Digital intraoral scanning is a hot topic in the field of oral digital technology.In recent years,digital intra-oral scanning has gradually become the mainstream technology in orthodontics,prosthodontics,and implant dentistry.The precision of digital intraoral scanning and the accuracy and stitching of data collection are the keys to the success of the impression.However,the operators are less familiar with the intraoral scanning characteristics,imaging process-ing,operator scanning method,oral tissue specificity of the scanned object,and restoration design.Thus far,no unified standard and consensus on digital intraoral scanning technology has been achieved at home or abroad.To deal with the problems encountered in oral scanning and improve the quality of digital scanning,we collected common expert opin-ions and sought to expound the causes of scanning errors and countermeasures by summarizing the existing evidence.We also describe the scanning strategies under different oral impression requirements.The expert consensus is that due to various factors affecting the accuracy of digital intraoral scanning and the reproducibility of scanned images,adopting the correct scanning trajectory can shorten clinical operation time and improve scanning accuracy.The scanning trajec-tories mainly include the E-shaped,segmented,and S-shaped methods.When performing fixed denture restoration,it is recommended to first scan the abutment and adjacent teeth.When performing fixed denture restoration,it is recommend-ed to scan the abutment and adjacent teeth first.Then the cavity in the abutment area is excavated.Lastly,the cavity gap was scanned after completing the abutment preparation.This method not only meets clinical needs but also achieves the most reliable accuracy.When performing full denture restoration in edentulous jaws,setting markers on the mucosal tissue at the bottom of the alveolar ridge,simultaneously capturing images of the vestibular area,using different types of scanning paths such as Z-shaped,S-shaped,buccal-palatal and palatal-buccal pathways,segmented scanning of dental arches,and other strategies can reduce scanning errors and improve image stitching and overlap.For implant restora-tion,when a single crown restoration is supported by implants and a small span upper structure restoration,it is recom-mended to first pre-scan the required dental arch.Then the cavity in the abutment area is excavated.Lastly,scanning the cavity gap after installing the implant scanning rod.When repairing a bone level implant crown,an improved indi-rect scanning method can be used.The scanning process includes three steps:First,the temporary restoration,adjacent teeth,and gingival tissue in the mouth are scanned;second,the entire dental arch is scanned after installing a standard scanning rod on the implant;and third,the temporary restoration outside the mouth is scanned to obtain the three-di-mensional shape of the gingival contour of the implant neck,thereby increasing the stability of soft tissue scanning around the implant and improving scanning restoration.For dental implant fixed bridge repair with missing teeth,the mobility of the mucosa increases the difficulty of scanning,making it difficult for scanners to distinguish scanning rods of the same shape and size,which can easily cause image stacking errors.Higher accuracy of digital implant impres-sions can be achieved by changing the geometric shape of the scanning rods to change the optical curvature radius.The consensus confirms that as the range of scanned dental arches and the number of data concatenations increases,the scanning accuracy decreases accordingly,especially when performing full mouth implant restoration impressions.The difficulty of image stitching processing can easily be increased by the presence of unstable and uneven mucosal mor-phology inside the mouth and the lack of relatively obvious and fixed reference objects,which results in insufficient ac-curacy.When designing restorations of this type,it is advisable to carefully choose digital intraoral scanning methods to obtain model data.It is not recommended to use digital impressions when there are more than five missing teeth.

Objective:To investigate effects of polydimethylsiloxane coating on the quality characteristics and qual-ity control methods of medium borosilicate glass tube injection bottles,including appearance,identification,physi-cal properties,water resistance of inner surface and element leaching amount.Methods:Nine batches of coated medium borosilicate glass tube injection bottles and corresponding medium borosilicate glass tube injection bottles from three companies were used to evaluate whether the quality control method of medium borosilicate glass tube in-jection bottles after polydimethylsiloxane film was modified,and to evaluate the effect of coating on the quality char-acteristics of bottles.Results:The coating did not have effect on appearance,identification and physical properties of medium borosilicate glass tube injection bottle.The coating process did not damage the original performance of the medium borosilicate glass tube injection bottle,and lead to the matters with special attention on the inspection method.The water resistance of the inner surface of the coated medium borosilicate glass tube injection bottle was improved.The leaching amounts of harmful elements such as arsenic,antimony,lead and cadmium before and after coating were low,indicating that the coating process did not increase the leaching risk of these harmful elements.The leaching amounts of elements were determined by ICP-OES,and no significant changes were found in most metal elements.Conclusion:The appearance,identification,physical properties and element leaching quality con-trol method of medium borosilicate glass tube injection bottle after poly dimethylsiloxane film coating do not need to be changed.The water resistance of the inner surface after coating is improved,and there is no significant adverse effect on other quality characteristics.

