OBJECTIVE: To quantitatively evaluate the accuracy of data obtained from liquid-interference surfaces using an intraoral 3D scanner (IOS) integrated with a compressed airflow system, so as to provide clinical proof of accuracy for the application of the compressed airflow system-based scanning head in improving data quality on liquid-interference surfaces. METHODS: The study selected a standard model as the scanning object, adhering to the "YY/T 1818-2022 Dental Science Intraoral Digital Impression Scanner" guidelines, a standard that defined parameters for intraoral scanning. To establish a baseline for accuracy, the ATOS Q 12M scanner, known for its high precision, was used to generate true reference values. These true values served as the benchmark for evaluating the IOS performance. Building on the design of an existing scanner, a new scanning head was developed to integrate with a compressed airflow system. This new design aimed to help the IOS capture high-precision data on surfaces where liquid-interference, such as saliva, might otherwise degrade scanning accuracy. The traditional scanning method, without airflow assistance, was employed as a control group for comparison. The study included five groups in total, one control group and four experimental groups, to investigate the effects of scanning lens obstruction, airflow presence, liquid media, and the use of the new scanning head on scanning process and accuracy. Each group underwent 15 scans, generating ample data for a robust statistical comparison. By evaluating trueness and precision in each group, the study assessed the impact of the compressed airflow system on the accuracy of IOS data collected from liquid-interference surfaces. Additionally, we selected Elite and Primescan scanners as references for numerical accuracy values. RESULTS: The scanning accuracy on liquid-interference surfaces was significantly reduced in terms of both trueness and precision [Trueness: 18.5 (6.5) vs. 38.0 (6.7), P < 0.05; Precision: 19.1 (8.5) vs. 31.7 (15.0), P < 0.05]. The use of the new scanning head assisted by the compressed airflow system significantly improved the scanning accuracy [Trueness: 22.3(7.6) vs. 38.0 (6.7), P < 0.05; Precision: 25.8 (9.6) vs. 31.7 (15.0), P < 0.05]. CONCLUSION The scanning head based on the compressed airflow system can assist in improving the accuracy of data obtained from liquid-interference surfaces by the IOS.
Imaging, Three-Dimensional/methods* ; Humans ; Dental Impression Technique/instrumentation*

In fixed prosthodontics, clear exposure of the preparation margin is the prerequisite for obtaining accurate digital impressions and improving the marginal fit of restorations. To resolve the issues associated with the cord retraction technique, such as pain, acute injury, and prolonged procedural time, this study proposes a new technology for intraoral digital impression taking with pneumatic gingival retraction. The new scanning head blows a high-speed airflow that instantaneously separates the free gingiva, locally exposing the subgingival preparation margin. Combined with the farthest point preservation stitching algorithm based on the distance from the normal vector and high-speed laser scanning photography, it achieves global preparation edge data and gingival reconstruction, realizing painless, non-invasive, and efficient precise acquisition of the preparation margin. Using this new technique, a patient with a full porcelain crown restoration on a posterior tooth was treated. The digital impression revealed a clear margin of the preparation, and the crown made from this data has a good marginal fit.

Objective To investigate the diagnostic value of enhanced MR subtracted venography (MRsV)in iliac vein stenosis. Methods 21 patients were recruited for unilateral venous circulation disorders,and they were all performed two kinds of MR venography,including time of flight (TOF)and MRsV.All raw data were reconstructed and maximum intensity proj ection (MIP)images were gained after post-processing in workstation.The image quality and diagnostic accuracy were evaluated by two experienced radiologists.All the results were analyzed,with P<0.05.Results 18 patients were enrolled in our study with good image quality,including 10 cases of unilateral iliac venous thrombosis,1 case of iliac venous stenosis infiltrated by tumor recurrence,3 cases of IVCS and 4 cases without iliac venous thrombosis.The sensitivity and specificity of MRsV-MIP were higher than TOF-MIP (100% vs 92.3%,100% vs 75%,respectively). There was significant difference in diagnostic accuracy between MRsV-MIP and TOF-MIP(χ2=4.827 2,P=0.028 0).Conclusion MRsV demonstrates better image quality and diagnostic performance than TOF in evaluation of iliac vein stenosis.MRsV has greater potential in providing the differential diagnosis evidence in venous stenosis.It could be established as an independent iliac venous imaging method.

