No abstract

A blind, two-way crossover clinical trial was carried out to compare the effectiveness of plaque removal between a new, light energy conversion toothbrush incorporated with a semiconductor of TiO2 (test) and a similar toothbrush without the semiconductor (control). The study was completed by 73 school children aged 13-15 years. Each toothbrush was used for a period of 3 weeks. The mean differences between baseline plaque scores and after subjects used the test and control brushes were analyzed by the paired t-test. The Soladey 2 toothbrush showed significantly more reduction of plaque on the buccal surfaces of all teeth than the control brush. There was no significant difference in the plaque removing ability of the two brushes on the lingual aspects of the mandible and on the lingual surfaces of the maxillary posterior sextant. As the buccal surfaces are more likely to allow light to reach the semiconductor during brushing than the lingual areas, it is possible that the reported photocatalytic property of the semiconductor may be involved in some way in the observed reduction of plaque.

No abstract

The relative glycogen synthetic and degradative activities of Actinomyces viscosus and Actinomyces naeslundii, freshly isolated from root surface caries and noncaries sites, were compared. The glycogen synthetic activity was measured by incubating glucose-(or sucrose-)grown resting cells with 100 mM glucose (or sucrose) and U-[¹⁴C]-glucose (or U-[¹⁴C]-sucrose) on a pH-stat maintained at 5.0, 6.0, and 7.0 for 1 h under anaerobic conditions. For the glycogen degradation assays, after the 1-hour incubation period, the cells were reincubated under similar conditions, but in the absence of external carbon sources. Carbohydrate utilization and total acid formation were also monitored. Both the glucose- and sucrose-grown cells of A. viscosus and A. naeslundii strains originating from root surface caries lesions synthesized approximately twice as much glycogen as the strains of noncaries origin. Although there were significant differences in the rates of glycogen synthesis, the rates of glycogen degradation were essentially the same for the Actinomyces strains from both caries and noncaries sites. However, the time required for glycogen degradation by the strains from caries sites was much longer. This study suggests that the abilities of A. viscosus and A. naeslundii originating from root surface caries lesions to synthesize large amounts of glycogen and to degrade this stored polymer slowly under conditions of starvation, particularly in an acidic environment, may be one of the factors contributing to the cariogenic potential of these organisms in root surface caries.

The influence of saliva on lactose-reversible adherence between strains of Actinomyces viscosus and Streptococcus sanguis or Streptococcus mitis was investigated. Because saliva agglutinated these organisms, it was necessary to develop models for studying streptococcal attachment to Actinomyces cells which did not depend upon mixed agglutination of both interacting organisms. One model involved the binding of radiolabelled streptococci to spermine-conjugated agarose beads coated with Actinomyces. This assay appeared to parallel previously described coaggregation reactions because coaggregation-positive streptococcal strains attached in much higher numbers to the Actinomyces-coated beads than did coaggregation-negative strains. Lactose and also saliva which had been depleted of streptococcal agglutinins strongly inhibited attachment of coaggregation-positive organisms. A second model involved use of sonic extracts of Actinomyces cells which agglutinated coaggregation-positive streptococcal strains, but not coaggregation-negative strains. This extract-induced streptococcal agglutination was also inhibited by lactose and by saliva samples collected from 6 donors representative of blood types A, B, and O.