It is known that electromyograms of the left and right masseter muscles (LMM, RMM) during bilateral clenching reveal difference in amplitude. This study was designed to investigate the difference in electromyographic activities of LMM and RMM during bilateral clenching in many subjects and compare the difference during bilateral clenching with that during unilateral clenching and peanuts chewing. The subjects were 66 healthy volunteers, 18-56 yr of age, without clinical evidence of dysfunction of the stomatognathic system, especially without pain with occulusion. Surface electromyograms from middle portion of both masseter muscles were recorded 274 times. Several electromyograms from each subject were recorded at intervals not less than 4 months. Electromyographic activity was expressed in relative values, ratio integrated value of electromyogram of RMM to that of LMM when LMM was predominant, and ratio LMM to RMM when RMM was predominant. For recording of electromyograms, each subject was asked to make several different mandibular movements ; bilateral clenching and unilateral clenching on the left and right sides, 1st and 2nd gum clenchings on the left and right sides, and chewing to swallowing of 3, 2, 1, and 3g peanuts. Main findings were as follows. 1. The difference of electromyographic activities between LMM and RMM during bilateral clenching was recognized in all cases except only one case. In 128 cases, activities of LMM were greater than those of RMM, and mean relative value of electromyographic activities was 78.6±13.3. In 145 cases, activities of RMM were greater, and mean relative value was 78.9±13.9. 2. In unilateral clenching on the side with predominant activity during bilateral clenching, activities of the clenching side were greater in most cases (from 88.3 to 96.6%), and in clenching on the other side with lesser activities during bilateral clenching, activities of the clenching side were greater in many cases (from 60.7 to 76.0%), but greater on non-clenching side in cases from 23.2 to 38.6%. 3. Electromyographic activities during peanuts chewing were greater on the side with predominant activity during bilateral clenching. 4. Relative value of electromyographic activity on bilateral clenching was in a statistically significant positive correlation with those of unilateral clenchings and peanuts chewing, and especially well correlated with those of unilateral clenchings on the side with lesser activities during bilateral clenching. Mean relative value of unilateral clenchings on the side with predominant activity during bilateral clenching was decreased, and that of unilateral clenching on the other side with lesser activities during bilateral clenching was increased, because the difference in most cases became greater during unilateral clenching on the side with predominant activity during bilateral clenching, and the differences were decreased or reversed in many cases during unilateral clenching on the other side. These results suggest that difference of activities in both masseter muscles during bilateral clenching influences those during unilateral clenchings and peanuts chewing.

