According to the fourth national oral health epidemiological survey report (2018), billions of teeth are lost or missing in China, inducing chewing dysfunction, which is necessary to build physiological function using restorations. Digital technology improves the efficiency and accuracy of oral restoration, with the application of three-dimensional scans, computer-aided design (CAD), computer-aided manufacturing (CAM), bionic material design and so on. However, the basic research and product development of digital technology in China lack international competitiveness, with related products basically relying on imports, including denture 3D design software, 3D oral printers, and digitally processed materials. To overcome these difficulties, from 2001, Yuchun Sun’s team, from Peking University School and Hospital of Stomatology, developed a series of studies in artificial intelligence design and precision bionics manufacturing of complex oral prostheses. The research included artificial intelligence design technology for complex oral prostheses, 3D printing systems for oral medicine, biomimetic laminated zirconia materials and innovative application of digital prosthetics in clinical practice. The research from 2001 to 2007 was completed under the guidance of Prof. Peijun Lv and Prof. Yong Wang. Under the support of the National Natural Science Foundation of China, the National Science and Technology Support Program, National High-Tech R&D Program (863 Program) and Beijing Training Project for the Leading Talents in S & T, Yuchun Sun’s team published over 200 papers in the relevant field, authorized 49 national invention patents and 1 U.S. invention patent and issued 2 national standards. It also developed 8 kinds of core technology products in digital oral prostheses and 3 kinds of clinical diagnosis and treatment programs, which significantly improved the design efficiency of complex oral prostheses, the fabrication accuracy of metal prostheses and the bionic performance of ceramic materials. Compared with similar international technologies, the program doubled the efficiency of bionic design and manufacturing accuracy and reduced the difficulty of diagnosis and cost of treatment and application by 50%, with the key indicators of those products reaching the international leading level. This program not only helped to realize precision, intelligence and efficiency during prostheses but also provided functional and aesthetic matches for patients after prostheses. The program was rewarded with the First Technical Innovation Prize of the Beijing Science and Technology Awards (2020), Gold Medal of Medical Research Group in the First Medical Science and Technology Innovation Competition of National Health Commission of the People’s Republic of China (2020) and Best Creative Award in the First Translational Medical Innovation Competition of Capital (2017). This paper is a review of the current situation of artificial intelligence design and precision bionics manufacturing of complex oral prosthesis.

Some kinds of chronic sialadenitis were recognized during the recent years. They have specific pathogenesis, clinical and histopathologic appearances, and require specific treatment. IgG4-related sialadenitis (IgG4-RS) is one of the immune-mediated diseases, characterized by tumefactive lesions. The incidence of IgG4-RS obviously increased during the past 30 years. The study on the potential relationship between occupational exposure to chemical substances and the incidence of IgG4-RS showed that subjects with occupational exposure to agents known to cause IgG4-RD had an increased risk for IgG4-RS. Surgical excision of involved SMG could not control the disease progression, which is not recommended for treatment of IgG4-RS. The combination of glucocorticoid and steroid-sparing agents is effective for treating IgG4-RS, and restores salivary gland function. Radioiodine induced sialadenitis (RAIS) is one of the common complications of postoperative adjuvant treatment of differentiated thyroid cancer by ¹³¹I. The incidence of the disease is related to radiation dosage. Clinically, the patients suffered from swelling and tenderness in the buccal or submandibular regions, especially during the mealtime. Imaging appearances are similar to those of chronic obstructive sialadenitis. Conservative managements, such as gland massage, sialagogues, are the mainstream methods in the treatment of RAIS. Sialendoscopy is feasible for RAIS, but not as effective as conventional obstructive sialadenitis (COS). Therefore the prevention of RAIS is crucial. Eosinophilic sialodochitis (ES) is a new type of chronic inflammatory disease of the salivary gland related to allergy. It has characteristics of swelling of multiple major salivary glands, strip-like gelatinous plugs discharged from the duct orifice of the gland,elevated level of serum IgE and eosinophils in peripheral blood, infiltration of eosinophils and IgE positive plasma cells in the tissues,allergic history, increased expression of allergy-related cytokines, such as IL-4,IL-5,IL-13, and eotaxin, which suggest allergic reactions as a potential pathogenesis of the disease. The clinical, laboratory, histological, and immunohistochemical characteristics of ES are significantly different from conventional obstructive sialadenitis (COS). Therefore, it is suitable to separate ES from COS. Conservative managements, such as self-maintenance therapy and anti- allergic modality are the choices of treatment for ES. Based on the results of our comprehensive studies a new classification of chronic sialadenitis is suggested.

Objective: To explore the correlation of cytochrome B-245 alpha chain (CYBA) rs4673 and cholesteryl ester transfer protein (CETP) rs12720922 polymorphisms with the susceptibility of gene-ralized aggressive periodontitis (GAgP). Methods: The study was a case-control trial. A total of 372 GAgP patients and 133 periodontally healthy controls were recruited. The CYBA rs4673 and CETP rs12720922 polymorphisms were detected by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). Logistic regression models were used to analyze the correlation of CYBA rs4673 and CETP rs12720922 variants with the susceptibility of GAgP. The interaction between the two gene polymorphisms to the susceptibility of GAgP was analyzed by the likelihood ratio test. The interaction model adopted was the multiplication model. Results: The mean age of GAgP group and control group was (27.5±5.2) years and (28.8±7.1) years respectively. There was significant difference in age between the two groups (P<0.05). The gender distribution (male/female) was 152/220 and 53/80 respectively, and there was no significant difference between GAgP group and controls (P>0.05). For CYBA rs4673, the frequency of CT/TT genotype in the GAgP group was significantly higher than that in the controls [18.0% (66/366) vs. 10.6% (14/132), P<0.05]. After adjusting age and gender, the individuals with CT/TT genotype had a higher risk of GAgP (OR=1.86, 95%CI: 1.01-3.45, P<0.05), compared with CC genotype. There was no statistically significant difference in distributions of the CETP rs12720922 genotypes (GG, AA/AG) between GAgP patients and healthy controls (P>0.05). A significant interaction between CYBA rs4673 and CETP rs12720922 in the susceptibility to GAgP was observed. The GAgP risk of the individuals with CYBA rs4673 CT/TT and CETP rs12720922 GG genotypes was significantly increased (OR=3.25, 95%CI: 1.36-7.75, P<0.01), compared with those carrying CC and AA/AG genotypes. Conclusion: CYBA rs4673 CT/TT genotype is associated with GAgP susceptibility. There is a significant interaction between CYBA rs4673 CT/TT genotype and CETP rs12720922 GG genotype in the susceptibility of GAgP.

Objective: To study the binding target of photosensitizer and bacteria in antimicrobial photodynamic therapy with computer-simulated target prediction and molecular docking research methods and to calculate the binding energy. Methods: The protein names of Porphyromonas gingivalis (Pg) were obtained and summarized in Uniprot database and RCSB PDB database; the structure diagrams of methy-lene blue were screened in SciFinder database, PubChem database, ChemSpider database, and Chemical Book, and ChemBioDraw software was used to draw and confirm the three-dimensional structure for target prediction and Cytoscape software was used to build a visual network diagram; a protein interaction network was searched and built between the methylene blue target and the common target of Pg in the String database; then we selected FimA, Mfa4, RgpB, and Kgp K1 proteins, used AutoDock software to calculate the docking energy of methylene blue and the above-mentioned proteins and performed molecular docking. Results: The target prediction results showed that there were 19 common targets between the 268 potential targets of methylene blue and 1 865 Pg proteins. The 19 targets were: groS, radA, rplA, dps, fabH, pyrG, thyA, panC, RHO, frdA, ileS, bioA, def, ddl, TPR, murA, lepB, cobT, and gyrB. The results of the molecular docking showed that methylene blue could bind to 9 sites of FimA protein, with a binding energy of -6.26 kcal/mol; with 4 sites of Mfa4 protein and hydrogen bond formation site GLU47, and the binding energy of -5.91 kcal/mol, the binding energy of LYS80, the hydrogen bond forming site of RgpB protein, was -5.14 kcal/mol, and the binding energy of 6 sites of Kgp K1 protein and the hydrogen bond forming site GLY1114 of -5.07 kcal/mol. Conclusion: Computer simulation of target prediction and molecular docking technology can initially reveal the binding, degree of binding and binding sites of methylene blue and Pg proteins. This method provides a reference for future research on the screening of binding sites of photosensitizers to cells and bacteria.

