Microanatomical study of the human accessory parotid glands was made. The materials were taken from 18 cadavers (more than 40-year-old) for dissection practice by dental students at Iwate Medical University. These accessory parotid glands were re-fixed in 10 per cent neutral buffered-formalin and embedded in paraffin in routin manners. Thin sections were stained with hematoxyline and eosin, periodic acid-Shiff and Alcian blue, and prepared for light microscopic observations to investigate the atrophy of the salivary gland parenchyma, mucous cell metaplasia and mononuclear cell infiltration. The results were as follows:

1. Microanatomical findillgs of the accessory parotid glands were basically identical to those of the parotid gland. However, the intralobular duct systems of the accessory parotid gland were poorly developed.

2. Varying degrees of atrophy of the salivary gland parenchyma were found in the same age-group, and no relationship was noted betweell the atrophy of the salivary gland parenchyma and aging.

3. Varying degrees of mucous cell metaplasia of acinar and ductal epithelial cells were found in all the accessory parotid glands examined.

4. Mucous cell metaplasia in the interlobular and excretory ducts was associated with periductal mononuclear cell infiltration, however, mucous cell metaplasia in the acini and intralobular duct showed no relationship to the inflammatory change.

5. In addition to the above microanatomical findings, the pathological significance of mucous cell metaplasia in the serous salivary glands was discussed.

Clinicopathological and histopathological studies on 85 cases of dentigerous cyst and primordial cyst were made. The results were as followws:

Of the 85 cases, 52 cases were dentigerous cyst, 27 cases were primordial cyst and 6 cases were multiple cyst. 35 of the 52 cases of dentigerous cyst occurred in the maxilla, and half of them occurred in the maxillary anterior region. 20 of the 27 cases of primordial cyst occurred in the mandible. 3 cases of primordial cyst and 2 cases of multiple cyst showed postoperative recurrence.

Keratinization of the epithelial lining with various degrees was noted in 30.8 per cent of the dentigerous cyst and in all of the primordial cyst. 15.4 per cent of the dentigerous cyst, 37.0 per cent of the primordial cyst and 66.7 per cent of the multiple cysts contained satellite cyst in the fibrous connective tissue wall. Melanocytes and melanin pigments were found in the epithelial lining of 7.4 per cent of the primordial cyst and 16.7 per cent of the multiple cyst, however, they could not be found in any cases of the dentigerous cyst.

Ultrastructurally, the keratinizing epithelium of the cysts showed regular stratification which was usually seen in the keratinizing squamous epithelium. On the other hand, the non-keratinizing epithelium showed no regular stratification, and showed wide intercellualr space, numerous intracytoplasmic small vesicles and short microvilli.

At the present time, doctors have focused their attention on EMG biofeedback for the treatment of mandibular dysfunction, and we in particular tried masseter muscle relaxation training through biofeedback of the frontal muscle for the purpose of voluntarily controling the masticatory muscles. We performed the above experiment and studied its relationship to some psychological characteristics. Fifteen male dental students in their twenties who did not show any signs of malocclusion or mandibular dysfunction were selected to carry out this experiment. These students then undertook 4 types of psychobgical tests (CMI, Y-G, MAS, SDS), and were divided according to those who did not show signs of psychological problems and those who did. The biofeedback training effect of the frontal muscle of these two groups was then examined, and as a result it was noted that those students who did not show any signs of psychological problems showed positive effects of masseter muscle relaxation. This effect was also shown to increase as the days progressed. On the otherhand, those who had slight psychological problems showed a similar response, but it was not statistically as significant.

From the above results, it may be said that when clinically undergoing masseter muscle relaxation through the process of frontal muscle biofeedhack training, it is important for the doctor to first grasp an understanding of the patient’s psychological character, and then to apply adequate training methods.

An improved double staining method was discussed for labeling of growth lines in hard tissues as well as identification of osteoid matrix simultaneously. For the experimental study, following procedures were made.

Male Wistar rats were injected subcutaneously with 1.0%lead-disodium-EDTA (30mg/kg), followed by a second injection five days later. Five days after the second injection, the animals were sacrificed by ether anesthesia. Their upper and lower jaws and femur were dissected and fixed in 10%neutral buffered formalin immediately. The specimens were cut in 3-5mm thickness to observe the staining quality of growth lines and osteoid matorix as well. After these procedures, two experimental studies were made.

