Objective To investigate the biomechanical effects of lingual metal-reinforced denture bases on edentulous implant-supported prostheses by three-dimensional finite element analysis,and provide references for the treatment of edentulous jaws.Methods Two implant-supported Locator-type overdenture models with lingual metal-reinforced and non-reinforced denture bases were constructed.A 150 N vertical load on the fovea of the posterior teeth,a 150 N oblique load on the fovea of the posterior teeth,and a 150 N vertical load on the anterior teeth were applied to simulate the centric occlusion,left and right lateral chewing,and anterior teeth cutting,and stresses on the tissues of two models were analyzed.Results When the posterior and anterior teeth were loaded vertically,the stress distribution on each organization was similar between the two denture base designs.The maximum stress difference was between 0 and 0.16 MPa.Under unilateral masticatory chewing,the range of stress concentration on denture base,implant and mucoperiosteum,and the maximum stress of the implant and peri-implant bone without metal reinforcement were significantly greater than those with metal reinforcement,and the maximum stress difference was between 0.59 MPa and 2.99 MPa.Conclusions Lingual metal-reinforced denture base can play a role in stress dispersion,or reduce the risk of bone resorption and denture base fracture to a certain extent.

Objective:To study the clinical efficacy of digital design combined with three-dimensional (3D) printing model minimally invasive extraction of complex impacted mandibular third molars.Methods:Eight patients who visited the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology from April 2023 to March 2024 were included, including 3 males and 5 females, aged from 27 to 57 years old. The impacted mandibular third molars of all patients were closely related to the mandibular canal, and part of the dental tissue entered the mandibular canal. Preoperative digital design was used to simulate the intraoperative tooth segmentation and bone removal operation of the power system and the segmented tooth dislocation path, and analyze the tooth extraction resistance. The mandibular teeth, mandibular canal and mandibular model were three-dimensionally printed using light-curing resin inkjet. During the operation, an endoscope was used combined with the 3D printed model to minimally invasively extract the impacted mandibular third molar. Quantitative sensory testing of the patient′s lower lip skin on the operated side was performed before surgery, 2 days after surgery, and 7 days after surgery. Clinical data such as operation time were collected. A paired sample t test was performed on the 2 and 7 days postoperative data and the preoperative data to compare the data differences.Results:All 8 patients successfully completed preoperative design, model printing and minimally invasive surgery. The number of teeth segmented in the preoperative design was (4.4±1.3), and the number of teeth segmented in the actual operation was (4.0±1.1). The operation time was (33.3±13.0) min. None of the patients had postoperative numbness of the lower lip or other postoperative complication. It was observed endoscopically that the inferior alveolar neurovascular bundle was exposed in the extraction socket during the operation. The patient′s pressure pain threshold 2 days after surgery (0.601±1.170) was significantly lower than before surgery (1.251±1.109) ( t=2.83, P=0.025). Conclusions:For complicated impacted mandibular third molars, digital design combined with 3D printing model can be used to perform minimally invasive extraction with the assistance of an endoscope.

Postzygotic mutations are acquired in normal tissues throughout an individual's lifetime and hold clues for identifying mutagenic factors.Here,we investigated postzygotic mutation spectra of healthy individuals using optimized ultra-deep exome sequencing of the time-series samples from the same volunteer as well as the samples from different individuals.In blood,sperm,and muscle cells,we resolved three common types of mutational signatures.Signatures A and B represent clock-like mutational processes,and the polymorphisms of epigenetic regulation genes influence the pro-portion of signature B in mutation profiles.Notably,signature C,characterized by C＞T transitions at GpCpN sites,tends to be a feature of diverse normal tissues.Mutations of this type are likely to occur early during embryonic development,supported by their relatively high allelic frequencies,presence in multiple tissues,and decrease in occurrence with age.Almost none of the public datasets for tumors feature this signature,except for 19.6％of samples of clear cell renal cell carcinoma with increased activation of the hypoxia-inducible factor 1(HIF-1)signaling pathway.Moreover,the accumulation of signature C in the mutation profile was accelerated in a human embryonic stem cell line with drug-induced activation of HIF-1α.Thus,embryonic hypoxia may explain this novel signature across multiple normal tissues.Our study suggests that hypoxic condition in an early stage of embryonic development is a crucial factor inducing C＞T transitions at GpCpN sites;and indi-viduals'genetic background may also influence their postzygotic mutation profiles.

Mixed reality is a new digital hologram technology after virtual reality and augmented reality, which combines the real world with the virtual world to form a new visualization environment. At present, mixed reality has been applied in various fields, but its application in medical field is still in the exploratory stage. With the rapid development of the digital age, the prospect of the combination of mixed reality and medicine is boundless. It is believed that mixed reality will bring subversive changes in medical training, disease diagnosis, doctor-patient communication, clinical diagnosis, treatment and so on in the near future. In this paper, the application of mixed reality in medicine was summarized.

