Predicting caries incidence is important in effectively preventing dental caries in the permanent teeth of elementary school children. We studied whether the improved Snyder test, when applied to first graders, could be useful in predicting future caries status. We followed the same group of children from the first to sixth grades.
The subjects were 739 children who entered elementary school in 1980, 1981, 1982. About half of them (373) were given topical fluoride applications twice a year using an APF gel. The improved Snyder test was performed during the child's first year of school and dental examinations were carried out annually for eight years. Tubes are containing glucose agar with bromocresol green and 0.5ml of saliva were cultured, and incubated at 37℃. We evaluated the depth of the first 4cm of the yellow part at 0.5cm intervals. The subjects were divided into three groups (L, M and H) based on the results of daily observations for three days. The L group included children with a score of 2.5 or less, the M group was between 3.0 and 4.0, and the H group was 4.5 or more. Caries prevalence was compared for the three groups.
The DMFT index for the L group was lower than that for the other two groups, and that for the M group was lower than for the H group, regardless of topical fluoride application. The DMFT rate for the maxillary and mandibular first molars of the L group was lower than that of the other two groups, regardless of topical fluoride applications. For those children who had not received fluoride applications, the DMFT rate for the maxillary incisors of the L group was lower than that of the other two groups, although there was no significant difference between the H and M groups. When topical fluoride had been applied to the three groups, the DMFT rate for the maxillary incisors in the H group was higher than that for the other two groups. However, there was no significant difference among the three groups.
These results suggest that the improved Snyder test is valid for predicting caries incidence in elementary school children, and that the test is particularly effective in predicting future caries incidence in those children who initially have low scores.

View full abstract

We attempted to gain information about the genetic basis of the pathogenicity of Bacteroides gingivalis.
Of 56 clinical isolates, 11 strains released bacteriophages of similar morphology when irradiated with ultraviolet light. The majority of bacteriophages had a hexagonal head 50 to 67nm in diameter with a long flexible tail of 200 to 267nm. A 5.7 kilobase plasmid was detected in two of the 56 strains by the use of agarose gel. Almost all strains produced trypsin, acid and alkaline phosphatase, collagenase, plasmin, and DNase, but no strains produced lecithinase or β-lactamase. As revealed by negative staining, all strains examined possessed surface appendages on and vesicles around the cell surface. Two morphologically distinct types of surface appendages, designated Type A and B, were observed. Type A appendages had extremely thin filaments with diameters of 5nm. Type B appendages, which were 10nm in diameter, were associated exclusively with strain 10013.
No correlation was found between lysogenicity and phenotypic characteristics. However, two strains carrying a plasmid were resistant to β-lactam antibiotics.

View full abstract

Identification by DNA-DNA hybridization and phenotypic characterization was carried out for Capnocytophaga isolated from a periapical lesion of an otherwise healthy adult, and from periodontal pockets and saliva of a child with acute leukemia.
Fifty-seven clinical isolates of Capnocytophaga were chosen for this experiment from the characteristic colony morphology spreading by gliding on blood agar plates. DNA-DNA hybridization was performed by the method of Ezaki et al. Capnocytophaga ochracea ATCC 27872, C. sputigena ATCC 33612 and C. gingivalis ATCC 33624 were labelled by photobiotin for DNA-DNA hybridization. Phenotypic characterization included colony morphology, gram staining, growth in 10% CO₂, end-product analysis, fermentation of 29 carbohydrates, production of indole and catalase, nitrate reduction, gelatin liquefaction, hydrolysis of starch, esculin, and o-nitrophenyl-β-D-galactoside (ONPG), growth in 20% bile, and API ZYM. Fifty-one strains fermented glucose, sucrose, maltose and mannose. Nine strains produced trypsin, and 7 strains were negative in ONPG. Based on phenotypic characterization, 33, 11, and 7 strains were identified as C. ochracea, C. sputigena, and C. gingivalis, respectively. Six strains were not identified. Based on DNA-DNA hybridization, 24, 26, and 7 strains were identified as C. ochracea, C. sputigena, and C. gingivalis, respectively. The coincidence rates of identification by phenotypic characterization based on DNA-DNA hybridization were 49% for C. ochracea, 36% for C. sputigena, and 100% for C. gingivalis.
In conclusion, ONPG is useful for differentiation of C. gingivalis from other species. However, since no phenotypic characterization was found to differentiate C. ochracea and C. sputigena, DNA-DNA hybridization is necessary for these two.

View full abstract

Prevotella intermedia strain 17 produces viscous material that is closely related to pathogenicity in the induction of abscesses in mice. Strain 17 cells possess both type B and C fimbriae aronud their cell surfaces. It has been disclosed that type C fimbriae from strain 17 are concenrned with hemagglutination activity and attachment to epithelial cells. We found two strains subcultured from strain 17 (175 and 178) which lost the ability to produce viscous material. We examined the pheno- and genotypic characteristics of these strains.
SDS-PAGE revealed that the protein pattern of these three strains was quite similar after TCA treatment. Bacteriophages similar in morphology and size were induced from these strains after irradiation by ultraviolet light. Fimbriae purified from strain 175 reacted strongly with antisera made against purified fimbriae from strain 17. These results indicate that strain 175 and 178 are mutants derived from strain 17. These mutant strains showed similar chemical properties with the parent strain, including API ZYM. However, strain 175 did not produce viscous material, and strain 178 did not produce viscous material and did not have surface appendages.
Therefore, this parent-mutant system in P. intermedia strain 17 is useful for examining the pathogenicity of viscous material production and surface appendages.

View full abstract

The relationship of wound healing to the progression of diabetic micro-angiopathy was examined in the streptozotocin-induced diabetic rats. After producing the wound on the lingual dorsum of these rats, successive changes in the microvascular architecture during the healing process were investigated under SEM on microvascular casts utilizing Ohta's plastic injection method.
Wound healing in rats 6 weeks after induction of diabetes was similar to that of controls. However, healing required 16 or more weeks after induction of diabetes. The wound healing tended to be delayed as the duration of diabetes increased and diabetic microangiopathy advanced.
In conclusion, the wound healing in diabetic rats were found to be closely in proportion to the progression of microangiopathy

View full abstract