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Treatment of maxillary ameloblastoma with different modalities: a retrospective analysis of 92 cases LUO Hao, YUAN Zhuang, WU Kai-liu, HE Jie, MENG Jian Shanghai Journal of Stomatology    2022, 31 (1): 71-74.   DOI: 10.19439/j.sjos.2022.01.015 Abstract （873）      PDF （860KB）（269）       Knowledge map    PURPOSE: To explore the appropriate surgical approach for each type of maxillary ameloblastoma. METHODS: The clinical data of 92 patients with maxillary ameloblastoma were retrospectively analyzed. All patients were pathologically diagnosed, followed up for 3-8 years after surgery, maxillofacial CT and panoramic images were taken regularly to observe the surgical outcomes. SPSS 22.0 software package was used for data analysis. RESULTS: The proportion of maxillary ameloblastoma in male and female patients was 3 to 1,with more male patients and the mean age was 45.77 years old. The total recurrence rate of 92 patients was 21.74%, among which unicystic ameloblastoma had no recurrence after different surgical procedures. Among 38 patients with typical maxillary ameloblastoma, 14 underwent curettage, 3 underwent decompression,16 underwent extended resection, 3 underwent subtotal maxillary resection, 1 underwent iliac bone transplantation after subtotal maxillary resection, and 1 underwent reconstruction with anterolateral thigh flap after subtotal maxillary resection. Among them, 18 had recurrence and 5 had canceration. Three patients with extrasseous/peripheral type underwent expanded resection and two underwent curettage,none of them had recurrence. One patient with metastasizing ameloblastoma recurred after extended resection. CONCLUSIONS: Maxillary ameloblastoma with unicystic type should be completely removed with minimal trauma. The recurrence rate of maxillary ameloblastoma via simple curettage or extended resection is still relatively high, which may be due to the large tumor involvement scope of these patients and the failure of complete tumor removal by curettage. For external/peripheral ameloblastoma and metastatic ameloblastoma, the involved jaw bone should be removed as much as possible to prevent recurrence. For malignant transformation of ameloblastoma, the tumor and jaw bone should be dissected during the operation to reduce recurrence rate. The primary site, cervical lymph nodes and lungs should be closely followed after operation to detect early metastasis. Reference | Related Articles | Metrics

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Comparative study on the accuracy of implant-borne single restoration by two production processes with Ti-base CAO Wei-yu, CAO Jie, LIU Bin-yi, XU Zhou, LU Wei-qing Shanghai Journal of Stomatology    2022, 31 (4): 414-417.   DOI: 10.19439/j.sjos.2022.04.015 Abstract （816）      PDF （606KB）（230）       Knowledge map    PURPOSE: To study on the accuracy of implant-borne single restoration by two production processes with Ti-base to provide experimental data for proper processes of single implant-borne restoration. METHODS: Thirty patients were selected with single posterior teeth missing from the Department of Oral Implantology of Shanghai Putuo District Eye Disease and Dental Disease Prevention and Treatment Institute. The patients were taken 2 traditional impressions clinically for two plaster model equipped with implant analogue. These models were then divided into 2 groups according to different production processes. The experimental group was scanned with the scan body installed in the model implant analogue, while the control group was scanned directly on the Ti-base abutment installed in the model implant analogue. The implant-borne single restorations of the two groups were cut along the buccal-lingual side and the distance between the measuring point to the Ti-Base abutment was observed by electron microscopy. In addition, the breaking limit of zirconia crown was observed, universal test machine was used to load direct force to the crown. SPSS 22.0 software package was used for data analysis. RESULTS: The gap between the implant-borne single restoration to the Ti-base abutment of the experimental group was significantly smaller than that of the control group. The difference between the two groups was statistically significant (P<0.05). However, by testing the breaking limit of zirconia crown, there was no significant difference(P>0.05). CONCLUSIONS: Using scan body to transfer the implant position and Ti-base abutment data information to the digital dental design software is more accurate and reliable than directly scanning the Ti-base on the model analogue. Using scan body is recommended for processing and manufacture of implant-borne singe restoration. Reference | Related Articles | Metrics

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Effect of zoledronic acid on mandibular socket healing process of mice at an early stage JIANG Run-yang, KANG Fei-wu Shanghai Journal of Stomatology    2022, 31 (4): 349-353.   DOI: 10.19439/j.sjos.2022.04.003 Abstract （796）      PDF （3074KB）（219）       Knowledge map    PURPOSE: To investigate how bisphosphonates affect early process of socket healing in mice model. METHODS: Eighteen 8-9 weeks C57BL/6 male mice were randomly divided into control and experimental group. Bisphosphonate-related osteonecrosis of the jaw（BRONJ）model was conducted by intraperitoneal injection of zoledronate（ZOL） and extraction of lower left first molar in mice. Three, five, seven day after surgery, the mice were sacrificed and paraffin-embedded slides were made. H-E staining was used to evaluate the gross condition. The distribution and amounts of osteoclasts were measured by TRAP staining. Finally, immunochemical staining was used to detect RUNX2 and CTSK level. All experiments were duplicated thrice, ImageJ was used for transformation of pictures and SPSS 20.0 software package was used for statistical analysis. RESULTS: In comparison with the control group, early process of socket healing in the experimental group was generally delayed. RUNX2,CTSK,TRAP expression level was decreased. On the whole, early bone remodeling process in ZOL injection group was suppressed. CONCLUSIONS: Zoledronic acid inhibited the migration of fibroblasts into socket, and reduced the expression of Runx2, hindering new bone formation. It also can reduce the expression of TRAP 3,5,7 days after tooth extraction and CTSK expression three days after operation, thus inhibiting the bone resorption function of osteoclasts. Reference | Related Articles | Metrics

