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Table of Content
01 June 2024, Volume 42 Issue 3
  • Multidisciplinary clinical decision-making of anterior diastema closure
    Yu Haiyang, Shui Yusen, Jiang Qingsong
    West China Journal of Stomatology. 2024, 42(3):  277-285.  doi:10.7518/hxkq.2024.2023460
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    Anterior diastema is a common esthetic defect in China. The general treatment for a patient with diastemata, including orthodontics and direct and indirect restorations, is a multidisciplinary clinical procedure covering the orthodontics, operative dentistry, general dentistry, and prosthodontics department. Given the diversity of departments and the complex etiology of this defect, decision-making regarding the closing methods and time selection is undefined and unintegrated, which makes the long-term stability of closure unpredictable. This article proposed an etiology-based decision tree with actual measurement of diastemata width for diastemata closure. The decisional steps include classifying the etiological factors based on patients' medical history and clinical manifestation to evaluate the stability of diastemata. After maintaining the stability of diastemata, contemporary and multidisciplinary treatment plans were selected in accordance with the measured width of diastemata and patients' cosmetic psychology, economics, and available time. These decision trees focus on the challenges of collaboration among dental departments, propose an objective and efficient ways for connections, and promote efficient and effective diastemata closure.

    Basic Research
    Temporal and spatial expression analysis of periostin in mice periodontitis model
    Li Yue, Xu Chunmei, Xie Xudong, Shi Peilei, Wang Jun, Ding Yi
    West China Journal of Stomatology. 2024, 42(3):  286-295.  doi:10.7518/hxkq.2024.2023336
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    Objective This study aimed to investigate the temporal and spatial changes in the expression of periostin during periodontal inflammation in mice. Methods A periodontitis model was constructed using silk thread ligation. Mice were randomly divided into five groups including control group, 4-day ligation group, 7-day ligation group, 14-day ligation group, and self-healing group (thread removal for 14 days after 14-day ligation). Micro-CT and histological staining were performed to characterize the dynamic changes in the mouse periodontal tissue in each group. RNAscope and immunohistochemical staining were used to analyze the pattern of changes in periostin at various stages of periodontitis. The cell experiment was divided into three groups: control group, lipopolysaccharide (LPS) stimulation group (treated with LPS for 12 h), and LPS stimulation removal group (treated with LPS for 3 h followed by incubation with medium for 9 h). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of periostin, transforming growth factor-β1 (TGF-β1), and matrix metalloproteinase 2 (MMP2). Results Significant alveolar bone resorption was observed 7 days after ligation. With increasing duration of ligation, the damage to the mouse periodontal tissue was aggravated, which manifested as increased osteoclasts, widening of the periodontal membrane space, and decreased alveolar bone height. Some degree of periodontal tissue repair was observed in the self-healing group. Periostin expression decreased at 4 and 7 days compared with the control group and increased at 14 days compared with 4 and 7 days. A significant recovery was found in the self-healing group. The qRT-PCR results showed that the expression of periostin and TGF-β1 in the LPS stimulation group decreased compared with that in the control group but significantly recovered in the LPS removal group. Conclusion Periostin expression in the PDL of mice showed a downward and upward trend with inflammation progression. The significant recovery of periostin expression after removing inflammatory stimuli may be related to TGF-β1, which is crucial to maintain the integrity of the PDL.

