This in vitro study was undertaken to evaluate the attachment of human periodontal ligament fibroblast-like cells to root surfaces treated with tetracycline HC1 (100 mg/ml, pH 1.9, 5 min, 37°C). 24 root fragments were obtained from 12 patients. These roots were prepared so that a comparison could be made between the initial attachments to instrumented diseased cementum (scaled and root planed), dentin and nondiseased cementum of tetracycline HC1 treated (test) and nontreated (control) root surfaces. Both test and control root fragments were incubated with human periodontal ligament fibroblast-like cells for 1 hour. The adherence of the fibroblast-like cells was determined by Light Microscope using an ocular grid system and orientation was evaluated by Scanning Electron Microscope. Results indicated that initial cell attachment was significantly enhanced on dentin surfaces of tetracycline treated root fragments (p<0.05).
The simple or branched invaginations of dens invaginatus were histologically observed by using 6 ground sections (2 molars and 4 incisors). In all the teeth, the invaginations have hypoplastic enamel showing a variable thickness and an irregular outline. The relatively thick enamel irregularly arranged the Retzius lines and prismless structures were present in the innermost layers besides the surface layers. In 4 teeth, enamel-free areas were partially found on the dentin surfaces, and afibrillar cementum occasionally covered the enamel-free areas as well as the enamel surfaces. The dentin of a molar tooth had giant tubules between the dichotomously branched invaginations and other giant tubules opened into the invagination floor. Some dentinal tubules in the terminal regions had abnormal structures similar to the Tomes' granules adjacent to the invaginations of the 2 molar teeth. In all the incisor teeth, a seam line of dentin fusion or a slit line succeeding to the dental pulp cavity was present in the dentin under the linguogingival ridge. Thus, the gross formation of dens invaginatus also causes the invagination to form locally abnormal structures, especially in the enamel regions; although some findings have been previously reported.