Complete denture construction is thought difficult for cases showing great absorption of the mandibular ridge. For such cases, we developed a method for making lower full denture for which plaster impression was used. Attention was paid to the weight and fluidity of the plaster, which did not attract attention to date, for the plaster impression used in complete denture construction. The best feature of this method is the adoption of Trayless Impression Technique for which plaster was used. This method allows recording of the space enclosed by the buccal mucosa, alveolar ridge, oral floor, and tongue without arbitrary general idea of dentists. Also, the following improvements were made to make up for demerits of the plaster and bring out merits. 1) The adoption of a board shaped resin block as the lower occlusal rim for preventing tongue space reduction and making the occlusal base lighter. 2) The adoption of the platform on the palatal side of the upper front prosthetic teeth for functional harmony. 3) When try-in is done, closed mouth impression is taken as the final impression afier the functional formation of polished surface and border moulding are done. Decisions on the basal seat, denture border, jaw relations and positional arrangement of prosthetic teeth are made easier for difficult cases of edentulous mandible in comparison with the conventional methods.

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Tooth crown traits of the Hui of Liao-ning province, China, were examined and compared with 23 East Asian populations in order to clarify the anthropological position of the Hui based on Mongoloid dental variation. Plaster models were taken from 81 male and 87 female students, 16 to 19 years of age, of the Hui tribe middle high school in Sheng-yang. Nineteen non-metric traits of tooth crown were classified using the Arizona State University dental anthropolpgical system and counted with the individual count method. The frequencies of 19 traits in the Hui were compared with 23 East Asian populations. On comparing the eight crown traits that indicated high frequencies were Double shoveling (UI1), Canine medial ridge (UC), Lingual cusp variation (LP2), Hypocone (UM2), Carabelli's trait (UM1), Protosylid (LM1), Deflecting wrinkle (LM1) and Cusp 7 (LM1), and low frequencies Winging (UM1^2), Interruption groove (UI2), Tuberculum dentale (UI2), Cannine distal accessory groove (UC), Odontome (UP1), Cusp 5 (UM1), distal trigonid crest (UM1), Cusp 6 (LM1) and Y-groove pattern (LM2). On comparing the eight crown traits that indicated significant differences between Sinodonty which is typical of Northeast Asia, and Sundadonty which is typical of Southeast Asia, the Hui had six Sinodont-like traits : Shoveling, Double-shovel, Carabelli's trait, Cusp 5, Deflective wrinkle and Y-groove pattern, and two Sundadont-like traits : Winging and 4 Cusp. Two major clusters were obtained from a cluster analysis on the Ward method among 23 East Asian populations and the Hui, based 19 crown traits. One was Sinodonty cluster, and the other Sundodonty cluster. The Hui was included in the Sinodonty cluster. The Sinodonty cluster were divided into two subclusters, one was the Han and Japanese group, and the other the Chaoxian and the Man group. The Hui was included in the latter. Furthermore, the multidimensional scaling analysis showed that the Hui was closest to the Chaoxian and the Man, and nearest to Sundadonty as contrasted with typical Sinodonty. Judging from the above analysis, it was proved that the dentition of the Hui was characteristic of both Sinodonty and Sunndadonty, and the Hui was the closest to the Chaoxian and the Man in the East Asian Mongoloid populations.

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To examine the effect of calcium supplement in combination with calcitonin and vitamin D_3 on the mandibular condyle, male Wistar rats aged 3 weeks were divided into 4 groups of control, low calcium, low calcium -normal diet, and low calcium -normal diet・calcitonin・vitamin D. Bone loss was induced from low calcium feeding for 3 weeks. Calcium supplement in combination of calcitonin (ECT) and activated vitamin D_3 (VD_3) was administered for another 3 weeks. Bone formation in mandibular condyle was investigated ultrastructurally. The results were as follows. 1. SEM findings : In contrast to control group, low calcium group showed irregularly-arranged bone trabeculae in subchondral ossification zone. Marked reduction in number of calcospherites was noted. Resorption lacunae showed shallow and indistinctly bordered. Compared with low calcium -standard diet group, low calcium -standard diet・ECT・vitamin D_3 group showed an increase in number of calcospherites within chondrocyte lacunae and an increase in number and width of trabeculae in ossification front. 2. TEM findings : In contrast to control group, a marked reduction in number of osteoblasts was noted in low calcium group. The number of steoclasts relatively increased, with irregularly shaped nuclei. Low calcium -standard diet・ECT・vitamin D_3 group showed dramatically increased osteoblasts with rounded, cubic, and oval shaped nuclei. There were abundant granular reticulum lying among many profiles of mitochondria. Osteoclasts decreased and ruffled borders showed flattened. The results of the present study indicate that calcium supplementation with ECT and activated vitamin D_3 administration has a positive effect on bone formation in mandibular condyle where bone loss was caused experimentally from inadequate calcium intake.