    Role of connexin 43 in a rat model of periodontitis-induced renal injury
    Xin Yu, Fu Ruobing, Xin Xirui, Shang Yaqi, Liu Xinchan, Yu Weixian
    West China Journal of Stomatology. 2024, 42(3):  296-303.  doi:10.7518/hxkq.2024.2023352
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    Objective This study aims to investigate the role of gap junction mediated by connexin 43 (Cx43) in renal injury induced by periodontitis in rats. Methods Twelve SPF-grade Wistar male rats were divided into a control group and a periodontitis group by using a completely random number table method, with six rats in each group. The control group rats were not treated, while the periodontitis group rats were subjected to wire ligation of the neck of their bilateral maxillary first molars to construct a periodontitis model. After 8 weeks of modeling, the rats were examined for clinical indicators of the periodontium. micro-CT scanning of the maxilla reconstructed its 3D structure and analyzed the absorption of alveolar bone. Histopathological changes in periodontal and renal tissues were detected. MitoSOX red reagent was used to determine reactive oxygen species (ROS) content in renal tissues. A biochemical reagent kit was used to detect serum oxidative stress biomarkers. Real-time fluorescent quantitative-polymerase chain reaction (qRT-PCR) was employed to determine Cx43, nuclear factor kappa-B (NF-κB) , interleukin (IL)-1β, IL-6, BCL2-Associated X (Bax), B-lymphomatoma-2 gene (Bcl-2), and Caspase-3 mRNA were determined. Western blot analysis was used to detect Cx43, NF-κB, IL-1β, Bax, Bcl-2 and Caspase-3 protein. Results micro-CT 3D reconstruction showed significant bone resorption of the first molar alveolar bone in the periodontitis group rats and decreased height of the alveolar ridge. The distance from the enamel cementum boundary to the top of the alveolar ridge in the periodontitis group was significantly higher than that inthe control group. The histopathological results showed a large number of inflammatory cells that infiltrated the periodontal tissue of the periodontitis group, and the alveolar bone was significantly absorbed. Rats in the periodontitis group also exhibited mild thickening of the glomerular basement membrane, dilation of the Bowman’s capsule, and destruction of the brush-like edge of the renal tubules in the renal tissue. The MitoSOX red staining results showed a significant increase in ROS content in the renal tissue of the periodontitis group. The biochemical test results showed that the levels of superoxide dismutase and glutathione in the serum of rats with periodontitis decreased, while that of malondialdehyde increased. The results of qRT-PCR and Western blot showed that the expression levels of Cx43, IL-1β, IL-6, Bax, Caspase-3 mRNA and Cx43, IL-1β, NF-κB, Bax, Caspase-3 proteins in the periodontitis group significantly increased compared with those in the control group, while the expression levels of Bcl-2 mRNA and protein decreased. Conclusion Periodontitis may activate NF-κB signaling molecules by upregulating the expression of Cx43 in rat kidney tissues, leading to increased levels of inflammation and apoptosis and ultimately inducing kidney injury.

    Role of the GRP78-c-Src signaling pathway on osteoblast differentiation of periodontal ligament fibroblasts induced by cyclic mechanical stretch
    Hu Jing, Cui Zhihua, Huang Keqiang, Su Rongjian, Zhao Song
    West China Journal of Stomatology. 2024, 42(3):  304-312.  doi:10.7518/hxkq.2024.2023354
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    Objective This study aims to investigate the influence of glucose regulated protein (GRP) 78 on osteoblast differentiation in periodontal ligament fibroblasts (PDLFs) under cyclic mechanical stretch and determine the underlying mechanism. Methods FlexCell 5000 cell mechanical device was applied to simulate the stress environment of orthodontic teeth. GRP78High and GRP78Low subpopulation were obtained by flow sorting. Gene transfection was performed to knockdown GRP78 and c-Src expression and overexpress c-Src. Western blot analysis was used to detect the protein expression of Runt-related gene 2 (RUNX2), Osterix, osteocalcin (OCN), and osteopontin (OPN). Immunoprecipitation assay was used to determine the interaction of GRP78 with c-Src. The formation of cellular mineralized nodules was determined by alizarin red staining. Results GRP78 was heterogeneously expressed in PDLFs, and GRP78High and GRP78Low subpopulations were obtained by flow sorting. The osteogenic differentiation ability and phosphorylation level of c-Src kinase in the GRP78High subpopulation were significantly increased compared with those in GRP78Low subpopulation after cyclic mechanical stretch (P<0.05). GRP78 interacted with c-Src in PDLFs. The overexpression c-Src group showed significantly increased osteogenic differentiation ability than the vector group (P<0.05), and the sic-Src group showed significantly decreased osteogenic differentiation ability (P<0.05) after cyclic mechanical stretch. Conclusion GRP78 upregulates c-Src expression by interacting with c-Src kinase and promotes osteogenic differentiation under cyclic mechanical stretch in PDLFs.

