At 3 rehabilitation homes for mentally disabled persons in Iwate prefecture, we investigated the prevalence of dental caries and missing teeth among the residents and the participants. The oral status was compared with National Survey of Dental Disease (1993) by age group, and intra-subjects factors were also analyzed.

The results were as follows:

1. The prevalence of dental caries among the present teeth of the subjects was similar to that found in National Survey in almost all age group.

2. The average number of missing teeth was higher among sublects than that found in National Survey in all age groups, especially in the elder groups.

3. There were significant differences in the average number of C₂ and the caries treatment rate by homes.

4. There was significant difference in the average number of C₄ between the residents and the porticipants. It was higher among the residents than among the participants.

5. In comparison by severity of mental disability according to political certification, there were significant differences in the average number of C₂ and FT. Concerning C₂,the average number arnong the subjects with the severe disability was higher than that among the subjects with the comparatively slight disability. While the average number of FT was lower among the subjects with the severe disability.

6. In comparison by the disorders complicated by mental disability, among the subjects with Down’s syndrome, the average number of missing teeth was higher than that found in the subjects without Down’s syndrome.

When some previous studies are taken into account, it is clarified that, in mentally disabled persons, the most serious problem concerning their oral condition is their tendency to lose their teeth at an earlier age than the normal. It is ako considered that the social factors related to their oral status should be investigated more extensively with regard to the findings in this study.

The COMMCAT IS-2000 imaging system (Imaging sciences internationaL Roebling, N.J.) is a tomographic machine for the dentomaxillofacial region. This machine has some advantages in that the operator can determine the slice lines on dental arch by scanning a plaster model and select six different X-ray tube motions: hypocycloidal, spiral, circular, elliptical, linear horizontal and linear verticaL The purpose of this study is to evaluate the usefulness of this machine for dentomaxillofacial cross-sectional tomography.

The accuracy of the placement of the slice layers on this machine was assessed by using eight human dry mandibles with metal markers located in central incisor, first premolar and first molar.The imaging layers determined on the dental arch were within error of one millimeter. Method error was calculated as the difference between direct measurement by using sliding caliper of 6 respective bovine dry bones and image measurements of height and width. There were no difference between the cross-sectional』image and actual bone. Images of test chart human dry mandibles were taken with 6 X-ray tube motions and the quality of each image was compared. The best image quality was required by hypocycloidal rnotion because obstructive shadows were few.

These results showed that the COMMCAT IS-2000 imaging system is a very useful tomographic machine for the examination of the mandible because it can reveal the quality and the quantity of bone.

Clinical findings of 396 temporomandibular disorders (TMD) patients who visited the Department of Fixed Prosthodontics, Iwate Medical University Dental Hospital from 1994 to 1998 were surveyed in terms of yearly changes in the number of patients, age distribution, gender ratio, chief complaint, initial symptoms, initiating factors, accessory symptoms, and past treatment history. Articular disc position and condylar deformity were also confirmed with MRI in 1940 ut of the patients.The ratio of TMD patients to total number of out-patients showed more than 10% throughout the years surveyed. The number of patients increased yearly. Age distribution showed a peak in their twenties both in male and female patients. Male-female ratio was found to be 1.0:2.8. The number of patients visiting without referral and those referred from general dental practitioners had increased. For the most distinctive point in this survey, it took patients an average of 40.5 months from their initial symptom occurrence to visit our clinic. From MRI findings, articular disc displacement was associated to the pain in temporomandibular joint and limitation on jaw openlng.

Considering the long term of improper management, we believe that early care for those patients lS necessary.

In order to establish the progressive Computer Color Matching (CCM) system for various restorations, a more precise method for incisal tooth color needs to be developed. The purpose of this study is the assessment of a newly developed CCM system for incisal tooth color. To reproduce the wide range of incisal tooth colors with numerous properties of translucency and chromaticity, six kinds of ceramics (two non-colored ceramics and four colored ceramics) were used, and colorimetric theories were applied to predict the incisal tooth color and free standing condition. The optimum scattering coefficients and absorbing coefficients for this CCM system were determined, and the precision of color reproducibility for the five kinds of ceramic targets and shade guides was analyzed. The color difference dE between the CCM sample and the target was under 3.5 for ceramic targets, and was under 3.0 for shade guides. Therefore, it can be said that the newly developed CCM system is an excellent color reproduction system for incisal tooth color, and has a high precision of color reproducibility.

Mode of invasion into blood vessels and lymphatic vessels of VX2 tongue cancer was morphologically investigated in order to clarify a metastatic mechanism of the cancer to cervical lymph nodes.

The suspension of VX2 cancer cells was transplanted into the rabbit tongue muscle. The tongue was excised on the 7 th and l4th days after transplantation. The excised specimen was processed for light and transmission electron microscopy.

