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Experimental gingivitis in ODU plaque-susceptible rats. III. Toxic activity of the rat dental plaque.

The toxicity tests of the dental plaque from ODU plaque-susceptible rats showed strong lethal effect on mice, and abscess forming effect on guinea-pigs. Bacterial cells isolated from the rat dental plaque also showed strong toxicity on both animals and capillary permeable activity on rabbits. Among these bacterial cells, Corynebacterium showed the strongest toxic effects on these animals. These facts suggested an important role of the dental plaque on initiation and development of gingivitis and that especially Corynebacterium may play an important role on gingivitis in ODU plaque-susceptible rats.

Animals

Degradation of maltose and starch by human saliva and by supernatants of dental plaque material.

The pH-decrease in dental plaque in vivo after mouth rinses with solutions of sucrose and maltose has been compared. No statistically significant differences were found between the results obtained with these two disaccharides. Pooled samples of parotid saliva, centrifuged whole saliva and dental plaque supernatants were separated with the isoelectric focusing technique. The results suggest that maltose is hydrolysed in parotid saliva by the salivary alpha-amylase and in dental plaque by enzymes from sources other than the salivary glands, probably microorganisms. No bacterial alpha-amylases, separated from salivary alpha-amylase, were found in whole saliva specimens or in dental plaque supernatants. Quantitative determinations of "maltase" and amylase activities in parotid saliva, centrifuged whole saliva and dental plaque supernatants from 10 subjects were carried out. The highest enzyme activity of "maltase" was found in the samples of dental plaque and the highest amylase activity in parotid saliva specimens.

Amylases

Studies on human dental plaque. 1. Physical and chemical characteristics and enzyme activities of pooled plaque extracts.

Human supragingival dental plaque was collected from patients with various degrees of caries and periodontal disease. Plaque extracts, prepared in five different solutions (four varied from pH 1.8 to 12.7; one contained urea), were analyzed by polyacrylamide gel electrophoresis, and tested for amylase and lysozyme enzyme activity. Because no qualitative or quantitative advantages of using the extremes of pH or urea were observed, all subsequent extracts were prepared in phosphate buffered saline at pH 7.3. Concentrated extracts were fractionated by gel filtration and characterized by polyacrylamide gel electrophoresis, peptide mapping, molecular weight estimation, determination of enzymatic activities and amino acid and carbohydrate analyses. Regions of similarity among the gels were revealed by comparing the electrophoretic patterns of pooled plaque extract, normal serum and whole saliva. The elution pattern of pooled plaque extract from a standardized Sephadex G-200 column indicated the presence of both high and low molecular weight proteins that might have correlated with the components of normal serum and saliva. A predominant and dialyzable third fraction had no correlate in either serum or saliva. The small peptides in this fraction were subjected to amino acid, carbohydrate and peptide map analyses. The most abundant amino acids were alanine, glutamic acid, glycine, valine, leucine, lysine and serine. These small components contained no neutral or amino sugars. Pooled plaque extract and the small peptides exhibited similar peptide maps.

Alanine

The effect of instruction and supervised toothbrushing on the reduction of dental plaque in kindergarten children.

Based upon the present study the following conclusions were reached: Supervised toothbrushing with instruction for preschool children significantly and consistently decreased dental plaque scores, when compared to the control group of the same children who had only supervision. While those subjects receiving toothbrushing instructions and supervision had significant plaque reductions, at no time did the plaque scores reach zero. A symmetrical but nonuniform distribution of dental plaque prior to toothbrushing was noted as follows: Posterior teeth had higher dental plaque scores than anterior teeth. More dental plaque was present on the buccal surfaces of the maxillary teeth than on the lingual surfaces. More dental plaque was present on the lingual surfaces of the mandibular teeth than on the buccal surfaces. The distribution of dental plaque following toothbrushing remained the same as the prebrushing pattern, but the amount of dental plaque was reduced by 31 percent. Constant reinforcement is necessary to maintain effective plaque control in pre-school children.

Child Behavior

Exocytosis of polymorphonuclear leukocyte lysosomal contents induced by dental plaque.