Objective: To investigate the effect of porous surface morphology of zirconia on the proliferation and differentiation of osteoblasts. Methods: According to different manufacturing and pore-forming methods, the zirconia specimens were divided into 4 groups, including milled sintering group (M-Ctrl), milled porous group (M-Porous), 3D printed sintering group (3D-Ctrl) and 3D printed porous group (3D-Porous). The surface micromorphology, surface roughness, contact angle and surface elements of specimens in each group were detected by scanning electron microscope (SEM), 3D laser microscope, contact angle measuring device and energy-dispersion X-ray analysis, respectively. MC3T3-E1 cells were cultured on 4 groups of zirconia discs. The cell morphology of MC3T3-E1 cells on zirconia discs was eva-luated on 1 and 7 days by SEM. The cell proliferation was detected on 1, 3 and 5 days by cell counting kit-8 (CCK-8). After osteogenic induction for 14 days, the relative mRNA expression of alkaline phosphatase (ALP), type Ⅰ collagen (Colla1), Runt-related transcription factor-2 (Runx2) and osteocalcin (OCN) in MC3T3-E1 cells were detected by real-time quantitative polymerase chain reaction. Results: The pore size [(419.72±6.99) μm] and pore depth [(560.38±8.55) μm] of 3D-Porous group were significantly larger than the pore size [(300.55±155.65) μm] and pore depth [(69.97±31.38) μm] of M-Porous group (P<0.05). The surface of 3D-Porous group appeared with more regular round pores than that of M-Porous group. The contact angles of all the groups were less than 90°. The contact angles of 3D-Ctrl (73.83°±5.34°) and M-Porous group (72.7°±2.72°) were the largest, with no significant difference between them (P>0.05). Cells adhered inside the pores in M-Porous and 3D-Porous groups, and the proliferation activities of them were significantly higher than those of M-Ctrl and 3D-Ctrl groups after 3 and 5 days’ culture (P<0.05). After 14 days’ incubation, ALP, Colla1, Runx2 and OCN mRNA expression in 3D-Porous groups were significantly lower than those of M-Ctrl and 3D-Ctrl groups (P<0.05). Colla1, Runx2 and OCN mRNA expressions in M-Porous group were higher than those of 3D-Porous group (P<0.05). Conclusion: The porous surface morphology of zirconia can promote the proliferation and adhesion but inhibit the differentiation of MC3T3-E1 cells.

Objective: To investigate the influence of chronic masseter hyperalgesia induced by 17β-estradiol (E2) and experimental occlusal interference (EOI) on underlying mechanism in hippocampus of ovariectomized (OVX) rats. Methods: In the study, 32 OVX rats were randomly divided into 4 groups (8 rats/group): The control group was OVX group, and 0 μg/d E2 (vehicle) injection was started 7 d after OVX without EOI; in the experimental group (1) OVX + E2 group, 80 μg/d E2 injection was started 7 d after OVX without EOI; in the experimental group (2) OVX + EOI group, vehicle injection was started 7 d after OVX and EOI was applied 17 d after OVX; in the experimental group (3) OVX + E2 + EOI group, 80 μg/d E2 injection was started 7 d after OVX and EOI was applied 17 d after OVX. Bilateral masseter muscle mechanical withdrawal thresholds were measured before OVX, 7 days after OVX (before E2 injection), 17 days after OVX (10 days after E2 injection and before EOI) and 24 days after OVX (7 days after EOI). Immunofluorescence staining was used to reveal phospho-extracellular signal regulated kinase 1/2 (p-ERK1/2)-positive neurons in CA3 of hippocampus. The protein expression of p-ERK1/2 in hippocampus was detected using Western Blot. Results: Compared with the control group [left side: (135.3±8.5) g, right side: (135.4±10.8) g], bilateral masseter muscle mechanical withdrawal thresholds of OVX+E2 group [left side: (113.3±5.6) g, right side: (112.5 ± 5.6) g] and OVX+EOI group [left side: (93.3±5.4) g, right side: 90.8±5.5) g] were decreased (P<0.01). Bilateral masseter muscle mechanical withdrawal thresholds were significantly lower in OVX+E2+EOI group [left side: (81.2±6.2) g, right side: 79.8±7.7) g] than in the control, OVX+E2 and OVX+EOI groups (P<0.05). The proportion of p-ERK1/2 positive neurons in the CA3 region of the hippocampus was increased in the control, OVX+E2, OVX+EOI and OVX+E2+EOI groups in turn, and the difference between the groups was statistically significant (P<0.05). p-ERK1/2 protein expression was increased in the control, OVX+E2 and OVX+EOI groups in turn, but the difference was not statistically significant (P>0.05). p-ERK1/2 expression was significantly higher in OVX+E2+EOI group than in the other three groups (P<0.05). Conclusion: High concentration of E2 could exacerbated EOI-induced chronic masseter hyperalgesia in ovariectomized rats, and its central mechanism may be related to the upregulation of the phosphorylation of ERK1/2 in hippocampus.

Objective: To compare the clinical efficacy of initial periodontal therapy in periodontitis patients with or without type 2 diabetes mellitus and its correlation with white blood cell counts. Methods: In this study, 32 chronic periodontitis patients without systemic disease (CP group) and 27 chronic periodontitis patients with type 2 diabetes mellitus (CP+DM group) were enrolled. At admission, all the patients went through periodontal examination and fasting blood examination(baseline). Probing depth (PD), attachment loss (AL), bleeding index (BI), plaque index (PLI), white blood cells (WBC) counts and fasting blood glucose (FBG) were recorded respectively, while hemoglobin A1c (HbA1c) was recorded only in CP+DM group. After that, initial periodontal therapy was performed. All the tests were repeated 3 and 6 months after treatment. The changes of periodontal clinical indexes and WBC levels were compared between the two groups before and after treatment, and the correlation between WBC and periodontal clinical indexes and glucose metabolism indexes were analyzed by generalized linear mixed model. Results: At baseline, the periodontal inflammation and destruction were similar in CP and CP+DM group, but the WBC level was significantly higher in CP+DM groups [(6.01±1.26)×10⁹/L vs. (7.14±1.99)×10 ⁹/L, P=0.01]. After 3 and 6 months of initial periodontal therapy, the mean PD, AL, BI, and PLI in CP+DM and CP groups were significantly lower than the baseline, and the PD in CP+DM group was further decreased by 6 months compared with 3 months [(3.33±0.62) mm vs. (3.61±0.60) mm, P<0.05]. However, none of these periodontal indexes showed significant difference between the two groups by 3 or 6 months. In CP+DM group, HbA1c at 3 months and 6 months were significantly lower than the baseline [(7.09±0.79)% vs. (7.64±1.16)%, P<0.05; (7.06±0.78)% vs. (7.64±1.16)%, P<0.05], and FBG was significantly lower than the baseline by 6 months [(7.35±1.14) mmol/L vs. (8.40±1.43) mmol/L, P<0.05]. The WBC level in CP group was significantly lower than the baseline level by 3 months [(5.35±1.37)×10 ⁹/L vs. (6.01±1.26)×10 ⁹/L, P<0.05], while that in CP+DM group was significantly lower than the baseline level by 6 months [(6.00±1.37)×10 ⁹/L vs. (7.14±1.99)×10 ⁹/L, P<0.05]. The analysis of genera-lized linear mixed model showed that WBC level was significantly positively correlated with PD and FBG (P<0.05). Conclusion: Initial periodontal therapy can effectively improve the periodontal clinical status of patients with or without type 2 diabetes mellitus, and have benefits on glycemic control in diabetic patients. However, the response of periodontal indexes and WBC level to initial therapy were relatively delayed in diabetic patients. WBC plays an important role in the correlation between diabetes mellitus and periodontitis.