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Comparison of the accuracy for evaluating cervical vertebral bone age and dental age of children in Shanghai WANG Miao-chen, SHEN Shi-hui, BAI Xue-bing, TAO Jiang Shanghai Journal of Stomatology    2022, 31 (1): 89-95.   DOI: 10.19439/j.sjos.2022.01.019 Abstract （668）      PDF （921KB）（193）       Knowledge map    PURPOSE: To compare the applicability and validity of dental age (DA) estimated by Willems method and cervical vertebral bone age (CVBA) evaluated by regression formula in estimating the chronological age of children in Shanghai. METHODS: Panoramic radiographs and lateral cephalograms were retrospectively collected from 320 subjects (160 males, 160 females), totaling 640 images. Discrepancies between chronological and estimated ages were statistically calculated by paired samples t test or Wilcoxon signed rank test using SPSS 25.0 software package. The accuracy of the two methods was comprehensively evaluated by comparing their standard deviation, mean absolute error (MAE) and the correct rate of acceptable range of estimated age error. RESULTS: The mean DA underestimated CA by 0.75±1.03 years for males and by 1.05±1.18 years for females; whereas the mean CVBA underestimated CA by 0.78±1.40 years for males and 0.53±1.31 years for females. MAE of Willems method was 1.15 years and the MAE of regression formula of CVBA was 1.20 years. The correct rate of clinically acceptable error of 0.5 years was 26.25% for Willems method and 27.19% for regression formula of CVBA. CONCLUSIONS: Willems method is more accurate than regression formula in indicating cervical vertebral skeletal age of adolescents in Shanghai children. Because of significant differences between CA and estimated ages, further modifications are urged to improve the accuracy of these two methods. Reference | Related Articles | Metrics

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Imaging characteristic of Stafne bone cavity：a retrospective study based on cone-beam CT HUANG Jin-cheng, ZHAO Hua-qiang, LI Guo-ju Shanghai Journal of Stomatology    2022, 31 (4): 439-444.   DOI: 10.19439/j.sjos.2022.04.020 Abstract （660）      PDF （1500KB）（298）       Knowledge map    PURPOSE: To guide clinical decision-making more efficiently via collecting and analyzing the imaging data of patients with Stafne bone cavity(SBC). METHODS: Six patients with SBC were retrospectively reviewed in Stomatological Hospital of Shandong University. By assessing cone-beam CT (CBCT) data, age, sex, complaint, cavity location, diameter at three dimension, maximal cross-sectional area of multi-planar reconstruction planes, content gray scale, morphological classification and its relationship with mandibular canal were recorded respectively. RESULTS: A total of 6 cases were inadvertently found on CBCT, with no symptoms. The locations of SBC were between mandibular molar region and mandibular angle, inferior border of mandible and mandibular canal, mostly at lingual side. Three were on the left and three were on the right. The bone cavity was elliptic and its long axis was consistent with the long axis of the mandible, with an average long axis diameter of (16.43±4.54) mm, horizontal axis diameter of (6.91±1.48) mm, vertical axis diameter of (10.24±2.10) mm. According to the multi-planar reconstruction planes readings, the maximal cross-sectional area of the bone cavity was (91.93±25.52) mm2, the maximal coronal area was (57.26±23.23) mm2, and the maximal sagittal area was (127.80±51.22) mm2. In view of the classification in the relationship between SBC marginal line and buccal cortical bone, there were 2 cases of type I cavity, 3 cases of type II cavity and 1 case of type III cavity. The connection between the bone cavity and the surrounding anatomical structure was classified into 3 conditions: covering penetration, adjacency and separation on the basis of the relative position between the cavity boundary with the mandibular inferior margin and the mandibular canal in sagittal plane. In addition, the content type could be primarily identified depending on estimation of corrected grey scale in the center of bone cavity. CONCLUSIONS: CBCT can make an intuitive and clear diagnosis of Stafne bone cavity, which brings great significance into the early clinical decision-making, thus not only avoiding unnecessary surgery, reducing the waste of additional medical resources, but also decreasing the physical and mental trauma of patients. Reference | Related Articles | Metrics

