摘要:

In ground sections from 100 unerupted human premolars examined by reflected and polarized light, the appearances of the outer enamel indicated a porous structure which was confirmed by SEM of three-dimensional methacrylate replicas. The width of the porous outer enamel was assessed from drawings of projected transparencies of buccolingual sections photographed by reflected light of 41 sections from 16 upper premolars and 30 sections from 12 lower premolars, as well as 12 sections from 5 partly erupted premolars. The findings indicate that the outer enamel of premolar teeth is porous at the time of eruption.

ISSN:0008-6568    

DOI:10.1159/000260184

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The affinity for hydroxyapatite of salivary factors inducing aggregation of some strains of Streptococcus mutans, Streptococcus sanguis and Streptococcus mitis was studied in vitro using unstimulated parotid saliva and a synthetic hydroxyapatite. Large variations were demonstrated in the affinities but the factor for strains within each serotype of S. mutans showed similar adsorption isotherms and required equal amounts of apatite for complete adsorption. This supports earlier findings of a high specificity for the aggregation-inducing substances. The factors for S. sanguis strains and the serotype d strains of S. mutans, recognized as members of the early plaque, showed the strongest affinity for apatite.

ISSN:0008-6568    

DOI:10.1159/000260185

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The ultrastructure of organic integuments on partially demineralized enamel surfaces from adolescent and adult bicuspids was investigated. The proximal surface of the extracted young bicuspids characteristically demonstrated an attachment zone most apically on the anatomic crown. Occlusal to this was a non-staining sulcular pellicle separating the attachment zone from the plaque zone. In the plaque zone morphologic variations within the pellicle were observed. The self-cleansing area of the buccal or lingual surface was characterized by a thin pellicle. Organic films from adult teeth were similar in ultrastructure to that found in the adolescent; however, the attachment zone and sulcular pellicle zone were not evident on the specimens observed, probably due to gingival recession causing these structures to be at a more apical position.

ISSN:0008-6568    

DOI:10.1159/000260186

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The present study deals with the production and properties of a fructosyltransferase from Actinomyces viscosus which was found to be an extracellular enzyme. In batch and in continuous cultures, the enzyme activity was low at high exogenous glucose concentration. This relationship may be indirect and result from secondary effects such as the production of inhibitory substances or proteolytic enzymes or, in the case of batch cultures, by retardation of growth. The properties of fructosyltransferase from A. viscosus were similar to those described for fructosyltransferases from other bacterial species.

ISSN:0008-6568    

DOI:10.1159/000260187

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The potential of Streptococcus mutans C67–1, Bacterionema matruchotii ATCC 14266, Bacterionema sp. Ny 205, Rothia sp. Ny 21 and Neisseria sp. Ny 204 to form plaque and initiate caries was tested in mono-associated Osborne-Mendel rats and in di-associated rats in combination with Veillonella alcalescens OMZ 193. The proportions of the strains were assessed in pooled plaque samples. A decrease in the proportion of V. alcalescens was observed during the experimental period. A reduction of dentinal fissure lesions was found in the rats di-associated with V. alcalescens and Strep, mutans. Electron micrographs of the fissures revealed that V. alcalescens was not established in the fissures of rats di-associated with this strain and Bacterionema sp., Rothia sp. or Neisseria sp.; in these di-associated rats no reduction of the caries activity was observe

ISSN:0008-6568    

DOI:10.1159/000260188

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The interaction between solutions of commercial monofluorophosphate (FPO32––) and amorphous and apatitic calcium phosphates was investigated at pH’s 4, 5, and 7. The affinity between FPO32–– and apatite is minimal at pH 7 but materially increases with decreasing pH. Coupled with this greater uptake, however, is an increasing propensity for hydrolytic breakdown to orthophosphate and F1––. The strong interactions of free F1–– and condensed phosphate contaminants with apatite do not appear to modify the weak FPO32–– attraction toward apatite at pH 7. Both the F1–– impurity initially present and the F1–– released by FPO32–– hydrolysis promote the formation of more stable F-containing apatites. This latter reaction may be the responsible factor for the caries-inhibiting effec

ISSN:0008-6568    

DOI:10.1159/000260189

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Plaque removed from subjects in a 1-ppm fluoride area was incubated in vitro with sucrose solutions. Following the pH decrease caused by fermentation, the fluid phase obtained by centrifugation contained free fluoride ions. The fluoride ion activity of the fluid phase increased when the pH decreased; the relationship was linear. The amount of fluoride ions in the fluid phase was positively associated with the ratio fluid phase/amount of plaque. The fluoride ion activity of the plaque appears to be related to the solubility of plaque components at the pH of the plaque. Incubation of plaque in saline, however, indicated that at pH 6 most of the fluoride in plaque is bound.

ISSN:0008-6568    

DOI:10.1159/000260190

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000260191

出版商:S. Karger AG    

年代:1976

数据来源: Karger