Method: One hundred and twenty shade guides for acrylic were used. They were subjected to spectrophotometeric test using the Vita Easyshade measuring device before disinfection (The baseline reading served as control). Disinfection methods included immersion for 10 minutes in one of the tested disinfectant solutions (5.25% sodium hypochlorite, 2% alkaline gluteraldehyde or 1.7% trialkyl ammonium propionate). The specimens were cleaned after disinfection; the cleaning methods included ultrasonic cleaning in distilled water for 5 minutes and for 10 minutes, steam cleaning for 30 seconds, and under tap water for 30 seconds ((n=10). The disinfection procedures were repeated 4 times and new measurements were made on each specimen after each disinfection cycle. Furthermore, this cycle was repeated after one day of immersion. A random selection of pilot sample of the acrylic shade guide tabs was studied in the same manner and compared to the baseline results. The L*a*b value were recorded and ΔE were calculated. Statistical analysis of data was conducted with repeated measures analysis of variance (ANOVA) and single factor analysis of variance (alpha=.05).
Result: All the disinfectant solutions used produced a perceivable change in color (E>1). Immersion time has the most significant effect on E (P<.001).
Conclusion: There was no preferred cleaning method that has significant reduction in color change. The recommended time of immersion by manufacturer should be followed. Overnight immersion for disinfection should be avoided. Compared to porcelain shade guides, acrylic shade guides showed more color change after disinfection.