PubMed Health⌕ Search

Biomedical subjects

Z Skobe

Publications and source records attributed to Z Skobe.

51 records · Page 3Linked to original sources
PubMed1979

Modification of etching patterns in bovine dental enamel.

It is presumed that the etching pattern is controlled by the residual organic content of dental enamel. Pretreatment with 1.ON NaOH sould remove the organic material and modify the etching pattern. SEM studies and other tests for physical and chemical properties show that the predicted modification of the etching pattern, when the tooth surface is pretreated with NaOH solution, occurs apparently without other changes or properties.

Acid Etching, Dental↗
PubMed1977

Enamel rod formation in the monkey observed by scanning electron microscopy.

Scanning electron microscopy of permanent tooth buds of the monkey confirmed that mineralizing interrod enamel surrounds Tomes' processes on three sides, forming pits that restrict enamel rod formation. The forming face of the enamel rod, which is the floor of the pit, angled toward the tooth surface at the apical edge of the pit, the side nearest the cervical region of the tooth. Consequently, the apical edge of each pit was the only site where both rod and interrod enamel were formed at the nascent tooth surface. The ameloblasts had two secretory surfaces. One was the microvillous surface of the short Tomes' process abutting the forming face of the enamel rod. The other surface, closer to the ameloblast, was between Tomes' processes, abutting the crests of interrod enamel which formed the pits. At each site forming enamel crystallites had specific orientations. Due to the angle of the forming face of the rod and the short Tomes' process, crystallites with both rod and interrod orientation form at the same time and the same plane within the apical (cervical) margin of each rod. It is hypothesized that indistinct boundaries between rod and interrod enamel at the apical margin of each rod are due to both secretory surfaces of ameloblasts secreting at the same time and at the same site.

Ameloblasts↗
PubMed1976

The secretory stage of amelogenesis in rat mandibular incisor teeth observed by scanning electron microscopy.

In the scanning electron microscope (SEM), the structural organization of rat incisor enamel was divided into five regions: the initial prismless layer at the dentin-enamel junction; the decussating rods of inner enamel; intermediate enamel, where the structure changes from inner to outer enamel; outer enamel with parallel rods; and the surface prismless layer. There were alterations in the orientation of the ameloblasts and characteristic changes in the morphology of the Tomes' processes during the secretion of each of these regions. Initially, the developing Tomes' processes were seen within shallow pits which also contained fibrous material from dentin matrix. During the deposition of inner enamel, alternate rows of Tomes' processes were held at right angles to each other by cytoplasmic projections which originated from the proximal regions of the Tomes' processes. The cytoplasmic projections reorganized to perpendicular orientation relative to the enamel surface during the synthesis of outer enamel. Tomes' processes of outer enamel appeared as elongated flaps extending parallel to the long axis of the tooth. In the late secretory stage, the microvillous projections disappeared and the Tomes' processes were withdrawn into button-shaped structures which coalesced to form a smooth surface that rested on the enamel.

Ameloblasts↗
PubMed1976

Selective adherence as a determinant of the host tropisms of certain indigenous and pathogenic bacteria.

The relationship between the selective abilities of bacteria to adhere and their predilections for colonizing different mammalian hosts was investigated by using bacteria indigenous to the tongue dorsum of humans and rats as models. Streptococcus salivarius and S. sanguis averaged 22.6 and 2.8%, respectively, of the cultivable bacteria recovered from swab samples of the tonges of five humans, but these organisms were not indigenous on the tongues of rats (Charles River strain). S. faecalis and serum-requiring diphtheroids were consistently prominant on the tongues of rats, but they were not detected on the tongues of the humans examined. The ability of these organisms to adhere to the tongue surface of the hosts was compared by introducing mixtures of streptomycin-resistant strains into the mouths of human volunteers and rats. S. salivarius adhered in higher proportions to the dorsal tongue surface of humans than did strains of S. faecalis and the serum-requiring diphtheroid. S. sanguis also adhered to human tongues better than the serum-requiring diphtheroid. However, S. faecalis and the serum-requiring diphtheroid sorbed in higher proportions to the tongues of rats. In an in vivo assay, human strains of S. pyogenes and S. salivarius attached in higher numbers to buccal epithelial cells derived from humans than to those obtained from rats, whereas the reverse was observed with a serum-requiring diphtheroid derived from rats. Collectively, these studies show that bacteria sorb with a high degree of specificity to the tissues of different mammalian hosts, and the relative adherence of the organisms studied correlated with their natural host tropisms. The selective adherence of S. salvarius and S. faecalis was similar to the tongues of conventional and germ-free rats, suggesting that the presence of an indigenous bacterial flora did not significantly influence their attachment selectivity. Moreover, the ability of these organisms to colonize the tongues of gnotobiotic rats lacking an indigenous flora paralleled their adherence selectivity. Direct scanning microscopic observations indicated that the tongue dorsum of conventional rats is highly papillated but contains relatively sparse bacterial populations. Indigenous organisms colonized the bases of papillae on the anterior tip and lateral edges of the tongue as discrete microcolonies, but bacteria were rarely observed on other papillae. This localized and restricted pattern of colonization and the spatial distribution of the microcolonies of indigenous bacteria present also suggest that antagonistic interactions are unlikely to account for the bacterial tropisms observed for colonization of the tongues of rats.