Objective: To compare the clinicopathologic features and prognosis of the different types of fibrous dysplasia (FD) of cranio-maxillofacial region, so as to provide a new reference for clinicians to treat these patients and make prognostic judgement. Methods: Clinical records, radiographic data and pathological information of 105 patients diagnosed with FD or McCune-Albright syndrome (MAS) at the Department of Oral Pathology, Peking University Hospital of Stomatology from January 2013 to December 2020 were collected. The patients were divided into 4 groups: monostotic FDs, polyostotic FDs, MAS and a specific type called craniofacial fibrous dysplasia (CFD) limited in the craniofacial region. The clinicopathological characteristics, treatment and follow-up data of each type were analyzed. Results: Of all the 105 patients, 46 were males and 59 were females, with a male-to-female ratio of 1 ∶1.3. The onset age ranged from 0 to 56 years and the median age was 12 years. On the basis of different involvement conditions, 4 types were divided. The most common type was monostotic FDs (43 cases, 40.95%), including maxilla (29 cases), mandibular (12 cases) and zygoma (2 cases). 32 cases (30.48%) were diagnosed with polyostotic FDs, 7 cases (6.67%) were MAS, and 23 cases (21.90%) were CFDs confirmed by computed tomography (CT) analysis. CFD was clearly distinct from other types of FD, such as the patient gender and the serum alkaline phosphatase level in peripheral blood before operative surgery. The pathologic findings of various types FD were quite similar, whilst the predominant fibrous tissue hyperplasia could be observed in polyostotic FDs and MAS types. Conclusion: The clinicopathologic features of FD in the cranio-maxillofacial region are different from the FD lesions in other parts of the body. The clinicopathological features of CFD are significantly different from those of monostotic and polyostotic FDs in the cranio-maxillofacial region. Therefore, the clinicians should pay attention to distinguish CFD in clinic, imaging and pathology aspects, so as to further clarify its features in clinic management and prognosis.

Objective: To investigate the clinicopathologic features and prognostic factors in oral basaloid squamous cell carcinoma. Methods: Retrospective analysis of oral basaloid squamous cell carcinomas patients who underwent tumor resection during the period from January 2002 to December 2020 in the authors’ hospital, especially the clinicopathologic characteristics of 28 cases with confirmed diagnosis and follow-up data. Immunohistochemistry was performed to define the helpful markers for differentiation diagnosis. The factors influencing the prognosis were evaluated based on Kaplan-Meier method. Results: The tongue and mouth floor (11 cases, 39.3%) were the most frequently involved sites, followed by gingiva (6 cases, 21.4%), buccal (5 cases, 17.9%), palate (4 cases, 14.3%), and oropharynx (2 cases, 7.1%). The majority of basaloid squamous cell carcinomas were in advanced stage, with 12 cases in stage Ⅱ and 16 cases in stages Ⅲ-Ⅳ. Twelve of 28 patients were identified to have cervical lymph node metastasis, which was confirmed by histopathological examination. The incidence rate of lymph node metastasis was 42.9% (12/28). Nine tumors recurred, with one metastasized to the lung. At the meantime, the 28 conventional squamous cell carcinomas were matched with the same stage, among which 13 cases were identified with cervical lymph node metastasis. The incidence rate of lymph node metastasis was 46.4% (13/28). Five cases recurred, with two cases that metastasized to the lung and one to the brain. The 5-year overall survival rates of the basaloid squamous cell carcinoma and conventional squamous cell carcinoma patients were 54.6% and 53.8%, respectively. Histopathologically, basaloid cells consisted of tumor islands without evident keratinization but frequently with comedo-like necrosis within the tumor islands. CK5/6 and P63 exhibited strongly positive in all the 28 cases, whereas neuroendocrine markers, CgA and Syn, were negative. Eight cases positively expressed P16; one case showed focal SOX10 positive but CK7 negative. Conclusion: The majority of oral basaloid squamous cell carcinomas present in advanced stage with a high tendency to lymph node metastasis, but the overall survival rates are not significantly different from conventional squamous cell carcinomas matched with the same stage. The human papilloma virus (HPV),as HPV-positivity rate is high, correlates to good prognosis. In addition, CK7 & SOX10 immunohistochemistry could contribute to differential diagnosis for basaloid squamous cell carcinoma with solid adenoid cystic carcinoma.

Objective: To investigate the characteristics of pathogen infection and to establish a prediction model of infections in oral squamous cell carcinoma patients undergoing surgery with free flap reconstruction. Methods: The retrospective cohort study consisted of 1 596 patients undergoing tumor resection and free flap reconstruction for oral squamous cell carcinoma from January 2018 to December 2020. According to the postoperative infection, the patients were divided into the infected group (n=154) and non-infected group (n=1 442). The characteristics of pathogens were analyzed in the infected patients. The primary outcome variable was postoperative infection, and Logistic regression was used to determine risk factors of the infection. The prediction model was established and the discriminatory accuracy of the model was evaluated using receiver operating characteristic (ROC) curve. Results: Totally 154 cases were infected in the 1 596 cases undergoing surgery with free flap reconstruction, and the infection rate was 9.65%. The most frequent sites of infection were the surgical wound and respiratory tract. A total of 268 pathogens were isolated and cultured, including 240 strains of Gram-negative bacteria, accounting for 89.55%, mainly Pseudomonas aeruginosa and Klebsiella pneumoniae; 23 strains of Gram-positive bacteria, accounting for 8.58%, mainly Enterococcus faecalis and Staphylococcus aureus; and 5 strains of fungi, accounting for 1.87%. The isolated Pseudomonas aeruginosa had high resistant rate to imipenem and meropenem, and was sensitive to antibiotics, such as ciprofloxacin. The isolated Staphylococcus aureus had high resistant rate to erythromycin and clindamycin, and was sensitive to vancomycin. According to the multivariate Logistic analysis, four independent variables were significantly associated with an increased risk of postoperative infection (P<0.05): clinical N category≥1, the American Society of Anesthesiologists (ASA) grade ≥2, tracheotomy and length of hospital stay >13 d. The prediction model was established based on these factors and the expression of the risk prediction model was as follows: predicted probability value P=1/(1+e^-a), a=-0.803+0.674×(clinical N category ≥1)+0.518×(the ASA grade ≥2)+0.918×(tracheotomy)+1.581×(length of hospital stay >13 d), Hosmer-Lemeshow χ²=10.647, P=0.223, the degree of fitting of the model was good. The area under the ROC curve was 0.818 and 95%CI of the model for predicting infection was 0.789-0.846. Conclusion: Oral squamous cell carcinoma patients undergoing surgery with free flap reconstruction are prone to have a high incidence of postoperative infection and Gram-negative bacteria are the main pathogens causing an infection. The established prediction model is of good predictive effect. Rational antimicrobial use coupled with awareness of infection control measures is paramount to reduce the incidence of postoperative infection in the oral squamous cell carcinoma patients undergoing surgery with free flap reconstruction.

Objective: To evaluate the clinical effect of root canal obturation therapy using cold flowable gutta-percha on young permanent teeth after apexification. Methods: Ninety cases of young permanent teeth with pulp necrosis or periapical periodontitis treated by apexification were randomly divided into two groups. The cases in each group were divided into single root canal and multiple root canal according to the number of the root canal, and divided into classifications Ⅰ, and Ⅱ/Ⅲ/Ⅳ according to Frank’s classification of root development after apexification. Cold flowable gutta-percha and warm gutta-percha obturation techniques were used for root canal obturation of the two groups. The operation time was recorded, and the patients’ therapy pain degree was evaluated by visual analog scale (VAS) immediately after operation. Periapical X-ray was performed after operation to evaluate the effect of the root canal filling. The total length of the root was divided into equal three parts on the X-ray film, and three-dimensional tightness of the apical, middle, and coronal region of the root canals were statistically analyzed respectively. Clinical examinations and X-ray examination were performed 6 and 12 months after the operation to evaluate the treatment success rate. Results: The operation time of cold flowable gutta-percha group was significantly lower than that of the control group, which were 51 s and 74 s (P<0.05); The percentages of pain and discomfort in the two groups were 26.67% and 40.00%, respectively. There were two cases of underfilling and no overfilling in both groups. The percentages of proper filling and tight three-dimensional obturation in the experimental and control groups were 71.11% and 60.00% respectively; and the percentages of tight three-dimensional obturation in the apical third areas were 86.67% and 66.67%, the difference was significant (P<0.05). There was no significant difference in the three-dimensional tightness between the two groups in the middle and coronal third areas. The percentages of tight three-dimensional obturation in classification Ⅰ groups were 86.67%, 83.33%, 93.33% and 76.67%, 90.00%, 96.67% in experimental and control group, respectively; The percentages of classification Ⅱ/Ⅲ/Ⅳ groups were 86.67%, 86.67%, 100.00% and 46.67%, 86.67%, 100.00%, respectively, and the difference was significant (P<0.05). There were no apical lesions that occurred in either group during the one-year review period. Conclusion: The application of cold flowable gutta-percha on young permanent teeth root canal obturation after apexification can achieve good obturation effect. The root obturation effect in the apical third area is significantly better than that of warm gutta-percha obturation techniques. Cold flowable gutta-percha can shorten the clinical treatment time and ameliorate the patients’ therapy comfort.

