Molar crown is not only very small and thin-wall, but also has complex profile, especially occlusal surface that distributes many cusps, ridges and fossas is obviously different. If conventional processing method is used, it is impossible to rapidly and exactly machine molar prosthesis. To enhance machining velocity and improve surface precision of molar crown, an algorithm of entity rapid offset based on STL format is put forward. Applying Zigzag tool path planning and micro-machining cutter, finishing tool path for high speed milling molar prosthesis is generated. In terms of Mikron UCP800 high-speed machine center, molar all-crown whose material is Zirconia is successfully machined.Through test results show that the algorithm of tool path generation works fast, and amount of tool paths is rather few, moreover cutter feeds placidly.

Objective To investigate the expression of glutathione S-transferase π (Glutathione S-transferase π, GST-π) protein in peripheral blood and brain of patients with drug-resistant epilepsy and refractory epilepsy rats. Meth?ods From January 2010 to March 2014, the expression of GST-πin the blood and brain of 32 cases of drug-resistant epi?lepsy underwent neurosurgery and 10 cases of cerebral vascular malformation underwent surgery were studied and com?pared. The expression of GST-πin the blood and brain in refractory epilepsy rats and normal rats were studied and com?pared. Results The specimen from 20 temporal, 6 frontal and 6 occipital lobes were obtained from drug-resistant epilep?sy patients. The expression levels of GST-πin the blood and brain in refractory epilepsy rats and normal rats were higher than those of the control groups (P<0.05). Conclusion GST-πmay be involved in the process of drug-resistant epilepsy. The GST-πexpression in blood may be used as a marker for resistance to anti-epileptic agents.

Molar crown is very small and has not only thin-wall, but also complex profile, especially, the occlusal surface of each molar crown has many cusps, ridges and fossae being differently distributed. When conventional processing method is used, it is impossible to machine molar prosthesis rapidly and exactly. To enhance machining velocity and improve the surface precision of molar crown, an algorithm of entity rapid offset-based STL format is put forward. By the application of Zigzag toolpath planning and micro-machining cutter, the finishing toolpaths for high speed milling molar prosthesis are generated. In terms of Mikron UCP800 high-speed machine center, the molar all-crown made of alloy aluminum material is successfully machined. The test results show that the algorithm of tool-path generation works fast, the number of toolpaths is small, and the cutter feeds smoothly.
Algorithms ; Computer-Aided Design ; Crowns ; Dental Prosthesis Design ; Humans ; Molar

The shape of dental arch for orthodontic diagnosis and treatment is of great significance. This paper presents an automated method for detecting the dental arch form. Firstly, 3D teeth data model is retrieved by the 3D-optical measuring system. Secondly, the occlusal plane is computed by interactively picking up four feature points. Thirdly, the feature point set is filtered by the rule and two-step curve fitting method is used to obtain the dental arch form. Finally, some examples are tested in this work and the results demonstrate that the proposed algorithm is effective and feasible.
Computer Graphics ; Computer Simulation ; Dental Arch ; anatomy & histology ; Dental Models ; Humans ; Imaging, Three-Dimensional ; methods ; Malocclusion ; diagnosis ; therapy ; Pattern Recognition, Automated

In order to satisfy the current demand for fast and high-quality prosthodontics, we have carried out a research in the fabrication process of the porcelain fused to metal crown on molar with CAD/CAM technology. Firstly, we get the data of the surface mesh on preparation teeth through a 3D-optical grating measuring system. Then, we reconstruct the 3D-model crown with the computer-aided design software which was developed by ourselves. Finally, with the 3D-model data, we produce a metallic crown on a high-speed CNC carving machine. The result has proved that the metallic crown can match the preparation teeth ideally. The fabrication process is reliable and efficient, and the restoration is precise and steady in quality.
Computer-Aided Design ; Crowns ; Dental Porcelain ; Dental Prosthesis Design ; Humans ; Metal Ceramic Alloys ; Molar

Seeing that the manual method to restore tooth has the disadvantages such as long "lead-time", assurance of quality highly depending on operator's technology, and real-time cure difficulty met by lots of dental patients coming up for tooth restoration, we put forward an algorithm of tool-path generation based on STL data model for roughing dental restoration. The algorithm can reconfigure the STL data of dental crown restoration quickly, can generates the multi-level offset wire-loop by the use of horizontal plane cutting triangle facets; and then on the basis of offset wire-loop, it can plan Zigzag and follow the contour machining tool path. The algorithm has been applied to Dental CAM software, through simulation machining, the result shows that it can not only generate interference-free tool path, but also save a lot of "lead-time" for dental restoration. Accordingly, the algorithm is of great value for reference in clinical application.
Algorithms ; Crowns ; Dental Restoration, Permanent ; methods ; Humans ; Software ; Therapy, Computer-Assisted ; methods

Objective:To evaluate our self-designed novel guide device for cannulated screwing in the treatment of femoral neck fracture.Methods:Between June 2019 and July 2020, 40 patients with femoral neck fracture were treated with cannulated screwing at Department of Orthopaedics, The Second Hospital Affiliated to Shanxi Medical University. They were divided into a manual group of 20 cases whose cannulated screwing was implemented by hand and a guide group of 20 cases whose cannulated screwing was implemented with the aid of our self-designed guide device. In the guide group, there were 5 males and 15 females, with an age of (48.4±10.2) years (from 18 to 63 years); there were 12 cases of types Ⅰ & Ⅱ and 8 cases of types Ⅲ & Ⅳ by the Garden classification. In the manual group, there were 8 males and 12 females, with an age of (49.8±8.4) years (from 18 to 60 years); there were 13 cases of types Ⅰ & Ⅱ and 7 cases of types Ⅲ & Ⅳ by the Garden classification. All fractures underwent closed reduction and internal fixation with 3 cannulated screws. The intraoperative fluoroscopy, operation time, femoral cortex drilling, angle between the guide pin and the femoral neck axis in the anteroposterior view, angle between the guide pin and the femoral neck axis in the lateral view, fracture healing time, Harris hip score and complications were compared between the 2 groups.Results:There was no significant difference in the preoperative general data between the 2 groups, showing comparability ( P>0.05). In the guide group, intraoperative fluoroscopy [(10.0±2.2) times], operation time [(41.8±5.6) min], femoral cortex drilling [(4.5±1.1) times], angle between the guide pin and the femoral neck axis in the anteroposterior view (3.0°±0.8°) angle between the guide pin and the femoral neck axis in the lateral view (3.9°±1.0°) and fracture healing time [(6.2±0.5) months] were significantly less or smaller than those in the manual group [(24.8±8.3) times, (60.0±15.3) min, (12.8±2.0) times, 7.2°±1.8°, 7.6°±2.6°, and (7.2±0.5) months] (all P<0.05). There was no significant difference in Harris hip score between the 2 groups ( P>0.05). None of the patients had wound infection, internal fixation displacement, fracture nonunion or screw breakage. Conclusions:Application of our self-designed guide device can shorten operation time, improve accuracy of needle insertion, and reduce drilling attempts in the femoral cortex, making cannulated screwing easier for femoral neck fractures.