Animals↗
PubMed1974

Interdental localization of Streptococcus mutans as related to dental caries experience.

The consistency of colonization of tooth surfaces by Streptococcus mutans was studied by sampling four approximal molar surfaces of 9- to 13-year-old children at weekly intervals. It was found that surfaces which harbored detectable levels of the organism tended to be consistently positive, whereas surfaces which were free of detectable levels of the organism also tended to remain that way. Of the total surfaces studied, 81.7% were either consistently positive or consistently negative throughout five consecutive weekly samplings. These data indicate that S. mutans does not uniformly colonize the surfaces of teeth. The consistent localized patterns of colonization observed suggest that S. mutans is not readily transmitted from one tooth surface to another within the mouth. Scanning electron microscope observations revealed that S. mutans colonized the teeth of monoinfected gnotobiotic rats as discrete localized colonies, whereas strains of Actinomyces naeslundii colonized in a more generalized manner. Efforts to sterilize tooth surfaces by application of iodine solution indicated that the populations of S. mutans on some surfaces could be affected for at least 11 to 13 weeks after treatment. The number of tooth surfaces colonized by detectable proportions of S. mutans was found to be far lower in a group of 18 children from Charlotte, N.C., with a low past caries experience than in 20 children from Danvers, Mass., with a high caries experience. The number of tooth surfaces infected with S. mutans therefore strongly paralleled the caries experience of these populations.

Actinomyces↗
PubMedDate not supplied

Role of sucrose in colonization of Streptococcus mutans in conventional Sprague-Dawley rats.

The role of sucrose in the colonization of S mutans strain 6715 in conventional Sprague-Dawley rats was studied. A diet with 56% sucrose favored the oral colonization of the test strain compared to diets with 56% glucose or fructose or to laboratory chow as determined by recoveries from extracted teeth ground in tissue grinders. S mutans strain 6715 cells became well established in all rats fed a high sucrose diet with cell inoculums ranging from 10(8) to the lowest effective dose of 10(5) CFU once orally administered; in rats on nonsucrose diets, inoculation with even the highest dose only infrequently resulted in the establishment of S mutans strain 6715. Sucrose- and glucose- grown cells appeared to behave similarly. Colonization of S mutans strain 6715 occurred in all rats fed diets with a sucrose content ranging from 56 to as low as 1%. The establishment of S mutans strain 6715 on the teeth of rats fed diets with a sucrose concentration of 0.1 or 0.01% was impaired and comparable to the diet containing 56% glucose. In rats fed a high glucose diet, uniform establishment and persistence of the test strain occurred after frequent inoculations with about 5 X 10(8) CFU. The colonization under these conditions appeared to be independent of the intestinal canal as a bacterial cell source. These data suggest the possibility that S mutans can establish itself in the human mouth in the absence of dietary sucrose. In rats fed a high glucose diet and inoculated with 10(7) CFU or less, the cells gradually disappeared from the teeth; in contrast, the test strain implanted well in rats fed the sucrose favors firmer attachment of initially weakly attached cells via in situ new glucan synthesis. S mutans strain 6715 also appeared to have some affinity for teeth in the absence of dietary sucrose that may be of ecological significance. Once firmly established in rats fed a high sucrose diet, S mutans strain 6715 maintained itself in high numbers on the teeth after a switch to a high glucose diet during a 14-week period.

Animals↗