Levels of mutans streptococci in plaque samples from margins of Class II amalgam (Dispersalloy), composite (P-10), and glass-ionomer (Ketac Silver) restorations were compared. Fifty-one children, each having one of the restorations in a permanent first molar, were part of an inter-individual comparison, giving 17 restorations of each material. The age of the children, the age of the restorations, and the salivary levels of mutans streptococci were comparable in the three groups. Another seven children--each having both a composite and a glass-ionomer restoration of the same age placed on contralateral premolar or molar teeth--were part of an intra-individual comparison. The percentage mutans streptococci of total CFU count in plaque was higher on composite (mean 13.7) and amalgam (mean 4.3) than on glass-ionomer (mean 1.1) restorations in the inter-individual comparison, and higher on composite (mean 4.2) than on glass-ionomer (mean 0.4) restorations in the intra-individual comparison. In both comparisons, the differences in values between samples from glass-ionomer restorations and samples from composite or amalgam restorations were statistically significant (p less than 0.05).
The predominant dental plaque flora of 15 female beagle dogs (1,3 and 6 year old) with naturally developed gingivitis was studied using a continuous anaerobic culturing technique. Supra-and sul^ingival plaque samples from the buccal aspect of the upper third premolar were cultured on various growth media and the organisms were partially characterized. The flora in all dogs was composed mostly of anaerobic Gram negative organisms. B. asaccharoiyticus (B. melaninogenicus ss. asaccharoiyticus) was found in both types of plaques in all animals and decompKJsed hydrogen peroxide suggesting catalase activity. F. nucleatum was found in higher proportions in the subgingival plaque as compared to B. asaccharoiyticus and actinomycetes. Spirochetes were found in 10 of 15 supra-and in 1 of 15 subgingival specimens. S. mutans, S. mitior, S. salivarius, Veillonella, Selenomonas or vibrios could not be detected in any of the plaque samples. A combined data analysis showed, that the total viable CFU and the proportions of Gram positive organisms were significantly higher in the supra-than the subgingival plaque. Although the proportions of Gram negative bacteria were higher in subgingival plaque, the differences between the two tyi>es of plaques excluding F. nucleatum were not significant.
Toothbrushes and toothpaste tubes used by persons infected with S. mutans were examined for the presence of this microorganism. Fifteen minutes after brushing > lO*" S. mutans were isolated from the toothbrushes and after ordinary storage for 24 h lC were recovered. From two out of 10 toothpaste tubes S. mutans was isolated from the orifice of tlie tube. The implications of these findings for the spread of the microorganism are discussed.
Artificial fissures were inserted in 3 subjects for 1-21 days. At a salivary concentration of lo3 colony-forming units (CFU) Strep. mutans@, fissures were colonized by this organism. The proportional distribution of Strep. mutans increased with time and comprised up to 6 per cent of the total number of organisms in the fissure at day 21. The total number of organisms in the fissure did not increase with time after 1 day. The salivary concentration of Strep. sanguis was about lo6 CFU/ml in all subjects. The proportional distribution of this organism in the fissure varied both between different individuals and with time in the same individual. When the artificial fissures were inserted during a regimen which reduced the salivary concentrations of Strep. mutuns, the organism did not colonize the artificial fissures, even though the salivary concentration of Strep. mutans after cessation of the regimen increased to levels generally associated with colonization. If the fissures had been inserted 2 weeks before the Strep. mutans reducing regimen was started, the reduction of the number of Strep. mutans in the saliva to levels generally not associated with colonization did not influence the proportional distribution of Strep. mutans in the artificial fissure. These observations indicate that the initial inoculum is a main determinant for the colonization of the artificial fissures by Strep. mutans.
Eighteen caries-active adolescents, each having both a class II conventional amalgam (Dispersalloy) and a glass-ionomer (Ketac Silver) tunnel restoration of the same age placed on a contralateral tooth, were part of a 3-year clinical study. At the 1- and 2-year examinations all test restorations were assessed as acceptable in all patients. At the 3-year assessment three amalgam restorations failed due to recurrent caries, and one glass-ionomer restoration failed due to marginal ridge fracture. During the entire study period, the requirement of restorative therapy because of primary proximal caries was significantly reduced (p < 0.05) on tooth surfaces adjacent to the glass-ionomer restorations as compared with that on tooth surfaces adjacent to the amalgam restorations.
The predominant cultivable dental plaque flora was studied in 10 adult female beagle dogs with advanced periodontitis. Supragingival and subgingival plaque from a maxillary third premolar (P3) was removed and cultured anaerobically on various growth media and all colonies were subcultured and partially characterized. Histopathological specimens of the plaque sampling sites showed significant loss of connective tissue attachment. Spirochetes were found in all samples. Anaerobic gram-negative organisms were predominant in both types of plaque accounting for about 55% of the cultivable organisms in the supragingival plaque and almost 75% in the subgingival plaque. Bacteroides asaccharolyticus was the most predominant organism in the supragingival plaque, whereas Fusobacterium nucleatum predominated in the subgingival flora. Streptococcal and actinomycotic species were common in the supragingival plaque, but their proportions, especially those of the actinomycetes, were decreased in the subgingival flora. In many respects the bacterial profile associated with disease resembled that reported in human periodontal disease.
A streptomycin-resistant strain of S. mutans was introduced into the mouth as adherent growth on an artificial fissure (AF). A second AF, which was initially sterile, was placed in a crown on the opposite side of the dentition. The labeled strain was not found in 8 initially-sterile AFs which were left in vivo for 2 to 6 days and were not examined with a dental explorer. The labeled strain was detected in 7 of 9 initially-sterile AFs which were probed with the dental explorer.
Interproximal plaque samples were collected from newly made class II conventional conservative amalgam (Dispersalloy) and glass ionomer (Ketac Silver) tunnel restorations in 20 adolescents. The percentage viable count of mutans streptococci in samples from glass ionomer restorations (mean 3.1%, median 0.7%) was significantly lower (p < 0.05) than in samples from amalgam restorations (mean 5.7%, median 3.1%). This suggests that plaque formed on such restorations might have a lower potential to induce recurrent caries than plaque formed on amalgam restorations.
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