[Independent innovation research, development and transformation of precise bionic repair technology for oral prosthesis].

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.

[Accuracy of three intraoral scans for primary impressions of edentulous jaws].

OBJECTIVE: To provide a reference for using intraoral scanners for making clinical diagnostic dentures of edentulous jaws by comparing the accuracy of three intraoral scanners for primary impression and jaw relation record of edentulous jaws. METHODS: This study contained 6 primary impressions of the edentulous patients. Each of the impressions consisted of the maxillary primary impression, the mandibular primary impression and the jaw relation record. For each of them, a dental cast scanner (Dentscan Y500) was used to obtain stereolithography (STL) data as reference scan, and then three intraoral scanners including i500, Trios 3 and CEREC Primescan were used for three times to obtain STL data as experiment groups. In Geomagic Studio 2013 software, trueness was obtained by comparing experiment groups with the reference scan, and the precision was obtained from intragroup comparisons. Registered maxillary data of the intraoral scan with reference scan, the morphological error of jaw relation record was obtained by comparing jaw relation record of the intraoral scan with the reference scan. Registered mandibular data with jaw relation record of intraoral scan and the displacement of the jaw position were evaluated. Independent samples t test and Mann-Whitney U test in the SPSS 20.0 statistical software were used to statistically analyze the trueness, precision and morphological error of jaw relation record of three intraoral scanners. The Bland-Altman diagram was used to evaluate the consistency of the jaw relationship measured by the three intraoral scanners. RESULTS: The trueness of i500, Trios 3 and CEREC Primescan scanners was (182.34±101.21) µm, (145.21±71.73) µm, and (78.34±34.79) µm for maxilla; (106.42±21.63) µm, and 95.08 (63.08) µm, (78.45±42.77) µm for mandible. There was no significant difference in trueness of the three scanners when scanning the maxilla and mandible(P>0.05). The precision of the three scanners was 147.65 (156.30) µm, (147.54±83.33) µm, and 40.30 (32.80) µm for maxilla; (90.96±30.77) µm, (53.73±23.56) µm, and 37.60 (93.93) µm for mandible. The precision of CEREC Primescan scanner was significantly better than that of the other two scanners for maxilla (P<0.05). Trios 3 and CEREC Primescan scanners were significantly better than i500 scanner for mandible (P<0.05). The precision of the i500 and Trios 3 scanners for mandible was superior to maxilla (P<0.05). The upper limit of 95% confidence intervals of trueness and precision of three scanners for both maxilla and mandible were within ±300 µm which was clinically accepted. The morphological error of jaw relation record of the three scanners was (337.68±128.54) µm, (342.89±195.41) µm, and (168.62±88.35) µm. The 95% confidence intervals of i500 and Trios 3 scanners were over 300 µm. CEREC Primescan scanner was significantly superior to i500 scanner(P<0.05).The displacement of the jaw position of the three scanners was (0.83±0.56) mm, (0.80±0.45) mm, and (0.91±0.75) mm for vertical dimension; (0.79±0.58) mm, (0.62±0.18) mm, and (0.53±0.53) mm for anterior and posterior directions; (0.95±0.59) mm, (0.69±0.45) mm, and (0.60±0.22) mm for left and right directions. The displacement of the jaw position of the three scanners in vertical dimension, anterior and posterior directions and the left and right directions were within the 95% consistency limit. CONCLUSION: Three intraoral scanners showed good trueness and precision. The i500 and Trios 3 scanners had more errors in jaw relation record, but they were used as primary jaw relation record. It is suggested that three intraoral scanners can be used for obtaining digital data to make diagnostic dentures and individual trays, reducing possible deforming or crack when sending impressions from clinic to laboratory.

[Visual sensitivity threshold of lateral view of nasolabial Angle changes in edentulous jaw patients].

OBJECTIVE: To study the visual sensitivity threshold of physician's naked eye to the difference of nasolabial angle in edentulous jaw patients, and to provide a reference value for the study of aesthetic evaluation of soft tissue profile for the difference of nasolabial angle that can be recognized by human eyes. METHODS: Three-dimensional facial images of three edentulous patients with different diagnostic dentures introoral were obtained. Lateral screenshots of each patient's three-dimensional facial image with the same scale were obtained by using reverse engineering software (Geomagic studio 2014).The screenshot of the patient's three-dimensional facial image with suitable lip support (The suitable lip support was confirmed by both patients and prosthodontists who had clinical experience for more than 20 years) was taken as the reference picture, and the remaining pictures were grouped with it respectively. All the pictures were observed in random order by the subjects. Fifteen dentists were asked to judge the difference of nasolabial angle between the two pictures of each group on the computer screen. The difference of nasolabial angle between the two pictures in each group was measured and calculated. The ROC curve was drawn, and the best cut-off value was calculated as the visual sensitivity threshold. RESULTS: The data of the 15 subjects were used to draw ROC curves separately. The maximum and minimum best cut-off values were 5.55 degrees and 3.12 degrees respectively. The ROC curve of the whole 15 subjects was drawn after data aggregation, and the best cut-off value was 5.36 degrees (AUC=0.84>0.5, P=0.000<0.05). When the difference of nasolabial angle was above 5.36 degrees, the subjects could recognize it effectively. CONCLUSION: There is a visual limit in the observation of the nasolabial angle with the naked eye. In this study, a visual sensitivity threshold of 5.36 degrees for the difference of the nasolabial angle was obtained. The difference of nasolabial angle below this value can be regarded as no clinical significance. This result provides a reference value for human eyes to recognize the difference of nasolabial angle in soft tissue profile aesthetic evaluation. It can be applied to the aesthetic evaluation of soft tissue profile and can be used as the error level of related research with nasolabial angle as an index for accuracy evaluation.

