Enamel caps are recognized as isolated projections on the intact enamel surfaces in normal human permanent teeth. We observed small dome-shaped projections forming parts of overlapping perikymatas with the isolated projections, small granule-shaped projections attached to the perikymatas, and smaller enamel cap-like projections in Tomes' process pits (TPP), besides the enamel caps. We also indicated that the cap-like projections in TPP may seal the punched-out deep pits in TPP as well as the enamel caps occluding the focal holes. On the enamel surfaces adjacent to hypoplastic enamel defects, the enamel caps and various-shaped and sized enamel projections or enamel-like deposits were observed. The floors of minor irregular enamel defects in a tooth showed large granule-shaped enamel crystallites or enamellike deposits. The floor layer of a large enamel defect was occupied with granule-shaped deposits composed of afibrillar cementum. Thus, some enamel-like deposits in the hypoplastic enamel may be such an afibrillar cementum.

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Accurate measurement of the condylar position is important for diagnosis and treatment of temporomandibular joint dysfunction. Conventional radiographic techniques have been used for this purpose and the recent advance of computed tomography (CT) is applicable to temporomandibular joints. The accuracy of CT in the measurement of the condylar position is still unclear. The purpose of this study was to evaluate the measurement accuracy of the condylar position on reformatted sagittal CT images. Six TMJs obtained from dried skulls were used. The TMJs were examined using a CT scanner with 1 mm thickness/interval in the axial and coronal directions. The visibility of the condyle and fossa on the reformatted sagittal images created were evaluated by measuring the joint space defined in our study. The results were as follows : 1) The superior surface of the condyle and the deepest part of the fossa were obscured in the reformatted images created from the axial scan and coronal scan projected at 60° to the F-H plane. 2) The reformatted images from the coronal scan projected at 90°, 80° or 70° to the F-H plane clearly depicted the condyle and fossa, the reproducibility of the measurement on these images mentioned above was less than 0.1 mm. The results indicated that the coronal scan from 90° to 70° to the F-H plane is more accurate than the axial scan for determining the condylar position on the reformatted sagittal images.

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Deformity of the jaw may be caused by the functional disharmony of the masticator muscle and malocclusion. The purposes of this study are to define the characteristics and to measure the thickness of the masseter muscle of the patients with jaw deformity using ultrasonography. Ten patients with jaw deformity and ten normal volunteers were examined using a 7.5 MHz linear array transducer to measure the thickness of the muscle on the axial plane and the echo level of the area defined in the center of the muscle in the rested and maximal clenching conditions. The results showed that 1) the thickness in the maximal clenching condition was thicker than that in the relaxed condition for the normal and the affected side of the patients although the significant change in thickness was not observed in the unaffected side of the patients, 2) the echo level in the maximal clenching condition was lower than that in the rested condition for the normal and the affected side of the patients although the significant decrease was not observed in the unaffected side of the patients, and 3) the thickness of the affected side in the relaxed condition was thinner than that of the normal. The results indicate that the patients with jaw deformity show the different properties of the a masseter muscle and the ultrasonography may be useful to analyze the jaw deformity.

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This study was carried out to determine statistical information concerning the crowns and the fixed partial dentures (total number, types and rate of crowns, number of vital or non-vital abutment teeth, etc.) which were placed in the outpatients in the First Department of Prosthodontics at Showa University Dental Hospital from April 1992 to March 1993. The following results were obtained : (1) The total number of crowns and fixed partial dentures produced were 1,256 ; among them, crowns totaled 1,074 (85.5%) and the fixed partial dentures, 182 (14.5%). (2) Most of the crowns were full cast crowns (584, 54.4%); second were porcelain fused to metal crowns (288, 26.8%). The resin faced cast crowns, 0 cases last year, steeply increased to 110 (10.2%). (3) The porcelain fused to metal crowns for the anterior teeth and the full cast crowns for premolar teeth occupied more than 50%, respectively. The full cast crowns for the molar teeth occupied approximately 90%. (4) Fixed partial dentures lacated in the posterior region were about 60%. Those in the anterior and the antero-posterior regions were about 20% each. (5) With regard to the relationship between the missing teeth and the abutment teeth of the fixed partial denture, the three-unit fixed partial dentures (one missing tooth with two abutment teeth) were most frequently treated in all regions. (6) The crowns made by the insurance dental service were 66.1% and the fixed partial dentures were 61.0%. (7) Concerning the abutment teeth of the crowns, non-vital teeth were 88.5%; non-vital teeth of the fixed partial dentures were 70.1%.

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Surface-overlapping projections with aggregated granular to dome-shaped structures, forming part of the abnormal perikymata region, were observed on the hypoplastic enamel surface with keyhole-shaped prisms by scanning electron microscopy. These projections ranging from about 4 to 6 pm in diameter were formed independently of the positions of the keyhole-shaped prisms and gradually changed into the surface prismless enamel with regular perikymatas towards the cervical margin. It is concluded, therefore, that the surface-overlapping projections are enamel structures, although the surface crystallites showed a fine sand-grain shape while the keyhole-shaped prisms consisted of larger needle-shaped crystallites.

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Intraoral radiographic examination may be essential to evaluate the results of the dental implantation during the longitudinal follow-up period. The purpose of this study was to evaluate the effects of the X-ray projection and the rotation of the fixture on the radiographic image. Three types of fixture, Brånemark (Nobelpharma), AFC (Asahi Optics) and ITI (Straumann) were used. These were mounted at the position of implantation in the mandible obtained from a cadaver. The relationship of the X-ray tube focus, the object, and the film was maintained constantly, and the distances between the focus and the object, and the focus and the film were 38 cm and 40 cm, respectively. The vertical angles were determined to be perpendicular to the long axis of fixture, 15 degrees from the above, and 15 degrees from the below. The fixtures were rotated 0 to 90 degrees on the longitudinal axis, and were radiographed. The results showed that 1) the images of the screw on the fixture were obscure on the right side when exposed from the above and on the left side when exposed from the below, 2) the images of the fixture were changed in the rotations depending on their own shapes, and 3) the identification of the cervical level was changed by the vertical angle depending on the width of the mandible. The results indicated that the X-ray projection should be maintained to be constant during the observation period and the images changed induced by the variations of projection should keep in mind.

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Extensive and profound knowledge and arts in relevant specialties are necessary in the treatment for adult maxillofacial deformity patients because these patients often suffer from highly functional, morphological and aesthetic problems. Therefore, team approach treatments have been applied for the patients recently. At the Showa University Dental Hospital, the team called MFC (Maxillo-Facial Conference), which consists of the departments of Orthodontics, Oral Surgery and Prosthodontics, has been organized and achieved admirable results through synthetic diagnosis, treatment planning and treatment. This article reports a case of an adult female who needed full mouth restorations with mandibular protrusion with a total crossbite, protrusive appearance in angles of the mandible and the mental tubercle, occlusal disharmony and cold water pain caused by broad abrasion.

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Five cases of second branchial cleft cyst were evaluated with computed tomography (CT). One case of them was also evaluated with magnetic resonance imaging (MRI). CT and MRI were helpful to diagnosis and surgery because of their demonstrating exact locations of these masses related to the deep structures in the neck, as reported previously.

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