A comparative evaluation of the accuracy and dimensional stability of various die materials
Iranmanesh, Mohammad Reza
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The accuracy and dimensional stability of two dental stones and three resinous die materials were evaluated and compared. An experimental round test block (stainless steel) with ruled cross lines was used to produce 35 Reprosil impressions which were later poured with the five die materials. The dimensional changes of these dies were compared with the size of the impressions to the nearest 0.001 mm at different time intervals: zero, 2, 24, 72 hours, one week, and two weeks. In addition, the surface reproducibility of four impression materials and their compatibility with the five die materials were investigated. Impressions were taken of the test block used above and another test block scored with six Knoop Hardness indentations as detail patterns. Four independent evaluators graded these impressions by means of a scanning electron microscope according to a scale provided. The compatibility of five different die materials with four impression materials was assessed by taking impressions of a round test block with ruled cross lines, pouring these impressions with the five die materials, and assessing the casts with scanning electron microscopy at x48 magnification by four evaluators as above. As anticipated, the dental stones underwent expansion and the resin dies contracted measurably. Velmix suffered the smallest percentage of change. Alfa-Die, with the greatest percentage of dimensional change proved the least accurate die material. Die-Keen, Blue Star, and Steadyplast, in descending order, were intermediate with respect to dimensional significant dimensional changes from zero time to two weeks whereas Velmix showed its small expansion in the first 24 hours and was thereafter stable. Blue Star exhibited continuous shrinkage for 72 hours before reaching a stable state. With respect to detail reproducibility Permlastic was manifestly less successful than Permadyne, Reprosil, or Genesis. Genesis however, was demonstrably more compatible with gypsum products than Reprosil, Pemadyne, or Permlastic. Conversely, Reprosil was more compatible with resinous materials than Permadyne, Permlastic, or Genesis respectively.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Includes colored photographs.Figure 12 unlabeled in both copies.Thesis (M.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1990 (Prosthodontics)Bibliography : leaves 48-57.
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