In 1976, epidemiologlcal investigatlons on dental caries prevalence were performed in 1888 schoolchildren aged 6-11 years in rural areas (five selected areas) of northern parts of Japan. Dental caries was recorded according to the criteria described by WHO (1971).

Among five areas surveyed in this study, investigations have also established that the fluoride contents of natural drinking water in Kitatsugaru areas are in the range of 0.3-3.2ppm and<0.1 ppm in other areas as reported in our previous reports.

The factors concerning on the caries prevarence due to localities also were evaluated in terms of percentage of children with DMF teeth, DMF per 100 erupted teeth, DMFT index, including percentage of decayed teeth,( ×100), of missing teeth (×100), of treated teeth (×100). These value as a criteria in localities were discussed on accunt of the evaluation for caries prevention progrum in each community.

As a criteria for caries experience, DMFT indices is useful to survey the trends of caries prevalence in schoolchildren (6-11yrs.). In this period, the trends are clearly represented, graphically, with regression lines relating ages to X and DMFT indices to Y axis and also it is useful to compare the differences in localities and the shift of the prevalence dependling the year of examinatlon.

Most of values on caries experience surveyed in this study in 1976, except the values in fluoride area (Kitatsugaru), were almost similar to that of the National survey in 1975 in this country.

It is evidence that differences in caries exprience due to localities were seen prominently in the percentages of treated teeth and missing teeth. However, it is not definite trends that higher percentage of treated teeth produces lower percentage of missing teeth in the locality. It is important task in the community dentistry that real caries prevention program should be based on as maintaining cariesfee teeth in individuals as possible.

The fluoride uptake in the enamel surfaces was measured in vitro. Test solutions of sodium fluoride (NaF, pH 7.0), acidurated phosphate fluoride (APF, pH 3.6), stannous fluoride (SnF₂, pH 2.1), ammoniacal silver fluoride〔Ag(NH₃)₂F, pH 9.6〕, ammonium fluoride (NH₄F, pH 6.3) were prepared containing 0.9% of fluoride concentration adjusted in the laboratory.

Extracted molars (10 samples, 20-25 years) were treated for 3 min with the five solutions and all samples were rinsed for 15 sec and then five samples were successively rinsed for 10 min. Six successive layers of enamel surface (up to about 85μm) were etched away by exposure to 1.0 ml of 0.5 M perchloric acid. Concentration of fluoride was determined by a combination fluoride electrode (ORION, 69-09) and calcium by atomic absorption spectrophotometry (HITACHI, 508 A).

The results were as follows:

1.The fluoride uptake due to treatment with each fluoride solution varied considerably, especially in the superficial layer.

2. A considerable difference in fluoride uptake was found. The APF produced the highest uptake until at the depth of 40μm, however, was not statistically significant because of its variation of fluoride reaction on the surface.

3. The order of fluoride concentration increased in the surface was the APF, SnF₂, NH₄F, Ag(NH₃)₂F and NaF solutions in turn.

4. In the case of the NH₄F, Ag(NH₃)₂F and NaF solutions, fluoride uptake showed a stalistically significant (p<0.01) increase at a distance of 3μm from the enamel surface.

5. The fluorid uptake at a distance of about 20μm below the enamel surface was slight in all solutions, except in the case of APF.

6. When the treated enamel was washed in distilled water for 10 min, fluoride distribution was drastically changed in the case of NH₄F and Ag(NH₃)₂F.

7. A significant increase of fluoride (P<0.01) was found from the surface to 5 μm of enamel by the SnF₂ treatment.

8. The fluoride levels after treatment followed a smilar pattern of control wheather washed or not. Furthermore, distribution of fluoride will be determined using the fomula of Y=bX^m for the relationship between fluoride concentration (ppm) and depth (μm) from the surface of enamel as a standerdized value.

The fine structure of ameloblasts was studied on the lower molar tooth germ of 3-7 days old mouse without subsequent decalcification. The results obtained were as follows.

1. Pre-formative stage of dentin

At this stage, ameloblasts were columnar shape, with large oval nuclei that filled the cell body. The terminal bars and terminal webs were recognized and a group of mitochondria was located the proximal end of cells. On the other hand, the distal terminal bars were not prominent but could be made out. The distal terminal webs were not observed on this stage. Tomes’ processes did not yet formed, and then the smooth distal end of cells were in contact with odontoblasts through the basement membrane.

2. Formative stage of dentin

From the end of pre-formative stage, the rough-surfaced endoplasmic reticulums and Golgi apparatuses well developed in the cytoplasm.

In the proximal end, each ameloblasts sent their proximal processes beyond the level of the proximal terminal bars deep into the stratum intermedium. In this region, there were many vesicles which should be concerned with the absorption. The distal end of cells changed markedly in shape on accunt of disappearance of the basement membrane and increasing of the vacuoles.

Arare case of herpes zoster involving the ophthalmic and maxillary division of the trトgeminal nerve was presented. A50-year-old woman was referred to our clinic, colnplaining of spontaneous pain in the anterior region of the right maxilla with three days duration. Extraoral examination revealed slight edematous swelling of the right upper and lower eyelid, dif-fuse swelling of the upper lip and the appearance of vesicles, which did not cross the midline, in†he area of the right nasal dorsum, nasal apex, nasal ala, upper lip and temple. Intraoral examination disclosed the appearance of vesicles, which did not cross the midline, in the region of the right hard palate and the anterior part of the right soft palate, with some findings of the ruptured vesicles and false membrane. Swelling wi th pus discharge was also se頭in the regjon of the labial gingiva of the right upPer central incisor. Diagnosis was clinically made as acute alveolar osteitis of the right maxilla and herpes zoster of the rightophthalmic and maxillary division of the trigcminal nerve. Symptomatic therapy was performed for herpes zoster with satisfactory result. No remarkable co-mplication and sequelae were developed.