The effect of water absorption on acrylic surface properties

Hugh Devlin, Prashant Kaushik

    Research output: Contribution to journalArticlepeer-review


    Purpose: The aim of the present study was to determine whether an increased water content during thermal cycling of hot water-treated acrylic was associated with a reduction in surface hardness and an increased opacity or whitening of the surface. Materials and Methods: Ten acrylic samples were treated with 30 soak cycles (cycle duration, 24 hours), using warm water (40°C) and an alkaline peroxide tablet (Efferdent® control group); a further ten samples were treated with boiling water (100°C) and one Efferdent® tablet (experimental group). Indentation hardness of the acrylic specimens was measured prior to and immediately following the completion of the warm and hot water treatments, using an automated micro-indentation system. The hydrated acrylic specimens were then allowed to air dry at room temperature (20°C) and were weighed weekly until they had obtained a constant dry weight. The loss in weight of the acrylic specimens represented the maximum water absorption. Results: The hot water-treated specimens were much whiter than the warm water-treated specimens. The mean reduction in hardness (H IT) of the acrylic specimens following the treatment with hot water and alkaline peroxide tablet was 12.9%. Treatment with warm water and alkaline peroxide resulted in a slight increase in mean hardness (2.63%). There was a significant correlation between the water content of the acrylic specimens after treatment and the percentage of change in indentation hardness (r = 0.495, p = 0.026). Conclusions: The hot water treatment of the acrylic was associated with a significant reduction in hardness. We attribute the whitening and reduction in the hardness of the hot water-treated specimens to absorption of water and a disruption of the acrylic surface structure. Copyright © 2005 by The American College of Prosthodontists.
    Original languageEnglish
    Pages (from-to)233-238
    Number of pages5
    JournalJournal of Prosthodontics
    Issue number4
    Publication statusPublished - Dec 2005


    • Indentation hardness
    • Plasticizing effect
    • Whitening of acrylic


    Dive into the research topics of 'The effect of water absorption on acrylic surface properties'. Together they form a unique fingerprint.

    Cite this