[Independent innovation research of functionally suitable denture digital system].

Fabrication of conventional complete dentures involves a complex restoration method, requiring significant time and typically involving primary impressions, definitive impressions, jaw relation records, clinic try-in, and complete denture placement, which has been used for nearly a century without change. A novel digital system named Functionally Suitable Denture (FSD) was researched and developed so as to reduce clinical steps, operation difficulties and errors of complete denture restoration. It pioneered a unique diagnostic complete denture aided by computer aided design (CAD) & 3D printing, by which, the functional impression, jaw relation, and try-in (3 steps) were simplified to 1 step, thus the number of visits to the dentist was reduced by 2 times. Moreover, for the first time, it put forward a CAD software of template matching based on the expert design, which was an efficient and intelligent design scheme, and the excellent denture experts' experience and skills could be inherited and iterated. The system included the 3D scanner with appropriate accuracy and high efficiency, the CAD software, the special 3D printer and process software, and the innovative clinical operation process. The Patent Cooperation Treaty (PCT) patent international search report showed that all the 15 claims of the technology were of novelty, creativity and industrial utility. All the digital products were independently developed and made by Peking University School and Hospital of Stomatology, China. The design and manufacture process of denture prosthesis was fast, simple and accurate. At the same time, personalized functional and aesthetic matching of the patients after wearing prosthesis was realized. It effectively solved the global problems of "slow, difficult and inaccurate" of the traditional manual technology of complete denture, and brought good news to edentulous patients. Compared with the traditional complete denture treatment, FSD system has a wide range of applications for different types of edentulous patients, including those with severe resorption of the alveolar ridge or a high occlusal force. Furthermore, the low-cost of 3D printers, compared with expensive milling machines, may make the approach more accessible. This review describes that our research is related to the development of the FSD system, including multi-source data acquisition technology, three generations of complete denture design software, 3D printing systems of individual tray and complete denture pattern, the clinical and laboratory operation process of the FSD system.

[Influencing factors of protein energy wasting in maintenance hemodialysis patients].

Objective: To analyze the influencing factors of protein energy wasting (PEW) in maintenance hemodialysis (MHD) patients. Methods: A multicenter cross-sectional study was conducted in eleven hemodialysis centers of Guizhou province between June and August 2018. Clinical data, physical parameters, body composition data and laboratory values of MHD patients were collected. Analysis of variance was used to assess the impact of the indicators on the prevalence of PEW. Factor analysis was carried out after further classifing the factors into several common factors, and logistic regression was used to analyze the impact of common factors on PEW. Results: The results of univariate analysis showed that somatic cell mass, lean weight, fat content, body mass index (BMI), grip strength, leg circumference, hip circumference, waist circumference, midpoint circumference of upper arm, triceps skin fold thickness, hemoglobin, albumin, prealbumin, serum calcium, phosphorus, serum magnesium, creatinine, parathyroid hormone were the influential factors of PEW (all P<0.05). Factor analysis indicated that the above indicators can be classified into five common factors. Logistic regression model showed that with the increase of the prevalence of PEW, the scores of common factors decreased, the absolute value of regression coefficient beta in sequence, was common factor 2 (ß=-2.258, P<0.001), common factor 4 (ß=-1.589, P<0.001), common factor 1 (ß=-1.144, P=0.001) and common factor 3 (ß=-0.740, P=0.016). Conclusion: The reduction of fat content, anemia, hypoproteinemia, disorder of calcium and phosphorus metabolism were important factors influencing PEW.

[Research and development of digital design and fabrication of complete denture].

Removable complete denture are still the primary prosthetic solution for edentulous patients. Functional pressure impression obtaining, jaw relation recording, personalized balance occlusion and highly precise fabrication of denture are difficult. The digital restoration technique represented by intraoral three-dimensional scanning and three-dimensional (3D) printing compensates for the shortages of the manual techniques, but there are still many limitations in the application of complete dentures. At present, a few computer aided design and computer aided manufacture (CAD/CAM) complete denture systems have been developed both domestically and abroad, and these system are mainly focused on the digital design and manufacture of denture, and are seldom used for the recording of impression and jaw relation. This review is based on the main clinical procedures of the traditional complete denture restoration, elaborating the research and application status of digital technique in each steps, in order to provide reference for clinical application.