Objective:To establish a finite element model of the mandibular first molar with three wall defects, simulate the repair effect of fiber post porcelain crown and modified inlay, and analyze the effect of crown defect location on abutment stress.Methods:One intact mandibular first molar was extracted due to periodontal disease. Conical beam computed tomography (CBCT) was used to obtain the data, Mimics, Geomagic, and Ansys software were used to construct the mandibular first molar model, and 8 groups of models (groups A, B, C, D of fiber post all-porcelain crown and groups E, F, G, and H of modified onlays) were established according to different locations and repair methods of the three wall defects. Four forces (F1, F2, F3 and F4) were selected to compare the maximum Von Mises stress and its distribution.Results:The extreme values of dentin Von Mises stress were 19.334 9-19.907 1 MPa(F1), 8.295 47-8.466 08 MPa(F2), 19.433 5-19.441 4 MPa(F3) for fiber post all-porcelain crown restoration (group A, B, C and D models), respectively. 36.109 3-36.199 8 MPa(F4); The maximum values of Von Mises stress were 19.493-19.864 8 MPa(F1) in modified high inputate restoration (E, F, G, H). 9.077 35-9.317 12 MPa(F2), 22.770 6-23.541 2 MPa(F3), 35.724 2-35.989 7 MPa(F4). There was little change among the models. The extreme value of dentin stress increased with the increase of loading Angle. Under the same defect mode, the extreme value of dentin stress in groups A, B, C and D was less than that in groups E, F, G and H at F2 and F3. At F1 and F4, the extreme values of dentin stress in the eight groups were similar, but the dentin stress concentration area in groups A, B, C and D was located on the tooth surface, and the stress concentration area appeared in the pulp chamber in groups E, F, G and H.Conclusions:The position of the defect has no significant effect on the repairing effect of the modified inlay and the fiber post porcelain crown. The fiber post porcelain crown is more beneficial to disperse the dentin stress.

Objective:To study the feasibility of a modified pancreatogastric anastomosis in laparoscopic duodenum preserving pancreatic head resection (LDPPHR).Methods:The clinical data of 25 patients with benign or low-grade malignant tumors of pancreatic head undergoing LDPPHR at the Second Hospital of Hebei Medical University from January 2019 to May 2023 were retrospectively analyzed, including 7 males and 18 females, aged (44.9±6.2) years old. According to the methods of pancreatic digestive reconstruction, patients were divided into the observation group ( n=10), who underwent the modified pancreatogastric anastomosis, and the control group ( n=15) who underwent conventional pancreaticojejunal anastomosis and jejuno-jejunal anastomosis. The general data, intraoperative pancreatic digestive reconstruction time, maximum levels of amylase in abdominal drainage within three days postoperatively, postoperative complications, and hospital stay were compared between the groups. Results:All procedures were performed successfully. The intraoperative pancreatic digestive reconstruction time was shorter in the observation group [(27.8±2.4) min vs. (45.8±3.6) min, P=0.010]. The intraoperative blood loss were comparable between the groups [(140.5±14.8) ml vs. (145.2±9.7) ml, P=0.843]. The maximum level of amylase in abdominal drainage within three days postoperatively was lower in the observation group [(809.1±185.5) U/L vs. (1 385.4±481.1) U/L, P=0.031]. No grade C pancreatic fistula or postoperative hemorrhage occurred in either group, and the incidence of grade B pancreatic fistula was lower in the observation group [20.0% (2/10) vs. 60.0% (9/15), P=0.048], with a shorter postoperative hospital stay [(7.9±1.3) d vs. (10.3±2.7) d, P=0.017]. No decrease of life quality or reoperation due to pancreatic fistula, hemorrhage or digestive tract malfunction occurred in either group within a median follow-up of 15.6 months. Conclusion:In LDPPHR, the modified pancreatogastric anastomosis could help shorten the pancreatic digestive reconstruction and lower the risk of postoperative pancreatic fistula.