Objective One of the major challenges to emergency department is to provide high quality and time sensitive service under limitation of human/material resources,along with patients population with extremely complex conditions.We presented a study that based on a big data got from real world and used wavelet transform technique to analyze time-dependent diseases spectrum patterns and evolution patterns,which will provide solid methodological support for optimizing resources configuration for acute care surgery service.Methods Record data of patients admitted to acute care surgery from 2007-2014 were collected by using data management tool (Avaintec,Helsinki,Finland).The data were cleansed and were transformed to continuing spectrum according to time series of admission time points (per 9 hours).Matlab was used for wavelet transform,and applied five levels of wavelet decomposition and calculated the best decomposition levels by K-mean algorithm for each level.Then we used aprori algorithm for data mining (frequent patterns mining).Results A total of 23 795 cases were enrolled and acute abdomens were made up biggest proportion of admission.Meanwhile,it is found that the spectrum of acute care surgery admission frequency was a complex rising sequence.After wavelet decomposition,signal wave A reflexed trends evolution in a given time scale,and noise wave D reflexed minutia at relevant time scale.In another words,a principal wave A1 represented fluctuation at a cycle of 16 days.Noise wave D1 reflected intensity level in this 16 days' cycle.For example,the 5 · 12 episodes of massive earthquake in 2008 were included in the study,it is found that a significant noise wave at D3 level that indicated a 4 days' cycle.Clinically,it indicated explosive admissions to acute care surgery in 4 days.Conclusions The admission spectrum to acute care surgery is a phenomenon of multi-scale.Based on wavelet decomposing,we can easily analyze the rule of admission spectrum from electronic records of patients and can be used for optimization the emergency medicine resources.

BACKGROUND:Intertrochanteric fracture is one of the common fracture, and accompanied by osteoporosis and high energy injury. The fracture line often descended, and induced A3 intertrochanteric fracture. This type of fracture is difficult to treat. Common intramedulary fixation includes proximal femoral nail anti-rotation and InterTan, which have high stability, are minimaly invasive, and have been extensively used. OBJECTIVE: To compare the biomechanical stability of A3 intertrochanteric fracture fixed with proximal femoral nail anti-rotation and InterTan by finite element analysis. METHODS:Three three-dimensional finite element models of the AO3.1, AO3.2 and AO3.3 intertrochanteric fracture fixed with proximal femoral nail anti-rotation and InterTan were established. Fixation was completed according to the requirement of Department of Orthopedics. Stress distribution of femur and fixator of different models was observed. Stress peak at different areas was compared in femur and fixation models. Biomechanical stability was analyzed. RESULTS AND CONCLUSION: The maximum pressure concentration area in AO3.1 intertrochanteric fracture with proximal femoral nail anti-rotation was located in the lateral proximal femur, and with Intertan was located in the medial proximal femur. The AO3.2 had little differences between two types of nails. The AO3.3 intertrochanteric fracture with proximal femoral nail anti-rotation was located in the medial proximal femur and the medial distal implant. There was no significant pressure concentration with InterTan. The von Mises pressure of six models was concentrated in the medial distal implant, and higher maximum von Mises pressure was found in the proximal femoral nail anti-rotation. There was significant difference of von Mises distribution between the lateral and medial implant with proximal femoral nail anti-rotation. Except the AO3.3 intertrochanteric fracture with proximal femoral nail anti-rotation, the maximum pressures of remaining models were located in the main nail and interlocking nail infal. These results concluded that the fracture fixed with InterTan exhibited fine fixation stability in the AO3.1 and AO3.3 intertrochanteric fracture. There was no significant difference of fixation stability between proximal femoral nail anti-rotation and InterTan in AO3.2. The von Mises distribution of InterTan for intertrochanteric fracture is more reasonable.