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Clinical and cone-beam CT analysis of 368 patients with temporomandibular joint disc perforation in different age groups LIU Huan-huan, CAI Heng-xing, WU Ye Shanghai Journal of Stomatology    2022, 31 (1): 67-70.   DOI: 10.19439/j.sjos.2022.01.014 Abstract （598）      PDF （544KB）（152）       Knowledge map    PURPOSE: The aim of this study was to investigate the clinical characteristics of disc perforation (DP) of temporomandibular joint (TMJ) at different ages. METHODS: Patients with TMJ disc perforation admitted to the Department of Trauma and Temporomandibular Joint Surgery Stomatological Hospital of Wuhan University, from April 2012 to May 2021 were included in this study. They were divided into 6 groups according to different ages. Clinical and CBCT radiographic features were analyzed. Clinical features included maximal interincisal opening, pain, clicking,and occlusal changes. Imaging features included condylar absorption flattening, hyperplasia or osteophyte formation, sclerosis, subchondral cysts, depression defects, and blurred anterior slope. The clinical and imaging characteristics of patients in different age groups were statistically analyzed. SPSS 26.0 software was used for statistical analysis, and Chi-square test was used to compare the distribution of clinical symptoms and imaging features in patients of different ages. RESULTS: A total of 368 patients were collected, including 24 males, with an average age of 27.63±15.90 years. There were 344 females with an average age of 32.61±15.61 years. The incidence of pain was 21.31%, occlusal change was 50.82%, and condylar absorption flat was 50.82% in the 10-19 age group. The incidence of pain in 20-29 age group was 31.06%, occlusal change was 53.42%, and condylar absorption flattening was 45.34%. In 50-59 age group, the incidence of pain was 83.33%, occlusal changes were 2.38%, and hyperplasia or osteophyte formation was 47.62%. In age group ≥60 years old, the incidence of pain was 82.86%, occlusal changes were 2.86%, and hyperplasia or osteophyte formation was 60%. CONCLUSIONS: In terms of clinical features, patients under 40 years old are more likely to have occlusal changes, while patients over 40 years old are most likely to have joint pain. Radiographically, patients under 40 years old are mainly characterized by bone loss in the condyle, while patients over 40 years old are mainly characterized by condylar hyperplasia. Reference | Related Articles | Metrics

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Clinical efficacy of the combination of miniscrew with clear aligner in controlling the roller coaster effect MA Xiao-qing, XIANG Fei, FAN Ming-yue, SONG Yi, WANG Xiao-hui, ZHANG Ling, QIAN Wen-hao Shanghai Journal of Stomatology    2022, 31 (2): 193-197.   DOI: 10.19439/j.sjos.2022.02.015 Abstract （563）      PDF （1173KB）（383）       Knowledge map    PURPOSE: To investigate the clinical efficacy of miniscrew in controlling the roller coaster effect in long-distance space closure with clear aligner. METHODS: Sixteen adult patients with bimaxillary protrusion were selected. All cases were treated with clear aligner and their four first premolars were extracted. G6 was designed in all cases. In the experimental group, four miniscrews were inserted at the beginning of treatment to control the teeth in three dimensions; while in the control group, the miniscrews were not applied until obvious roller coaster effect appeared. Paired t test was used to analyze the data with Graphpad Prism 6.0 software package. RESULTS: All the extraction space was closed successfully and the lateral profile was improved significantly. The torque of the upper incisor was under well control and no roller coaster effect happened in the experimental group; while in the control group, the lingual inclination of the upper incisors and open bite of the posterior teeth developed(P<0.05). After the miniscrews intrusion of the upper anterior teeth, the occlusion relationship improved significantly. CONCLUSIONS: Miniscrews effectively prevents and eliminates the roller coaster effect in the process of long-distance space closure with clear aligner. Reference | Related Articles | Metrics

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Effect of three mixing methods on air bubbles and solidification state of alginate impression materials ZHOU Yi-an, XIAO Song, XIE Xue-mei, WANG Yu-hua Shanghai Journal of Stomatology    2023, 32 (1): 12-16.   DOI: 10.19439/j.sjos.2023.01.003 Abstract （530）      PDF （658KB）（179）       Knowledge map    PURPOSE: To evaluate the effect of full-automatic mixing machine method, clockwise manual mixing and combined eight-shaped manual mixing on air bubble content, flowability, temperature, working time and setting time of alginate impression materials. METHODS: With the same condition, alginate impression materials were mixed by three different methods. The number of bubbles, area, flowability, temperature, working time and setting time were evaluated with SPSS 24.0 software package. RESULTS: The number of bubbles in the automatic mixing group was (2.30±2.50), and the area was (0.17±0.18) mm2, which was less than the number of clockwise manual mixing group (59.60±14.19), and the total area (7.41±2.24) mm2 (P<0.01). The flowability of the clockwise manual mixing group [(39.52±0.85) mm] was less than that of the full-automatic mixing group [(50.78±0.90) mm] and the combined eight-character manual mixing group [(50.36±1.75) mm](P<0.01).The setting time of the material mixed by three methods was eligible for clinical use. CONCLUSIONS: The mixing method of alginate impression material has an effect on material's bubble content, flowability and temperature changes. The impression materials mixed by full-automatic mixing method are better in terms of bubble content, flowability and other properties. If manual mixing is used, combined eight-shaped manual mixing method can help reduce impression bubbles and deformation, and improve flowability. Reference | Related Articles | Metrics