    Correlation between FOXN3-SIN3A complex expression in peripheral blood and non-syndromic cleft lip and palate in Xinjiang
    Duolikun·Wufuer , Dilibaier·Yimingjiang , Kamilijiang·Maimaitiming , Li Jun, Wulifan·Tuoleheng
    West China Journal of Stomatology. 2024, 42(3):  313-318.  doi:10.7518/hxkq.2024.2023340
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    Objective This work aimed to study the correlation between FOXN3-SIN3A complex expression and non-syndromic oral clefts (NSOC) in Xinjiang. Methods In this study, 60 patients with NSOC attending the People’s Hospital of Xinjiang Uygur Autonomous Region were recruited into the case group, including 30 cleft lip with or without cleft palate (NSCL/P), 30 cleft palate only (CPO), and 30 healthy children in the control group. The expression levels of FOXN3, SIN3A, and NEAT1 in peripheral blood of each group were detected by high-throughput second-generation sequencing technology and quantitative reverse transcription polymerase chain reaction (RT-qPCR). Receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to analyze the diagnostic efficiency of NSOC. Results The comparison of the NSOC and control groups showed that FOXN3, SIN3A, and NEAT1 genes increased compared with the control group. The differences were all statistically significant (P<0.05). The AUCs of FOXN3, SIN3A, and NEAT1 in the NSCL/P group were 0.933 [95%CI=(0.864, 1.000)], 0.822 [(95%CI=(0.713, 0.932)], and 1.000[95%CI= (1.000, 1.000)], respectively. The AUCs of FOX-N3, SIN3A, and NEAT1 in the CPO group were 0.891 [95%CI=(0.806, 0.976)], 0.688 [95%CI=(0.552, 0.824)], and 1.000 [95%CI=(1.000, 1.000)], respectively. Conclusion The results showed a correlation between the rising gene expression of FOXN3, SIN3A, and NEAT1 in peripheral blood and the occurrence of NSOC in Xinjiang. This work provides a theoretical basis for further study of the FOXN3-SIN3A complex as biomarkers to facilitate the early screening, disease prediction, and early prevention of NSOC.

    Global analysis of DNA methylation changes during experimented lingual carcinogenesis
    Liu Hua, Yue Wanyuan, Shao Shuai, Sun Jiaping, Yang Ying, Dai Xiaoming
    West China Journal of Stomatology. 2024, 42(3):  319-328.  doi:10.7518/hxkq.2024.2023416
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    Objective This study aims to assess the role of DNA methylation changes in tongue cancer through a comprehensive analysis of global DNA methylation alterations during experimental lingual carcinogenesis. Methods C57BL/6J mice were subjected to 16-week oral administration of 4-nitroquinoline-1-oxide (4NQO, 50 mg/L). Lingual mucosa samples, being representative of normal tissue (week 0) and early (week 12) and advanced (week 28) tumorigenesis, were harvested for microarray and methylated DNA immunoprecipitation sequencing (MeDIP-Seq). The mRNA and promoter methylation of transforming growth factor-beta-signaling protein 1 (SMAD1) were evaluated with real-time quantitative reverse transcription polymerase chain reaction and Massarray in human lingual mucosa and tongue cancer cell lines. Results The cytosine guanine island (CGI) methylation level observed at 28 weeks surpassed that of both 12 weeks and 0 weeks. The promoter methylation level at 12 weeks exceeded that at 0 weeks. Notably, 208 differentially expressed genes were negatively correlated to differential methylation in promoters among 0, 12, and 28 weeks. The mRNA of SMAD1 was upregulated, concurrent with a decrease in promoter methylation levels in cell lines compared to normal mucosa. Conclusion DNA methylation changed during lingual carcinogenesis. Overexpression of SMAD1 was correlated to promoter hypomethylation in tongue cancer cell lines.

