Abstract
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 language | English |
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Pages (from-to) | 233-238 |
Number of pages | 5 |
Journal | Journal of Prosthodontics |
Volume | 14 |
Issue number | 4 |
DOIs | |
Publication status | Published - Dec 2005 |
Keywords
- Indentation hardness
- Plasticizing effect
- Whitening of acrylic