no difficulty to wear or take off the dentures. The maxillary and mandibular dentures showed good retention, stability, mastication function and articulation. There was no tenderness in the one week and one month′s follow-up. And the chewing efficiency was satisfactory. Conclusion This case report successfully designed and fabricated mandibular removable partial dentures for patients with microstomia through intraoral scanning and 3D printing technology. Thus, this work provides a new method and idea for treating partial edentulous dentition with microstomia.

Effect of personalized miniscrew-assisted rapid palatal expander on expansion of the median palatal suture in adults

WANG Chunlin,LAN Zedong,MAO Qin,LIN Difu,XU Chanjuan,LIU Conghua

2020, 28(10):  657-663.  DOI: 10.12016/j.issn.2096-1456.2020.10.008

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Objective To investigate the manufacturing procedures of personalized miniscrew-assisted rapid palatal expanders (pMARPE) using digital technologies and to evaluate the effect of the expanders when expanding the midpalatal suture of an adult. Methods Digital technologies were used to make pMARPE, which was used to treat a 21-year-old woman with maxillary transverse deficiency (MTD). The relevant literature on MARPE was reviewed. Results PMARPE could be manufactured using intraoral digital scanning, computer-aided design and computer-aided manufacturing(CAD/CAM ), and 3D printing technologies. After expansion, the width of the anterior midpalatal suture, posterior midpalatal suture and maxillary skeletal width increased by 3.9 mm, 3.2 mm and 4.7 mm, respectively. There was no significant change in the inclination of maxillary first molars, and the height of alveolar ridge decreased slightly. It could be seen that using digital technologies to manufacture personalized expanders was possible for MARPE , and the initial stability of miniscrews played an important role in the expansion success rate, the increase of molar inclination is composed of many parts, and the decrease of alveolar ridge height may be overestimated due to the measurement method, as shown by a literature review. Conclusion The midpalatal suture of an adult patient with MTD could be expanded by pMARPE. However, the effect of this expander on the inclination of the first molar and alveolar bone height needs to be further studied with a larger sample size.

Review Articles

Advances in Treponema denticola and oral diseases

PENG Ruiting,CHENG Lei,PENG Xian

2020, 28(10):  664-667.  DOI: 10.12016/j.issn.2096-1456.2020.10.009

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Treponema denticola is an important pathogenic Treponema pathogen in the human oral cavity. Early studies have found that Treponema denticola is closely related to the occurrence and development of periodontal diseases. With the development of technical methods in recent years, many studies have shown that Treponema denticola not only can participate in periodontal diseases through a variety of mechanisms but also can play an important role in the development of various oral diseases. Treponema denticola is detected in high concentrations in peri-apical diseases and peri-implant diseases, and its surface protein is also prevalent in oral tumor samples. This paper reviews the research progress of Treponema denticola in periodontal diseases, pulp peri-apical diseases, peri-implant diseases and oral tumors, and summarizes the relevant mechanisms. For example, Treponema denticola can cause immune regulation disorder, destroy the epithelial barrier, induce bone absorption, promote the occurrence and development of inflammation through a variety of surface proteins, including chymotrypsin-like protease complex (CTLP), major outer sheath protein (Mosp), Td92, and LOS. It can also escape complement-mediated killing effects through surface FhbB lipoproteins and promote the occurrence and development of oral tumors by regulating the tumor microenvironment. These theories provide a theoretical basis for further understanding the development of oral diseases, controlling the infection of Treponema denticola, and exploring more effective treatment strategies.