Objective:To investigate the application value of laparoscopic pancreatic tumor enucleation (LapEN).Methods:The retrospective and descriptive study was conducted. The clinical data of 47 patients who underwent LapEN in Second Hospital of Hebei Medical University from September 2016 to June 2022 were collected. There were 18 males and 29 females, aged (49±12)years. Observa-tion indicators: (1) surgical situations; (2) postoperative complications; (3) postoperative recovery; (4) follow-up. Measurement data with normal distribution were represented as Mean± SD, and measurement data with skewed distribution were represented as M( Q1, Q3) or M(range). Count data were described as absolute numbers. Results:(1) Surgical situations. All 47 patients underwent LapEN successfully, with the operation time as (135±19)minutes and the volume of intraoperative blood loss as 100(50,100)mL. (2) Postoperative complications. Of the 47 patients, there were 12 patients with postoperative pancreatic fistula, 3 patients with postoperative abdominal infection, 1 case with postoperative hemorrhage, 1 case with postoperative gastric emptying disorder. (3) Postoperative recovery. Of the 47 patients, there were 13 cases with pancreatic solid pseudopapillary neoplasm, 12 cases with insulinoma, 11 cases with pancreatic serous cystadenoma, 7 cases with pancreatic intraductal papillary mucinous neoplasm (branched type), 4 cases with pancreatic mucinous cyst-adenoma. The tumor diameter of 47 patients was 1.9(1.6,2.3)cm and all patients with R 0 resection. There was no patient with perioperative death in the 47 patients. The postoperative duration of hospital stay and total hospital expenses of 47 patients was (13±4)days and (6.8±1.2) ten thousand yuan, respectively. (4) Follow-up. All 47 patients were followed up for 14(range, 8?18)months. None of the 47 patients had new onset diabetes or situations required postoperative exocrine replacement therapy, and no patient died. Conclusion:LapEN is safe and feasible for patients with pancreatic benign tumor or low potential malignancy.

Objective:To investigate the clinical efficacy of laparoscopic radical resection of hilar cholangiocarcinoma (LRHCCA).Methods:The retrospective and descriptive study was constructed. The clinicopathological data of 211 patients who under LRHCCA in the Second Hospital of Hebei Medical University from May 2014 to June 2022 were collected. There were 135 males and 76 females, aged (63±8)years. Observation indicators: (1) surgical situations; (2) postoperative situations; (3) follow-up. Measurement data with normal distribution were represented as Mean± SD, and measurement data with skewed distribution were represented as M( Q1, Q3) or M(range). Count data were described as absolute numbers or percentages. The Kaplan-Meier method was used to calculate survival rate and draw survival curve. Results:(1) Surgical situations. All 211 patients underwent LRHCCA successfully, with the operation time as 350 (300,390)minutes, volume of intraoperative blood loss as 400(200,800)mL, and intraoperative red blood cell transfusion as 2.0(range, 0-15.0)U, respectively. As partial portal vein invasion, 10 of 211 patients underwent portal vein resection and reconstruction. Results of intraoperative histopathology examination showed negative margin of portal vein. The operation time, volume of intraoperative blood loss, intraopera-tive red blood cell transfusion of the 10 patients was (400±53)minutes, 1 200(range, 800-3 000)mL, 5.5(range, 4.0-15.0)U, respectively. (2) Postoperative situations. Of the 211 patients, there were 63 cases of the Bismuth type Ⅰ, 65 cases of the Bismuth type Ⅱ, 22 cases of the Bismuth type Ⅲa, 26 cases of the Bismuth type Ⅲb, 35 cases of the Bismuth type Ⅳ. The R 0 resection rate was 95.73%(202/211). There were 202 patients identified as adenocarcinoma of the bile duct, including 7 cases with poorly differentiated tumor, 189 cases with moderate to poorly differentiated tumor, 3 cases with moderate to well differentiated tumor, 3 cases with well differentiated tumor. There were 8 patients with poorly differentiated biliary mucinous adenocarcinoma, 1 patient with intraductal papillary neoplasm with high-grade epithelial dysplasia. There were 24 cases of stage Ⅰ, 98 cases of stage Ⅱ, 30 cases of stage ⅢA, 34 cases of stage ⅢB, 19 cases of stage ⅢC, 6 cases of stage ⅣA. Of the 211 patients, there were 25 cases with postoperative biliary fistula, 11 cases with postoperative abdominal infection, 3 cases with postoperative bleeding as anastomotic bleeding after biliary fistula, 2 cases with postoperative gastric emptying disability, 1 case with postoperative acute liver failure. There were 7 patients undergoing postoperative unplanned reoperation, including 3 cases with emergency operation for hemostasis, 4 cases with abdominal exploration debridement and drainage for severe abdominal infection. There were 3 cases dead during perioperative period, including 1 case of acute liver failure, 1 case of systemic infection and multiple organ failure, 1 case of exfoliated deep venous thrombosis of lower extremities and acute pulmonary embolism. The postoperative duration of hospital stay was (15±5)days of the 211 patients and (17±4)days of patients undergoing portal vein resection and reconstruction. The cost of hospital stay of the 211 patients was (11.7±1.7)ten thousand yuan. (3) Follow-up. Of the 211 patients, 188 patients were followed up for 21(range, 4?36)months. The median survival time of 188 patients was 22 months, and the postoperative 1-, 2- and 3-year survival rate was 90.9%, 43.1% and 18.7%, respectively. Conclusion:LRHCCA is safe and feasible, with satisfactory short-term effect, under the coditions of clinicians with rich experience in laparoscopic surgery and patients with strict surgical evaluation.