    Clinical Research
    Morphological study of distal furcation in mandibular first molars based on cone beam computed tomography images in Beijing population
    Zhu Jie, Liu Ya
    West China Journal of Stomatology. 2024, 42(3):  329-333.  doi:10.7518/hxkq.2024.2023348
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    Objective This retrospective study explored the incidence of independent distal-lingual root (DLR) in mandibular first molars and the morphologic features of distal furcations through cone beam computed tomography (CBCT) in Beijing population. Methods A total of 401 CBCT images of both mandibular first molars existed were included. The sex of the patients, the incidence of DLR, the distal root trunk length (DRT), the locations of distal furcation entrance (DFE), and the separation angle of distal furcation (ADF) were recorded. Results The incidence rates of DLR were 33.2% on the subject level and 26.8% on the tooth level. The incidence of DLR was not different between genders but was higher on the right sides. The DRT values were 4.15 mm±1.02 mm. The ADF was 65.56°±11.56°. The DFE was located lingually, and 97.2% DFE was located more apically than buccal/lingual furcations. Conclusion A high incidence of DLR was found in the Beijing population. The DRT was longer than buccal and lingual sites. The DFE was located lingually with a wide separation. Understanding the morphological features of distal furcation can help clinicians to make proper treatment plans.

    Integration of autonomous maximal smile 3D image with digital 3D dental model and investigation of its accuracy
    Tang Zhenxing, Qian Yuran, Ren Ruiting, Song Wanzhong, Li Yu
    West China Journal of Stomatology. 2024, 42(3):  334-339.  doi:10.7518/hxkq.2024.2023407
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    Objective This study aims to establish an approach to integrate autonomous maximal smile (AMS) 3D facial image with digital 3D dental models to demonstrate the digital orthodontic set-up in the 3D facial context. Methods Using Geomagic Studio software, the AMS 3D facial image and pre-treatment dental model were manually and globally registered. Subsequently, the pre-treatment dental model was substituted with the predicted post-treatment dental model. The intraoral region of the AMS 3D facial image was removed, achieving a conjunctive display of the AMS 3D facial image and the post-treatment dental set-up. The distances between four groups of corresponding landmark pairs on the AMS 3D facial image and the pre-treatment dental set-up were calculated, and the accuracy of the registration operation was evaluated by paired t-test. Results The novel approach effectively facilitated the integration of AMS 3D facial images with the pre-treatment and predicted post-treatment 3D dental models. The average distances between the pairs of points were (1.19±0.55) mm and (1.55±0.59) mm for the two registrations, respectively. Notably, no statistically significant difference was observed between the two measurements (P>0.05), indicating a high agreement (intraclass correlation coefficient=0.914). Conclusion This study established an approach to integrate AMS 3D facial images with digital 3D dental models. Through this approach, the digital orthodontic set-up design can be displayed in the context of a 3D facial image, which may help to improve the quality of outcome set-up in digital orthodontics, such as clear aligner therapy.

    Clinical analysis of 346 minor patients with maxillofacial fractures
    Yan Kaixin, Li Maoye, Chang Xinnan, Li Hui, Zheng Xiaohui, Liu Lei
    West China Journal of Stomatology. 2024, 42(3):  340-345.  doi:10.7518/hxkq.2024.2023445
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    Objective This study aims to analyze the clinical epidemiology, diagnostic and treatment characteristics of minor patients with maxillofacial fracture and provide a reference for the prevention and treatment. Methods The clinical data of minor patients with maxillofacial fracture in Departmentof Traumatic and Plastic Surgery, West China Hospital of Stomatology, Sichuan University, from January 1, 2015 to December 31, 2020 were retrospectively studied and statistically analyzed in terms of age, gender, etiology, anatomic sites and treatment modalities. Results The mean age of the patients was (10.65±5.15) years, and the male-to-female ratio was 1.91∶1. High fall was the primary cause of maxillofacial fractures in minors aged 0-6 years. Traffic accident injuries were the main cause of maxillofacial fractures in minors aged 7-12 and 13-17 years. About 65.13% of the midface and 83.08% non-condylar fractures were mainly treated by surgery, and condylar fractures were treated conservatively in 74.73% and by surgical treatment in 25.27%. Conclusion The etiology of maxillofacial fractures in minors differs at different ages, so prevention strategies should be adjusted according to age. Surgical treatment has become the preferred treatment modality for midface and non-condylar fractures. Conservative treatment is still the main treatment method for condylar fractures, but the proportion of surgical treatment increases.

