The use of vacuum-formed resin sheets as spacers for putty-wash impressions

Comparative evaluation of three noninvasive gingival displacement systems: An in vivo study

Aim:

An attempt is made to investigate clinical efficacy of cord, paste system, and a strip gingival retractile materials. This study aims to evaluate and compare the gingival retraction efficacy of retraction strip along with conventional retraction cord and paste system.

Material and Methods:

This in vivo experimental study was carried out on 30 patients. Three different gingival retraction systems were used to evaluate the amount of vertical and lateral displacement.

Based on selection criteria, 30 individuals requiring fixed dental prosthesis with respect to mandibular first molar were selected. Tooth preparation for metal ceramic restoration with subgingival finish line was performed. Gingival displacement was accomplished with ultrapak cord, merocel strip, and magic foam cord immediately, 7 and 14 days after the tooth preparation, respectively. The amount of gingival displacement in vertical and lateral directions was measured at mesiobuccal, midbuccal, and distobuccal regions of the prepared tooth. The vertical retraction was measured intraorally by using digital vernier caliper, and postgingival displacement impression was used to measure lateral gingival retraction. Stereomicroscopic images of impression under ×10 resolution were transferred to image analyzer to measure the lateral displacement. The obtained data analyzed in one-way ANOVA and Bonferroni test were used to determine the significant difference at P < 0.05 level.

Results:

ANOVA test showed the significant difference between the materials tested with respect to the mean vertical and lateral gingival retraction (P = 0.001). Multiple comparisons by Bonferroni test revealed a significant difference in vertical and lateral displacement among the materials tested.

Conclusions:

Merocel strip provided the maximum amount of vertical and lateral tissue displacement, followed by ultrapak cord and least with magic foam cord which was statistically significant.

Effects of the space for wash materials on sulcus depth reproduction with addition-curing silicone using two-step putty-wash technique

Aim of this study was to investigate effects of space thickness and consistency of wash materials on sulcus depth reproduction with silicone impressions, low (L), medium (M), and very high consistency (VH), using two-step putty-wash technique. Impressions were taken from truncated cones with 50-, 100-, or 200-μm-wide sulci, using the combinations L+VH or M+VH and different space thickness for wash materials: 2 mm (ST2), 1 mm (ST1), and approximately 25 μm (ST0.025). Sulcus depth reproduction tended to increase with increasing sulcus width. Sulcus reproduction of ST0.025 was deeper than those of the other groups. At 100- and 200-μm sulcus widths, sulcus reproductions of ST1 and ST2 with L+HV were deeper than with M+HV. Regardless of consistency, the thin spacer produced deep reproduction. Adequate 0.5 mm sulcus reproductions were obtained with 100 and 200 μm wide sulci and 1- and 2-mm spacer widths, combined with low consistency impression material.

Dimensional accuracy of stone casts obtained with multiple pours into the same mold

Aim. The aim of the present study was to compare the dimensional accuracy of stone casts obtained with vinyl polysiloxane molds through the double-impression technique with three pours into the same mold. Methods. A stainless steel master model was constructed simulating a three-unit fixed prosthesis. Twelve impressions were taken of this master model with addition silicone, using the double-impression technique. Three pours of type IV gypsum were then made into each mold, thus producing 36 casts. The pours were made 1 hour, 6 hours and 24 hours after the impression procedure. Next, intra- and interabutment measurements were made in a coordinate measuring machine. Results. Comparative analysis of the dimensional accuracy of stone casts resulting from multiple pours was not statistically significant in pours first and second (P > 0.05). These values, however, were statistically significant at third pour in the height in abutment 1 and upper distance interabutment. Conclusion. The wait time (1 hour, and 6 hours) observed before pouring the stone into the same molds did not cause significant dimensional accuracy of the casts.