Objective:We aimed to evaluate the predictive value of pre-implantation biopsy combined with Lifeport for the short-term prognosis of kidney allograft from donation after citizen death (DCD).Methods:Data from a total of 34 patients who had undergone kidney transplantation in Jinling Hospital from December 2017 to December 2019 were retrospectively analyzed. Histopathological data from pre-implantation biopsy , Lifeport parameters and recipient kidney transplant function at 3 months post-surgery were collected. The performances of histopathological indexes , and Lifeport parameters to predict delayed graft function (DGF) and estimated glomerular filtration rate (eGFR) at 3 months post-surgery were observed evaluated.Results:13 cases of DGF occurred, accounting for 38.2%. Serum creatinine at death and resistance index (RI) at 0.5 h, 1 h, 2 h and 4 h after Lifeport hypothermic machine perfusion (HMP) in the DGF group was significantly higher than that in the non-DGF group. Histologically, the acute tubular injury (ATI) score of the DGF group was higher than that of the non-DGF group, whereas the Remuzzi score was not statistically different between the two groups. The eGFR at 3 months post-transplant was moderately correlated with the RI at 4 h HMP and the Remuzzi score (RI: r=-0.48, P<0.001; Remuzzi score: ρ=-0.42, P=0.01), but no correlated with ATI score of the donor kidney. Although Remuzzi score was not correlated with kidney allograft recovery time (ρ=-0.25, P=0.16), it was inversely correlated with eGFR at 3 months post-transplant (ρ=-0.42, P=0.01). Combined use of Lifeport HMP 4-hour RI and ATI score increased the sensitivity and specificity of predicting DGF to 100% (95% CI: 75.3%-100%) and 90.5% (95% CI: 69.6%-98.8%) respectively. Conclusions:The serum creatinine at death, Lifeport RI, and ATI score of the DGF group were significantly higher than those of the non-DGF group, and the eGFR at 3 months post-transplant was correlated with the Lifeport RI and Remuzzi score. Combined use of ATI score and RI at 4 hours of Lifeport perfusion improved the sensitivity and specificity of predicting DGF .

Objective    To investigate the safety and efficacy of 3D single-portal inflatable mediastinoscopic and laparoscopic esophagectomy for esophageal cancer. Methods    Clinical data of 28 patients, including 25 males and 3 females, aged 51-76 years, with esophageal squamous cell carcinoma undergoing single-portal inflatable mediastinoscopic and laparoscopic esophagectomy from June 2018 to June 2019 were retrospectively analyzed. Patients were divided into two groups according to different surgical methods including a 3D mediastinoscopic group (3D group, 10 patients) and a 2D mediastinoscopic group (2D group, 18 patients). The perioperative outcome of the two groups were compared. Results    Compared with the 2D group, the 3D group had shorter operation time (P=0.017), more lymph nodes resected (P=0.005) and less estimated blood loss (P=0.015). There was no significant difference between the two groups in the main surgeon's vertigo and visual ghosting (P>0.05). The other aspects including the indwelling time, postoperative hospital stay, pulmonary infection, arrhythmia, anastomotic fistula, recurrent laryngeal nerve injury were not statistically significant between the two groups (P>0.05). Conclusion    The 3D inflatable mediastinoscopic and laparoscopic esophagectomy for esophageal cancer, which optimizes the surgical procedures of 2D, is safe and feasible, and is worthy of clinical promotion in the future.

Objective    To investigate the short-term follow-up results of inflatable mediastinoscopy combined with laparoscopy in the treatment of esophageal cancer. Methods    Clinical data of 102 patients with esophageal cancer who underwent minimally invasive esophagectomy were enrolled in our hospital from January 2017 to January 2019. Patients were divided into two groups according to different surgical methods, including a single-port inflatable mediastinoscopy combined with laparoscopy group (group A, n=59, 53 males and 6 females, aged 63.3±7.6 years, ranging from 45 to 75 years) and a video-assisted thoracoscopy combined with laparoscopy group (group B, n=43, 35 males and 8 females, aged 66.7±6.7 years, ranging from 50-82 years). The short-term follow-up results of the two groups were compared. Results    Compared with the group A, the rate of postoperative pulmonary complication of the group B was significantly lower (18.64% vs. 4.65%, P<0.05). There was no significant difference between the two groups in other postoperative complications (P>0.05). The 6-month, 1-year, and 2-year survival rates were 96.61%, 89.83%, and 73.33%, respectively in the group A, and were 95.35%, 93.02%, and 79.17%, respectively in the group B. There was no significant difference in short-term survival rate after operation (P>0.05). Conclusion    In the treatment of esophageal cancer, the incidence of pulmonary complications of inflatable mediastinoscopy combined with laparoscopy is lower than that of traditional video-assisted thoracoscopy combined with laparoscopy, and there is no significant difference in other postoperative complications or short-term survival rate between the two methods. Inflatable mediastinoscopy combined with laparoscopy for radical esophageal cancer is a relatively safe surgical method with good short-term curative effects, and long-term curative effects need to be further tested.