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In prosthesis for the anterior teeth, care must be given to forming the maxillary lingual surface and positions of the mandibular incisal edges in harmony with jaw movement and to forming lengths of the maxillary anterior teeth and degree of overlap of the upper and lower anterior teeth not in interference with pronounciation. It is also necessary to consider esthetics for the anterior teeth. Therefore, with a view to clarifying characteristics of the face at rest and at function, positional relations at rest between incisal edges of the maxillary anterior teeth and the conjugate of the lips were measured with 50 males in their twenties as subjects. Visibility of the upper and lower anterior teeth during pronounciation of five vowels was also examined. The results were as follows : 1. When the lips were not tense at intercuspal position, the incisal edges of the upper central incisors were 2.0±1.6mm below the conjugate of the lips. The incisal edge positions ranged from 5.8mm below the conjugate of the lips to 2.2mm above. 2. Clinical coronal lengths of the upper anterior teeth were 10.8±1.0mm for the central incisors, 9.2±0.9mm for the lateral incisors, and 10.2±1.1mm for the canines. For the lower teeth, the lengths were 8.6±1.0mm for the central incisors, 9.0±1.0mm for the lateral incisors, and 10.5±1.2mm for the canines. 3. The lengths of the upper anterior teeth exposed at pronounciation of five vowels were i>e≒a>u>o for the central and lateral incisors, and i>e≒a>u=o for the canines. For the lower jaw, the lengths were i>e>a>u>o for all the teeth. 4. The ratios of vertical lengths of the upper anterior teeth exposed at pronounciation of five vowels were 1__- : 2__- : 3__-=1 : 0.4 : 0.2 for 'a', 1 : 0.7 : 0.3 for 'i', 1 : 0.1 : 0.0 for 'u', 1 : 0.5 : 0.2 for 'e', and 1 : 0.0 : 0.0 for 'o'. 5. The ratios of vertical lengths of the lower anterior teeth exposed at pronounciation of five vowels were 1^^- : 2^^- : 3^^-=1 : 1.0 : 0.9 for 'a', 'i', 'e', 1 : 0.5 : 0.1 for 'u', and 1 : 0.6 : 0.0 for 'o'. 6. The clinical surface areas of the upper jaws projected on the coronal plane were 79.4±9.8mm^2 for the central incisors, 47.6±6.4mm^2 for the lateral incisors, and 43.4±6.9mm^2 for the canines. For the lower jaws, they were 38.2±5.7mm^2 for the central incisors, 40.0±5.7mm^2 for the lateral incisors, and 42.6±6.9mm^2 for the canines. 7. The ratios of surface areas of the upper anterior teeth exposed at pronounciation of five vowels were 1__- : 2__- : 3__-=1 : 0.2 : 0.1 for 'a', 1 : 0.4 : 0.1 for 'i', 1 : 0.0 : 0.0 for 'u', 1 : 0.3 : 0.1 for 'e', and 1 : 0.0 : 0.0 for 'o'. 8. The ratios of surface areas of the lower anterior teeth exposed at pronounciation of five vowels were 1^^- : 2^^- : 3^^-=1 : 0.9 : 0.6 for 'a', 1 : 1.0 : 0.8 for 'i', 1 : 0.4 : 0.0 for 'u', 1 : 0.9 : 0.6 for 'e', and 1 : 0.5 : 0.0 for 'o'.

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Ultrastructural changes of the von Ebner's gland of the rat were examined by transmission electron microscopy with use of 0.1% polychlorinated biphenyls diet (PCB group) and vitamin-A-deficient diet (V.A def. group). Weaning male rats aged 3 weeks, weighing 38-45g, were used in this study. The results obtained are as follows : 1. Pair-fed controls increased their body weight during the experimental period. Growth rates of the two experimental groups were markedly decreased as compared with their controls. The animals fed PCB began to show depilation, diarrhea and eye mucus. 2. Vitamin A content in serum of the rats fed on 0.1% PCB diet decreased to onethird of that of controls, suggesting that PCB causes reduction of vitamin A in serum. 3. The secretory granules of the acinar cells of the rats fed on 0.1% PCB diet were stained less by toluidin blue than those of the rats given control diet. 4. Electron microscopically, the nuclei of the acinar cells showed irregular outlines and pyknosis after 0.1% PCB diet feeding. Rough endoplasmic reticulum cisternae were remarkably enlarged. Golgi apparatus was atrophied and it produced myelin figures. Some mitochondria contained myelin figures and irregularly arranged cristae. Large vacuoles and autophagic vacuoles were increased in number. Lumen and intercellular canaliculus were expanded. Myelin figures and/or membraniform substances appeared in the lumen. 5. Structural changes of the acinar cells induced by vitamin A deficiency were the same as those induced by PCB except for myelin figures in mitochondria. Namely, the nuclei of the acinal cells showed pyknosis. Cisternae of the rough endoplasmic reticulum were strongly enlarged and contained less electron-dense amorphous substances. Autophagic vacuoles contained scroll-like lamellae and lipid droplets. Large vacuoles contained myelin figures and amorphous substances. The secretory granules fused with each other. These fused granules appeared less dense than the nonfused granules. Acinal lumen and intercellular canaliculus distended and they contained membraniform substances. 6. The granules of the duct cells treated with PCB were fewer than controls. Many dense granules were observed in the apical portion of the vitamin-A-deficient epithelia and the apical surfaces of the cells showed apocrine processes.