On the light microscopic examination the peripheral portions of VX2 cancer nests revealed irregular boundaries, and the cancer cells invaded the vascular vessels at these portions. Observation with the transmission electron microscopy showed invasion of cancer cells into the venules and lymphatic vessels. Immunocytes were more frequently observed in the venules than in the lymphatic vessels. The invading cancer cells had no basernent membranes and connected each other loosely. Between the endothelial cells of the both venule/lymphatic vessel and the cancer cells, focal contacts were seen as high density electron bands. The interendothelial space of each vascular endothelium was open in the areas invaded by the cancer cells. The three-dimensionally reconstructed image showed that the cancer cells have invaded into the internal lumen of the lymphatic vessel at only one place.

The results of this study suggest that VX2 cancer cells existing in the peripheral portion of the cancer nest has invaded into lumen through the interendothelial space of both venule and lymphatic endotheliums.

The expression of apoptosis (AP) in oral lichen planus (OLP) was examined immunohistochemically, and the involvement of AP in the pathogenesis of OLP was evaluated. Moreover, the expression of Fas and FasL in lymphocytes that infiltrated in and under the mucosal epithelium was studied, and their roles as AP-inducing factors were also evaluated.

The materials were 30 specimens obtained from 30 patients clinically and histopathologically diagnosed to have OLP at the First Department of Oral and Maxillofacial Surgery, Iwate Medical University School of Dentistry during the past 16 years (1982-1997). Sixteen speciments of normal oral mucosa (NOM) were used as a control group. The TUNEL method was used for the detection of AP-cells, and the percentage of positive cells in 1,0000 or more epithelial cells based on this method was defined as the apoptotic index (AI). Fas and FasL were detected by the immunohistochemical technique, The localization pattern of Fas and FasL in the mucosal epithelium was classified into 4 types (Total type, Partial type, Non detected type and Complex type), arld the frequency of AP-positive cells among epithelial cells and lymphocytes infiltrating under the epithelium was categorized into 4 grades(Grade 0,Ⅰ,Ⅱ,Ⅲ). The relationships of the localization pattern of Fas and FasL and the frequency of AP-positive cells with AI were evaluated.

While AP was expressed sparsely from the upper layer of the stratum spinosum to the stratum granulosum in NOM, it was expressed through the full thickness of the mucosal epithelium in OLP and particularly densely from the stratum basale to the lower layer of the stratum spinosum. In mucosal epithelial cells, AI was significantly increased in OLP compared with NOM. Concerning the relationship between histological findings and AI, AI tended to increase as more lymphocytes infiltrated,

The expression patterns of Fas and FasL in the mucosal epithelium were more diverse in OLP than in NOM. Also, AI tended to be higher in the whole type than in the partial type. However, no close relation was observed between the degree of expression of Fas and FasL in the mucosal epithelium and AI, and no clear correlation was noted between the degree of expression of Fas in the mucosal epithelium or of FasL in lymphocytes infiltrating into the proper layer and AI.

From these results, AP is estimated to be involved in histological changes in OLP. Although lymphocytes infiltrating under the mucosal epithelium were suggested to be involved in the expression of AP, an involvement of AP-inducing factors other than Fas and FasL is also suspected.

The purpose of this study was to invesitigate the effects of the physical consistency of the diet on the metabolites of the masseter muscle on rats fed a pelleted or a powdered diet. The effects were evaluted with ¹H-NMR (nuclear magnetic resonance) spectroscopy (¹H-MRS) and biochemistry. The other purpose was to examine the relationship between the each type of muscle fiber through identification by ATPase staining and of the metabolites also between the masseter muscle.

Male Wistar rats were divided into two groups, those fed a pelleted diet and those fed a powdered diet, at 3 weeks of age. Rats were fed adlibitum untill 9 or 12 weeks. The contents of the metabolites in the masseter muscle were observed by ¹H-MRS. The ratio of different fiber types was determined by ATPase staining.

The following results were obtained.

1. The weight of the masseter muscle of the pelleted diet group was significantly greater than that of the powdered diet group at both 9 and 12 weeks.

2. The share of the cross-sectional area of type 2A fibers in the pelleted diet group was significantly greater than that of the powdered diet group.

3. The contents of creatine and taurine in the pellet diet group were significantly greater than in those in the powdered diet group at 9 weeks of age. The contents of creatine, taurine, anserine, and anserine+carnosine at 12 weeks of age were significantly greater than in those at 9 weeks of age in the pelleted diet group.

4. From the results of a discriminant factor analysis employing the contents of creatine, taurine, anserine and carnosine, there was 100% accuracy in predicting between the pelleted and the powdered diet group at 9 weeks. At 12 weeks there were 91.7% and 83.3% accuracy.