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Comparative study on the effect of microscopic revascularization and apexification in the treatment of pulp necrosis of permanent teeth LIN Xiao-ming, SU Jiang-ling, PU Cui-ping Shanghai Journal of Stomatology    2022, 31 (3): 318-321.   DOI: 10.19439/j.sjos.2022.03.019 Abstract （529）      PDF （564KB）（260）       Knowledge map    PURPOSE: To compare the curative effect of microscopic revascularization and apexification in the treatment of pulp necrosis of permanent teeth. METHODS: Seventy-five cases of pulp necrosis in young permanent teeth were divided into two groups according to different treatment methods. Group A (n=30) underwent revascularization under microscope, while group B (n=45) underwent apexification. The treatment effect and pain improvement of the two groups were compared. The changes of the wall thickness and root canal length of the affected teeth before and after treatment were observed, and the bone-like deposition rate after treatment was recorded. SPSS 23.0 software package was used for statistical analysis. RESULTS: There was no significant difference in the length of root canal between the two groups before treatment (P>0.05); there was no significant difference in the length of root canal in group B before and after treatment (P>0.05); the length of root canal in group A was significantly longer than that in group B 6 months after treatment(P<0.05). There was no significant change in the thickness of root canal wall in group B before and after treatment (P>0.05). The thickness of root canal in group A was significantly higher than that in group A 6 months after treatment (P<0.05). Bone-like deposition rate of group A was significantly higher than that of group B 1 month and 6 months after treatment (P<0.05). The total effective rate of group A and B was 90.00% and 84.44%, the difference was not statistically significant (P>0.05). The cure rate of group A was 70.00%, which was significantly higher than that of group B (48.89%, P<0.05). COCLUSIONS: Microscopic revascularization for pulp necrosis of young permanent teeth can effectively promote root development, lengthen root canal and increase the thickness of canal wall, which is better than apexification. Reference | Related Articles | Metrics

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MRI findings of parotid acinic cell carcinoma in 19 consecutive cases XIAO Hua, TAO Xiao-feng, ZHU Wen-jing, CHEN Qian-qian Shanghai Journal of Stomatology    2022, 31 (3): 322-326.   DOI: 10.19439/j.sjos.2022.03.020 Abstract （461）      PDF （1403KB）（179）       Knowledge map    PURPOSE: To describe the MRI features of acinar cell carcinoma of parotid gland (AciCC) and to evaluate the diagnostic value of MR functional imaging. METHODS: A total of 269 cases of maxillofacial AciCC confirmed by surgery and pathology were analyzed. Among them, nineteen subjects with AciCC in the parotid gland underwent preoperative MRI examination (non-enhanced scan for one case, enhanced scan for 18 cases), seventeen patients underwent diffusion-weighted imaging scan, and 15 patients underwent dynamic contrast-enhanced scan. MRI findings of 19 patients were retrospectively analyzed. The lesion size, location, morphology, margin, internal composition, enhancement pattern and functional imaging characteristics were analyzed. SPSS 25.0 software package was used for statistical analysis. RESULTS: Among 269 cases of maxillofacial AciCC, there were 108 males and 161 females, male: female = 1:1.49, aged from 4 to 89 years, with a mean age of (45.95±17.33) years. 84.4% (227/269) were located in the parotid gland. On MRI images, 78.9% (15/19) had well-defined margin, 57.9% (11/19) were round or oval, and 36.8% (7/19) were lobed nodules. One case had irregular morphology and peripheral invasion. The range of maximum diameter was 6-56 mm, averaging (24.8±15.3) mm. Internal composition showed 57.9% (11/19) were cystic solid, 42.1% (8/19) were solid, 31.6% (6/19) had bleeding. T2-weighted MRI showed 52.6% (10/19) with envelope structure, 15.8% (3/19) with low signal separation inside, 38.9%(7/18) had uniform enhancement, and 61.1%(11/18) had uneven enhancement. Functional imaging showed the mean ADC value of tumor was (1.026±0.194)×10-3 mm2/s(n=17). 86.7%(13/15) TIC was type Ⅱ. CONCLUSIONS: Most maxillofacial AciCC are located in the parotid gland. It is difficult to distinguish AciCC from benign tumors with conventional MRI in morphology. The ADC value of AciCC is lower than that of benign tumors, and the type of TIC curve is mostly type Ⅱ. Combination of morphology and functional imaging can improve the diagnostic accuracy of this disease. Reference | Related Articles | Metrics

