Kazuya Honda

Practical model “3DX” of limited cone-beam X-ray CT for dental use

Abstract Objective: The authors have developed a clinical model of limited cone-beam X-ray CT for dental use and started to use the model in clinical practice. It is called “3DX multi image micro CT” (3DX, J. Morita, Kyoto, Japan). Presented here is a report about the result. Method: We made a design of limited cone-beam X-ray CT so that it could be most effective for dentistry use. This machine is a kind of cone-beam type X-ray CT equipped with a 4-in. imaging intensifier (II) as a sensor. The size of the X-ray at its rotational center is 29 mm high and 39 mm wide. While a subject is seated for shooting, a focal spot and the X-ray rotational center are put into agreement with a light beam of X, Y and Z directions. Images are taken under the exposure condition of 80 kV (X-ray tube voltage) and 2 mA (X-ray tube electric current). Exposure time is 17 s, during which 512 frames of two-dimensional images are recorded. These images are reconstructed with a personal computer into digital images in a columnar field of 38 mm in diameter and 29 mm in height. It takes about 10 min to carry out arithmetic calculation for the image reconstruction. Clinical use of this machine started in January 2001 at the Department of Radiology, Nihon University of Dental Hospital. Result: The 3DX produced highly clear, three-dimensional tomographic images of impacted teeth. Conclusion: Since the 3DX is capable of producing clear images with a small radiation dose, we consider it to be effective as a tool to support three-dimensional imaging diagnosis for dental implants, impacted teeth, etc.

Analysis on the guided bone augmentation in the rat calvarium using a microfocus computerized tomography analysis

OBJECTIVES Guided bone augmentation (GBA) in its most challenging form is the creation of new bone through the guidance of bone cells to an area beyond the original outer skeletal envelope. We used a microfocus computerized tomography (R_mCT) system to examine bone augmentation beyond the skeletal envelope in the rat calvarium. STUDY DESIGN The calvarium was exposed and critical-size 5-mm defects were prepared bilaterally. Two resin caps were placed with or without hydroxyapatite (HA), and images of bone augmentation within the resin cap were obtained using R_mCT. RESULTS The experimental site showed bone regeneration beyond the skeletal envelope. Bone continuity was observed between the defect edge and HA. In contrast, no new bone formation was observed beyond the skeletal envelope at the control site. The bone volume increased significantly at the experimental site compared with the control site in a time-dependent manner. CONCLUSIONS The R_mCT system enabled the continuous observation of guided bone augmentation with graft materials in rat calvarium.

Use of a replica graft tooth for evaluation before autotransplantation of a tooth. A CAD/CAM model produced using dental-cone-beam computed tomography

A 33-year-old man was referred by a local dentist for autotransplantation of the right mandibular third molar to the site of the left mandibular first molar. Before the operation, dental-cone-beam computed tomography was performed to measure the dimensions of the graft tooth and the bone volume of the socket. The three-dimensional (3D) structure of the graft tooth was created from the 3D imaging data. A replica of the graft tooth was produced using a stereolithographic CAD/CAM system before autotransplantation. A socket of the appropriate size and structure was created and the graft tooth was extracted immediately before grafting. This procedure shortened the time needed to fit the graft tooth into the socket and reduced injury to the periodontal membrane. The postoperative outcomes of autotransplantation of the tooth were good.

Interventional radiology of synovial chondromatosis in the temporomandibular joint using a thin arthroscope

This case report describes, for the first time, the use of interventional radiology following arthroscopy with a thin arthroscope for the diagnosis and treatment of synovial chondromatosis (SC) of the temporomandibular joint (TMJ). Therapeutic joint irrigation concomitant with arthroscopic observation of the superior joint compartment (SJC) was performed in a patient with functional TMJ pain caused by SC. The thin arthroscope was inserted with the aid of an X-ray fluoroscope. Arthroscopy confirmed that the SC was at disease stage II and that synovitis existed throughout the SJC. The initial maximal interincisor opening (MIO) was 30 mm, while after the joint-irrigation procedure the MIO was 40 mm. In addition, the TMJ pain was greatly reduced after joint irrigation. Our findings demonstrate that interventional radiology with a thin arthroscope is clinically useful for the diagnosis and primary treatment of patients with painful SC in the TMJ.

