Prognostic Elements of the "Bone Factor" Analysis

ULTRASTRUCTURAL CHANGES OF THE PERIODONTAL FIBERS AND THEIR ATTACHMENT IN RAT MOLAR PERIODONTIUM INCIDENT To ORTHODONTIC TOOTH MOVEMENT Rygn, P. Scand. J. Dent. Res., 81:467, No. 6, 1973. To study the alteration of collagen fibrils in the periodontal ligament and their attachment to cementum and alveolar bone in pressure zones of rat molars, tooth movement was carried out in 67 Wistar rats of both sexes while 11 rats without any experimental appliance served as controls. In the experimental group one maxillary first molar was moved buccally with a fixed appliance which was activated to provide a constant force of 5, 10, or 25 g. At the end of experimental periods of 30 minutes to 28 days specimens containing the experimental tooth and adjacent periodontal structures were obtained and observed with the electron microscope. A disarrangement of fibrils, most frequently observed at some distance from the root surface, was seen after 24 hours. After experimental peri­ ods of 3-7 days fibrillar elements showed loss of functional orientation and dense packing. Occasionally nonstriated fila­ ments, formed by longitudinal splitting of collagen fibrils were observed in localized areas. The occurrence of nonstriated filaments was highest in the hyalinized tissues from the 14-day specimens with the amount less than 5% of the field observed in the electron microscope. Regeneration predominated in the 14 28-day specimens. The apposition of cementum and alveo­ lar bone had stopped during hyalinization, as shown by dis­ tinct demarcation lines. The new cementum and bone deposited during the period of repair appeared more granular and stained more lightly as compared to the old hard tissues. Re­ search Laboratories, School of Dentistry, University of Bergen, Arstadveien 17, N-5000, Bergen, Norway. PLAQUE ACCUMULATION ON DIFFERENT DENTAL FILLING MATERIALS Skjorland, K. K. Scand. J. Dental. Res., 81:538, No. 7, 1973. In the first part of the experiment round disks of silicate, composite, and amalgam filling materials were prepared and placed on agar/sucrose medium or hung in liquid medium containing sucrose. Streptococcus mutans O M Z 176 and O M Z 52-3 were inoculated into the media. At the end of seven days the accumulated plaque on the surfaces was scraped off and measured by the orcinol method. In the second part of the experiment, filling materials were fitted to acrylic plates which were placed on each side of the mandible of six patients. Each was instructed to rinse hourly with sucrose solution and to avoid eating and toothbrushing during the eight hour test peri­ od. The plaque was scraped off and measured. The silicate disks on agar medium had a marked inhibitory effect on bac­ terial growth. Thick layers of plaque formed on the composite and amalgam discs and zones of inhibition were not ob­ served. In sucrose medium, abundant amounts of plaque were formed on composite materials and some amalgam discs, with less on amalgam or silicate discs. This same difference in plaque formation was found in vivo. Department of Operative Dentis­ try, Dental Faculty, University of Oslo, Geitmyrsveien 71, Oslo 4, Norway. TOPOGRAPHY OF PRINCIPAL FIBERS Kuam, E. Scand. J. Dent. Res., 81:553, No. 7, 1973. The principal fiber bundles remaining on the root surface of human premolars from individuals ages 10-12 extracted as part of orthodontic treatment were examined by means of the scan­ ning electron microscope. The principal periodontal fibers were seen to consist of smaller units. Upon approaching the tooth, the outer portion of the fiber bundle interlaced with an exten­ sive fibrous coating located at a slight distance from the root surface. Traversing the cementum, were distinct principal fiber bundles which were arranged in an orderly fashion and ran obliquely towards the cemento-dentinal junction. Longitudinal fibers were observed to be connected by smaller fiber bundles joined at right angles. At the cemento-dentinal junction, the fiber bundles branched, producing an irregular border between dentin and cementum. Department of Orthodontics, University of Oslo, Geitmyrsveien 71, Oslo 4, Norway. IN VIVO AND IN VITRO STUDIES ON A NEW PEROXIDECONTAINING TOOTHPASTE Rundegren, J., Fornell, J., and Ericson, T. Scand. J. Dent. Res., 81:543, No. 7, 1973. An experimental dentifrice containing hydrogen peroxide was tested in vitro for its bactericidal effect and in vivo for its effect on gingival inflammation, exudation, plaque formation, and bacterial composition. In the first part of the experiment, dif­ ferent amounts of the hydrogen peroxide paste were mixed with suspensions of Streptococcus mutans, Streptococcus san­ guis and a fusobacteria cultivated from monkey, incubated and viable microorganisms determined. In the second part eight dental students served as test subjects. Plaque Index and Gin­ gival Index were recorded and gingival exudation was measured. Four students received a placebo paste and four others the hydrogen-peroxide-containing paste and at the end of two 14-day testing periods, indices were again recorded. Samples of bacteria collected and cultivated for anaerobic strains showed that the number of organisms was reduced after use of the test paste. The results revealed significant effects in vitro and in vivo. The mode of application of the paste was considered responsible for the less pronounced effect recorded for approximal Plaque and Gingival Indices. Odontologisk Fakultet, Fack S-40033, Goteborg 33, Sweden.