Objective: To investigate the effect of a noval radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma jet on crosslinking of dentin collagen. Methods: (1) Twenty intact third molars were collected. The middle dentin discs were prepared for each tooth by low-speed water-cooled Isomet saw, and then immersed in 10% (mass fraction) H₃PO₄ solution for 16 h to obtain fully demine-ralized dentin collagen. The twenty dentin discs were then randomly divided into five groups. The control group was untreated while the four experimental groups were treated by plasma jet with gas temperature of 4 ℃ for different times (20 s, 30 s, 40 s, and 50 s). The structure and crosslinking degree of dentin collagen were characterized by attenuated total reflection-Fourier transform infrared spectroscopy. The surface morphology of demineralized dentin was observed by scanning electron microscope, and the microstructure was observed by transmission electron microscope. (2) Fourty non-caries third molars were collected to prepare 5 g fine dentin powder, then completely demineralized with 10% H₃PO₄ solution. The control group was untreated, while the four experimental groups were treated by plasma jet for 20 s, 30 s, 40 s and 50 s. The crosslinking degree of each group was determined by ninhydrin colorimetric method. (3) Forty intact third molars were collected to obtain dentin strips. Only two central symmetrical dentin strips (nasty 80) were taken from each tooth and immersed in 10% H₃PO₄ solution for 16 h to obtain fully demineralized dentin collagen. Eighty dentine collagen fiber strips were randomly divided into five groups. The control group was untreated and the axial surfaces of dentin collagen fiber strips in the expe-rimental groups were treated with the plasma jet for 20 s, 30 s, 40 s and 50 s. The ultimate tensile strength of dentin was measured by universal mechanical machine. Results: (1) The surface morphology of demineralized dentin observed by scanning electron microscope showed that the network structure of collagen fibers on the surface of demineralized dentin treated with the plasma jet for 20 s, 30 s and 40 s could maintain the uncollapsed three-dimensional structure, and part of the microstructure was destroyed after plasma jet treated for 50 s. After being treated by plasma jet for 20 s, 30 s and 40 s, the three-dimensional structure was uncollapsed, and the typical periodic transverse pattern of natural type Ⅰ collagen fiber could be seen. The results of infrared spectra showed that the secondary conformation of dentin collagen fibers was the same as that of the control group after being treated with the plasma jet, and the intensity of amide band was significantly increased after being treated for 30 s and 40 s. (2) The results of ninhydrin crosslinking test showed that the crosslinking ratio of dentin collagen treated by plasma jet for 30 s and 40 s was the highest, and the difference was statistically significant (P<0.05). (3) The results of dentin ultimate tensile strength showed that the control group was (1.67±0.24) MPa, and the plasma jet treated 20 s, 30 s, 40 s and 50 s groups were (4.21±0.15) MPa, (7.06±0.30) MPa, (7.32±0.27) MPa, and (6.87±0.17) MPa, which were significantly different from that of the control group (P<0.05). Conclusion: The novel RF-APGD plasma jet treatment can promote the crosslinking degree of demineralized dentin collagen and improve their ultimate tensile strength.

Objective: To investigate the effect of acid stimulation on salivary flow rate and compositions of human parotid and submandibular glands, so as to provide basis for comprehensive evaluation of salivary gland function in both health and disease status. Methods: In the study, 210 healthy participants’ whole saliva samples were collected under passive drooling, and their parotid gland and submandibular gland secretions were collected by negative pressure suction. 2% citric acid was dropped on the tip of tongue every 1 min for acid stimulation for a total of 5 times to collect stimulated whole saliva, parotid and submandibular gland saliva. The collected saliva was weighed and saliva flow rate was calculated. The K⁺, Na⁺, Cl^-, Ca²⁺, total protein, total phosphorus and α-amylase in saliva samples were detected by biochemical analyzer, and the changing features of flow rate and compositions of different kinds of saliva were compared and analyzed. Results: After acid stimulation, saliva flow rate significantly increased. The increase proportion of parotid gland saliva (10.7 folds) was much higher than that of submandibular gland saliva (2.9 folds). The concentrations of Na ⁺, Cl^-, Ca²⁺, total protein and α-amylase in parotid gland saliva increased significantly (P<0.05), but there was no significant difference in total phosphorus and K ⁺ (P=0.89,P=0.34). The concentration of Na⁺ and Ca²⁺ in saliva of submandibular gland increased significantly(P<0.05), the concentration of total phosphorus decreased significantly(P<0.05), and the concentration of Cl^- increased, but the difference was not significant(P=0.068). There was no significant difference in total protein, K⁺ and α-amylase (P=0.85,P=0.07,P=0.95). The compound secretion rate of total phosphorus in saliva of submandibular gland remained unchanged(P=0.066), while the secretion rate of K ⁺, Na⁺, Cl^-, Ca²⁺, total protein and α-amylase significantly increased(P<0.01). The compound secretion rate of K ⁺, Na⁺, Cl^-, Ca²⁺, total protein and total phosphorus and α-amylase in parotid gland saliva increased(P<0.01). The concentrations of Na ⁺, Cl^-, K⁺, total phosphorus, total protein and α-amylase in parotid were higher than those in submandibular gland (P<0.01), and the concentration of Ca ²⁺ in submandibular gland saliva was significantly higher than that in parotid (P<0.001). Conclusion: The response of parotid to acid stimulation is stronger, and the secretion of submandibular gland is more stable. Acid stimulation significantly influences the concentrations of electrolytes in saliva, and the composited secretion rate is an evaluation index to reflect both flow rate and composition concentration of saliva. The parotid gland plays an important role in the secretion of total protein, total phosphorus and α-amylase in saliva, and the submandibular gland is the main source of Ca²⁺ in saliva.

Objective: To compare the effects of resin base and different retention depth on the fracture resistance of mandibular molars restored with nano-ceramic endocrowns. Methods: Forty mandibular molars selected and randomly divided into 5 groups: ① The control group which was consisted of intact teeth, ② the non-resin base group, ③ the 2 mm retention depth group, ④ the 3 mm retention depth group, ⑤ the 4 mm retention depth group, respectively. After tooth preparation, in vitro root canal therapy was conducted, which was followed by endocrown design, production and adhesive of groups ②-⑤. All the samples were under load (N) of the universal mechanical testing machine after embedding. The fracture pattern of each sample was observed under stereomicroscope. Then the microstructure of the fracture surface was observed by scanning electron microscopy. Results: The fracture loads of each group were respectively: the control group fracture load was (3 069.34±939.50) N; experimental groups: fracture load of (2 438.04±774.40) N for the group without resin base; fracture load of (3 537.18±763.65) N for the group with 2 mm retention depth. The fracture load of the retention depth 3 mm group was (2 331.55±766.39) N; the fracture load of the retention depth 4 mm group was (2 786.98±709.24) N. There was statistical significance in the effect of resin base and different retention depth on the fracture loads of molars restored with nano-ceramic endocrown (P<0.05). Repairable fractures in each group were as follows: control group 2/8, non-resin base group 1/8, retention depth of 2 mm group 1/8, retention depth of 3 mm group 2/8, and retention depth of 4 mm group 0/8. The effects of the retention depth and the presence of resin base on the fracture resistance of the resin nano-ceramic endocrowns were statistically significant (P<0.05). Scanning electron microscopy showed more arrest lines and small twist hackles on the fracture surface of the restorations with resin base (retention depths of 2 mm, 3 mm, and 4 mm), with cracks extending towards the root. In addition to the characteristics above, more transverse cracks parallel to the occlusal surface, pointing outwards from the center of the pulp cavity retention, were also observed on the fracture surface of the non-resin base restorations. Conclusion: When molar teeth with nano-ceramic endocrowns are restored, resin base and the retention depth of 2 mm help the teeth to obtain optimal fracture strength.