    Concentrated growth factor and collagen as barrier materials in alveolar ridge preservation for posterior teeth: a prospective cohort study with one-year follow-up
    Zhu Zhanfeng, Yang Tingting, Chen Qinyi, Qiu Weien, Li Yongshan, Lin Yilan, Ban Yu
    West China Journal of Stomatology. 2024, 42(3):  346-352.  doi:10.7518/hxkq.2024.2023458
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    Objective This study aims to evaluate the efficacy of concentrated growth factor (CGF) membrane and collagen as barrier materials in sealing the alveolar socket in alveolar ridge preservation (ARP) in the posterior region during a one-year follow-up. Methods A total of 24 patients who underwent ARP in the posterior region were selected for inclusion and randomly assigned to the CGF group (12 cases) and Collagen group (12 cases). The patients in both groups underwent extraction of posterior teeth. The extraction sockets were filled with a bone substitute to the level of the pre-extraction buccal and lingual or palatal alveolar bone plates. The wounds in the CGF group were closed with a fabricated CGF overlaying the upper edge of the bone substitute material, whereas those in the Collagen group were closed with Bio-Oss Collagen. The implants were placed after 6 months. The evaluation was based on implant retention, re-grafting rate, and vertical and horizontal alveolar ridge bone volume changes measured by cone beam computed tomography (CBCT). Data were statistically analyzed using SPSS 28.0 software. Results No patient withdrew throughout the follow-up period. No implant failure and no severe peri-implant or mucosal soft tissue complications were observed. Six months after the operation, the degree of vertical alveolar ridge height resorption in the CGF group was lower than that in the Collagen group (P<0.05). There were no statistically difference between the groups at 1 year after the operation (P>0.05). The amount of bone reduction in horizontal alveolar ridge width showed no difference between the groups at 6 months and 1 year after surgery (P>0.05). Conclusion CGF membrane and Bio-Oss Collagen as barrier materials for posterior ARP inhibited reduction in alveolar ridge bone mass.

    Effect of artificial aging on optical properties of ultra-translucent zirconia ceramics of different brands
    Chen Luona, Zhang Xin, Tian Zhengyu, Wang Jian
    West China Journal of Stomatology. 2024, 42(3):  353-358.  doi:10.7518/hxkq.2024.2023372
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    Objective This work aimed to evaluate the effect of artificial aging on the translucency and color difference (ΔE) of ultra-translucent zirconia and provide a reference for clinical application. Methods The discs of ultra-translucent zirconia from six brands (Wieland, 3M ESPE, Amann Girrbach, Kuraray Noritake, Upcera, and Besmile) were cut and sintered according to each manufacturer’s product instructions; the experimental groups were named ZNT, LVP, AG, KAT, UPC, and BSM, respectively. IPS e.max Press was used as the control group (PLT). The specimens (n=6) were prepared with a diameter of 14 mm and a thickness of 1 mm. The specimens were subjected to artificial aging treatment according to the following conditions: in an autoclave at 134 ℃ at 0.2 MPa for 4, 8, and 12 h. According to the CIE1976Lab system, the CIE L*, a*, and b* values of the specimens before and after aging were measured by a co-lorimeter. The translucency parameter (TP) and ΔE were calculated. Results The mean TP values of each group before aging inorder were PLT>KAT>AG>ZNT>BSM>UPC>LVP. We found no significant difference in translucency in all experimental groups after aging for 4 and 8 h compared with those before aging. After 12 h of aging, the TP values of the KAT and ZNT groups were not significantly different from those before aging, but the TP values of the AG, BSM, LVP, and UPC groups were significantly lower than those before aging (P<0.05). The TP value of the control group was significantly higher than that of the other experimental groups at different stages (P<0.05). ΔE=3.3 was considered the visible color difference, and ΔE was less than 3.3 in all groups after 4 h of aging. After aging for 8 h, ΔE of the UPC group was slightly higher than 3.3. ΔE of the BSM and UPC groups was greater than 3.3 after 12 h of aging. Conclusion The TP and ΔE of different brands of ultra-translucent zirconia may change after various aging times. The translucency of some zirconia showed a decreasing trend and the color difference showed an increasing trend with the aging time.