Magnetic resonance imaging of the temporomandibular joint: a study of inter- and intraobserver agreement

ObjectiveThe purpose of this study was to estimate the inter- and intraobserver agreement for interpreting magnetic resonance (MR) images of the temporomandibular joint (TMJ).MethodsThe study was based on MR images of 30 TMJs. The images were interpreted by seven observers for disk configuration, disk position, joint fluid, bone marrow changes, and diagnosis. The observers were not calibrated. Kappa statistics were used.ResultsThe kappa values were, for interobserver agreement of disk configuration, 0.10; for disk position in the sagittal plane with closed mouth, 0.35; for a combination of closed mouth and open mouth, 0.44; for disk position in the coronal plane, 0.17; for joint fluid, 0.36; for bone marrow changes, 0.01; and for diagnosis, 0.39. Intraobserver agreement was generally higher than interobserver agreement.ConclusionAgreement on disk position in the sagittal plane, on presence and amount of joint fluid, and on diagnosis was fair to moderate. Agreement on disk configuration, on disk position in the coronal plane, and on bone marrow changes was poor.

Relationship between the thickness of the roof of glenoid fossa, condyle morphology and remaining teeth in asymptomatic European patients based on cone beam CT data sets

OBJECTIVES The aim of this study was to examine the relationship between the roof of the glenoid fossa (RGF) thickness and condyle morphology and the influence of the number of remaining teeth and age. METHODS Cone beam CT data sets from 77 asymptomatic European patients were analysed retrospectively in this study. The thinnest area of RGF was identified among the sagittal and coronal slices on a computer screen; distance measurement software was used to measure the thickness. Moreover, we applied a free digital imaging and communications in medicine viewer for classification of condyle head type. It was also used to analyse any relation between RGF thickness and the number of remaining teeth. We performed a correlation analysis for RGF, age and missing teeth. Finally, we investigated combining sagittal condyle morphological characterization with coronal condyle morphology in relation to the number of joints and RGF thickness. RESULTS The Kruskal-Wallis test revealed no significant differences in RGF thickness among any of the coronal condyle head morphology groups (p > 0.05). There were significant differences in the thinnest part of RGF in relation to the sagittal plane for condyle morphological characterization, because we observed increased RGF thickness in joints with osteoarthritis features (p < 0.05). There is a non-significant correlation between the thinnest part of the RGF and the number of remaining teeth (p > 0.05). CONCLUSIONS We found that the RGF thickness is unaffected by the coronal condyle head morphology and the number of remaining teeth. Osteoarthritic changes (sagittal condyle morphology) have an effect on RGF.

Discrepancy of coronal morphology between mandibular condyle and fossa is related to pathogenesis of anterior disk displacement of the temporomandibular joint

OBJECTIVE To evaluate whether morphological discrepancy between the mandibular condyle and fossa of the temporomandibular joint (TMJ) is related to disk displacement on magnetic resonance imaging (MRI). STUDY DESIGN This study included 61 patients with unilateral internal derangement based on both MRI and clinical examination. Coronal morphologies of the condyle and fossa were divided into four groups based on Öbergs classification. According to the coronal morphology of the condyle and fossa, all joints were dichotomized into either harmonized group or a discrepancy group (e.g., angled condyle and concave fossa). The incidence of discrepancy and the relationship of the discrepancy to other findings on MRI were statistically evaluated. RESULTS The discrepancy had a significantly higher incidence on the affected side. The discrepancy correlated with incidence of disk deformity on the affected side. CONCLUSION Morphological discrepancy between the condyle and fossa is related to development of anterior disk displacement in the TMJ.

