Triboelectric charging of polytetrafluoroethylene antithrombotic catheters.

This study proposes that a polytetrafluoroethylene (PTFE) electret tube charged by frictional electricity can prevent the solidification of the indwelling catheter in blood vessels. Coagulation in intravascular indwelling catheters may discontinue the treatment because of thrombus-derived bacteria-adhesion infections or poor blood removal. Current commercially available intravascular catheters lack complete antithrombotic measures, even with heparin or urokinase antithrombotic coatings. Herein, we tested the effectiveness of an antithrombotic treatment that prevents coagulation using a static electric charge on the interior of the PTFE tube via the triboelectric effect by rubbing the tube's inner wall with a round glass rod. The anticoagulation properties were evaluated by enclosing a sample of blood in an electret tube and observing the coagulase adhering to the inner wall using a microscope. To confirm the effectiveness of this treatment, the charge-distribution on the inner surface of the electret tube was measured, surface irregularities were observed, and the elements on the surface were analyzed. The surface potential inside the electret tube was - 366.4 V, which proved effective for an antithrombotic treatment, as it discouraged coagulation, and the triboelectric charging process caused neither surface element denaturation nor significant surface irregularities. The nearly uniform negative surface charge on the inside of the tube was responsible for the antithrombotic effect because no surface irregularities or change in the surface element denaturation was observed. Triboelectrically charged PTFE electret tubes are highly useful for intravascular indwelling catheters.

Optical impression method to measure three-dimensional position and orientation of dental implants using an optical tracker.

OBJECTIVES: The aim of this study was to devise an optical impression method that could make impressions of dental implants accurately and rapidly. MATERIALS AND METHODS: Four paper markers (4 × 3 mm, 8 × 6 mm, 16 × 12 mm, and 24 × 18 mm) and one titanium marker (8 × 6 mm) were prepared to determine the measuring accuracy of the three-dimensional optical tracker. For a proposed and conventional impression taking method, we compared the reproduction accuracies of the positions and orientations of dental implants and the times to obtain impressions. Finally, we fabricated computer-aided designing (CAD)/computer-aided manufacturing (CAM) superstructure frameworks to determine the adaptation accuracy. RESULTS: The 8 × 6-mm titanium marker was optimal among the prepared markers. Dental implants made by the proposed and conventional impression taking methods had measurement errors of 71 ± 31 µm and 32 ± 18 µm, respectively. The proposed method took a significantly shorter time to obtain an impression than did the conventional method. The connection between the CAD/CAM superstructure frameworks and four implant analogs had uplifts of 55 ± 10 µm, 94 ± 35 µm, 2 ± 1 µm, and 66 ± 3 µm. CONCLUSION: Our proposed method and fabricated titanium markers enabled us to measure the positions and orientations of dental implants both accurately and rapidly. We then used the reproducible measurement results for the positions and orientations of the dental implants to fabricate CAD/CAM superstructure frameworks within an acceptable accuracy range.

Application of haptic device to implant dentistry--accuracy verification of drilling into a pig bone.

To enable accurate implant placement and precise drilling following preoperative simulation, we developed the BoneNavi system. To realize more precise drilling when the holes are upsized, two methods of surgical guiding were attempted in the present study. One involved using multiple surgical guides with titanium tubes of different diameters, and the other involved using a single surgical guide but employing titanium drill guide tubes with different diameters. Drilling accuracy of the two newly developed methods was examined and compared with the results of drilling into a pig bone using only the initial surgical guide. Deviations of the position and angle with the two novel methods were similar: 0.17 mm and 1 degree respectively. As for the control group whereby drilling was done using only the initial surgical guide, the deviations were 0.25 mm and 3.50 degrees--which were significantly larger than those achieved with the two novel methods. In light of the results obtained, our newly developed BoneNavi system is especially applicable for severe clinical cases that require precise implant placement.

CAD/CAM fabrication and clinical application of surgical template and bone model in oral implant surgery.

