Dimensional Stability and Surface Details Reproduction of Two Extended-Pour Alginate Materials: A Function of Chemical Disinfection and Storage Time. An In- Vitro Study

Abstract

Background: Many new extended-pour irreversible hydrocolloid impression materials have been marketed with claims that they demonstrate enhanced surface details accuracy and dimensional stability for up to 120 hours of storage. However, no data in the literature about the effect of storage time on surface details and dimensional stability of extended-pour impression materials upon disinfection. In this study we aimed to evaluate the effect of two chemical disinfection methods and three storage times on dimensional stability and surface details reproduction of 2 extended-pour alginates in comparison with a conventional one.Methods: A total of 243 alginate impressions were recorded from a custom metal die using Tropicalgin (conventional), Hydrogum5 and Chroma print (extended-pour) alginates. Impressions were categorized into 9 groups according to disinfection method (non-disinfected, sprayed or immersed) and storage time (0, 72, 120 hours). After storage in sealed plastic bag with a damp cotton roll, all impressions were poured with type IV dental stone. The stone models were then examined for surface details and dimensions using a magnifier (×10) and digital caliper to assess whether a 25 µm-line on the metal die was completely reproduced over the full 25 mm length and its dimensions compared to the original die. Data were analyzed using one-way (ANOVA) and Tuckey’s post-hoc test, and KrusKal Wallis test and Mann-Whitney's test.Results: With immediate pouring all alginates showed accurate surface details regardless of the disinfection condition, except for immersed Tropicalgin (P<0.05). The extended storage affected surface details of all materials. After 72h, only non-disinfected extended-pour alginates showed dimensional stability. However, after 120h of storage all materials regained dimensional stability except sprayed Tropicalgin.ConclusionsExtended-pour alginates hardly proved to be more advantageous than traditional alginate in terms of surface details accuracy. Disinfection methods had some adverse effects on surface details and dimensional accuracy of both extended-pour and conventional alginate. Extended-pour alginate proved dimensional stability after 120h. It is recommended to immediately pour all alginates whether conventional or extended-pour. Further studies are needed to evaluate impression materials directly to control the confounding variable like gypsum expansion and storage environment in terms of humidity and temperature.