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Effects of two implant systems on peri-implant soft tissue CAO Wei-yu, CAO Jie, LIU Bin-yi, XU Zhou Shanghai Journal of Stomatology    2022, 31 (3): 305-308.   DOI: 10.19439/j.sjos.2022.03.016 Abstract （448）      PDF （535KB）（158）       Knowledge map    PURPOSE: To investigate the effect of different implant systems on peri-implant soft tissue. METHODS: Forty patients requiring single implant therapy in posterior teeth at Dental and Ophthalmic Clinic of Putuo District from December 2020 to February 2021 were selected. Ten patients were implanted with bone level implants and 30 patients with soft tissue level implants. Periodontal exploration was performed at the buccal side, lingual side, mesial and distal axial angle of the implants, and the gingival crevicular fluid of these locations were taken to detect the enzyme level. The probing depth, aspartate aminotransferase (AST) and alkaline phosphatase (ALP) level of the two groups were compared at the day, 3 months, 6 months and 12 months after crown restoration. Statistical analysis was completed by SPSS 17.0 software package. RESULTS: The probing depth and ALP level of soft tissue level implants were significantly lower than those of bone level implants at the day, 3 months, 6 months and 12 months after crown restoration(P<0.05). At the day when crown restoration was accomplished, AST of soft tissue implant was significantly lower than that of bone level implant(P<0.05). AST in gingival crevicular fluid of bone level implants decreased rapidly in the following three time periods, and close to that of the soft tissue level implants(P>0.05) at last. CONCLUSIONS: Both bone level implants and soft tissue level implants have good clinical effects, but peri-implant soft tissues of the soft tissue level implants show better stability. Reference | Related Articles | Metrics

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Effect of different adduction methods of maxillary incisor in adolescents on the shape of alveolar bone XIE Qin, LIN Shan, LIN Li, LI Duo Shanghai Journal of Stomatology    2022, 31 (3): 290-294.   DOI: 10.19439/j.sjos.2022.03.013 Abstract （448）      PDF （595KB）（167）       Knowledge map    PURPOSE: To explore the influence of different adduction methods of maxillary incisor in adolescents on the shape of alveolar bone. METHODS: Three hundred and twenty-eight maxillary incisors were collected from 82 patients with jaw protrusion deformity treated in Union Hospital of Fujian Medical University from June 2018 to June 2019. 135 incisors were included in the oblique adduction group, and 193 incisors were included in the root control adduction group. All patients took cone-beam CT(CBCT) to measure the adduction of the maxillary incisor and the changes in alveolar bone height, thickness, and bone density. Statistical analysis was performed with SPSS 18.0 software package. RESULTS: The length of the maxillary incisor to the mid-palatine vertical surface(IE-MP), the long axis of the maxillary incisor and the posterior inferior angle of the palatal plane (LAI-PP) in oblique adduction group were significantly greater than root control adduction group(P<0.05). The length of the maxillary incisor from the apex of the maxillary incisor to the mid-palatine vertical surface(RA-MP) in the oblique adduction group was significantly smaller than the root control adduction group (P<0.05). Postoperative L1, L2, L3, P1, T1 of the oblique adduction group were significantly lower than preoperative values(P<0.05), and postoperative P2, P3, T2, and T3 were significantly higher than preoperative value(P<0.05). Postoperative L1, L2, and L3 of the root control adduction group were significantly higher than those before operation (P<0.05), and postoperative P1, P2, P3, T1, T2, and T3 were significantly lower than those before operation(P<0.05). The changes of L2, L3, P3, T3 of the oblique adduction group were significantly higher than the control root adduction group(P<0.05), and the changes of L1, P1, P2, T1, T2 of the oblique adduction group were all significantly lower than the control root adduction group(P<0.05). There was no significant difference in bone mineral density of the upper and lower jaws between the two groups before and 6 months after operation(P>0.05). CONCLUSIONS: When adolescents' maxillary incisors are retracted in a wide range, the labial apical area, the palatal alveolar ridge area of the oblique adduction group, and the palatal root neck of the root control adduction group are all high-risk areas for alveolar bone resorption. Reference | Related Articles | Metrics