Objective: To evaluate the relevant indicators affecting difficulty in the extraction of impacted mandibular third molars and score difficulty of different operation and risk indicators, so as to build an intuitive and accurate scale to help operators make more accurate analysis and prediction of difficulty before the operation. Methods: Based on literature and the clinical review, the difficulty indicators of tooth extraction were summarized. Firstly, 10 doctors from Peking University School and Hospital of Stomatology who had been engaged in alveolar surgery for a long time established an expert nominal group, and then rated whether the summarized indicators needed to be retained in the form of face-to-face questionnaires. A level 1 and 2 item frame for evaluating difficulty in the tooth extraction was formed after discussion; Then Delphi method was used to send a questionnaire to 30 experts by e-mail. After two rounds of scoring and modification, the scale of difficulty in the extraction of impacted mandibular third molars was formed. Results: The recycling rate of two rounds of questionnaires was 100.0%,which showed that the experts were very enthusiastic about the study; The authority coefficients (Cr) of the two rounds of Delphi expert consultation were both 0.92, which showed that the results were representative and authoritative. After two rounds of grading and revision, the variable coefficient (CV) decreased and the Kendall’s concordance coefficient (W) increased, which were statistically significant: In the first round, the CV was 0.24 and W was 0.56 (P<0.001), and in the second, the CV was 0.19 and W was 0.72 (P<0.001), which indicated that there was a good convergence among the expert opinions. Finally, a scale of difficulty in the tooth extraction containing 12 items at level A and 37 items at level B was formed, including operation difficulty indicators, risk difficulty indicators and common difficulty indicators. Conclusion: Based on comprehensive literature retrieval, the study has put forward the concept that difficulty in the extraction of impacted mandibular third molars is composed of operation difficulty and risk difficulty. Using Delphi method, the long-term clinical experience and professional knowledge of experts are transformed into quantitative indicators as a scoring scale. The scale has certain representativeness and authority.

Objective: To compare the retentions of different designs of cobalt-chromium (Co-Cr), pure titanium (CP Ti), and titanium alloy (Ti-6Al-4V) removable partial denture (RPD) circumferential clasps manufactured by selective laser melting (SLM) and to analyze the stress distribution of these clasps during the removal from abutment teeth. Methods: Clasps with clasp arm size A (1.9 mm width/1.1 mm thickness at the body and 0.8-taper) or B (1.2 times A) and 0.25 mm or 0.50 mm undercut engagement were modeled on a prepared first premolar die, named as designs A1, A2, A3, and A4, respectively. The density and elastic modulus of SLM-built Co-Cr, CP Ti, and Ti-6Al-4V were measured and given to different groups of clasps. The density, elastic modulus, and Poisson’s ratio of enamel were given to the die. The control group was the cast Co-Cr clasp with design A1, to which the density and elastic modulus of cast Co-Cr alloy were given. The Poisson’s ratio of all metals was 0.33. The initial 5 N dislodging force was applied, and the maximum displacement of the clasp along the insertion path was computed. The load was reapplied with an increment of 5 N than in the last simulation until the clasp was completely dislodged. The retentive force range of different groups of clasps was obtained. The retentive forces of the SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with equivalent computed retentive force range to the control group were validated through the insertion/removal experiment. The von Mises stress distributions of these three groups of SLM-built clasps under 15 N loads were analyzed. Results: SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with designs B1 or B2, and Co-Cr clasps with design A2 had higher retentive forces than those of the control group. SLM-built CP Ti and Ti-6Al-4V clasps with design A1 had lower retentive forces than those of the control group. SLM-built Co-Cr clasp with design A1 and SLM-built CP Ti and Ti-6Al-4V clasps with design A2 had equivalent retentive forces to those of the control group. The insertion/removal experiment showed that the measured retentive forces of these three groups of SLM-built clasps were (21.57±5.41) N, (19.75±4.47) N, and (19.32±2.04) N, respectively. No statistically significant measured retentive force difference was found among these three groups of SLM-built clasps (P>0.05). The maximum von Mises stress of these three groups of SLM-built clasps exceeded their responding yield strength except for the Ti-6Al-4V one. Conclusion: SLM-built Co-Cr circumferential clasps had higher retention than CP Ti and Ti-6Al-4V ones with the same clasp arm size and undercut engagement. The retention of SLM-built circumferential clasps could be adjusted by changing the undercut engagement and clasp arm size. If SLM-built circumferential clasps are used in clinical practice, the Ti-6Al-4V clasp with clasp arm size A and 0.50 mm undercut engagement is recommended considering the long-term use of RPD in the patient’s mouth.

Objective: To evaluate the clinical characteristics and effectiveness of pulpotomy in mature permanent teeth with bioceramic putty repairmen iRoot and mineral trioxide aggregate (MTA). Methods: Pulpotomy was performed on mature permanent premolars and molars with carious exposures at the Department of General Dentistry of Peking University School and Hospital of Stomatology,from November 2017 to September 2019. The patients were randomly divided into 2 groups, Group iRoot (n=22) and Group MTA (n=21). In Group iRoot, bioceramic putty repairmen iRoot was used as pulp capping agent, while in Group MTA, mineral trioxide aggregate was used as pulp capping agent. All the patients had signed informed consent forms. The clinical efficacy was evaluated by clinical examinations (temperature and electrical activity test) and imaging examinations 3, 6, and 12 months after surgery. Blinding was used for the patients and evaluators, but due to the obvious differences in the properties of the two pulp capping agents, the blinding method was not used for the treatment provider (the attending physician). Results: There was no significant difference in gender, average age, dentition and tooth position distribution between the two groups (P>0.05). In the study, 7 cases were lost to follow-up 12 months after operation (4 cases in Group iRoot, and 3 cases in Group MTA). One case in each of the two groups had transient sensitivity at the end of the 3-month follow-up, and the pulp vitality was normal at the end of the 6-month follow-up. One case in Group iRoot showed sensitivity at the end of the 12-month follow-up. The success rates of the two groups at the end of 12-month follow-up were 100%, and the cure rates were 94.4% (Group iRoot) and 100% (Group MTA), respectively, and the difference was not statistically significant (P>0.05). No cases in Group iRoot had obvious crown discoloration, while 3 cases in Group MTA had. Conclusion: The clinical characteristics and effectiveness of pulpotomy in mature permanent teeth with bioceramic putty repairmen iRoot were similar with MTA. Bioceramic putty repairmen iRoot is an acceptable material when used in pulpotomy of mature permanent teeth. Because it is not easy to cause tooth discoloration after treatment and is convenient to operate, bioceramic putty repairmen iRoot has a better clinical application prospect.

Objective: To compare the clinical efficacy of combined application of glycine powder air-polishing and mechanical submucosal debridement in non-surgical treatment of peri-implant diseases. Methods: A randomized controlled clinical study was carried out on patients diagnosed with peri-implant diseases in the Department of Periodontology, Peking University School and Hospital of Stomatology, between May of 2020 and June of 2021.Twenty-eight patients with totally sixty-two implants were enrolled.The patients were randomly divided into the test group and control group. The patients in the test group (13 subjects/32 implants) received mechanical submucosal debridement using titanium curettes combined with application of glycine powder air-polishing, while the control group (15 subjects/30 implants) received mechanical submucosal debridement using titanium only. Clinical parameters, such as plaque index (PLI), pocket probing depth (PPD), bleeding index (BI) and the percentage of suppuration on probing on implants’ level (SoP%) were measured at baseline and 8 weeks after non-surgical intervention. Changes and group differences of clinical parameters of the implants before and 8 weeks after non-surgical intervention were compared. Results: Mean PLI, PPD, BI of both the test group and control group significantly reduced 8 weeks after non-surgical intervention (P<0.05). Compared with the control group, the test group achieved lower BI (2.7±0.8 vs. 2.2±0.7, P<0.05), more reduction of BI (0.6±0.7 vs. 1.1±0.6, P<0.01) and more reduction of SoP% (21.9% vs. 10%, P<0.05) after non-surgical intervention. Both the control and test groups exhibited comparable PLI and PPD reductions (P>0.05). For the implants diagnosed with peri-implant mucositis, the test group revealed more signi-ficant reduction in BI and SoP% than the control group (1.0±0.7 vs. 0.4±0.7, P=0.02; 6.3% vs. 0, P=0.012). There was no significant difference existing in PLI and PD improvement between the control group and test group (P>0.05). For the implants diagnosed with peri-implantitis, there was no significant difference existing in PLI, PPD, BI and SoP% improvement values between the test and control groups (P>0.05). No complications or discomforts were reported during the study. Conclusion: Both treatment procedures could relieve the inflammation of peri-implant soft tissue. Non-surgical mechanical submucosal debridement combined application of glycine powder air-polishing is associated with significant reduction of soft tissue bleeding and suppuration on probing especially in the implants diagnosed with peri-implant mucositis.