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The fitness of root canal obturation by the thermomechanical condensation method was examined with use of ten extracted human teeth. The obturated condition of root canal and reaching of the guttapercha to the apical seat were examined first on radiograms. Then each root was cut up and divided into three parts of mid-canal, apical third and root apex, and observed by scanning electron microscopy. The results were as follows : 1. On radiograms, obturation was good at the mid-canal portion in nine cases out of ten cases. At the apical third and root apex portions, obturation was good in eight cases out of ten cases. 2. Reaching of the guttapercha to apical seat was "flush" in eight cases out of ten cases and two cases were "over". 3. Scanning electron microscopically, obturation was good at the mid-canal portion in six cases out of ten cases and four cases were rather poor or poor. At the apical third and root apex portions, obturation was good in four cases out of ten cases and six cases were rather poor or poor.

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A high molecular weight mucin (HMM) was purified from human submandibular-sublingual saliva, by gel filtration on Sephadex G-200 and Sepharose CL-2B in 4 M guanidine-HCl. The HMM preparation did not contain other salivary proteins, indicating high degree of purity of the preparation. It was composed of 18.2% protein, 79.5% carbohydrate (GalNAc, GlcNAc, Fuc, Gal and NANA) and 2.3% sulfate. Gel electrophoresis of HMM revealed only a band in the stacking gel by silver and PAS staining. Reducton of HMM by 2-mercaptoethanol before electrophoresis resulted in a PAS staining-detactable band in the stacking gel and a silver staining band with apparent Mr of 120, 000. The isolated 120, 000 Mr component consisted of 40% protein and 60% carbohydrate (GalNAc, GlcNAc, Fuc, Gal and Man). The amino acid composition and Mr of the 120, 000 Mr component are similar to those of "link" components in mucins from other secretions suggesting that the subunit structure of salivary HMM is similar to that of other mucins.

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Denture plaque is not limited merely to food debris and dental deposits, oral bacteria and their products are also involved. These are known to cause denture stomatitis. Denture wearers, however, are not fully informed of the necessity of plaque control. An examination by questionaire therefore was made on their understanding of denture plapue and the status of denture plaque control practice among denture wearers. In addition, the effects of denture brushes and denture cleanser were examined. The results were as follows : In spite of an overwhelming number of the denture wearers who were annoyed by smears and deposits on their dentures, many of them never received any instruction on cleaning methods for the denture. Those who did not take care of their dentures daily counted for 20%. As for the means of denture cleaning, most of them used ordinary tooth brushes. Very few of them have ever used denture brushes and denture cleanser. The region difficult for denture plaque to deposit was the palatal area of the upper denture and denture brushes were very effective for this area. The regions easy for denture plaque to deposit and difficult to remove denture plaque were the alveolar ridge area of the upper denture and the basal area of the lower denture. Denture brushes were effective and the use of denture cleanser greatly increased the effect of removing denture plaque.

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An investigation was performed on 721 patients who received treatment at the Orthodontic Department of Kyushu Dental College during a 5 year period from 1977 to 1981, concerning distribution of sex, age, and time of first treatment, kinds of malocclusion, orthodontic appliance used for active treatment, etc., on the bases of the gnathostatic models, x-ray cephalograms and clinical records which were obtained from these patients. The results were as follows : 1) Out of the 721 total number of the patients, male numbered 243 (33.7%), and female 478 (66.3%). In other words, female accounted for two thirds of the total. 2) Analyzed by the kinds of malocclusion, the number of mandibular protrusion cases was the largest among the total number of the patients, that of crowding cases came next and that of maxillary protrusion cases came third, that of cleft lip, jaw and/or palate cases came fourth. 3) In the frequency of using different kinds of orthodontic appliances for treatment, the use of multi-banded appliances ranked top, that of lingual arch appliances ranked second, that of chin caps ranked third and that of head gear appliances ranked fourth. There was observed remarkable decrease in the use of activator and plate appliances during a five year period since 1977.