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Effect of titanium nitride coatings with different thickness on microhardness and cutting efficiency of nickel-titanium instruments LIU Dan, YU Jing-tao, QIU Li-hong Shanghai Journal of Stomatology    2022, 31 (1): 58-61.   DOI: 10.19439/j.sjos.2022.01.012 Abstract （425）      PDF （710KB）（179）       Knowledge map    PURPOSE: To investigate the effect of titanium nitride (TiN) coatings with different thicknesses on microhardness and cutting efficiency of nickel-titanium (NiTi) instruments, and to provide a basis for improving the efficiency of clinical root canal preparation. METHODS: Fifteen KV4 NiTi alloy sheets and sixty KV4 rotary NiTi files were selected and randomly divided into 5 groups: uncoated group, coating 1 h group, coating 2 h group, coating 3 h group and coating 4 h group. A layer of TiN coatings of different thicknesses was prepared on the surface of the coated groups by controlling the deposition time. The film thickness of each group was measured by scanning electron microscopy (SEM). The microhardness of each group of NiTi alloy sheets was measured by a Vickers hardness tester. Sixty transparent resin modules were selected and each resin module was prepared with one NiTi file. The cutting efficiency of each group was measured by the weight loss method. SEM was used to examine the surface of NiTi instruments in 5 groups before and after preparation. One-way variance analysis was used to determine the statistical differences with SPSS 22.0 software package. RESULTS: With the increase of the thickness of titanium nitride coating, the microhardness of NiTi alloy gradually increased(P<0.05). With the increase of the thickness of titanium nitride coating, the cutting efficiency of NiTi instrument was improved, and the cutting efficiency was the largest when the coating thickness was 860 nm(P<0.05). The surface morphology of the coated group was better than that of the uncoated group. CONCLUSIONS: The thickness of TiN coating affects microhardness and cutting efficiency of the nickel-titanium instruments, the microhardness and cutting ability enhanced as the thickness increased. If the thickness is too large, the cutting efficiency will be reduced. Reference | Related Articles | Metrics

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Evaluation of the effect of Insignia system in customized orthodontic treatment LIU Fan, LIU Lin, WANG Yan-hong Shanghai Journal of Stomatology    2022, 31 (1): 96-99.   DOI: 10.19439/j.sjos.2022.01.020 Abstract （417）      PDF （484KB）（330）       Knowledge map    PORPOSE: To investigate the effect of Insignia system in customized orthodontic treatment. METHODS: A total of 71 patients with malocclusion undergoing orthodontic treatment in Dalian Stomatological Hospital from March 2018 to August 2019 were enrolled, and divided into two groups according to random number table methods. Patients in non-customized group received Damon Q self-locking brackets, while patients in customized group received individualized brackets combined with Insignia appliance. The patients were revisited every 8 weeks in initial phase and thereafter every 6 weeks. The clinical efficacy, number of visits, time required for treatment planning and treatment duration were compared between the two groups. The severity of malocclusion, changes after treatment and improvement before and after treatment were evaluated by peer assessment rating (PAR). The complications and loose brackets during treatment were observed. SPSS 20.0 software package was used to analyze the data. RESULTS: The total effective rate of customized group was significantly higher than that of non-customized group (P<0.05). No significant difference was found in treatment duration between the two groups(P>0.05). The number of visits and time required for treatment planning of customized group were significantly longer than those of non-customized group(P<0.05). After treatment, the midline, tooth dislocation, molar buccal occlusion, overbite, overjet and weighted PAR total scores increased in both groups, and the increase was more significant in customized group(P<0.05). The gingival bleeding rate showed no significant difference between the two groups(P>0.05), while the rate of loose brackets was significantly higher in customized group than in non-customized group (P<0.05). CONCLUSIONS: Compared with non-customized system, insignia customized system has more visits, longer treatment planning time and higher bracket loosening rate, but its effect is better. In general, it has little effect on the treatment duration and does not increase the bracket shedding rate. Reference | Related Articles | Metrics

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Study of the mandibular changes after treatment of Class Ⅱ division 2 malocclusion in adolescents ZHOU Ming-zhi, WANG Lin, WANG Liang, WU Ke, QIN Yan-jun, ZHAO Chun-yang Shanghai Journal of Stomatology    2022, 31 (4): 389-394.   DOI: 10.19439/j.sjos.2022.04.010 Abstract （407）      PDF （886KB）（237）       Knowledge map    PURPOSE: To evaluate the mandibular and dentoalveolar changes in Class Ⅱ division 2 malocclusion adolescents after treatment. METHODS: Thirty-six patients treated in our hospital were selected. Twelve skeletal Class Ⅱ division 2 adolescents were served as the experimental group, while 12 skeletal Class Ⅱ division 2 adults were selected as the control group 1, 12 skeletal Class Ⅰ adolescents were selected from those who have undergone fixed orthodontic treatment as the control group 2. Cone-beam CT (CBCT) was taken before and after treatment. The lateral cephalometric radiographs generated from CBCT data were committed to explore the changes of the mandible and dentoalveolar bone before and after orthodontic treatment among three groups. Statistic analysis was completed by SPSS 21.0 software package. RESULTS: After orthodontic treatment, the mandibular length (Go-Gn), mandibular ramus height (Co-Go), mandibular protrusion (SNB), mandibular dentoalveolus protrusion (SNId), lower facial height (S-Go, ANS-Me, ANS-Me/N-Me) increased and the fossa of chin decreased significantly in Class Ⅱ division 2 adolescents (P<0.05). The differences of SNB, SNId, ANS-Me/N-Me between Class Ⅱ division 2 and Class Ⅰ adolescents decreased. CONCLUSIONS: The growth potential of the mandible is released after treatment of Class Ⅱ division 2 malocclusion adolescents, promoting mandibular growth and reconstruction. Reference | Related Articles | Metrics