Objective: To propose a set of two-dimensional clinical classification of fractured implants based on the follow-up of fracturing pattern of implant body and peri-implant bone defect morphology of 32 fractrued implants, and summarize the treatment decisions of fractured implants according to this new set of classification, so as to provide guidance for clinical practice. Methods: During 25 years of clinical practice, clinical records of 27 patients of 32 fractured implants in 5 481 patients with 10 642 implants were made. The fracturing pattern of implant body, implant design, peri-implant bone defect morphology and treatment options were analyzed. A set of two-dimensional clinical classification based on the morphology and bone absorption of implant fracture was proposed. The treatment decision-making scheme based on the new classification of implant fracture was discussed. Results: In the new classification system, vertical fracture of implant neck (Type 1 of implant fracture morphology, F1) and horizontal fracture of implant neck (Type 2 of implant fracture morphology, F2) were common, accounting for 50% and 40.6% respectively, while deep horizontal fracture of implant body (Type 3 of implant fracture morphology, F3) (9.4%) were rare, while the three types of bone defects (D1, no bone defect or narrow infrabony defects; D2, wide 4-wall bone defects or cup-like defects, D3, wide 3-wall or 2-wall defects) around implants were evenly distributed. In the two-dimensional classification system of implant fracture, F1D1 (31.3%) and F2D2 (25%) were the most frequent. There was a significant positive correlation between F1 and D1 (r=0.592, P < 0.001), a significant positive correlation between F2 and D2 (r=0.352, P=0.048), and a significant negative correlation between F1 and D2 (r=-0.465, P=0.007). The most common treatment for implant fracture was implant removal + guided bone regeneration(GBR) + delayed implant (65.6%), followed by implant removal + simultaneous implant (18.8%). F1D1 type was significantly related to the treatment strategy of implant removal + simultaneous implantation (r=0.367, P=0.039). On this basis, the decision tree of implant fracture treatment was summarized. Conclusion: The new two-dimensional classification of implant fracture is suitable for clinical application, and can provide guidance and reference for clinical treatment of implant fracture.

Objective: To establish a deep learning algorithm that can accurately determine three-dimensional facial anatomical landmarks, multi-view stacked hourglass convolutional neural networks (MSH-CNN) and to construct three-dimensional facial midsagittal plane automatically based on MSH-CNN and weighted Procrustes analysis algorithm. Methods: One hundred subjects with no obvious facial deformity were collected in our oral clinic. Three-dimensional facial data were scanned by three-dimensional facial scanner. Experts annotated twenty-one facial landmarks and midsagittal plane of each data. Eighty three-dimensional facial data were used as training set, to train the MSH-CNN in this study. The overview of MSH-CNN network architecture contained multi-view rendering and training the MSH-CNN network. The three-dimensional facial data were rendered from ninety-six views that were fed to MSH-CNN and the output was one heatmap per landmark. The result of the twenty-one landmarks was accurately placed on the three-dimensional facial data after a three-dimensional view ray voting process. The remaining twenty three-dimensional facial data were used as test set. The trained MSH-CNN automatically determined twenty-one three-dimensional facial anatomical landmarks of each case of data, and calculated the distance between each MSH-CNN landmark and the expert landmark, which was defined as position error. The midsagittal plane of the twenty subjects’ could be automatically constructed, using the MSH-CNN and Procrustes analysis algorithm. To evaluate the effect of midsagittal plane by automatic method, the angle between the midsagittal plane constructed by the automatic method and the expert annotated plane was calculated, which was defined as angle error. Results: For twenty subjects with no obvious facial deformity, the average angle error of the midsagittal plane constructed by MSH-CNN and weighted Procrustes analysis algorithm was 0.73°±0.50°, in which the average position error of the twenty-one facial landmarks automatically determined by MSH-CNN was (1.13±0.24) mm, the maximum position error of the orbital area was (1.31±0.54) mm, and the minimum position error of the nasal area was (0.79±0.36) mm. Conclusion: This research combines deep learning algorithms and Procrustes analysis algorithms to realize the fully automated construction of the three-dimensional midsagittal plane, which initially achieves the construction effect of clinical experts. The obtained results constituted the basis for the independent intellectual property software development.

Objective: To analyze the marginal roughness and marginal fitness of chairside computer-aided design and computer-aided manufacturing (CAD/CAM) laminate veneers with different materials and thicknesses, and to provide a reference for the clinical application of laminate veneers. Methods: The butt-to-butt type laminate veneers were prepared on resin typodonts, the preparations were scanned, and the laminate veneers were manufactured by chairside CAD/CAM equipment. The laminate veneers were divided into four groups (n=9) according to the materials (glass-matrix ceramics and resin-matrix ceramics) and thickness (0.3 mm and 0.5 mm) of the veneers, with a total of 36. The marginal topo-graphies of each laminate veneer were digitally recorded by stereomicroscope, and the marginal rough-nesses of the laminate veneers were determined by ImageJ software. The marginal fitness of the laminate veneers was measured by a fit checker and digital scanning and measuring method. At the same time, the mechanical properties of glass-matrix ceramic and resin-matrix ceramic bars (n=20) were tested by a universal testing device. Results: The marginal roughness of 0.3 mm and 0.5 mm glass-matrix ceramic laminate veneers was (24.48±5.55) μm and (19.06±5.75) μm, respectively, with a statistically significant difference (P<0.001). The marginal roughness of 0.3 mm and 0.5 mm resin-matrix ceramic laminate veneers was (6.13±1.27) μm and (6.84±2.19) μm, respectively, without a statistically significant difference (P>0.05). The marginal roughness of the glass-matrix ceramic laminate veneers was higher than that of the resin-matrix ceramic laminate veneers with a statistically significant difference (P<0.001). The marginal fitness of 0.3 mm and 0.5 mm glass-matrix ceramic laminate veneers were (66.30±26.71) μm and (85.48±30.44) μm, respectively. The marginal fitness of 0.3 mm and 0.5 mm resin-matrix ceramic laminate veneers were (56.42±19.27) μm and (58.36±8.33) μm, respectively. There was no statistically significant difference among the 4 groups (P>0.05). For glass-matrix ceramics, the flexural strength was (327.40±54.25) MPa, the flexural modulus was (44.40±4.39) GPa, and the modulus of resilience was (1.24±0.37) MPa. For resin-matrix ceramics, the flexural strength was (173.71±16.61) MPa, the flexural modulus was (11.88±0.51) GPa, and the modulus of resilience was (1.29±0.27) MPa. The flexural strength and modulus of glass-matrix ceramics were significantly higher than those of resin-matrix ceramics (P<0.001), but there was no statistically significant difference in the modulus of resilience between the two materials (P>0.05). Conclusion: The marginal roughness of CAD/CAM glass-matrix ceramic laminate veneers is greater than that of resin-matrix ceramic laminate veneers, but there was no statistically significant difference in marginal fitness among them. Increasing the thickness can reduce the marginal roughness of glass-matrix ceramic laminate veneers, but has no effect on the marginal roughness of resin-matrix ceramic laminate veneers.

Objective: To evaluate the accuracy of trephine bur drilling at different depths guided by dynamic navigation system in 3D printing in vitro model. Methods: A model at the depth of 5 mm, 10 mm, and 15 mm from the outer surface of which hemispherical cavities was reserved and the 3D printing technology was used to make the standardized model with Veroclear resin. The cone beam CT (CBCT) was taken and the data were imported into the dynamic navigation software (DCARER, China) to establish navigation path programming. Under the guidance of dynamic navigation, a trephine bur with a diameter of 4.5 mm was used to complete the access operation. At each depth, 10 approaches were completed. The postoperative model CBCT was taken. The approach trajectory under navigation was reconstructed and compared with the designed path. The two-dimensional distance deviation, depth deviation, three-dimensional distance deviation, and angle deviation between the actually prepared path and the designed path were calculated. Results: At the depth of 5 mm, the two-dimensional distance deviation between the end position of the prepared path and the designed path was (0.37±0.06) mm, the depth deviation was (0.06±0.05) mm, the three-dimensional distance deviation was (0.38±0.07) mm, and the angle deviation was 2.46°±0.54°; At the depth of 10 mm, the four deviations between the end position of prepared path and the designed path were (0.44±0.05) mm, (0.16±0.06) mm, (0.47±0.05) mm, and 2.45°±1.21°, respectively; At the depth of 15 mm, the four deviations were (0.52±0.14) mm, (0.16±0.07) mm, (0.55±0.15) mm, and 3.25°±1.22°, respectively. With the increase of entry depth, the three-dimensional and depth accuracy of dynamic navigation system decreased (P<0.01), and the positioning angle deviation had no relation with the entry depth (P>0.01). Conclusion: Dynamic navigation technology can achieve high positioning accuracy in the depth range of 15 mm, but its deviation increases with the increase of entry depth.