The first study was made for labeling of growth lines in hard tissues. Specimens were demineralized in a 10% EDTA solution containing 5% sodium sulfide at 4°C for 2-3 weeks, After demineralization, they were submitted into block staining in 0.1% gold chloride solution for 60 minutes, and rinsed in 5% sodium thiosulfate solution for 20 minutes. After that, they were dehydrated in ascending ethanol, and embedded in paraffin. Then, 7μm thin sections were made. After deparaffinization, sections were stained with 0.1% gold chloride solution for 1-2 hours, and rinsed in 5% sodium thiosulfate solution for 20 minutes.

The second study was made for labeling of growth lines in hard tissues and osteoid matrix. Specimens were dehydrated in ascending ethanol. And then, they were immersed in freshly prepared 0.5% cyanuric chloride in anhydrous methanol containing 1.0% N-methyl morpholine for approximately two days at room temparature. Remaining procedures for the staining were the same of that first study.

Growth lines in hard tissues were clearly observed with no disadvantageous effects caused by the dehydrating in the first study. In the second study, labeling lines in hard tissues and osteoid matrix were observed in the paraffin-embedded specimens simultaneously.

An experimental study was carried out on endodontic treatment for perforation in the region of tooth furcation.

After pulpectomy and root canal filling, the region of furcation was perforated using round burs. The perforated space was then filled with Cavit^®, MPC^®, Obuturation Gutta^®, Amalgam, and Eugedain^®. Periodontal tissue adjacent to the perforated regions was examined hstopathologically after certain durations of time with particular attention to the extent of chronic inflammatory changes.

Chronic inflammatory changes of the periodontal tissue in the region of the perforation were found in every experimental group and proliferation of the gingival epithelia was found in many cases. The extent of chronic inflammatory changes was slight in group filled with Amalgam, while in other groups which were filled with Cavit^®, MPC^®, Obturation Gutta^®, and Eugedain^® the extent of inflammatory changes was from moderate to severe.

In conclusion, the results of the present study suggest that repair of perforation in the furcation area is difficult.

A clinicostatistical survey was made of 41 cases given general anesthesia for emergency surgery during a ten-year period (1975-1984) at Iwate Medical University Dental Hospital. The number of cases under general anesthesia for emergency surgery each year showed no special tendency to increase. Age: 18 cases (44%) were less than ten years of age. Diseases: Traumatic injury in 23 cases (56%), wound infection in 6 cases (15%), postoperative hemorrhage in 5 cases (12%), and others. Physical status: P. S.=28 cases (68%), P. S.2=13 cases (32%), P. S. 3, 4, 5 were not present. Premedication: A combination of a Belladonna agent and a minor tranquilizer was administered in many cases. Starting time of general anesthesia for emergency surgery: 35 cases (85%) started between 9:00 a. m. and 9:00 p. m.. A few case was begun at midnight.

Induction: Rapid induction was used most (70%), followed by slow induction (30%). Intubation: Orotracheal (51%) or nasotracheal (34%) intubation was the usual way in most cases, but in a few cases tracheostomy (15%) was chosen. Anesthetic agent: GOF was used most (80%), followed by GOE (12%). Anesthetic time: Cases under 4 hours occupied the largest percentage (90%). Complication after anesthesia: Laryngeal edema was observed after general anesthesia in 2 cases, but recovery was made in several hours.

A case of hamartoma of the dental lamina rest (Baden, et al.,1968) with marked proliferation of the epithelial component, developing in the left lower canine gingiva of a 49-year-old Japanese woman, is presented. Epithelial cells showed a cord-or ribbon-like arrangement and were scattered throughout the dense fibrous connective tissue with partial hyalinosis. Various-sized and-shaped hard tissues with dentin-or cement-like appearance were closely associated with both fibrous and epithelial components. Ultrastructural examination suggested that the epithelial cells were less active.

In addition to the above histological findings, clinical findings, histogenesis and pathological entity of cases diagnosed as hamartoma of the dental lamina rest were discussed.

A case of internal resorption, found in the upper right deciduous canine, was reported in the present paper.

The results of clinical, radiographical and histological examinations are as follows:

Radiographic examination of internal resorption revealed a large oval andw ell-circumscribed radiolucent area within the middle part of a nonperforated root.

A histological examination of internal resorption revealed that various parts of the resorbed dentine wall showed a wavy appearance which was similar to that of Howship’s lacunae. The pulp tissue structure was not visible by microscopy, since autolysis of the pulp with infection was marked.