[in Japanese]

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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 Department of Fixed Prosthodontics at Showa University Dental Hospital from April 1993 to March 1994.
The following results were obtained :
(1) The total number of crowns and fixed partial dentures produced were 1,202; among them, crowns totaled 1,022 (85.1%) and the fixed partial dentures, 180 (14.9%).
(2) Most of the crowns were full cast crowns (572, 56.0%); second were porcelain fused to metal crowns and resin faced cast crowns. The former decreased to 183 (17.9%). The latter steeply increased to 183 (17.9%).
(3) The resin faced cast crowns for the anterior teeth occupied approximately 70%. The full cast crowns for premolar teeth occupied approximately 50%. The full cast crowns for the molar teeth occupied approximately 90%.
(4) Fixed partial dentures located 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 the anterior and the posterior regions. The five-unit fixed partial dentures (two missing teeth with three abutment teeth) were treated in the antero-posterior regions.
(6) The crowns covered by the insurance dental service were 74.3% ; the fixed partial dentures ware 76.7%.
(7) Concerning the abutment teeth of the crowns, non-vital teeth were 88.8%, implant abutments were 0.9% ; non-vital teeth of the fixed partial dentures were 75.4%.

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The tangential ground surfaces of the occlusal enamel in maxillary premolar teeth, extracted from young orthodontic patients, were observed by scanning electron microscopy after EDTA etching. At the junctions of the prism orientation disorders, various abnormal-shaped prisms containing many circular shapes were scattered in a similar way to our recent study on the lingual enamel of maxillary incisor teeth. Abnormal-shaped prisms were also observed in the areae adjacent to the clear spiral region of prisms in the gnarled enamel, however, they were not found in the spirally arranged prisms which agreed to our previous observations. On the other hand, one or a few abnormal-shaped prisms were occasionally present in the regions showing an ordinal orientation of the prisms. From our present observations and a large number of previous studies on abnormal-shaped prisms, such prisms commonly appear in human enamel although their average to the entire enamel prisms in a tooth is low. Thus, we suggest that abnormal-shaped prisms, especially circular structures as a primitive type of enamel prisms, are always found to be present.

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The present study was designed to establish a new method for evaluating experimental pain in humans by modifying the visual analogue scale (VAS), which is often used for to estimate pain in clinical treatment. The modified-VAS method was a combination of standard (50 or 55°C) and test (various temperature) heat stimulation at intervals of 5 minutes ; the magnitude of pain to test stimulation was marked on the VAS as a percent of pain magnitude to standard stimulation. When the combination of the standard and the test stimulations was repeated several times with the same stimulus intensity at the same stimulus area in each subject each point marked on the VAS was close. In the second trials performed 2 weeks later, the point of each subject was close to the point of the first trials. When test stimuli were applied with various stimulus intensities, the relation between the stimulus intensity and the magnitude of pain was linear on a doublelogarithmic scale, a finding that indicates that this relationship was followed by the power function. These results suggest that the modified-VAS is a convenient and reliable method for evaluating experimental pain in humans.

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We examined the usefulness and safety of Interpore200 (Interpore International, Irvine, California) in oral and maxillofacial surgery. The material used for implantation was a porous, granular, hydroxyapatite reproduction of coral of the genus porites with a pore size of 425 to 600μm in blocks, 5×5×10 mm in size. In this study, 60 patients with cysts of the maxilla and mandible (40 patients); cleft lip, alveolus and palate (10 patients); tumors (4 patients); and other lesions (6 patients) were treated with this material. The clinical usefulness in each case was evaluated on the basis of clinical effectiveness and safety, and graded as extremely useful, moderately useful, slightly useful, marginally useful, or useless.
Results were as follows : 1) The overall condition of the 60 subjects was good. 2) The clinical usefulness rate was 80.0%. 3) No severe postoperative complications were observed. However, elimination of hydroxyapatite granules (26.7%), diastasis (26.7%), inflammation (5.0%), and hematoma (1.7%) did occur. These complications might have been related to the method or technique of operation.
The results of this study suggest that Interpore200 is useful for reconstruction of osseous defects in oral and maxillofacial surgery.

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The aim of this study was to evaluate the clinical effect of alloplastic grafts using hydroxyapatite (HA) granules. Forty-six sites in 34 patients with beyond moderate periodontitis participated in this study. The HA were placed up to the height of the bone ridge of periodontal bone defects during the flap surgery. Clinical examinations were performed before and 1 year after the surgery. At the postsurgical evaluation, probing pocket depth was decreased and gingival condition improved. In particular, the anterior teeth showed more improvement than the molar teeth. Furthermore, the HA remains rate in anterior teeth was higher than in molar teeth. These results suggest that the HA is effective for treatment of the periodontal bone defects, especially for the anterior teeth.

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A new method for fabricating ceramic crowns using a CAD/CAM process with the originally developed dental CAD/CAM machine was developed. A stone model of the prepared abutment and adjacent teeth was digitized with a non-contact laser digitizer equipped in the machine. Subsequently, a crown fitting the abutment with the approximate contour was designed automatically by computer, and the NC program for CAM was prepared. A crown was fabricated by milling a crystalline glass ceramic block automatically with computer-aide program. The crown was set in the stone mold with zinc phosphate cement. The thickness of the cement layer was measured on the sectioned surface with a project profile meter. The thickness of the cement layer was 10 to 150 μm, and the discrepancy was larger on the occlusal sides than on margin. Because several factors affect the accuracy of the fabricated crown, further developments we needed to improve accuracy.

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A new method for fabricating inlay restorations with copy milling and laser digitizing was developed. A wax pattern prepared from a stainless steel tapered inlay mold was digitized with a non contact laser digitizer affixed to the originally developed dental CAD/CAM machine. Subsequently an inlay was fabricated by milling a composite resin block automatically with a computer-aided program. The inlay was set in the metal mold to examine adaptation accuracy. The fabricated inlay was 0.56% longer than the mold a finding that suggests that our system is promising but we still need more improvements, especially to the laser digitizing method.

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This report presents a case of Angle class II division 1 with excessive overjet. Because arch length discrepancy is difficult to correct, a combination of distalization of the maxillary molars with cervical headgear and exaggerating the curve of Spee to the dental arches was applied to facilitate tooth alignment.
Levelling of the arch is a widely used orthodontic procedure. Results of posttreatment evaluation showed that orthodontic treatment in which the curve of Spee is slightly exaggerated can effectively correct Angle class II with arch length discrepancy when there is a question of retention.

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Recently orthodontic treatment has been used in conjunction with treatments from other fields of dentistry (periodontology, prosthetology and oral surgery). As a result, we had an opportunity to treat a case of adult malocclusion, which gingival recession was associated with traumatic occlusion of the lower left central incisor. We report treatment procedures and results in this case and discuss significant future problems in integrated dental care through clinical consideration.

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