Linear dimensional changes in plaster die models using different elastomeric materials

Abstract

Dental impression is an important step in the preparation of prostheses since it provides the reproduction of anatomic and surface details of teeth and adjacent structures. The objective of this study was to evaluate the linear dimensional alterations in gypsum dies obtained with different elastomeric materials, using a resin coping impression technique with individual shells. A master cast made of stainless steel with fixed prosthesis characteristics with two prepared abutment teeth was used to obtain the impressions. References points (A, B, C, D, E and F) were recorded on the occlusal and buccal surfaces of abutments to register the distances. The impressions were obtained using the following materials: polyether, mercaptan-polysulfide, addition silicone, and condensation silicone. The transfer impressions were made with custom trays and an irreversible hydrocolloid material and were poured with type IV gypsum. The distances between identified points in gypsum dies were measured using an optical microscope and the results were statistically analyzed by ANOVA (p < 0.05) and Tukey's test. The mean of the distances were registered as follows: addition silicone (AB = 13.6 µm, CD = 15.0 µm, EF = 14.6 µm, GH = 15.2 µm), mercaptan-polysulfide (AB = 36.0 µm, CD = 36.0 µm, EF = 39.6 µm, GH = 40.6 µm), polyether (AB = 35.2 µm, CD = 35.6 µm, EF = 39.4 µm, GH = 41.4 µm) and condensation silicone (AB = 69.2 µm, CD = 71.0 µm, EF = 80.6 µm, GH = 81.2 µm). All of the measurements found in gypsum dies were compared to those of a master cast. The results demonstrated that the addition silicone provides the best stability of the compounds tested, followed by polyether, polysulfide and condensation silicone. No statistical differences were obtained between polyether and mercaptan-polysulfide materials.

The Dimensional Stability of Elastomeric Dental Impression Materials

“…We concluded that the dimensional stability of addition silicone did not significantly change, not even after 96 hours since the impression was made (linear dimensional changes did not exceed 1%). These results agree with the previous studies of other researchers [10,16,18]. By contrast, condensation silicone was less stable.…”

“…Surprisingly, although dimensional stability decreased over a period of time, the model cast after 96 hours was still acceptably accurate. Condensation silicone contraction was also under 1 %, which differed from the results of previous researchers, who measured contraction of up to 2, 97 % [18]. This can be partially explained by the use of a universal adhesive which may have improved dimensional stability of the impression material, and stable environmental conditions (temperature and moisture) of the storage space [19,20].…”

Effect of Contact Time Between Silicone Impression Materials and Stone on Dimensional Stability of Resultant Cast

“…In Faria's study, the accuracy of condensation silicone was similar to additional silicone using the double-mix technique (6). Nevertheless, Pereira et al reported that among all the elastomeric impression materials, additional silicone had the highest accuracy and condensation silicone had the lowest accuracy (15). The results of the present study showed that the type of impression material did not have a statistically significant effect on the dimensional stability of the casts, which could be due to the high accuracy of both materials and technique used for the impressions.…”

Performance of dental impression materials: Benchmarking of materials and techniques by three-dimensional analysis

“…Making replicas from the object to be analyzed allows for reinforcement with supporting materials, and can be used for a complete surface mapping with an electrical probe and an X-Y table 14) . Often, the accuracy of different elastomeric impression materials for final impressions (e.g., fastsetting, silicones, vinyl siloxanethers) is assessed by measuring intra-and inter-arch distances of study models [15][16][17] or by analyzing distances and angles of single abutments with specified geometrical dimensions 18,19) . Image analysis of tooth contours allows for free-form shape analysis of the more complex geometries of prepared teeth 20,21) .…”