    Effect of laser and coating surface treatment on the bond strength of zirconia ceramics
    Du Qiao, Niu Guangliang
    West China Journal of Stomatology. 2024, 42(3):  359-364.  doi:10.7518/hxkq.2024.2023369
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    Objective This study aims to investigate bond strength between zirconia and resin cement through surface treatments with Er: YAG laser, Nd: YAG laser, and Si-Zr coating. Methods Seventy-five round pre-sintered zirconia discs with a diameter of 18 mm and a thickness of 1.5 mm were prepared by a powder compactor. Fifty discs were randomly divided into five groups of 10 discs each and were subjected to five surface treatments: no treatment (control group), sandblasting with alumina particles (sandblasting group), Er: YAG laser treatment (Er: YAG laser group), Nd:YAG laser treatment (Nd: YAG laser group), and Si-Zr coating treatment (Si-Zr coating group). The discs were then bonded to composite resin columns with resin cement. The shear bond strength of each group was tested with a universal tester. Roughness tester, scanning electron microscope (SEM), and energy dispersive spectroscopy were used to analyze surface performance. Results The bond strength of the Si-Zr coating group was higher than that of the remaining groups (P<0.05). The difference in bond strength between the sandblasting group and the Er: YAG laser group was not statistically significant (P>0.05), but both of them had higher bond strength than the Nd: YAG laser group (P<0.05). The Si-Zr coating group had the highest surface roughness (P<0.05). The surface roughness of the sandblasting, Er: YAG laser, and Nd: YAG laser groups was higher than that of the control group (P<0.05), but the difference among the three groups was not statistically significant (P>0.05). SEM observations showed irregular scratches on the surface of the sandblasting group and large pits with holes on the surface of the Er: YAG and Nd: YAG laser groups. In the Er: YAG laser group, the crystal structure was replaced by a smooth surface with a large amount of microcracks due to partial melting. Complex porous structures that comprised “island-like” structures and mass pores among the grains were observed on the surface of the Si-Zr coating. Only Zr, O, and Y were detected on the surfaces of the control, Er: YAG laser, and Nd: YAG laser groups. Al was found on the surface of the sandblasted group, and a higher proportion of Si was detected on the surface of the Si-Zr coating group. Conclusion Er: YAG laser and Nd: YAG laser treatment on the zirconia ceramic surface could increase roughness and improve the bond strength to resin cement. Si-Zr coating treatment is an effective alternative for increasing the roughness and bond strength of zirconia surface and is superior to sandblasting and laser treatments.

    Implantology
    Accuracy evaluation of a universal dental implant guide for simulating implantation in posterior area on dental molds
    Wang Ruibin, Xu Mingzhang, Wang Lan, Zheng Ziyang, Deng Yunyi, Zeng Maoyun, Yuan Lingling, Peng Peizhao, Liu Qiqi, Yu Ke
    West China Journal of Stomatology. 2024, 42(3):  365-371.  doi:10.7518/hxkq.2024.2023379
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    Objective This study aims to compare the accuracy of self-developed universal implant guide (SDG), 3D printed digital guide (DG), and free hand (FH) simulated implantation in the posterior tooth area of dental models. Methods Ten junior dentists were selected to place three implants in the 35, 37, and 46 tooth sites of the mandibular models (35, 36, 37, and 46 missing teeth) by using SDG, DG, and FH, and the process was repeated again to take the average value. Cone beam computed tomography (CBCT) was used to evaluate the global coronal deviation, global apical deviation, depth deviation, and angular deviation between the actual position and preoperative planned position. Results The coronal deviation and apical deviation of the three implant sites in the SDG group were not significantly different from those in the two other groups (P>0.05). The depth deviation and angular deviation in the SDG group were smaller than those in the DG group (P<0.05) and FH group (P<0.05), respectively. All deviations at site 37 in the SDG group were not different from those at site 35 (P>0.05), while the depth and angular deviation at site 37 in the DG group were higher than those at site 35 (P<0.05). Conclusion The precision of the self-developed universal dental implant guide can meet the requirements of clinical posterior implantation.