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Comparison of three root canal disinfection methods for removal of Enterococcus faecalis under minimally invasive root canal treatment SHAN Xiao-yang, SUN Li-qing, WANG Yue-yue, YANG Nan, SUN Hui-bin Shanghai Journal of Stomatology    2022, 31 (1): 17-23.   DOI: 10.19439/j.sjos.2022.01.004 Abstract （389）      PDF （1490KB）（205）       Knowledge map    PURPOSE: To obtain an efficient and simple root canal disinfection method based on minimally invasive root canal treatment by comparing different root canal disinfection methods between minimally invasive root canal treatment and conventional root canal treatment. METHODS: Sixty-six extracted maxillary first molars were randomly divided into experimental group (computer-guided precision minimally invasive root canal treatment) and control group (conventional root canal treatment). All teeth were prepared to ProTaper universal F2, and Enterococcus faecalis infection models were established.Each group was randomly divided into three subgroups, sodium hypochlorite+EDTA root canal irrigation, sodium hypochlorite+EDTA+ultrasonic and sodium hypochlorite +EDTA +Er: YAG laser. After root canal disinfection,the samples were collected by paper tip method and cultured, and colony forming units (CFU) values of each sample were calculated. Then dentin debris was prepared and collected with F3 file. After being diluted and cultured, the CFU value was calculated. Statistical analysis was performed by SPSS 26.0 software package. RESULTS: Comparison of the amount of bacterial inner wall of root canal between the experimental group and the control group showed that the germicidal efficacy of group C and group B were significantly better than that of group A (P<0.05), but there was no significant difference between group B and group C(P>0.05). In the experimental group, there was significant difference between group B1, C1 and A1 (P<0.05). The results of group B1 and C1 were lower than that of group A1, but there was no significant difference between group B1 and group C1(P>0.05). In the control group, there were significant differences between group B2, C2 and A2 (P<0.05). The results of group B2 and C2 were lower than that of group A2, but there was no significant difference between group B2 and C2(P>0.05). Comparison of the amount of bacteria in dentin debris between the experimental group and the control group showed that the effect of group C was the best, followed by group B, and group A, and there were significant differences between three groups(P<0.05). CONCLUSIONS: The disinfection effect of Er:YAG laser or ultrasound assisted computer-guided precision minimally invasive root canal treatment is similar to conventional root canal treatment, and Er:YAG laser is better than ultrasound in removing bacteria from dentinal tubules, which is more suitable for minimally invasive root canal treatment. Reference | Related Articles | Metrics

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Influence of bilateral coronoidectomy on temporomandibular joint stress distribution after costochondral graft reconstruction: a finite element analysis MAO Yi, CHEN Xu-zhuo, QIN Hai-yi, ZHEN Jin-ze, QIU Ya-ting, HUO Liang, ZHANG Shan-yong Shanghai Journal of Stomatology    2022, 31 (2): 126-131.   DOI: 10.19439/j.sjos.2022.02.003 Abstract （376）      PDF （1861KB）（162）       Knowledge map    PURPOSE: To explore the effect of bilateral coronoidectomy on stress distribution after reconstruction of temporomandibular joint (TMJ) by costochondral graft. METHODS: Ten groups of models were established to simulate costochondral graft reconstruction with simultaneously different distances (0, 2, 4, 6, 8 mm) of mandibular advancement, with or without coronoidectomy. Force and stress distribution in the rib-cartilage area were analyzed by finite element analysis. RESULTS: In the process of bilateral joint reconstruction with simultaneously mandible advancement ranging from 0 mm to 8 mm, when the coronoid processes were retained, the forward deformation of the cartilage occurred and the shear force decreased in turn, from 113.2 N to 26.7 N on the left side and from 133.7 N to 1.9 N on the right side. When the coronoid processes were removed, the cartilage deformed backward and the shear force increased successively, from 94.6 N to 188.5 N on the left and 70.1 N to 157.7 N on the right. The stress in the neck was obviously concentrated when mandible advanced 8 mm. CONCLUSIONS: Coronoidectomy has an important impact on stress distribution in the TMJ area, and keeping the coronoid process is beneficial to maintain the mechanical balance. Bilateral CCG reconstruction with coronoidectomy for lengthy mandible advancement (≥ 8 mm) may lead to prominent increase in shear force beyond CCG resistance, resulting in a costal-cartilage junction fracture. Reference | Related Articles | Metrics

