Objective: The study investigated the effect of a disinfection procedure on the surface hardness and color stability of a light-polymerized polyurethane (Eclipse) and three polymethyl methacrylate (PMMA) denture base polymers: Meliodent, a conventional heat-polymerized; Lucitone 199, a high impact heat-polymerized: ProBase, an auto-polymerized PMMA. Methods: Twenty rectangular-shaped specimens (65x10x2.5 mm) were fabricated from each material according to the manufacturer's instruction and stored in water at 37°C for 30 days. Specimens were randomly selected (n=10), scrubbed for 1 minute with 4% chlorhexidine gluconate and immersed in 1% sodium hypochlorite disinfectant for 10 minutes before tested for Vickers hardness (VH). The controls were not disinfected. Color changes (ΔE*) were measured using Dataflash® 100 colorimeter at 10 minutes (T10) and 1 hour (T60) after immersion in the disinfectant. Data was analyzed using ANOVA, Scheffe's and t-test at 95% confidence level. Results: ANOVA showed a significant difference in the VH values for the four materials (p<0.05) with Eclipse exhibiting the highest and ProBase the lowest. The VH for Meliodent and Lucitone 199 were not significantly different (*, µ). Eclipse demonstrated a significant decrease in VH after disinfection while the others were not affected. There was a significant color change for ProBase specimens between 10-minute and 1-hour immersion in sodium hypochlorite disinfectant
|
Material |
Vickers Hardness |
Color change |
||||
|
Control Mean (SD) |
Disinfected Mean (SD) |
p-value (t-test) |
T10 |
T60 |
p-value (t-test) |
|
|
ProBase |
12.1±1.5 |
11.4±1.0 |
0.101 |
0.41±0.24 |
0.86± 0.62 |
0.039 |
|
Lucitone 199 |
15.0±0.6* |
15.2±0.5µ |
0.517 |
0.39±0.21 |
0.38± 0.18 |
0.261 |
|
Meliodent |
16.3±0.6* |
16.2±0.8µ |
0.135 |
0.33±0.15 |
0.37±0.13 |
0.713 |
|
Eclipse |
18.8±0.9 |
17.4±0.7 |
0.010 |
0.58±0.33 |
0.64±0.38 |
0.564 |
Conclusion: The hardness of Eclipse was reduced by the disinfectant procedure and ProBase demonstrated a color change after 1hour immersion in sodium hypochlorite disinfectant.