    Experimental study on implant-abutment locking force and abutment subsidence in a pure Morse taper connection implant system
    Ren Bihui, Xu Yehao, Dai Jieting, Guo Shuigen, Wei Hongwu
    West China Journal of Stomatology. 2024, 42(3):  372-381.  doi:10.7518/hxkq.2024.2023387
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    Objective This test aimed to investigate the factors affecting the locking force between the implant and abutment and the amount of abutment subsidence in pure Morse taper connection implant systems. Methods With reference to the Bicon implant abutment connection design, different types of implant specimens and their corresponding types of abutments were fabricated. The implant-abutment locking taper was uniformly 1.5°. The locking depths were 1.0, 2.0, and 3.0 mm. The diameters of the locking column were 2.5, 3.0, and 3.5 mm. The thicknesses of the outer wall of the implant were 0.15 and 0.30 mm. The loading forces of the testing machine were 200, 300, and 400 N. At least 10 specimens of each group of implant-abutment were used. All specimens were loaded in the same manner using a universal testing machine (finger pressure + specified loading force, five times). The total height of the implant-abutment was measured before finger pressure, after finger pressure, and after the testing machine was loaded for five times to calculate the amount of sinking of the abutment. Finally, the implant and abutment were pulled apart using the universal testing machine, and the subluxation force was observed and recorded. Results The test loading force, locking depth, and locking post diameter had an effect on the implant-abutment locking force and abutment subsidence. The implant-abutment locking force increased with the increase in the test loading force, locking depth, and locking post diameter (R=0.963, 0.607, and 0.372, respectively), with the test loading force having the most significant effect. Abutment subsidence increased with the increase in test loading force (R=0.645) and decreased with the increase in locking depth and locking post diameter (R=-0.807 and -0.280, respectively), with locking depth having the most significant effect on abutment subsidence. No significant correlation was found between the thickness of the outer wall of the implant and the change in the magnitude of the implant-abutment locking force. However, an increase in the thickness of the outer wall of the implant decreased the amount of abutment subsidence, which was inversely correlated. Conclusion The locking force of the implant-abutment can be increased by adjusting the design of the pure Morse taper connection implant⁃abutment connection, increasing the locking depth and locking post diameter, and increasing the amount and number of times the abutment is loaded during seating. Problems, such as loosening or detachment of the abutment, can be reduced. The recommended abutment to be loaded should be no less than five times during seating to prevent the abutment from sinking and causing changes in the occlusal relationship in the later stages. Preliminary occlusal adjustments should only be conducted in the early stages of the use of temporary restorations, and final restorations and occlusal adjustments are recommended to be performed after using the abutment for a period of time.

    Effects of flapless and flapped implantations on soft tissue: a systematic review and Meta-analysis
    Chen Yunyi, Sun Ciji, Li Hong
    West China Journal of Stomatology. 2024, 42(3):  382-393.  doi:10.7518/hxkq.2024.2023341
    Abstract ( 84 )   HTML ( 7 )   PDF(pc) (3705KB) ( 22 )   Save
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    Objective This study aimed to systematically compare the effects of flapless and flapped implantations on the surrounding soft tissues of dental implants. Methods Nine databases were searched, including PubMed, Embase, Cochrane Library, Web of Science, Clinical Trials, OpenGrey, OpenDoar, Scopus, and Ovid, from January 1, 2013, to August 27, 2023. Randomized controlled trials comparing flapless implantation with flapped implantation for restoration of missing teeth were included. Meta-analysis was conducted on studies that met the inclusion criteria by using RevMan 5.3 and Stata 14.0. Results A total of 1 245 articles were retrieved, and 17 studies were ultimately included. The results of Meta-analysis showed that flapless implantation resulted in better healing of the soft tissues around the dental implants than flapped implantation. Moreover, flapless implantation showed superior changes in implant success rate [mean difference (MD)=1.06, 95% confidence interval (CI) (1.02, 1.10), P=0.004], the width of keratinized gingival changes [MD=0.10, 95%CI (0.00, 0.20), P=0.04], and probing depth [MD=-0.60, 95%CI (-0.67, -0.53), P<0.000 01], with statistically significant differences. The final combined results of modified plaque index [standardized mean difference (SMD)=-0.41, 95%CI (-0.81, 0.00), P=0.05] and modified sulcus bleeding index [SMD=-0.44, 95%CI (-0.78, -0.10), P=0.01] showed superiority over flapped implantation. The papillary presence index was higher in the flapless implantation group than in the flapped implantation group. No statistically significant differences were observed in plaque index and gingival indices changes between the two groups. Conclusion Flapless implantation can achieve higher implant success rate, smaller changes in the width of keratinized gingival, and smaller probing depths than flapped implantation. It also has advantages in terms of modified plaque index, modified sulcus bleeding index, and papillary presence index.

