---

ABSTRACT
 
Background and Aim: Corrosion may be a consequence of disinfecting and cleansing of partial denture chromium – cobalt frameworks using chemical disinfectants and cleansers. There is short information in literature about the effect of these solutions, in comparison with each other, on the corrosion rate of chromium – cobalt alloy. The present study was designed to compare corrosion rate of the chromium – cobalt alloy in disinfecting solutions.
 
Materials and Methods: In this experimental in-vitro study, corrosion rates of 35 chromium-cobalt immersed in7disinfecting solutions were determined.  As a complementary test , samples were immersed in two groups of solutions which showed the least and the most corrosion rates as measured by electrochemical tests for a period of one week and their surface and also surface of one untreated control sample was photographed under a scanning electron microscope . Corrosion rates obtained, were statistically analyzed using variance analysing test and multiple comparisons were made using Tukey HSD and Dunnett tests.
 
Results: The corrosion rates of chromium cobalt sample in the studied solutions from the highest to lowest , were : Sodium Hypochlorite 1%, Fittydent 1 tab/250ml , Micro 10+ 5% , Korsolex Plus 3% , Deconex 53 Plus 2% . Corrosion rates were statistically different in the studied solutions (P<0.05). SEM photographs showed no evidence of corrosion on control sample and samples immersed in Decomex 53 Plus 2% , but localized corrosion was observed on samples immersed in Sodium Hypochlorite 1% .
 
Conclusion: The present study indicated that Sodium Hypochlorite at the concentration of 1% or more for the purpose of disinfection and cleansing of chromium-cobalt not be used.
 
 

---

                        ABSTRACT
 
Background &Aim: Wear of acrylic teeth after passing years is still one of the main problems in dentistry that may lead to loss of chewing function, decrease of facial vertical height and unpleasant smile.This study aimed to evaluate the comparison of wear resistance of President &Ivoclar teeth against natural teeth.
Materials &Methods: In this Experimental Study, 64 samples of second premolar teeth that included 24 upper & lower second premolar of President teeth and 24 upper & lower second premolar of Ivoclar teeth and 16 upper & lower natural teeth, were included. The samples divided into 6 groups (5 case and 1 control), Each of 5 case groups included 12 samples, and the control group included 4 samples. After that, 3D images of each samples were provided by lab 3D scanner and then all of the samples (case and control) were put in the incubator (37°c ) for 24h.  After that, they were put in thermocycler After these processes, samples were scanned for the second time.Finally, 3D scans were superimposed.In the comparison of difference between samples volume ,Repeated Measure ANOVA Test, was used.
Results: after wear procedure with chewing stimulator, control group (natural teeth) had less wear vs president and ivoclar teeth, significantly CP<0.05). But President& Ivoclar teeth had not significant difference when they against each other (p>0.05). President  & Ivoclar teeth when against to the natural teeth had more wear vs when they put against each other (p<0.05).
Conclusions: It seems, wear of artificial teeth was more when they put against natural teeth. But there was not different between president and Ivoclar teeth.