Objective:To study the safety and therapeutic effects of the modified pancreaticogastrostomy based on the concept of " Hong's one-stitch method" in digestive tract reconstruction in pancreatic surgery.Methods:The clinical data of 44 patients who underwent modified pancreaticogastresstomy at the Department of Hepatobiliary Surgery, the Second Hospital of Hebei Medical University from May 2022 to October 2022 were analyzed retrospectively. There were 23 males and 21 females , with a median age of 54 years old (range 18 to 70 years old). The operation time, intraoperative blood loss, postoperative condition and complications were analysed.Results:All the 44 patients completed the operation successfully. There were 29 patients who underwent laparoscopic pancreaticoduodenectomy, 11 patients laparoscopic duodenum-preserving pancreatic head resection, 1 patient laparoscopic central pancreatectomy, and 3 patients open pancreaticoduodenectomy. The time required for the pancreaticogastrostomy was (15.4±1.0) min in laparoscopic surgery, and (9.1±0.5) min in open surgery. There were 2 patients who developed grade A pancreatic fistula (4.55%, 2/44) and 7 patients gastric emptying disorder (15.91%, 7/44). There were no grade B or C pancreatic fistula, biliary fistula, gastrointestinal anastomotic fistula, abdominal infection, postoperative bleeding and perioperative death.Conclusion:The modified pancreaticogastrostomy for digestive tract reconstruction in pancreatic surgery was safe and reliable. It effectively reduced the incidence of postoperative pancreatic fistula and improved prognosis of patients.

Objective:To evaluate the effect of different numbers and location of fiber post on stress distribution of fiber post-all-ceramic crown restored mandibular first molar, with application of finite element method.Methods:Intact human mandibular first molars were used to build three-dimensional finite element models, restored with fiber post core and all ceramic crown. Three-dimension finite element model with 7 different post designs(according to the numbers and location of fiber post inserted into root canal) were created with soft wares of Mimics, Geomagic and Ansys. The von Mises criterion was applied for comparing the maximum von Mises stress value of dentin and stress concentration areas in 7 models maximum load (F1, 225 N), vertical load (F2, 225 N), inclined load (F3, 225 N) and horizontal load (F4, 225 N).Results:Under maximum load, vertical load, inclined load and horizontal load, the maximum von Mises stress value of dentin were 21.854-22.629 MPa (F1), 20.945-21.369 MPa (F2), 21.637-22.513 MPa (F3) and 37.922-38.277 MPa (F4), when the mandibular first molar defect was restored with fiber post core and all ceramic crown. There was little difference in maximum von Mises stress values and stress distribution among the 7 groups. Increasing the number of Posts has no significant effect on the stress distribution of the original post. The maximal Von Mises stress on dentine increased when the horizontal direct loads increased.Conclusions:The number and location of posts have little influence on maximum stress values and stress distribution, when the mandibular first molar defect was restored with fiber post core and all ceramic crown.