    Case of precise full-mouth occlusal reconstruction guided by digital occlusal function analysis
    Guo Yanling, Li Jiaxin, Liu Xinran, Yue Yuan, Wei Na, Wang Min, Hao Liang
    West China Journal of Stomatology. 2024, 42(3):  394-402.  doi:10.7518/hxkq.2024.2023448
    Abstract ( 244 )   HTML ( 6 )   PDF(pc) (7105KB) ( 34 )   Save
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    The clinical demand for occlusal reconstruction increases rapidly with increasing number of patients who have lost their normal occlusion because of tooth wear and dentition defects. Occlusal reconstruction is a special type of restoration defined as a comprehensive restoration of the function of the stomatognathic system by reestablishing a uniform and stable occlusal relationship between the upper and lower dentitions. Occlusal function analysis is an important part of occlusal reconstruction to achieve accurate restoration design and adjustment. Digital occlusal function analysis was conducted to monitor the movement of the mandible and obtain related data for the parameter design of occlusal reconstruction. Preoperative design, intraoperative adjustment, and postoperative verification were achieved, thereby improving the efficiency and accuracy of occlusal reconstruction.

    Digital technology-assisted extraction of impacted maxillary third molar located between the furcation of maxillary second molar by root dislocation: a case report
    He Lanxi, Jurat·Omar , Zhou Zihang, Yu Jian, Wang Zhaoling, Chen Hongyu
    West China Journal of Stomatology. 2024, 42(3):  403-408.  doi:10.7518/hxkq.2024.2023362
    Abstract ( 71 )   HTML ( 4 )   PDF(pc) (3223KB) ( 16 )   Save
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    Most of the maxillary impacted third molars are located in the maxillary tuberosity, where the vision and operation space are limited. This paper reports a case of surgical extraction of the left maxillary horizontal superhigh impacted third molar, which is located between the roots of the adjacent teeth and is closely related to the maxillary sinus. The digital simulation technology was used to reconstruct a three-dimensional visual image of the patient’s maxilla, related teeth, and other adjacent anatomical structures to assist in finding the optimal surgical method accurately. Root dislocation before the crown not only protects the roots of the adjacent tooth, but also reduces the risk of maxillary sinus lining damage or perforation during operative procedures, improves the efficiency of the operation, and reduces surgical trauma, which conforms to the concept of minimally invasive surgery and provides a new idea and experience for the clinical extraction of such maxillary impacted third molars.

    Non-surgical treatment of maxillary lateral incisor double dens invaginatus type Ⅲ with apical periodontitis
    Chen Hong, Zhang Ronghua, Zhao Yuan
    West China Journal of Stomatology. 2024, 42(3):  409-414.  doi:10.7518/hxkq.2024.2023291
    Abstract ( 78 )   HTML ( 642 )   PDF(pc) (3936KB) ( 36 )   Save
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    Dental invagination is an abnormality of the crown or root development induced during tooth germ development when the enamel-forming apparatus or epithelial root sheath overpopulates and folds into the papilla. In severe cases, the invaginated channels are connected to the pulp and periodontal tissues, often causing endodontic and periapical diseases. The complex anatomical pattern of this disease adds difficulty in its preoperative diagnosis and clinical operation. In this paper, we report a case of non-surgical treatment assisted by cone beam CT and microscopy for maxillary lateral incisor double dens invaginatus type Ⅲ (Ⅲa and Ⅲb) with apical periapical infection. After 1-year follow-up, the affected tooth was asymptomatic and the periapical lesion was significantly reduced.