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.

Development of a multi-layered virtual tooth model for the haptic dental training system.

A virtual reality (VR) haptic dental training system could be a promising tool for future dental education. One major challenge is to develop a virtual tooth model which similarly reflected a real tooth having multiple layers with different mechanical hardness in each layer. The multi-layered virtual tooth model was successfully constructed in our virtual system.

Metal artifacts in MRI from non-magnetic dental alloy and its FEM analysis.

Artifacts in MR(Magnetic Resonance) images of oral cavity produced from non-magnetic metal restorations was verified by measuring the image of index finger and a cylinder of fat test piece with a type 4 gold alloy ring using a compact MRI equipment. In the images of finger, portion around the ring disappeared. However, it was nearly restored with a cut ring.

Fabrication of three-dimensional cell constructs using temperature-responsive hydrogel.

A morphologically controlled three-dimensional (3D) cell construct composed of only cells and having no scaffold material might be a valuable biologic material for tissue engineering applications, as the scaffold materials can cause delay of tissue regeneration in some conditions. To obtain such a 3D cell construct, a 3D thermoresponsive hydrogel (poly-N-isopropylacrylamide) was prepared as a mold material that changes its volume depending on the temperature. Three-dimensional osteoblast cell constructs with a variety of morphologies as well as a monolayered cell sheet were obtained by decreasing the surrounding temperature of the hydrogel designed with a predefined shape and formed by curing in a polymer mold manufactured via 3D printing.

Effect of calcium ion concentrations on osteogenic differentiation and hematopoietic stem cell niche-related protein expression in osteoblasts.

Apatite biomaterials have potential not only as cell vehicles for engineering bone tissue but also as regulators of calcium (Ca) concentration in situ for controlling osteoblast functions, for example, osteogenic differentiation and fate management of hematopoietic stem cells (HSCs). To design apatite materials having optimal chemical properties for the latter purpose, more detailed investigations into what effect Ca concentrations have on osteoblast functions is crucial. In this study, osteoblasts were cultured at different Ca concentrations, and the temporal alterations in osteogenic differentiation and HSC niche-related protein (angiopoietin-1, 2 [Ang1, 2]) expression were investigated.

Regulation of the protein-loading capacity of hydroxyapatite by mercaptosuccinic acid modification.

Loading and releasing protein in a controllable way is extremely important for the protein vehicles used in bone tissue engineering. To obtain a suitable carrier material for basic proteins, such as BMP or bFGF, hydroxyapatite particles containing mercaptosuccinic acid (mercaptosuccinic acid (Mer), (Mer-HAp)) were synthesized. Physicochemical evaluation of Mer-HAp suggested that Mer was contained in HAp particles: it either simply adsorbed onto HAp crystals or was trapped among the HAp crystals.

Large-area electron beam irradiation for surface polishing of cast titanium.

Cast titanium is a known hard-to-polish material, and its final polishing step is a perpetual challenge. The best way to tackle this challenge lies in automatic and non-mechanical polishing methods. Against this background, the suitability of large-area electron beam (EB) irradiation was examined in this study.

Virtual reality simulation training for dental surgery.

In dentistry the exquisite hand skill is required for daily treatments, However, dental students have little chance to treat patients in the clinical training So, present study constructed a process simulation to train the hand skill for tooth extraction, especially impacted wisdom tooth that was an example of the difficult case by using virtual reality haptic device.

Dental haptic simulator to train hand skill of student - calibration method to realize visual haptic environment.

In prior work, we have developed dental training simulator to train hand skill of student (HHDTS). In the present study, we performed calibration between haptic device coordinate system and half-mirror coordinate system for our system to realize real clinical situation. As a result, the user can overlay the CG (turbine) onto the stylus of haptic device and intract to the CG (tooth) directly.

Simulation of osteotomy and support for surgery using VR haptic device.

A novel computer-assisted 3-D simulation for osteotomy and CAD/CAM fabrication of surgical splints consider the relative inter-bone interference and space after bone translation were developed. CT image of a patient for osteotomy was operated and simulation of surgery for deformation, segmentation, displacement of the bone was processed effectively by virtual reality haptic device PHANTOM. CAD of a bite splint before surgery and after bone displacement was done in the process of simulation.

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.

Fabrication of freeform bone-filling calcium phosphate ceramics by gypsum 3D printing method.

