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Biomedical subjects

P Birek

Publications and source records attributed to P Birek.

23 records · Page 2Linked to original sources
PubMed1989

Measurements of probing velocity with an automated periodontal probe and the relationship with experimental periodontitis in the Cynomolgus monkey (Macaca fascicularis).

The Toronto Automated Periodontal Probe allows simultaneous measurements of gingival attachment level and probing velocity. The efficacy of probing velocity in measuring the integrity of the dento-gingival junction was studied and compared with loss of gingival attachment level, gingival inflammation, tooth mobility and gingival crevicular fluid collagenolytic activity. The gingiva around the maxillary and mandibular incisor teeth of 2 monkeys were first brought to clinical health by daily prophylaxis. Baseline measurements were made and inflammation was then induced around the maxillary incisors by withdrawing plaque control and by placing silk ligatures subgingivally. The mandibular incisors served as controls. After 10 weeks, the ligatures were removed and the teeth scaled and polished daily for 1 week. The plaque index and gingival index reached maximum values within 1 week; crevicular fluid flow was significantly increased at 1 and 3 weeks but mobility did not change significantly. There was progressive loss of the gingival attachment level, which peaked at 10 weeks on experimental teeth; there was no significant loss on control teeth. Probing velocity around experimental teeth exhibited large and significant increases above controls between 1 and 3 weeks, coinciding with the largest weekly losses of the gingival attachment level. Thus probing velocity may be a useful clinical method for the ancillary measurement of early loss of the gingival attachment level. It can also detect biophysical changes in the dento-gingival junction of progressive inflammatory lesions.

Animals↗
PubMed1987

Gingival attachment level measurements with an automated periodontal probe.

The accurate and reproducible measurement of gingival attachment level is essential for studying the progression of periodontitis in human populations. An automated periodontal probe has been developed which measures gingival attachment level using the occlusal or incisal surface of the tooth as a fixed landmark and which transfers data directly to a computer. The probing force is adjustable and is regulated by changing the air pressure. A mercury level switch maintains uniform probe angulation during measurements. The reproducibility of measurements obtained with the automated periodontal probe was examined by making duplicate gingival attachment level measurements at 784 sites in 9 patients 1 week apart and comparing the difference between the paired values. A probing force of 0.30 N was used. There was no significant difference in the frequency distributions of measurement differences between either maxillary versus mandibular teeth or anterior versus posterior teeth. The data demonstrate that this device can be used to measure gingival attachment level without the need for stents or estimation of the level of the cementoenamel junction and that reproducible data can be obtained and automatically stored in a computer for subsequent analysis.

Adult↗
PubMed1980

Epithelial rests of Malassez in vitro. Phagocytosis of collagen and the possible role of their lysosomal enzymes in collagen degradation.

Cells from porcine epithelial rests of Malassez were cultured in vitro with collagen prepared from rat tail tendons. Serial sections of the cultures were prepared for examination in the electron microscope. Some of the material was processed to demonstrate activity of acid phosphatase. Electron microscopy showed that the epithelial cells had phagocytosed collagen in vitro, and study of the serial sections indicated that much of the phagocytosed collagen was contained wholly within the cells. Reaction product indicating sites of acid phosphatase activity was found to be associated with intracellular collagen, and some of the intracellular fibrils exhibited nonsymmetrical loss of material and also localized loss of banding, suggesting intracellular digestion of collagen. A lysosomal fraction was prepared from epithelial cells cultured from the rests of Malassez, and this was shown using biochemical assays to contain activities of thiol-dependent cathepain, cathepsin D, beta-D-glucuronidase, aryl sulfatase, and acid phosphatase. The lysosomal fraction had the capacity in vitro to depolymerize and digest collagen obtained from rat tail tendon. It was concluded from these observations and results that epithelial cells cultured from the rests of Malassez can digest collagen in vitro. The findings suggests a possible mechanism whereby the epithelial cells can destroy the extracellular substance of connective tissue during their well known participation in cyst formation in vivo.

Amino Acids↗