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.

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.

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The aim of this study was to evaluate the effect of gender and knowledge of color in dentistry on the visual shade-matching ability of dental students with no experience in shade matching and without identification skills. Materials and Methods: A total of 32 color-normal participants, 16 female (F) and 16 male (M), completed all phases of the experiment. The control group did not listen to a 60-minute lecture (FNL = females that did not listen; MNL = males that did not listen); the other group listened to a lecture about color in dentistry (FL = females that listened; ML= males that listened). The Toothguide Training Box (TTB) (VITA Zahnfabrik) was used. The final exam consisted of a total of 15 lightness-chroma-hue tasks. The correct selection of lightness (L*), chroma (C*), and hue (h*) was observed, as was the computed shade-matching score, Σ∆E* ab , for each participant. Mann-Whitney U test was used for statistical analysis of the data (α = .05) (SPSS 22.0 for Windows [IBM]). Results: Gender was found to play an important role in shade matching. The FL group selected L* better (L* = 12.11) in comparison with the MNL group (L* = 11.00), which is not significantly different (P = .19). The FL group selected L* better in comparison with the ML group (L* = 10.57), which is not significantly different (P = .10). The FNL group selected C* statistically significantly better (C* = 9.86) than did the ML group (C* = 8.57) (P = .016). The shade-matching score, Σ∆E* ab , for group FL (Σ∆E* ab = 22.50) and group ML (Σ∆E* ab = 31.79) was marginally statistically significant (P = .06). Conclusion: A 60-minute lecture from the field of color in dentistry has a minimal impact on tooth-shade matching, whereas gender plays an important role.

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