[Quantitative evaluation of printing accuracy and tissue surface adaptation of mandibular complete denture polylactic acid pattern fabricated by fused deposition modeling technology].

Objective: To quantitatively evaluate the adaptation of polylactic acid (PLA) pattern of mandibular complete denture fabricated by fused deposition modeling (FDM) technology. Methods: A mandibular complete denture digital model was designed through a complete denture design software based on a pair of standard maxillomandibular edentulous plaster model and their occlusion bases. Ten PLA mandibular complete dentures were printed with a FDM machine. The dentures were scanned with and without the plaster model using a three-dimensional (3D) scanner. In Geomagic software, the scanning data of printed dentures were registered to its computer aided design (CAD) data, and the printing error was analyzed using the multipoint registration command. For quantitatively evaluating the adaptation of the denture, the data of plaster model and PLA denture were registered to the whole data of denture located in the plaster model using the best-fit alignment command, the 3D deviation of the plaster model and tissue surface of the denture represent the space between them. The overall area was separated into three parts: primary stress-bearing area, secondary stress-bearing area and border seal area, and the average deviations of these three parts were measured. The values were analyzed using analysis of variance. Results: Compared with the CAD data, the printing error was (0.013±0.004) mm. The overall 3D deviation between PLA denture and plaster model was (0.164±0.033) mm, in which the primary stress-bearing area was (0.165± 0.045) mm, the secondary stress-bearing area was (0.153 ± 0.027) mm, the border seal area was (0.186 ± 0.043) mm. These showed a good fit in the majority parts of the FDM denture to the plaster model. No statistically significant difference was observed between the three areas (F=1.857, P=0.175>0.05). Conclusions: Combined with the 3D scanning, CAD and FDM technology, a FDM 3D printing process of complete denture for injection moulding can be established. As a result, high efficiency and low cost can be used to print out the complete denture, to lay the basis for further clinical applications.

[Postoperative computed tomography: study of 10 cases on reactive ring-enhancement in brain].

This paper presents 10 cases with CT appearances of postoperative reactive ring-enhancement in the brain, which were not reported in our country. The mechanisms and differential diagnosis of postoperative ring-enhancement are discussed with reports in the literature. The ring-enhancement at surgical margin is the reactive change of the brain traumatized by operation and related to postoperative pathological processes such as breakdown of blood-brain barrier, vascular granulation and luxury perfusion. This paper demonstrates that reactive ring-enhancement appears as early as 2-4 wk and may last as long as 7 wk after operation. It disappears gradually in 7 wk and cannot exist over 3 mon after operation. In the first 3 mon after operation, peripheral enhancement around the surgical site may be operative reaction, or residual tumor and cerebral abscess. The presence of ring-enhancement beyond 3 mon should be viewed as evidence of pathological process other than postoperative change. This paper emphasizes that ring-enhancement at margin of the surgical site with fine clinical manifestations in the early postoperative period is probably normal postoperative reaction. Close follow-up enhanced CT scan proves to be an effective measure to avoid misdiagnosis and unnecessary reexploration.

[Diagnostic evaluation of coronal CT scan in skull and brain diseases].

Coronal computed tomography findings in 30 cases of skull and brain diseases, including glioma 6 cases, meningioma 4 cases, acoustic neurinoma 3 cases, intraorbital tumor 3 cases, paranasal sinus tumor 3 cases, pituitary adenoma 2 cases, craniopharyngioma 2 cases, nasopharyngeal carcinoma 2 cases, empty sella 1 case, subdural hematoma 1 case, infarction 1 case, subarachnoid cyst 1 case, and metastasis 1 case are reported. The results show that as an adjunct to the axial computed tomography coronal CT scan provides valuable additional diagnostic informations. Coronal CT methods are also discussed.

[Surgical treatment of primary pulmonary cryptococcal granuloma--report of 4 cases].

Primary pulmonary cryptococcal granuloma is not common in Sichuan. The diagnosis of this disease is difficult to make because the patient has no characteristic symptoms and the chest X-ray findings of the mass are not easily differentiated from carcinoma of the lung. The incidence of this disease is apparently increasing. Pulmonary cryptococcosis may be disseminated hematogenously to the meninges and cryptococcal meningitis is very difficult to treat. If the pulmonary lesion is localized, the patient's general condition is good with no evidence of systemic lupus erythematosis, diabetes, leukemia or lymphoma, partial resection of the lung is indicated. But, if the patient has a history of recent cryptococcal meningitis, surgery must be deferred. Four cases of primary pulmonary cryptococcal granuloma have been treated surgically supplemented with medical therapy in the First Affiliated Hospital from 1986 to 1987. Follow-up of more than one year showed good results in each case.