Consequently, it was suggested that the physical consistency of the diet might influence the contents of metabolites and the share area of the fiber type in the masseter muscle.

Pathological examinations diagnosed in the department of oral pathology of Iwate Medical University in 1998, were statistically reviewed.

A total of 728 biopsy was discovered among 614 cases (Male:255, Female:359). And the cases were found most frequently in the seventh decade. Thirty three frozen section diagnoses were revealed.

In histological classifications of the lesions (age), odontogenic lesions consisted of 3 ameloblastomas (16.0±7.0), 5 odontomas (23.0±24.7) and 2 malignant ameloblastomas. The non-odontogenic benign lesions were 25 fibrous hyperplasias (54.9±16.1), 13 irritation fibromas (60.1 ±9.4), 19 hyperkeratoses (1eukoplakia) (61.3±11.9), 7 epithelial dysplasias (68.6±1LO), 13 hemangiomas (48,5±21.6), 5 papillomas (61.0±22.2), 5 pleomorphic adenomas (37.0士16.0).

And non-odontogenic malignant lesion consisted of 49 squamous cell carcinomas (60.6±14.8), 3 malignant melanomas (75.0±2.2), 2 verrucous carcinomas (78.0±2.0), 2 adenoid cystic carcinomas, 2 mucoepidermoid carcinomas, 2 adenocarcinomas and 2 malignant lymphomas. The odontogenic cyst consisted of 41 radicular cysts (40.8±13.1), 13 primordial cysts (38.3±18.2) and 18 dentigerous cysts (30.1±17.2). The non-odontogenic cyst consisted of 39 mucoceles (21.3±18.0), 29 postoperative maxillary cysts (51.0±11.7) and 8 incisive canal cysts (51.9±19.6). In addition, 27 Sjögren syndromes (55.2±16.8), 10 lichen planus (59.1±10.0) and 20 epulides (chronic localized hyperplastic gingivitis) (42.7±16.7) were revealed.

There is a high incidence of anterior crossbite in the Japanese population. It is possible that crossbite involving functional factors, such as premature contact, may change to§keletal crossbite. Therefore, it is important to remove the functional factors early to promote a normal growth pattern. We commenced orthodontic treatment very early for a patient with anterior crossbite associated with premature contact and obtained a good result.The patient was a 3-year-1-month-old girl at the first consultation. In the initial phase, an activator was placed to prevent premature contact and this contributed to improving crossbite. Thereafter, we observed long-term growth status and treated the patient with a multi-bracket appliance. As a result, the patient showed stable occlusion and a good aesthetic profile.This report suggests that early orthodontic treatment of crossbite leads to a normal growth pattern of the jaw bone and stability of occlusion.

Among 29 primary cases of mandibular ameloblastoma treated in a 21-year interval from September, 1975 to August, 1996, we conducted an additional investigation of l8 cases in which conservative therapy was pursued to investigate indications of conservative therapy for mandibular ameloblastoma by clarifying their clinical courses, recurrence sites, and treatments. Recurrence was seen in 3 cases (16.7%); their radiographic examinations were unilocular in 2 cases and multilocular in l case, and their histological examinations had a plexiform pattern in 3 cases. Tumor recurrence occurred in 3 out of 18 cases (16.7%). Causes of recurrence were deemed to be an overlooked tumor near the original site of the mandible in l case and a residual tumor peripheral to the mandibular canal or the mesial tooth germ in 2 cases. Even in cases of recurrence, we treated them by conservative therapy of the mandible, and they have remained in good condition.

It is considered that orthodontic treatment is difficult for open bite which is associated with habits such as finger sucking and tongue thrusting. If these habits are not broken, the orthodontic treatment will not be successful. Furthermore, if these habits are not broken and the open bite is not treated, the open bite will shift skeletal one. For three cases with open bite in the growth period, we tried to treat open bite by means of habit breakers.We used three types of habit breakers; atongue crib, a lingual arch with spur, and a plate with spur. In these cases, it was shown that these three habit breakers have similar effectiveness in treatment of open bite. The improvement of open bite is caused by extrusion of the anterior teeth and is seen on analysis in the superimposition of cephalometric radiogram of the view at pre-treatment used of habit breaker and post-treatment. After active treatment by multi-bracket appliance, relapse of anterior overlap was not seen, and occlusion was stable.After active treatment, whether the tongue thrusting habit and abnormal anterior position of tongue was improved or not dominates the prognosis. In order to stabilize occlusion, it is necessary, in a patient with a serious tongue thrusting habit, to acquire a normal tongue function and to harmonize tongue function and muscle circumference of the oral cavity by means of a retainer with spur, and also by myofunctional therapy.