Rabbit polymorphonuclear leukocytes were incubated with a sonically treated suspension of pooled dental plaque to determine if the plaque would induce release of lysosomal enzymes from the polymorphonuclear leukocytes. Cells incubated with plaque at 37 degrees C released significantly greater amounts of the lysosomal enzymes, beta-glucuronidase and lysozyme, than did cells incubated with plaque at 0 degrees C or without plaque at 37 degrees C. This response was both dose and time dependent. Release of the cytoplasmic enzyme lactate dehydrogenase was minimal, and there were no significant differences in lactate dehydrogenase release between cells at 0 and 37 degrees C, or without plaque. These results indicate that dental plaque can induce the selective release of lysosomal enzymes, which could be involved in the periodontal injury produced by dental plaque.

Animals

The effect of topical application with an organic and inorganic fluoride compound on the inhibition of dental plaque in humans.

Accumulation of dental plaque for 3 and 7 days respectively was determined by calculating the difference between the postcollection and precollection weights of enamel slabs attached to orthodontic bands cemented to the upper first molars of 3 subjects. Pretreatment of the enamel slabs with amine-fluoride or -chloride respectively-at an equivalent amine concentration-prevented plaque deposition on the slabs, whereas pretreatment with sodium monofluorophosphate was less effective. The fluoride concentrations of all fluoride-pretreated enamel slabs were similar. No convincing demonstration of significant differences between the treatments could be predicted in view of the discrepancy in results at the 3- and 7-day test periods.

Adult

A longitudinal epidemiological study on dental plaque and the development of dental caries--interim results after two years.

1. During the two-year period, caries developed at 20% of the target premolar sites. The attack rate for these surfaces was similar in the plaque panel and the other subjects in the study. 2. The microbial composition of plaque samples from caries-free sites and from carious sites before and after radiographic detection of lesions was broadly similar. 3. Numerical domination of particular sites by S mutans before detection of caries can occur, but has only been observed so far in 2 of 15 sites. 4. Pooled date from sites which have developed lesions indicate a rise in the isolation frequency and mean numbers of S. mutans after detection of caries. This trend was particularly obvious in the one subject who developed bilateral lesions by the second examination and in three of four sites where caries was detected at the fourth examination. Similar observations have been made with lactobacilli. 5. In two of 15 instances no isolations of S mutans were made from sites which developed caries. 6. To date, no single species appears to be uniquely associated with the onset of dental caries.

Cell Count

A microbiological study of normal flora of macropod dental plaque.

The percentage bacterial composition of dental plaques from 12 macropods was determined. The major group of organisms was gram-positive filamentous and pleomorphic rods whose median representation was 92.2%. These were mainly Actinomyces viscosus (median value 62.5%) and Bacterionema matruchotii (median value 23.2%). Streptococci were poorly represented (median value 4.2%) as were anaerobic gram-negative organisms. Aerobic gram-negative bacteria were identified as neisseriae and Moraxella sp. The macropod plaque flora was compared with that of human beings and rodents and the differences discussed in relation to dietary differences and the early externalization of the marsupial young.

Actinomycetaceae

Microbial composition of monkey dental plaque (Macaca arctoides and Macaca fascicularis).

The supragingival and subgingival dental plaque flora of Macaca arctoides and Macaca fascicularis monkeys were examined using mylar strip impressions, direct smears, and culture techniques. In smears, samples generally contained 40--50% cocci, 20--30% rods 8--20% fusiform bacteria, and 4--5% each of filaments, vibrios and spirochetes. Differences in the ratios of the various bacterial groups related to age and sex were found. Several monkey bacterial species were similar to those in human dental plaque. The present results indicate that the Macaca female monkey can be a suitable animal model for the experimental studies of dental diseases.

Aerobiosis

Dental plaque ecology related to caries and periodontal diseases.

Dental plaque consists of a dynamic microbiota which responds to ecological changes. There are major technical difficulties in obtaining representative plaque samples and in dispersing, cultivating, identifying and quantifying the microbial components. Cumulative findings on plaque microbiota associated with dental caries and different forms of periodontal disease support the specific plaque hypothesis. However, the data do not permit designation of any single organism as the distinct aetiological agent. The characteristic pattern is autogenic succesion, in which one or more microbial species alter the plaque environment and are replaced or succeeded by other species.

Bacteria