OBJECTIVES: A novel implant surgery support system with computer simulation for implant insertion and fabrication of a surgical template that helps in drilling bone was developed. A virtual reality haptic device that gives the sense of touch was used for simulation and a surgical template was fabricated by CAD/CAM method. Surgical guides were applied for two clinical cases. MATERIAL AND METHODS: Three-dimensional (3D) jaw bone images transferred from DICOM data filmed by CT scanner were fed to the software and manipulated using the haptic device. The site for implant insertion was determined after evaluating the quality of bone and position of the mandibular canal. The surgical template was designed with ease using the free design CAD function of haptic device. The surgical template and bone model were fabricated by a fused deposit modeling machine. Two clinical cases were applied using the present system. RESULTS: Simulation to determine the site of implant insertion and fabrication of the surgical bone templates were successfully done in two clinical cases, one for three implant insertion in lower right jaw and the other is for seven implant insertion in lower edentulous jaw, respectively. During surgery, the templates could be firmly adapted on the bone and drilling was successfully performed in both cases. CONCLUSION: The present simulation and drilling support using the surgical template may help to perform safe and accurate implant surgery.

Application of virtual reality force feedback haptic device for oral implant surgery.

A novel support system for implant surgery was tried out, which involves manipulating a three-dimensional (3-D) computed tomography (CT) image of a jawbone with a virtual reality force feedback haptic device. Through this virtual system, the haptic experience of bone drilling with vibration and the sound of the contra-angle handpiece could be realized. It is expected to be useful for training inexperienced dentists and educating dental students. The simulation of oral implant insertion was also focused on. A simple cylindrical implant model was inserted into a 3-D image of the jawbone by operating the haptic device, with consideration of bone condition. A rectangular solid object that served as a bone-supported surgical template was adopted, and the shapes of the bone and the implant were subtracted from the object. In this manner, the CAD of the surgical template with impressions of the bone and the implant guide holes for insertion was realized. The surgical template was milled with a computer-controlled milling machine (CAM). Surgical template accuracy was examined with an edentulous gypsum bone model having six holes for implant insertion. Simulation of the oral implant insertion and CAD/CAM of the surgical template were conducted. The milled surgical template was fitted on the gypsum bone model, and CT images were taken. Cross-sections of the guide holes in the surgical template were imaged, and misalignment between the guide holes of the surgical template and the drilled holes on the jawbone was measured. The average misalignment is less than 0.2 mm, and it indicates that the present system is potentially applicable to oral implant surgery.

A novel method of removing artifacts because of metallic dental restorations in 3-D CT images of jaw bone.

CT images, especially in a three-dimensional (3-D) mode, give valuable information for oral implant surgery. However, image quality is often severely compromised by artifacts originating from metallic dental restorations, and an effective solution for artifacts is being sought. This study attempts to substitute the damaged areas of the jaw bone images with dental cast model images obtained by CT. The position of the dental cast images was registered to that of the jaw bone images using a devised interface that is composed of an occlusal bite made of self-curing acrylic resin and a marker plate made of gypsum. The patient adapted this interface, and CT images of the stomatognathic system were filmed. On the other hand, this interface was placed between the upper and lower cast models and filmed by CT together with the cast models. The position of the marker plate imaged with the dental casts was registered to those adapted by the patient. The error of registration was examined to be 0.25 mm, which was satisfactory for clinical application. The damaged region in the cranial bone images as an obstacle for implant surgery was removed and substituted with the trimmed images of the dental cast. In the method developed here, the images around the metallic compounds severely damaged by artifacts were successfully reconstructed, and the stomatognathic system images became clear, and this is useful for implant surgery.

3D shape measurement of dental casts using medical X-ray CT.

Three-dimensional (3D) digitizing and computerization of dental casts is a trend in dentistry especially for orthodontics to substitute stone casts. Generally used laser scanners have a blind side in the measurement of undercuts. As alternative equipment that can digitize regardless of the undercut, the potential of recent multi-slice medical CT was examined. In 3D shape reconstruction, the CT window level affects the size of the object. It was examined, and a CT window level of 800 was found to be suitable. However, the size became slightly smaller than the real object. Then, a correction ratio of 1.002, 1.015 and 1.013 on the X-, Y- and Z-axis was given, and error within 0.08% was accomplished. The measurement and 3D imaging of dental casts was completed within 10 min. The reproducibility of the complicated morphology of dental casts was slightly inferior to that of the latest laser scanners, but the accuracy and operationality regardless of the undercut is noteworthy for clinical application.