Computer assisted mandibular reconstruction using a custom-made titan mesh tray and removable denture based on the top-down treatment technique.

PURPOSE: The purpose of this report is to propose a computer assisted mandibular reconstruction procedure, utilizing a custom-made Ti-mesh tray with particulate cancellous bone and marrow, and a removable denture. This procedure was based on the top-down treatment technique, and reviews the case of a representative patient with mandibular continuity defect. METHODS: The patient was a 74-year old female with a chief complaint of facial asymmetry and masticatory dysfunction. Due to gingival carcinoma, she underwent a segmental mandibulectomy on the left mandibule. On the VR space, using 3-D reconstructed computer tomography data, the residual right-side mandibular fragment was repositioned based on the condylar position and the occlusal relation. The mandibular fragment was then mirrored for a central sagittal plane. The position of the mirrored object was slightly arranged with the occlusal relation. Through the above operations, the landmark configuration, for the custom-made Ti-mesh tray as a virtual simulation model, was fabricated. On the physical model, we produced a custom-made Ti-mesh tray with a commercial Ti-mesh sheet. Surgical treatment was carried out using the tray. The denture pattern was designed by a dental technician on the VR space, fabricated using a 3D printer, and modified to create an impression tray with resin. Using the impression, the temporary removable denture was fabricated. CONCLUSIONS: We propose a computer assisted design for a custom-made Ti-mesh tray and a removable denture, based on the Top-down treatment concept. We feel this technique is advantageous in reconstructing functional occlusion, and in accurately regaining dental and facial esthetics.

Structural equation modeling for alteration of occlusal plane inclination.

PURPOSE: Occlusal plane inclination is important to maintain a normal opening closing/biting function. However, there can be several causes that lead to alterations of the occlusal plane. The purpose of this study was to observe variations of occlusal plane inclination in adult patients, and to uncover the factors affecting changes in occlusal plane inclination with aging. METHODS: Subjects were 143 patients. A cephalometric image was taken of these patients. In this study, our inquiry points were age, 3 variables on intra-oral findings, and 7 variables on cephalometric analysis. To evaluate the possible causes that affect occlusal plane inclination, factor analysis was carried out, and each component was treated as factors, which were then statistically applied to a structural equation model. Statistical analysis was carried out through the SPSS 20.0 (SPSS Inc., Chicago, USA). RESULTS: In all patients, Camper-occlusal plane angle (COA) ranged from -25.7 to -4.9° (Mean±SD: -6.4±5.36). In the 60 patients who had no missing teeth, COA ranged from -11.6 to -4.9° (Mean±SD: -3.3±3.31). From the results of the structural analysis, it was suggested that the occlusal plane changes to counter-clockwise (on the right lateral cephalograms) with aging. CONCLUSION: In this study, variations of occlusal plane inclination in adult patients were observed, and the factors affecting changes in occlusal plane inclination with aging were investigated via factor analysis. From our results, it was suggested that the mandibular morphology change and loss of teeth with aging influence occlusal plane inclination.

Application of photogrammetry for analysis of occlusal contacts.

INTRODUCTION: The conventional 2D-analysis methods for occlusal contacts provided limited information on tooth morphology. This present study aims to detect 3D positional information of occlusal contacts from 2D-photos via photogrammetry. We propose an image processing solution for analysis of occlusal contacts and facets via the black silicone method and a photogrammetric technique. MATERIALS AND METHODS: The occlusal facets were reconstructed from a 2D-photograph data-set of inter-occlusal records into a 3D image via photogrammetry. The configuration of the occlusal surface was reproduced with polygons. In addition, the textures of the occlusal contacts were mapped to each polygon. DIFFERENCE FROM CONVENTIONAL METHODS: Constructing occlusal facets with 3D polygons from 2D-photos with photogrammetry was a defining characteristic of this image processing technique. It allowed us to better observe findings of the black silicone method. Compared with conventional 3D analysis using a 3D scanner, our 3D models did not reproduce the detail of the anatomical configuration. However, by merging the findings of the inter-occlusal record, the deformation of mandible and the displacement of periodontal ligaments under occlusal force were reflected in our model. EFFECT OR PERFORMANCE: Through the use of polygons in the conversion of 2D images to 3D images, we were able to define the relation between the location and direction of the occlusal contacts and facets, which was difficult to detect via conventional methods. CONCLUSION: Through our method of making a 3D polygon model, the findings of inter-occlusal records which reflected the jaw/teeth behavior under occlusal force could be observed 3-dimensionally.

Influence of filler on bite impression material in transillumination method for occlusal examination.