Objective: To clarify the clinical characteristics of influenza pneumonia in the elderly patients and the relationship between D-dimer and the severity of influenza pneumonia. Methods: In the study, 52 hospitalized patients older than 65 years with confirmed influenza pneumonia diagnosed in Peking University People’s Hospital on 5 consecutive influenza seasons from 2014 were retrospectively analyzed. General information, clinical symptoms, laboratory data, treatment methods and prognosis of the patients were collected. The relationship between D-dimer and pneumonia severity was analyzed, and receiver operating characteristic (ROC) curve was used to evaluate the predictive value of D-dimer. Results: Among the 52 patients, 31 were male (31/52, 59.6%), the average age was (77.1±7.4) years, and 19 of them (36.5%) were diagnosed with severe pneumonia. About 70% patients presenting with fever. In the severe group, the patients were more likely to complain of dyspnea than in the non-severe group (14/19, 73.7% vs. 10/33, 30.3%, P=0.004), severe pneumonia group had higher level of CURB-65 (confusion, urea, respiratory rate, blood pressure, and age>65), pneumonia severity index (PSI), C-reactive protein, urea nitrogen, lactate dehydrogenase, fasting glucose, and D-dimer (P value was 0.004, <0.001, <0.001, 0.003, 0.038, 0.018, and <0.001, respectively), albumin was lower than that in the non-severe group [(35.8±5.6) g/L vs. (38.9±3.5) g/L, t=-2.348, P=0.018]. There was a significant positive correlation between the D-dimer at the first admission and PSI score (r=0.540, 95%CI: 0.302 to 0.714, P<0.001), while a significant negative correlation with PaO₂/FiO₂ (r=-0.559, 95%CI: -0.726 to -0.330, P<0.001). Area under the curve of D-dimer was 0.765 (95%CI: 0.627 to 0.872). Area under the curve of PSI was 0.843 (95%CI: 0.716 to 0.929). There was no statistically significant difference in test efficacy between the two (Z=2.360, P=0.174). D-dimer level over 1 225 μg/L had a positive predict value for influenza pneumonia in hospital death with a sensitivity of 76.92% and a specificity of 74.36%. Conclusion: Influenza pneumonia in the elderly always has atypical symptoms, dyspnea is a prominent feature in severe cases, D-dimer level is associated with the severity of influenza pneumonia, and greater than 1 200 μg/L has a good predictive value for in-hospital death in the elderly.

Objective: To explore the relationship between high altitude polycythemia (HAPC) and peptic ulcer bleeding, in order to provide the evidence for the clinical diagnosis and treatment of peptic ulcer disease in Tibet of China. Methods: A retrospective case-control study was conducted. Patients who hospitalized in the Department of Gastroenterology with the diagnosis of peptic ulcer bleeding from January 1, 2015 to April 30, 2021 in Tibet Autonomous Region People’s Hospital were enrolled in the case group, and patients who hospitalized in the Department of Urology without tumor and without the history of peptic ulcer and gastrointestinal bleeding during the same period were selected as the control group. In the study,1 ∶1 case matching was conducted between the two groups according to the gender, age (±2 years), ethnic group (Tibetan, Han), and the residence altitude level (grouped by<4 000 m or ≥4 000 m), and 393 cases were included in the case group and the control group respectively. All the patients had lived in Tibet with the altitude >2 500 m for more than 1 year, and with age ≥ 18 years. The risk factors of peptic ulcer bleeding (place of residence, smoking, alcohol, the use of NSAIDs/anticoagulants, and combined with chronic diseases, such as HAPC, hypertension, diabetes mellitus, heart disease, hyperlipidemia, cerebrovascular disease, chronic lung disease, joint disease) were analyzed and compared between the two groups. Results: There were 28 (7.1%) patients with HAPC in the case group, and 5 (1.3%) in the control group. The incidence of HAPC in the case group was significantly higher than those in the control group, P<0.001, and the OR value was 5.953. Multivariate Logistic regression analysis showed that HAPC (OR=5.270, 95%CI: 1.806-15.380), living in cities and towns (OR=2.369, 95%CI: 1.559-3.602), alcohol (OR=3.238, 95%CI:1.973-5.317) and the use of NSAIDs/anticoagulants (OR=20.584, 95%CI: 2.639-160.545) were the independent risk factors for peptic ulcer bleeding in Tibet. After adjusting for the possible confounding factors, such as living in cities and towns, alcohol, and the use of NSAIDs/anticoagulants, HAPC was associated with an increased risk of peptic ulcer bleeding in Tibet, and the OR value was 5.270. Conclusion: HAPC was associated with a significantly increased risk of peptic ulcer bleeding in Tibet. Patients with HAPC and peptic ulcer should be diagnosed and treated actively, in order to avoid gastrointestinal bleeding and other serious complications.

Objective: To compare the completion time of endotracheal intubation and laryngeal mask implantation in operating room and on slope of ski resort, and to discuss the optimal method of estab-lishing artificial airway on slope of ski resort. Methods: The simulator was placed with the head under the feet on slope of ski resort. The artificial airway was established by tracheal intubation assisted by video laryngoscope (endotracheal intubation group) and laryngeal mask placement (laryngeal mask group) respectively by an anesthesiologist who wore full set of ski suits, helmets, goggles, gloves and ski boots. Each method was repeated 5 times, and the operation time of artificial airway establishment was recorded. While the simulated human was placed flat on the operating table in an operating room of a hospital, and the artificial airway was established by the same anesthesiologist using the same methods. Time was recorded and repeated for 5 times. The completion time of endotracheal intubation and laryngeal mask placement in the operating room and on the ski slope were compared. Results: The operating time of tracheal intubation in the operating room was longer than that of laryngeal mask placement [(79.8±10.4) s vs. (53.4±2.7) s, P=0.005], and the operating time of endotracheal intubation on the ski slope was longer than that of laryngeal mask placement [(209.2±32.7) s vs. (72.2±3.1) s, P=0.001]. The time of endotracheal intubation group on the slope of the ski resort was longer than that in the opera-ting room(t=-7.851, P=0.001). The time of laryngeal mask group on the slope was longer than that in the operating room (t=-19.391, P<0.001). Conclusion: On ski slope, both of tracheal intubation assisted by video laryngoscope and laryngeal mask placement can quickly complete the establishment of artificial airway, but the time required is longer than that in the operating room. The time of laryngeal mask placement to establish artificial airway is shorter than that of tracheal intubation assisted video laryngoscope, which may have a certain advantage in ski rescue.

Objective: To investigate the expectations of patients for total knee arthroplasty (TKA), and to analyze its influencing factors. Methods: Experimental design: Single center, retrospective, multiple regression analysis. The data including the age, height, and weight of 108 patients undergoing unilateral TKA due to end-stage osteoarthritis were obtained. The patients’ preoperative Hospital for Special Surgery (HSS) knee arthroplasty expectation score, the Western Ontario and McMaster Universities (WOMAC) score, Knee Society score (KSS), the MOS 36-item short-from health survey (SF-36) score, and visual analogue scale (VAS) were evaluated, and the 30-second chair-stand test (30-CST), 40-meter fast-paced walk test (40-FPWT), 12-level stair-climb test (12-SCT), 3-meter timed up-and-go test (TUG), 6-minute walk test (6-MWT), and recorded daily steps for 7 consecutive days were performed. The SPSS 22.0 software was used for statistical analysis. The observed values of various data were described. Pearson correlation analysis was used to evaluate the correlation between various parameters, and the multi-factor linear regression analysis was used to investigate the influencing factors of the patients preoperative expectation scores. Results: The average expectation score of this group of patients was 58.98±5.44. In the Pearson correlation analysis, the patient’s preoperative expectation had a weak correlation to the result of the patient’s 12-SCT, TUG, 6-MWT, KSS function score, and SF-36 mental component score (correlation coefficient 0.1-0.3). The patient’s preoperative expectation had a moderate correlation to the patient’s daily average steps, 30-CST, 40-FPWT, KSS, WOMAC and its pain, stiffness, function scores, SF-36 physical functioning, role-physical, bodily pain, vitality, and physical component score (correlation coefficient 0.3-0.6). In the multivariate linear regression analysis, only the results of 30-CST and the role-physical, bodily pain and vitality in the SF-36 scale were related to the patient’s expectation score (P<0.05). Conclusion: The estimated expectation score of patients before TKA is not high. Patients with more severe preoperative pain, worse physical function, and lower overall health are more eager to improve after surgery. Thus surgeons must communicate fully with patients with unrealistic expectations before surgery in order to obtain more satisfactory results postoperatively.