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Research on the pathogeny of black tooth stain and association between black tooth stain and primary dentition caries in children MIAO Fen, MA Hao-ran, LIU Zi-han Shanghai Journal of Stomatology    2022, 31 (3): 282-285.   DOI: 10.19439/j.sjos.2022.03.011 Abstract （375）      PDF （544KB）（224）       Knowledge map    PURPOSE: To investigate the related factors of black tooth stain in primary teeth of 3~5 years old children and caries status of primary dentition in these children. METHODS: From December 2019 to August 2020, 182 3~5 years old children with black tooth stain and 200 children without pigmentation were investigated by oral examination and questionnaire survey to their guardians, while caries status , distribution range of the pigment, factors associated with black tooth stain were evaluated. SPSS 20.0 software package was used for data analysis. RESULTS: Children with black tooth stain had fewer dental caries. The lingual surfaces of the mandibular anterior teeth were the most affected sites. Factors associated with black tooth stain were foods with soy sauce and brushing teeth with parents' help. CONCLUSIONS: There is a negative correlation between the occurrence of primary dentition caries and blacktooth stain, but there is no significant correlation between formation of black tooth stain and most environmental factors. Reference | Related Articles | Metrics

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Evaluation of the effect of digital crown extension guide in aesthetic restoration of anterior teeth WANG Xue-chun, WANG Yong, XU Xiao-bo, HAO Xin-he Shanghai Journal of Stomatology    2022, 31 (3): 260-264.   DOI: 10.19439/j.sjos.2022.03.007 Abstract （375）      PDF （749KB）（448）       Knowledge map    PURPOSE: To evaluate the clinical effect of three-dimensional digital smile design (3D-DSD) combined with double positioning crown extension guide in aesthetic restoration of anterior teeth. METHODS: Twenty patients who needed aesthetic crown lengthening and full crown restoration of upper anterior teeth were selected and randomly divided into the experimental group and control group, with 10 cases in each group. The experimental group carried out 3D-DSD, after confirming the plan, 3D printed double positioning crown extension guides were used to guide aesthetic crown lengthening, and full crown was completed 3 months after operation. The control group used traditional aesthetic crown lengthening and full crown restoration. PES/WES evaluation was performed before operation, three months and six months after operation. Visual analogue scales(VAS) were used to evaluate patient satisfaction 6 and 7 months after surgery, and the repeatability evaluation of VAS was conducted. The correlation between PES/WES score and overall satisfaction was analyzed 6 months after operation. SPSS 23.0 software package was used for statistical analysis. RESULTS: The PES/WES scores of the two groups of patients at 3 months and 6 months after operation were higher than those before operation(P<0.05). The two groups showed that the scores of the experimental group were significantly higher than those of the control group for PES 3 months after operation, PES and WES 6 months after operation(P<0.05).Satisfaction survey results showed that the intra-group correlation coefficient of the two VAS results was 0.956(P<0.05),and crown length-to-width ratio, smile curve, personality characteristics, patient participation and overall satisfaction in the experimental group were better than those of the control group(P<0.05).The results of Speraman correlation analysis showed that PES and WES scores at 6 months after operation were positively correlated with overall satisfaction (rs1=0.905, P<0.001; rs2=0.460, P=0.041). CONCLUSIONS: 3D digital smile design combined with double positioning crown extension guide guides the anterior aesthetic crown lengthening and restoration treatment, which can improve the effect of pink and white aesthetics after treatment and patient satisfaction. Reference | Related Articles | Metrics

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Clinical effect and related influencing factors of implant and implant-natural tooth in dental restoration DUAN Yong-hua, YU Min, PAN Liang, LIN Hua-jun, GUO Mei-ling Shanghai Journal of Stomatology    2022, 31 (1): 84-88.   DOI: 10.19439/j.sjos.2022.01.018 Abstract （368）      PDF （576KB）（170）       Knowledge map    PURPOSE: To investigate the clinical effect and related influencing factors of implant and implant-natural tooth in dental restoration. METHODS: A total of 67 edentulous patients receiving dental implantation in Shangrao People's Hospital from May 2016 to June 2017 were enrolled, including 34 cases of implant-natural tooth supported restoration (combined group) and 33 cases of implant restoration (single group). During the 3-year follow-up, the repair effect and bone resorption of the two groups were evaluated. The general data of patients were collected, then the influencing factors of implant failure were screened. Statistical analysis was performed using SPSS 20.0 software package. RESULTS: The success rate of dental restoration was 93.65% in combined group, and 95.08% in simple implant group, with no significant difference between the two groups (P>0.05). The bone resorption of the alveolar ridge in combined group was significantly higher than that in simple implant group 1 and half years after operation (P<0.05). The proportion of female, maxillary posterior area, dental pulp disease, grade IV bone mineral density loss, diabetes mellitus, smoking history, implant diameter>4.5 mm, length>12 mm, periodontal probe depth>3 mm, and sulcus bleeding index≥2 were significantly higher in implant failure group than in implant success group (P<0.05). Bone mineral density loss, diabetes mellitus, smoking history, sulcus bleeding index≥2 and periodontal probe depth>3 mm were the risk factors of implant failure(P<0.05). CONCLUSIONS: Both implant and implant-natural tooth are effective in dental restoration, and implant-natural tooth restoration has good short-term efficacy, while bone mineral density loss, diabetes mellitus, smoking history, sulcus bleeding index≥2 and periodontal probe depth>3mm are the risk factors of implant failure. Reference | Related Articles | Metrics