Transformation of gypsum model fabricated by three-dimensional printing (3DP) into hydroxyapatite (HA) by treating in ammonium phosphate solution is possible. However, 3DP powder supplied by the manufacturer contains unknown additives which may be questionable for biomaterials. Accordingly, pure plaster of Paris (POP) powder was used for fabrication in the present study.

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.

Biomimetic fabrication of fibrin/apatite composite material.

Bidirectional diffusion of the Ca and PO4 solutions into the fibrin gel was performed at various pH conditions and fluoride concentrations to generate organic/inorganic composite materials mimicking biomineralization. The minerals produced in this system had a higher crystallinity than those generated by the solution mineralization system. The minerals generated in fibrin gel varied depending on the pH conditions as follows: Dicalcium phosphate dihydrate (DCPD) in the noncontrolled pH solution, the DCPD and octacalcium phosphate (OCP) mixture at pH 7.

Three-dimensional cell and tissue patterning in a strained fibrin gel system.

Techniques developed for the in vitro reproduction of three-dimensional (3D) biomimetic tissue will be valuable for investigating changes in cell function in tissues and for fabricating cell/matrix composites for applications in tissue engineering techniques. In this study, we show that the simple application of a continuous strain to a fibrin gel facilitates the development of fibril alignment and bundle-like structures in the fibrin gel in the direction of the applied strain. Myoblasts cultured in this gel also exhibited well-aligned cell patterning in a direction parallel to the direction of the strain.

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.

Transformation of 3DP gypsum model to HA by treating in ammonium phosphate solution.

Three-dimensional printing (3DP) is a CAD/CAM built-up using ink-jet printing technique. Commercially available 3DP system can form only gypsum model and not for bioceramics. On the other hand, transformation of hardened gypsum into hydroxyapatite (HA) by treatment in ammonium phosphate solution was found lately.

Measurement of masticatory movement by a new jaw tracking system using a home digital camcorder.

The aim of this study was to confirm the precision of our simple and inexpensive jaw tracking system which combined the use of a digital camcorder and a motion capture software developed lately. A marker was attached to the mandibular incisors of the subject, and a mirror was assembled beside the subject's face to detect antero-posterior movement during chewing. Jaw movements, including the mirror images, were recorded by a digital camcorder.

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.

New evaluation method by microfocus radiograph CT for 3D assessment of internal adaptation of all-ceramic crowns.

The aim of this study was to evaluate the effectiveness of the microfocus radiograph CT system in examining the adaptation of all-ceramic crowns three-dimensionally and non-destructively. The computed tomograms of the crown and abutment model were filmed by microfocus radiograph CT. Using a volumetric rendering software, images of gaps were extracted and reconstructed three-dimensionally, and their volume data analyzed.

Fabrication of porous particulate for the scaffold by applying solution spraying method.

A simple and novel method--in the form of solution spraying--was developed to fabricate biodegradable, porous poly(L-lactic acid) (PLLA) particulates for scaffold. PLLA pellets were dissolved in an organic solvent. Then, 5 % PLLA-dioxane solution was sprayed using an air-assisted atomizer with a nozzle diameter of 2.

Dentoalveolar growth of patients with complete unilateral cleft lip and palate by early two-stage furlow and push-back method: preliminary results.

Objective: This study examined dentoalveolar growth changes prior to the time of palatoplasty up to 3 years of age by the early two-stage Furlow and push-back methods.

Subjects: Thirty-four Japanese patients with complete unilateral cleft lip and palate (UCLP) treated with either a two-stage Furlow procedure (Furlow group: seven boys, eight girls) from 1998 to 2002 or a push-back procedure (push-back group; 12 boys, 7 girls) from 1993 to 1997.

Method: Consecutive plaster models were measured by three-dimensional laser scanner, before primary palatoplasty, before hard palate closure (Furlow group only), and at 3 years of age.

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.

Application of dentition and facial morphology integration system for occlusal correction.

A system to provide quantitative information on the angle between dentition and face was developed using a three-dimensional (3D) integrated configuration measured by a non-contact 3D digitizer. The integrated configuration angles between the Camper's plane and occlusal plane on the sagittal and the horizontal projected planes were obtained. Clinical application for a patient to improve the tegmenta of the anterior tooth by setting a temporary bridge on her lower dentition was attempted.