St. Louis Testing Laboratories

This single (examiner) blind, randomized, 4-week study compared the safety and efficacy of a new electric toothbrush (experimental) regarding plaque removal and reducing gingivitis with two other brushes, an electric brush (control electric) and a manual toothbrush (control hand). Ninety-six subjects with 1) a minimum of 15 suitable teeth in acceptable occlusion; 2) a minimum gingivitis score of 0.9; and 3) a minimum plaque score of 1.8 were entered into the study. The subjects were randomly assigned to one of 3 groups: a control hand group (31 subjects), an experimental group (32 subjects), and a control electric group (33 subjects). Device use instructions were given according to the manufacturer's recommendations. Two examiners separately determined either gingival scores or plaque scores at baseline and 4 weeks. In regard to gingivitis, use of all 3 brushes for the study period showed statistically significant improvements in gingivitis scores (P values less than 0.01) within each of the 3 groups. Between group analyses of covariance showed that of the 3 groups, the control hand group improvement was better than both the experimental and the control electric groups (P less than 0.05). When interproximal gingivitis scores were analyzed separately, similar improvements were noted. Regarding effectiveness of plaque removal during a single brushing event at the initial and final visits, each of the 3 brushes was effective in reducing plaque for every tooth surface scored (P values less than 0.01). However, between group analyses of covariances showed that the experimental group was better than the other two (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The paper deals with those tests which are involved in specifications. The discussion is from the standpoint of the purpose and significance of the various standard tests which are made rather than that of the technic of the details of testing. A considerable number of data are given. The subjects treated are purpose and importance of tests of cable; insulation resistance test; high voltage test; dielectric loss and power factor test; “ionization” test; bending test; accelerated life test; preparation of samples for high-voltage tests and tests of components. The possible significance of wide variation in some of the properties of cable is discussed. The relation found between time and voltage based on a large number of tests of both three conductor and single conductor cable is discussed at considerable length. A test for stability of the impregnating compound is described as is also a proposed standard load for dielectric-loss testing. Some data are given showing the effect of repeated bending on lead and how that effect is influenced by the tensile stress in the lead. The paper concludes with a list of the ways by which, in the author's opinion, progress can be made in the improvement of the quality and the design of paper-insulated high-tension cable.