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This report describes a new method of monitoring mandibular condyle movements in three dimensions with a B-mode ultrasonographic transducer. Ultrasonographic examinations of masses in the temporomandibular joint can be a valuable diagnostic aid. It has the advantages of being noninvasive, rapid, easily repeated and relatively inexpensive. However, clinical use and acceptance of this technique will require further development.

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We report here the two histopathologically different tumors in the oral cavity of a patient with von Recklinghausen's disease. The patient, a 59-year-old woman, visited our clinic with a chief complaint of two tumors at the hard palate mucosa and at the lower lingual gingiva. At first we diagnosed the case as neurofibromas, one of the oral manifestation of von Recklinghausen's disease, and then surgically removed the tumors by the same method under the local anesthesia. Histopathologically, the tumor at the hard palate was diagnosed as pyogenic granuloma with hyperplasia of capillary vessels. The other one at the lower lingual gingiva was diagnosed as neurofibroma, which was composed of Schwann cells, fibrilloblasts and collagen fibers. Over a 4 month period after surgical excision, neither recurrence nor malignant change has been observed.

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A case of six supernumerary teeth impacted in the maxilla and mandible is presented. The patient was a 13-year old female who presented a chief complain of falure in eruption of permanent incisors. The patient showed the clinical characteristics such as, short statures, broad base of nose, ocular hypertelorism, high arched palate, open bite, and failure in eruption of permanent teeth. The characteristic roentgenological findings of the patient were delayed closure of sutures, numerous wormina bone ormation, aplastic clavicle, underdeveloped palanasal sinus, and multiple supernumerary teeth. The above clinical and roentgenological characteristic findings were developed symptom of uncommon congenital disease such as cleidocranial dysostosis.

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A case of parosteal osteogenic sarcoma in a 44-year-old woman was encountered. A diagnosis of benign bone tumor was made at initial incisional biopsy and the diagnosis of parosteal osteogenic sarcoma was made upon recurrence. Consequently, segmental mandibular excision was performed. The patient, 8 years after operation, is progressing well without postoperative local recurrence or metastasis.

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Micro-organisms and their products, as toxins and enzymes, in dental plaque cause periodontal disease. Especially their endotoxins are thought to be direct and indirect inducers of periodontal disease. Endotoxin (lipopolysaccharide, LPS) was inoculated into gingival tissue, dental pulp, and extraction wound and induced inflammation and focus in tooth and periodontal tissues. In the advance of the lesion, humoral factors such as immunoglobulins and complements and induced cells such as macrophages and osteoclasts were studied quantitatively. The purpose of this article is to review the effect of endotoxin on the level of the humoral factors and the number of induced cells from the above experiments. After gingival inoculation of endotoxin, complements in gingiva were activated soon and that activation elicited cell infiltration and triggered off succeeding immunological response. The activation of complements was decreased soon and increased again. This biphasic activation of complements in periodontal tissue will reflect temporal local imbalance between the supply from systemic humor and the consumption as a result of activation by endotoxin. In endotoxin-inoculation into dental pulp, from the time of establishment of inflammation in the pulp to the time of formation of focus of apical crest, the level of anti-LPS immunoglobulin G increased greatly, while the level of the other humoral components changed slightly. Antibodies of this class seemed to play a protecting role in the case of infection in dental pulp. In the extraction wound, macrophages appeared soon after tooth extraction and began to decrease in number after 12 hr. Instead of macrophages, osteoclasts began to increase in number at that time. These results showed that endotoxin activated complement directly, elcited the cell infiltration, and rose the level of specific antibody. Endotoxin also induced indirectly repair of inflammation and increased the number of osteoclasts.

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