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The purposes of this research are to grasp the actual conditions of oral health care in the area and to find a goal for the oral hygienic activities which meet the actual conditions of the area. Therefore, we needed to investigate the population as widely as possible from the infants to the aged people. We adopted O'leary's Plaque Control Record (OPCR) as the index for this investigation. The reason is that the Welfare Ministry specified OPCR as the plaque disclosing method for the Health-care Insurance Plan. However, OPCR presents a problem in enlightening activities of the oral hygiene of the area. Contrary to the public's understanding, the higher the score is, the worse the oral condition is. The degree of Skill in Oral Health Care (SOHC) was defined anew to overcome the shortcomings of OPCR. The formula is SOHC={log (100/OPCR)} 100. The subjects examined numbered 509 ranging from 6 to 20 years old (263 boys and 246 girls). These subjects were classified into 10 groups, by age and sex, and examined. The result is shown in the following. 1. In the average number of deciduous teeth present per person, differences were recognized in the groups of 9-11 years old, and values of boys were higher than those of girls (p<0.01). 2. In the average number of permanent teeth present per person, differences were recognized in the groups of 9-11 years old, and values of girls were higher than those of boys (p<0.01). 3. Difference were recognized only between the groups of 18-20 years old as a result of comparing values of OPCR between the boys and girls of the group of the same age (p<0.01). 4. In boys, the group of 6-8 years old was the highest in OPCR value as compared with the 4 other groups (p<0.01). 5. In girls, the group of 6-8 years old was the highest in OPCR value as compared with the 4 other groups (p<0.01, p<0.05) and the group of 18-20 years old was the lowest (p<0.01). 6. The graph of SOHC was easier to explain in comparison with that of OPCR.

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Magnetic resonance imaging (MRI) is accepted as a valuable method for evaluating and diagnosing various diseases in medical and dental area. On the other hand, dental magnetic attachments have been applied as one of the most suitable retainers of removable prostheses. The dental magnetic attachment is an advanced procedure for the restoration, whereas the dental magnetic attachment is one of the causes of MRI artifacts and/or distortions. In this study the results obtained by a survey in general hospitals on MRI artifacts caused by dental metals, especially dental magnetic attachments, are reported. The results obtained were as follows ; 1. MRI artifacts are experienced in most hospitals. Most radiologists did not regard the effect of the magnetic alloy as the cause, although they thought dental metals in oral cavity were the main cause of MRI artifact. 2. Although about a half of radiologist were aware of the presence of the magnetic attachments, few of them had little experience in taking pictures of the patients with magnetic attachment or magnetic keepers by using MRI. 3. Even when dental metals and magnetic keepers in oral cavity were considered to produce the MRI artifacts, none of radiologists asked dentists to remove them. They tried to solve the trouble of MRI artifacts by themselves. 4. Prothodontists should give much more information about the dental magnetic attachment to radiologists and medical doctors in addition to improving the magnetic attachment and investigating materials to minimize the effect on MRI.

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Today, the use of endosseous implants in dentistry is a well recognized method of treatment. An important prerequisite for the long-term success of endosseous implants is that the implant itself and its surrounding hard and soft tissue maintained loading forces without damage. The aim of this study was to examine the chronological changes of occlusal forces on the distribution of neurofilament protein (NFP) positive nerve fibers in the tissue of peri-implant bone. The bilateral 2nd, 3rd and 4th mandibular premolars and the 1st molars were extracted from nine mongrel dogs. After 4 months of healing, screw-type titanium alloy (Ti-6Al-4V) implants with anode-oxidized layer were inserted in the mandible. Three months after insertion, the implants on the molar site were loaded by occlusal forces, while the premolar site were unloaded. After a further 1 week, 4 weeks, 12 weeks, the dogs were transcardiacally perfused, and the specimens were prepared for the hematoxylin-eosin stain, Ungewitter's silver-nitrate method based on the modification of Powers, and the immunohistochemical NFP-positive stain by the labelled streptavidin biotin method. There sections were examined under light microscopy and histomorphometric analysis was performed. The results obtained in this study were summarized as follows : 1. In the one week loaded site, the implant surface was occupied by either bone marrow or fibrous tissue, and in the four weeks loaded site, a significant increasing in bone tissue was observed. However, the NFP-positive nerve fiber was not found on any surface of loaded or unloaded implant-bone interface. 2. In the region in between the area that 200μm away from the implant surface, there was no significant difference in the bone formation in all periods. However, there was a tendency of much more bone formation in the loaded site than in the unloaded site. Also, in the case of loaded site, many of the NFP-positive nerve were found in this region. From the finding of the increase in nerve distribution and its morphological change into tree-like ramification inside the implant surrounding bone, it suggested that proper occlusal forces may be involved with the mechanoreceptive function. 3. In the region 200μm away from the implant surface, bone formation was observed in both of loaded site and unloaded site, especially at the loaded site. Some of the NFP-positive nerve fibers were observed in bundled style in stead of single fiber style. Totally, the nerve distribution was very similar to that of implant surrounding bone as described above, and there was no difference between the loaded site and unloaded site. 4. Different from osseointegrated type implants, in this study although in the loaded implants, the tree-like ramifications or Ruffini endings in the periodontal ligament could not be recognized. However, the existence of NFP-positive nerve fibers around the loaded implants has indicated the probable formation of mechanoreceptor in the peri-implant bone tissues.

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The treatment by porcelain laminate veneer's method is widely diffused in esthetic dentistry, since the volume of a drilling through the tooth is a minimum. However this method is restricted by the occlusion types, bruxism, or bad habit, etc. Moreover the literature on this method indicates that the volume of a drilling through the enamel needs 0.5mm in thickness, but its use is difficult for Japanese with small teeth except for those with large teeth. In this paper, we will introduce a bleaching method on vital discolored teeth. This method is an epock-making treatment which restores esthetics by application of a medicine to the enamel surface.

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