Aims: To evaluate the effect of three different cleanser on the color stability of three different types of artificial teeth. Materials and methods: sixty samples of artificial anterior teeth were prepared which are Acry-Rock, RMH teeth and Porcelain teeth and immersed in three types of denture cleanser(Bony plus, Protefix and soda+ vinegar) for 8 hours and the color of the teeth was measured by Easyshade's spectrophotometer at 3 intervals(1,2and4weeks). Results: Showed that the a'b values of ceramic teeth and L value of RHM teeth were significantly differencent after 2 week of immersion in three type of denture cleanser. Analysis of variance demonstrated that L'a'b value for ceramic teeth and RHN teeth were statistically significant after 4 week immersion in three type of denture cleanser, The result of color change (ΔE) for three denture cleansers of three periods of immersion were clinically accepted. Conclusion: Long period of immersion of artificial teeth in denture cleanser cause significant color change for L*a*b* values but they were clinically accepted.

Artificial teeth --- Denture cleanser --- Spectrophotometer

Aims: To evaluate the effect of microwave disinfection on transverse strength and hardness of acrylic resin denture base materials. Materials and methods: The samples were 112 samples (56 heat cured acrylic resin and 56 microwave cured acrylic resin) they were prepared in dimensions of 65± 0.3x10±0.03x2.5 ±0.03 mm (length, width and thickness respectively) for transverse strength test and 30x15x3±0.03 mm (length, width and thickness respectively) for indentation hardness test. The sam-ples were divided into seven disinfection groups; each one contain five samples which were (control, 900 W or 540W for 3min either inside glass flask containing 150 ml of distilled water)or along with glass flask containing 150 ml of distilled water or alone. The collected data were analyzed using analy-sis of variance (one way ANOVA) at P ≤ 0.05 and Duncan's multiple range test. Results: the transverse strength of microwave acrylic resin samples were significantly decreased except samples that disinfect-ed by 540 watt microwave energy for 3 minute with water inside microwave oven. The hardness num-ber for heat cured acrylic denture base showed no significant differences compared to control group while hardness number of microwave acrylic resin were significantly decreased in relation to control group. Conclusions: Transverse strength of microwave acrylic resin that disinfected with microwave was decreased except at 540 watt for 3 minutes with water a side in microwave oven. While heat cured acrylic resin after microwave disinfection was significantly increased compared with the control sam-ple. Rockwell hardness number for microwave acrylic resin significantly decrease in relation to control group; while for heat cured acrylic denture base showed no significancy comparing with the control group.

microwave --- disinfection --- Transverse strength --- hardness.