Dimensional stability of acrylic resins after dry or water storage

Objectives: This study evaluated the effect of post-cured time (immediate, 1, 24, 48 and 72 h) and of the storage (water or dry) on the linear dimensional stability of two autopolymerizing acrylic resins largely used in prosthodontics (Dencor-DE and Duralay-D). Methods: Specimens were made by using a stainless steel mold (50 X 0.5 mm) with reference points and processed according to the manufacturers' instructions. The distances between these points were measured with a Nikon optical comparator (perfilometer). The differences between the linear dimension of each specimen and the measurements made on the stainless steel mold were calculated and expressed as percentage change. Twenty specimens were made for each material (n=10). Results: The data were analyzed with 3-way ANOVA and Tukey's tests (alpha=.05). Both materials showed progressive (P<.05) shrinkage after dry storage. No changes (P>.05) were observed after 48 h for resin DE (- 0.56 %) and 24 h for resin D (- 0.38 %). Following storage in distilled water at room temperature, no linear dimensional changes (P>.05) were observed after 24 h for DE resin (- 0.35 %) and after 72 h (- 0.01 %) for D resin. Resin D showed the smallest values of linear dimensional changes after water storage for 24 h. In both storage conditions, material D demonstrated smaller linear dimensional changes than material DE. Conclusion: Resin D demonstrated better dimensional stability than DE. Both resins showed higher linear dimensional changes after dry storage.