Computer aided design, numerically controlled milling, additive manufacturing and other digital technologies have been widely used in clinical practice of prosthodontics. The application of these technologies not only changed the design and manufacturing workflow of removable partial denture (RPD), but also improved the production efficiency of dentures, and changed the design and manufacturing concept of dentures. A large number of researches on computer aided design and computer aided manufacturing (CAD/CAM) of RPD have emerged in recent years, including researches on the properties of selective laser melting metal powder and other new dental materials, the innovative design of retainers, connectors, artificial teeth and other denture components, high precision manufacturing of the RPD framework, denture base and artificial teeth, quantitative laboratory evaluations of the accuracy, adaption and mechanical properties of RPD with new structures and made of new materials, clinical evaluations of RPD and others. This paper introduces these recent developments in CAD/CAM of RPD.

Objective:To quantitatively evaluate the accuracy of multi-color and multi-hardness dental models printed by using the photopolymer jetting (PJ) technology, and to provide protocol for the clinical application.Methods:A maxillary partially edentulous (Kennedy class Ⅱ subclass 1) standard digital model obtained through scanning and processing was selected as reference data. Five monochromatic DLP (digital light processing) models with single hardness were printed by printer DLP-800d based on DLP technology (DLP group), and five multi-color and multi-hardness PJ models were printed by printer J300Plus based on PJ technology (PJ group). Scan the printed model and register the scanning data to the reference data in Geomagic Studio 2013 software. The three-dimensional (3D) deviations of the whole and each area, including residual dentition, abutments adjacent to the edentulous area, gingiva, gingiva in the distal-extended edentulous area, gingiva in other edentulous areas, gingiva supporting the removable partial denture (RPD), were calculated and represented by the root mean square error (RMS) value. The smaller the RMS value was, the higher the trueness of printing was. The scanning data of the five models in the same group were registered in pairs to calculate the 3D deviation. The smaller the RMS value was, the higher the precision of printing was. The threshold of clinical acceptability was 200 μm. Statistical analysis was performed to compare the difference of trueness and precision between the two groups.Results:The overall trueness of the DLP group [57.70 (2.10) μm] was significantly better than that of the PJ group [71.00 (7.70) μm]. The overall precision of the DLP group [15.20 (5.05) μm] was significantly better than that of the PJ group [37.55 (15.55) μm]. The overall trueness and precision of both groups were within the clinically acceptable range.Conclusions:The domestic PJ printer used in this study can print multi-color and multi-hardness dental models with good trueness and precision, which can provide integrated 3D printing technology support for realizing the simulation of regional hardness differentiation between soft and hard tissues of dental models.

Objective    To investigate the safety and efficacy of naked eye 3D thoracoscopic surgery in minimally invasive esophagectomy. Methods    Clinical data of 65 patients, including 50 males and 15 females aged 47-72 years, with esophageal cancer who underwent minimally invasive thoracoscopic esophagectomy from October 2018 to April 2019 were retrospectively analyzed. Patients were divided into two groups according to different surgical methods including a naked eye 3D thoracoscopic group (group A: 30 patients) and a traditional 2D thoracoscopic group (group B: 35 patients). The effects of the two groups were compared. Results    The operation time in the group A was significantly shorter than that in the group B (P<0.05). The number of dissected lymph nodes in the group A was more than that in the group B (P<0.05). The thoracic drainage volumes on the 1th-3th days after operation in the group A were significantly larger than those in the group B (P<0.05), but there was no significant difference between the two groups on the 4th-5th days after operation (P>0.05). The indwelling time in the group A was longer than that in the group B (P<0.05). Postoperative hospital stay, pulmonary infection, arrhythmia, anastomotic leakage, and recurrent laryngeal nerve injury were not significantly different between the two groups (P>0.05). Conclusion    Naked eye 3D thoracoscopic surgery for minimally invasive esophagectomy is a safe and effective surgical procedure. Compared with traditional 2D minimally invasive thoracoscopic surgery, it is safer in operation and more thorough in clearing lymph nodes. The operation is more efficient and can be promoted.