الفهرس 
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Abstract
When there is a partial or complete loss of teeth, unusual stresses are placed on the remaining teeth, gums and bone that cause negative effects on the daily functions from eating to speaking and on patient’s appearance. So the need for partial and complete dentures remains very high to avoid these problems. The multiple advantages of polymethyl methacrylate (PMMA) make it the most dominant polymer used as denture base material because of its favorable characteristics, such as the ease of processing, lack of toxicity, low cost, stability in the oral environment, light weight and appropriate esthetic. This material is not ideal in every aspect; PMMA has weak mechanical properties including impact and flexural strengths. Therefore, the resins should be reinforced using different materials to enhance their properties. The PMMA denture base resin is susceptible to colonization of microorganisms in the oral cavity. Many factors are affecting the adhesion of microorganisms and formation of the biofilm on the surfaces of PMMA resins such as surface roughness, poor denture hygiene, porosity, continual denture wearing, etc.
This study aims at enhancing and improving the mechanical and antifungal properties of Polymethyl methacrylate in dental applications by blending it with chitosan(CS) and cellulose acetate(CA). The impact strength test, flexural strength test and microbial test of the specimens were performed.
A total of ninety eight specimens were prepared according to the international standard specifications (49 specimens for impact test, 49 specimens for flexural test). The specimens were divided into 4 groups: control group A (100% PMMA), study group B (PMMA+CS), study group C (PMMA+CA) and study group D (PMMA+CS+CA). Each study group was divided into 2 subgroups according to the ratios of the additives of CS and CA. The evaluation of the antimicrobial activity of the specimens was performed by DROP plate method using serial dilution.
The specimens were characterized using Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscope (SEM).
The impact strength was significantly low when compared with the control group. The values of the flexural strength increased for the specimens containing 2.5% of (CS), 2.5% and 5% of (CA).
SEM images showed that the surface characteristics deteriorated and became more irregular in shape and rough in the impact study groups when compared with the impact control group. The surface characteristics were enhanced and improved in the flexural study groups when compared with the flexural control group except the study group (C2) that contains 5% of (CS) which showed high surface roughness and irregular.
The values of C. albicans colonies decreased significantly at 2.5% of ( CS) and 5% of (CS). There was a slight decrease in the values of C. albicans at 2.5% and 5% of (CA). Also, C .albicans decreased significantly at 2.5% of (CS) with 2.5% of (CA) and at 5% of (CS) with 5% of (CA) to PMMA.
In conclusion, the study indicated that PMMA when mixed with (CS) and (CA) retains better mechanical properties and antifungal activity.