Research progress on periodontal regeneration of replanted teeth after complete avulsion

GAO Juan,ZUO Wen,WANG Xuan

2020, 28(10):  668-672.  DOI: 10.12016/j.issn.2096-1456.2020.10.010

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Complete avulsion of teeth are one of the most serious traumatic dental injuries. The preferred treatment is tooth replantation. When teeth usually cannot be treated in time, the periodontal membrane on the root surface becomes necrotic , and the success rate of replantation is greatly reduced. How to use seed cells, growth factors and scaffold materials to promote periodontal tissue regeneration, improve periodontal membrane healing of replanted teeth, and achieve successful replantation of completely dislocated teeth is an urgent problem. Periodontal ligament stem cells (PDLSCs) express stem cell markers, have the potential to undergo multicellular differentiation and have important application value in periodontal tissue regeneration and repair. Fibroblast growth factor-2 (FGF-2), basic fibroblast growth factor (bFGF), lysobisphosphatidic acids (LPA) and other related regulatory factors promote periodontal tissue regeneration. Seed cells combined with scaffold materials can promote periodontal tissue regeneration and repair periodontal tissue defects. At present, studies have shown that PDLSCs and other seed cells have the potential for periodontal tissue regeneration and have been widely studied in experimental animal models of periodontitis and bone defects. However, there are few reports on the application of replanted teeth after complete avulsion, and its mechanism is not clear. In this paper, the research progress of periodontal tissue regeneration after total dislocation replantation is reviewed. We expect to apply periodontal tissue regeneration research to the replantation of fully dislocated teeth to achieve periodontal membrane healing of fully dislocated replanted teeth to provide a theoretical basis for future clinical work.

Effect of Er: YAG laser irradiation on the bonding strength of permanent teeth

WEI Yanan,CHEN Yun,LI Zhiyan

2020, 28(10):  673-676.  DOI: 10.12016/j.issn.2096-1456.2020.10.011

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The concept of “minimally invasive dentistry” aims to provide conservative treatment of cavities in which sound dentin is removed. Because the Er: YAG laser can selectively remove caries, the smear layer is removed, dentin tubules are exposed after the preparation of substrate conditioning, and its advantages of precision, safety and painlessness are deeply valued. At the same time, the bonding strength between the prepared dentin surface and the filling material is different due to the different parameters of the Er: YAG laser. In this paper, the principle of dentin bonding, the mechanism of Er: YAG laser action, after treatment of dentin with different parameters (power, energy density, pulse duration, and irradiation distance), whether there is thermal damage to pulp tissue, the ultramicro morphology of dentin surface, the bonding properties of different bonding systems and the filling materials between irradiated hard tissues were reviewed. An appropriate parameter range (power ≤ 10 Hz, energy density ≤ 60 mJ, and pulse duration ≤ 50 μs) combined with water spray cooling will not cause thermal damage to the pulp tissue, while the higher power, energy density and pulse duration of laser treatment for dentin will lead to melting, carbonization, cracks, narrowing of the gap between collagen fibers, etc., which will limit the penetration of adhesives and have a negative impact on bonding. However, whether the adhesive systems based on the smear layer are suitable for dentin after laser treatment needs to be further explored.

Effects of chronic stress caused by occlusal disorder on the body

JIANG Jiayang,LI Baosheng,LI Yuyang,ZHANG Huiyan,JIN Zhuohua,OU Yanzhen,MENG Weiyan

2020, 28(10):  677-680.  DOI: 10.12016/j.issn.2096-1456.2020.10.012

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Occlusal disorder is an abnormal condition in which the static and dynamic relations between the upper and lower teeth are not well aligned . The most common occlusal disorder in clinical practice is the inability to reach the intercuspal position due to early contact of individual points or occlusal interference due to occlusal high points, which can lead to periodontal tissue damage, decreased masticatory function, temporomandibular joint and muscle discomfort; these results can occur through the overactivation of the locus coeruleus-sympathetic-adrenal medullary system and hypothalamic-pituitary-adrenal axis induce elevated serum corticosteroid levels, which leads to chronic stress in the body. This article reviews the effects of chronic stress caused by occlusal disorder on bone tissue, stomatognathic system, emotional health and cognitive function. It has been found that occlusal disorders not only result in the loss of bone in the oral cavity, the reduction of bone mass in the whole body and damage to the local function of the stomatognathic system but also negatively affect the body’s anxiety, sleep, cognitive function and spatial memory ability as a result of the neuroendocrine changes . In recent years, concern about occlusal disorders has been on the rise. Early detection and timely adjustment of uncoordinated occlusion has become an issue that cannot be ignored in the clinic.