A Longitudinal Study of the Effect of Experimental Osteoporosis on Bone Trabecular Structure in the Rat Mandibular Condyle

Abstract The authors performed a longitudinal study of the microstructural changes occurring in the mandibular condyle during osteoporosis using the findings obtained from micro-CT. The subjects used in this study were eight Sprague-Dawley rats. Among them, five were administered the immunosuppressant drug FK506 by injection for five weeks, while the other three were administered saline solution in the same manner. Micro-CT images were taken of the bilateral mandibular condyle, hip, and knee joints in all animals on days 1, 8, 15, 22, 29, and 36 following injection. Six indices of morphometric analysis were compared between the two groups. Significant differences were observed in BV/TV, Tb.Th, Tb.N, and Tb.Sp in the mandibular condyle, while trabecular bone density appeared to decrease in the immunosuppressant group on three-dimensional (3D) imaging. And, in comparison with the mandibular condyle and femur, they were similar. These results suggested that osteoporosis affects not only the femur, but also the mandibular condyle.

Development of the Tarsometatarsal Skeleton by the Lateral Fusion of Three Cylindrical Periosteal Bones in the Chick Embryo (Gallus gallus)

An avian tarsometatarsal (TMT) skeleton spanning from the base of toes to the intertarsal joint is a compound bone developed by elongation and lateral fusion of three cylindrical periosteal bones. Ontogenetic development of the TMT skeleton is likely to recapitulate the changes occurred during evolution but so far has received less attention. In this study, its development has been examined morphologically and histologically in the chick, Gallus gallus. Three metatarsal cartilage rods radiating distally earlier in development became aligned parallel to each other by embryonic day 8 (ED8). Calcification initiated at ED8 in the midshaft of cartilage propagated cylindrically along its surface. Coordinated radial growth by fabricating bony struts and trabeculae resulted in the formation of three independent bone cylinders, which further became closely apposed with each other by ED13 when the periosteum began to fuse in a back‐to‐back orientation. Bone microstructure, especially orientation of intertrabecular channels in which blood vasculature resides, appeared related to the observed rapid longitudinal growth. Differential radial growth was considered to delineate eventual surface configurations of a compound TMT bone, but its morphogenesis preceded the fusion of bone cylinders. Bony trabeculae connecting adjacent cylinders emerged first at ED17 in the dorsal and ventral quarters of intervening tissue at the mid‐diaphyseal level. Posthatch TMT skeleton had a seemingly uniform mid‐diaphysis, although the septa persisted between original marrow cavities. These findings provide morphological and histological bases for further cellular and molecular studies on this developmental process. Anat Rec 293:1527–1535, 2010.

An image-guided technique for puncture of the superior temporomandibular joint cavity: clinical comparison with the conventional puncture technique

OBJECTIVE The objective of this study was to compare an image-guided puncture technique (IGPT) with conventional puncture technique (CPT) with respect to accuracy of needle entry, maximal mouth opening, and pain in pumping manipulation treatment of internal derangement of the temporomandibular joint (TMJ). STUDY DESIGN The subjects comprised 178 patients with internal derangement of the TMJ with closed lock. Treatment was provided using CPT in 102 cases and IGPT in 76 cases. Three variables, number of repunctures, maximal mouth opening distance, and pain threshold according to a visual analogue scale, were measured and compared between IGPT and CPT groups. RESULTS Access to the superior joint cavity was achieved without correcting the puncture point in 97% of patients who underwent IGPT and 82% of patients in the CPT group. Significant differences were seen in 1-week maximal mouth opening and pain threshold between IGPT and CPT groups (P < .05 each) and resetting of the puncture point was significantly less frequent using IGPT compared with CPT (P < .05). CONCLUSIONS IGPT is effective for pain mitigation and improves mouth opening during the early postoperative period after pumping manipulation treatment.