Viability of fibroblasts in cell culture after treatment with different chemical retraction agents.

Prior to fixed prosthodontic impression procedures, temporary horizontal retraction of the free gingival tissue should be accomplished apically to the preparation finishing line. The mechanical-chemical method using cotton retraction cords of various sizes impregnated with various retraction chemicals is the most commonly employed retraction technique. Most retraction agents have pH values from 0.8 to 0.3, and are therefore hazardous to the cut dentine and periodontal tissues. Sympathomimetic vasoconstrictors introduced recently have a pH of 5.6, and are free of systemic side-effects. The present study using the dye exclusion test, colony forming ability test and colorimetric assay was undertaken to evaluate cytotoxic effects of four chemical retraction agents on cultured V-79 fibroblasts, and the dependence of cytotoxicity on the agent concentration and time of exposure. Original concentrations of retraction agents produced stronger cytotoxic effects than dilutions of 1:1 and 1:10. The most aggressive agent, 25% aluminium chloride, took only 1 min to damage all cell cultures. The proportion of cells damaged after 10 min of exposure to tetrahydrozoline was 60%, which was significantly less compared with other chemicals tested. With the colony forming ability test using retraction agents diluted to 1:10 the greatest number of colonies emerged in samples treated with tetrahydrozoline (statistical significance: P < 0.01). The colorimetric assay showed equal cytotoxic effects for 25% aluminium sulphate and tetrahydrozoline. The colorimetric test used in the study has proved an ergonomic, accurate and reliable test for cytotoxicity determination.

Gingival tissue inflammatory response following treatment with chemical retraction agents in Beagle dogs.

A normal finding of a clinically healthy gingiva is minimal inflammatory infiltration of subepithelial connective tissue which increases after exposure of gingiva to retraction agents. The study investigates and compares the inflammatory potential of four retraction agents on the gingival connective tissue. The gingiva of Beaagle dogs was exposed for 10 minutes to chemical agents. Byopsies were taken one hour, 24 hours and 7 days after treatment. Morphometric analysis of treated and control gingiva was performed on parasagittal tissue sections to compare the gingival tissue inflammatory potential of four retraction chemicals. Retraction agents produced no significant effect on connective tissue under the junctional epithelium. On the other hand the connective tissue under sulcular epithelium exhibits extensive inflammatory infiltration. The most aggressive retraction agent being Racestyptine and the least Visine, which therefore could be recommended for clinical practice.

Study of mandibular kinetics by COSIG. Computerized sirognathograph system.

Several programs for coupling Sirognathograph to personal computer are available on the market (Maruyama's SGG Analyzing System Radke's Bio-Pac-Software, Fabris's Computersystem for Sirognathograph S) or are in various non commercial versions used in research (Lewin, Micheler, Proeschel). The COSIG System consists of the software and the hardware (Sirognathograph S--Siemens, XY 575 Recorder Esterline Angus, Personal computer IBM XT, IBM Graphics, Printer, A/D converter Tecmar Labmaster, Roland Plotter 880 DXY). The COSIG software records simultaneously X, Y, Z data from SGG, store and retrieve them. Mandibular movements are presented in time plot mode, in the three planes, in speed and acceleration plots, using different magnifications, direction color code, deliberate observation times, enables zero adjustments and storing of particular situation with comments on it within the file. Simultaneously graphic presentation goes by XY recorder, while stored data are screen printed by Graphic printer or color and black and white plotted by XY plotter. Standard patient examination using COSIG comprises three files i.e. border movement potential, contact movements and chewing standard bolus has been proposed.