The purpose of this present study was to investigate the influence of material filler and RGB values' fluctuation on creating a calibration curve, which indicates the relationship between material thickness and transmitted light brightness using the transillumination method. Creating the calibration curves were carried out through the following three methods; 1) the conventional method creates the calibration curve with a formula of thickness, 2) the maximum value method, with samples of a specified thickness, and 3) the actual value method, with a microscope. Furthermore, the reliability of each curve was verified via scanned artificial tooth data. In addition, the characteristics of light decrement were investigated. From our results, it was suggested that the filler diameter must be considered when the calibration curve is created using the bite impression material with a filler. In addition, it was suggested that the RGB values' fluctuation did not influence the calibration curve.

Design for functional occlusal surface of CAD/CAM crown using VR articulator.

In this present study, we introduce an approach that utilizes the VR articulator to mimic lateral excursions and design a functional occlusal surface. We then take the resultant occlusal surface from this approach and compare it with a conventional method. As a result, we developed a novel CAD/CAM system which can render a functional occlusal surface, via a VR articulator. The marginal fit and occlusion in our CAD/CAM crown was sufficient to apply to the clinic.

Characteristics of mandibular movements in patients with square mandible.

OBJECTIVE: The aim was to report the kinetics of masticatory muscles using a 4-dimensional muscle model and kinetically investigate the etiology of square mandible (SQM) in vivo. STUDY DESIGN: To ascertain the mandibular movements in patients with SQM, we compared a group of 11 SQM patients with painless limited mouth opening to a matched group of 11 healthy volunteers who acted as control subjects. Mandibular movements were recorded using a 6-degrees-of-freedom jaw-tracking device, with the incisal and kinematic condylar as analytic points. RESULTS: For the control group, mean tracking distance for the incisal point was 50.1 +/- 6.8 mm, whereas for the SQM group mean tracking distance was 27.1 +/- 2.8 mm. With lateral excursions, the control group's mean tracking distance of the incisal point was 9.9 +/- 2.01 mm, and the SQM group's was 8.1 +/- 1.64 mm. CONCLUSION: Despite a sufficient lateral excursion, motion of the mandible was limited by some factors at opening and suggests that the mode of lateral movements in SQM patients may differ slightly from those in healthy individuals.

Evaluation of the simulation robot for mandibular movements with the patient-specific 3-dimensional plaster model and mandibular movement data: clinical application of the physical simulation robot.

We developed a multi-phase simulation system for patients with jaw deformity and dysfunction as a collaborate study between our departments. The intended application of the physical simulation robot was to evaluate its function based on well it quantitatively measured the movement of the individual patient. This physical simulation robot consists of a 6-degree-of-freedom robotic manipulator and a plaster model of patient-specific bone geometry. Each plaster model was mounted on the serial-articulated robotic manipulator. To establish the accuracy of the robot movement, the programmed movement of the robotic arm was validated using an optical tracking device. The results of the physical simulation robot corresponded with the data from the 4D analysis system. We could construct interactive relations between the 4D analysis system that was presented by virtual reality and the simulation robot which was constructed from physical simulation.

[Application of a jaw motion tracking device that measures six degrees of freedom using optoelectronic].

PURPOSE: A jaw motion tracking device that measures six degrees of freedom has recently been developed. Understanding jaw motion is useful, but previous measurement methods were impractical for use in dental clinics. The overall aim of this study was to demonstrate the simple operation, low cost, and high precision of a recently developed jaw tracking device. In addition, this study explored its potential clinical applications. METHODS: In this study, we compared two jaw motion tracking devices: a digital system type of device and an optical type of device. First we established a baseline occlusal plane from which to measure jaw motion in the same subject with both devices. The jaw motion signals were sampled at a frequency of 100 Hz. The subjects were three healthy women (mean age +/- SD = 26.3 +/- 1.2 years) who were recruited from among the crown-and-bridge faculty of Tsurumi University of Dentistry. The jaw motions measured were open-close movement, sagittal border movement, and frontal border movement. In addition, the kinematic axis point was calculated from the sagittal border movement. Data from the digital system type of device and data from the optical device were compared. The data were selected to measure rotation and translocation, i.e. jaw position about protrusion, both laterotrusion and maximal opening of the mouth. RESULTS: The root mean square (RMS) error of position measurement was 0.163 mm with MM-JI-E and 0.178 mm with the optical type of device. The RMS error of jaw motion measurement with the optical type of device was maximum at 0.8mm and minimum at 0.1mm. This was similar to that with digital system type of jaw motion tracking device. CONCLUSION: This study showed the possibility of developing clinical applications for this jaw motion device.