Objective: Thoracoabdominal aortic aneurysm is one of the most challenging aortic diseases. Open surgical repair remains constrained with considerable perioperative morbidity and mortality. The emergence of a hybrid approach utilizing visceral debranching with endovascular aneurysm repair has brought an alternative for high-risk patients. This study aimed to compare the short- and long-term outcomes between hybrid and open repairs in the treatment of thoracoabdominal aortic aneurysms. Methods: In this retrospectively observational study, patients with thoracoabdominal aortic aneurysm treated in a single center between January 2008 and December 2019 were reviewed, of whom 11 patients with hybrid repair, and 18 patients with open repair were identified. Demographic characteristic, operative data, perioperative morbidity and mortality, freedom from reintervention, and long-term survival were compared between the two groups. Results: In the hybrid repair group, the patients with dissection aneurysm, preoperative combined renal insufficiency, and American Society of Anesthesiologists (ASA) score of 3 or more were significantly overwhelming than in the open repair group. The operation time of debranching hybrid repair was (445±85) min, and the intraoperative blood loss was (955±599) mL. There were 2 cases of complications in the early 30 days after surgery, without paraplegia, and 1 case died. The 30-day complication rate was 18.2%, and the 30-day mortality was 9.1%. The operation time of the patients with open repair was (560±245) min, and the intraoperative blood loss was (6 100±4 536) mL. Twelve patients had complications in the early 30 days after surgery, including 1 paraplegia and 4 deaths within 30 days. The 30-day complication rate was 66.7%, and the 30-day mortality was 22.2%. The bleeding volume in hybrid repair was significantly reduced compared with open repair (P<0.001). Besides, the incidence of 30-day complications in hybrid surgery was significantly reduced (P=0.011). During the follow-up period, there were 4 reinterventions and 3 deaths in hybrid repair group. The 1-year, 5-year, and 10-year all-cause survival rates were 72%, 54%, and 29%, respectively. In open repair group, reintervention was performed in 1 case and 5 cases died, and the 1-year, 5-year, and 10-year all-cause survival rates were 81%, 71%, and 35%, respectively. There was no significant difference between hybrid repair and open repair in all-cause survival and aneurysm-specific survival. Conclusion: Hybrid approach utilizing visceral debranching with endovascular aneurysm repair is a safe and effective surgical method for high-risk patients with thoracoabdominal aortic aneurysms. The incidence of early postoperative complications and mortality is significantly reduced compared with traditional surgery, but the efficacy in the medium and long term still needs to be improved.

Objective: To assess the potential dosimetric effects of arms movement in patients with Cyberknife spine tumors. Methods: In the study, 12 patients with thoracic and lumbar tumors were retrospectively selected respectively. The contour of the patient’s arms was sketched and the CT density was modified to be equivalent to air in order to simulate the extreme case when the arm was completely removed from the radiation fields. The dose of simulated plan was re-calculated with the original beam parameters and compared with the original plan. The changes of V₁₀₀, D₉₅, and D₉₀, conformity index (CI) and heterogeneity index (HI) in planning target volume (PTV), as well as D_max, D_1cc and D_2cc in the spinal cord, stomach, esophagus, and intestines were analyzed by comparing with the original plans. Results: Compared with the original treatment plan, V₁₀₀, D₉₅, D₉₀ and CI of PTV for the simulated plan was increased by 0.86%, 2.02%,1.97% and 0.80% respectively, the difference was statistically significant (P<0.05). D_max, D_1cc and D_2cc of spinal cord was increased by 2.35%, 0.59% and 1.49% on average, compared with the original plan, the difference was statistically significant (P<0.05). The difference was statistically significant only in average D_2cc of stomach, which was increased by 1.70%, compared with the original plan (P<0.05). There was no significant difference in dose change of eso-phagus and intestine between the original and simulated plans. Conclusion: This study analyzed the most extreme arm position in spinal tumor of radiation therapy based on Cyberknife. It was found that the change of arm position had little effect on dosimetry. In addition, with the change of arm position, the dose in PTV and organ at risk (OAR) increased, but the increase was relatively small. Therefore, in some special cases where the patient really can’t keep the arm position consistent during treatment, reasonable adjustment can be accepted. However, in order to ensure accurate radiotherapy, patient position should be as stable and consistent as possible.

Objective: To compare the operation complexity and accuracy of traditional splint impression technique and impression technique with prefabricated rigid connecting bar system for full-arch implants-supported fixed protheses in vitro. Methods: Standard mandibular edentulous model with six implant analogs was prepared. The implants were placed at the bone level and multiunit abutments screwed into the implants. Two impression techniques were performed: the traditional splint impression technique was used in the control group, and the rigid connecting bar system was used in the test group. In the control group, impression copings were screwed into the multiunit abutments and connected with autopolymerizing acrylic resin. Open tray impression was fabricated with custom tray and polyether. In the test group, cylinders were screwed into the multiunit abutments. Prefabricated rigid bars with suitable length were selected and connected to the cylinders with small amount of autopolymerizing acrylic resin, and open tray impression was obtained. Impression procedures were repeated 6 times in each group. The working time of the two impression methods were recorded and compared. Analogs were screws into the impressions and gypsum casts were poured. The gypsum casts and the standard model were transferred to stereolithography (STL) files with model scanner. Comparative analysis of the STL files of the gypsum casts and the standard model was carried out and the root mean square (RMS) error value of the gypsum casts of the control and test groups compared with the standard model was recorded. The trueness of the two impression techniques was compared. Results: The work time in the test group was significantly lower than that in the control group and the difference was statistically significant [(984.5±63.3) s vs. (1 478.3±156.2) s, P<0.05]. Compared with the standard model, the RMS error value of the implant abutments in the test group was (16.9±5.5) μm. The RMS value in the control group was (20.2±8.0) μm. The difference between the two groups was not significant (P>0.05). Conclusion: The prefabricated rigid connecting bar can save the chair-side work time in implants immediate loading of edentulous jaw and simplify the impression process. The impression accuracy is not significantly different from the traditional impression technology. The impression technique with prefabricated rigid connecting bar system is worthy of clinical application.

Objective: To automatically construct lips symmetry reference plane (SRP) based on posed smile, and to evaluate its advantages over conventional digital aesthetic design. Methods: Eighteen subjects’ three-dimensional facial and dentition data were gathered in this study. The lips SRP of experimental groups were used with the standard weighted Procrustes analysis (WPA) algorithm and iterative closest point (ICP), respectively. A reference plane defined by experts based on regional ICP algorithm, served as the truth plane. The angle error values between the lips SRP of WPA algorithm in the experimental groups and the truth plane were evaluated in this study, and the lips SRP of ICP algorithm of the experimental groups was calculated in the same way. The lips SRP based on posed smile as a reference for aesthetic design and evaluate preliminary clinical application. Results: The average angle error between the lips SRP of WPA algorithm and the truth plane was 1.78°±1.24°, which was smaller than that between the lips SRP of ICP and the truth plane 7.41°±4.31°. There were significant differences in the angle errors among the groups (P<0.05). In the aesthetic design of anterior teeth, automatically constructing the lips SRP of WPA algorithm based on posed smile and the original symmetry plane by re-ference compared with the prosthetic design, the subjects’ scores on the lips SRP of WPA algorithm based on posed smile (8.48±0.57) were higher than those on the original symmetry plane (5.20±1.31). Conclusion: Automatically constructing the lips SRP of WPA algorithm based on posed smile was more accurate than ICP algorithm, which was consistent with the truth plane. Moreover, it can provide an important reference for oral aesthetic diagnosis and aesthetic analysis of the restoration effect. In the aesthetic design of anterior teeth, automatically constructing the lips SRP of WPA algorithm based on posed smile can improve the patients’ satisfaction in esthetic rehabilitation.