To explore the technical process and the therapeutic effect of using sequential surgical guide with independent intellectual property rights assisting immediate implantation and restoration of the full arch, with the support from the periodontal splint for mobile supporting teeth, patients with severe periodontitis who planned to undergo immediate full arch implantation were recruited from August 2019 to December 2020 at the Department of Prosthodontics, Department of Periodontology, Department of Implantology and First Clinical Division, Peking University School and Hospital of Stomatology. Through the procedure of collecting preoperative maxillofacial data, making systematic diagnostic design, making periodontal splints fixation, producing surgical guide, and carrying out guided surgery for full arch immediate implantation, eight cases were included. By registering the postoperative cone-beam CT (CBCT) with the preoperative data, the difference between the actual three-dimensional position of the implants and the virtual design was observed, and the accuracy of the implant placement position guided by the sequential guide was statistically analyzed using SPSS 25.0 software. Analysis indicators include coronal and apical global displacement, coronal horizontal and vertical displacement, apical horizontal and vertical displacement, and angular deviation. Results revealed that the 8 patients [2 males and 6 females, aged (49.0±9.3) years (38-65 years)] of recruited cases included 7 cases of maxilla and 1 cases of mandible. A total of 48 implants, of which 44 implants were placed upright and 4 were placed tilted, 16 implants in the anterior region and 32 implants in the posterior region. No guide plate fracture or damage to important anatomical structures were reported. The overall displacement at the coronal point [(0.83±0.48) mm] and the global displacement at the apical point [(1.36±0.57) mm] were within the clinically acceptable safety range, and the horizontal displacement and vertical displacement at the coronal point, horizontal displacement and vertical displacement at the apical point, and the angle deviation of implants axial have no statistic significant difference in the anterior and posterior region ( P>0.05). Periodontal splints combined with sequential surgical guides to assist patients with severe periodontitis for immediate full arch implantation and immediate restoration can expand the indications of guide assisted implant surgery. It meets the safety requirements in clinical applications.

Objective:To use a self-developed, prefabricated cap for making interocclusal records in implant-supported fixed prosthetic treatment, and to evaluate its effect of clinical application and accuracy of transferring intra-oral intercuspal position.Methods:Series of prefabricated caps for occlusal recording of implant-supported fixed prostheses were designed based on the healing abutments, and fabricated with three-dimensional (3D) printing. According to the inclusion and exclusion criteria, 12 partially edentulous patients who visited the Department of Prosthodontics, Peking University School and Hospital of Stomatology between November 2020 and September 2021, had lost no fewer than 2 contiguous teeth in distal extension (Kennedy Class Ⅰ or Ⅱ), and had received implant placement 3 months ago were enrolled. Self-control study design was used. Two occlusal records of each included case were obtained by the following 2methods:for the test group, appropriate prefabricated caps were used; and for the control group, polyvinyl siloxane occlusal record was directly set on the healing abutments. The working casts were mounted on the mechanical articulator using the 2 groups of occlusal records successively. Accuracy of occlusal relationship of the mounted casts was evaluated. Diagnostics test was performed to obtain the sensitivity and positive predictive value, which were determined in photographs by comparing the intra-oral occlusal contact points with those in the mounted casts, point-by-point. Virtual casts were taken by intraoral and extraoral scans in intercuspal position and imported to Geomagic Studio 2014. Then the root mean square values of occlusal clearance space between the upper and lower occlusal surfaces of remaining posterior teeth, and the deviations of the interocclusal position of the occlusal surfaces of the remaining teeth in the mandibular arches when superimposing the maxillary arches of the intraoral and extraoral scans were calculated. As a self-control design, paired t test was used. Results:Twelve participants were enrolled, including 3 men and 9 women aged (52.6±12.1) years, and 36 missing teeth. The prefabricated caps could fit on the healing abutments with good retention and stability. The sensitivity of the test group (0.73±0.14) was significantly better than that of control group (0.63±0.12, P<0.01), with no significant difference in positive predictive value between the 2 groups ( P>0.05). The deviations of the interocclusal position of the occlusal surfaces of the remaining teeth were (357.0±140.2) μm for the test group, and (399.4±206.3) μm for the control group, with no significant difference between them ( P>0.05). Conclusions:Interocclusal position record based on prefabricated cap in this study for implant-supported fixed prosthetic treatment can improve the consistency between the intra-oral occlusion and the occlusion in dental casts. This technique has good accuracy, clinical convenience and usability.