Aims: To determine the effect of different curing times of a new method of polymerization by infrared radiation on the absorption and solubility in water of acrylic resin materials for denture base. Materials and Methods: In this study two types of denture base materials cured by heat were used (Traditional or Conventional and High Impact), the entire number of prepared specimens were (80) which grouped into: A-Control group: Consisted of two types of acrylic resin specimens polymerized by conventional water bath .B-Experimental group: Consisted of two types acrylic resin specimens polymerized by infrared radiation (IR) at different times of curing cycles. In each group; specimens were divided equally, some related to water sorption test others for solubility test. The mean of mass change of the material after they saturated with water and dried out of it was used, then analysis of data was done using one-way analysis of variance and Duncan test. Results: Statistically, no differences existed between Traditional and High Impact acrylic resin cured by water bath in water sorption and solubility tests. The mean values for previously mentioned tests in two types of acrylic resin had been decreased significantly by changing type of curing from conventional water bath to (IR) method. Conclusions: The selection of appropriate time and type of curing method may optimize the level of absorption and solubility in water for previously mentioned materials.

Aims: To evaluate the effect of some commercially available new denture cleansers on the hardness of acrylic denture base and teeth materials. Materials and method: Samples were prepared from heat cured acrylic resin denture base material and teeth. After that, half of the samples for each group were immersed for ½ hr per day in the denture cleanser throughout one month, the other half of the samples immersed for 8 hr per day in the denture cleanser through one month. The denture cleansers used are three solutions prepared freshly everyday for immersion of the samples. The hardness of the samples were tested by using Vickers hardness tester, the mean is taken for each group and evaluated by using one way analysis of variance test and Duncan's multiple range test to compare the groups. Results: The results demonstrated that there were significant differences in the hardness of acrylic resin denture base material with different denture cleansers and duration of immersion (P < 0.0001), and there were significant differences in the hardness of acrylic resin teeth with different denture cleansers and duration of immersion (P < 0.0001). The results also revealed that the cross linked teeth had a higher hardness value than the acrylic resin teeth. Conclusions: The type of denture cleanser and duration of immersion had an effect on the surface hardness of acrylic resin teeth and denture base materials. The cross linking of acrylic resin materials increase the resistance of the material to the action of solvents.

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Aims:To investigate the effect of the thickness of relining material, curing method (water bath or microwave), and the surface treatment by methyl methacrylate on transverse and tensile strength of relined acrylic resin denture base. Materials and methods: A pilot study was done by preparing 65 samples to evaluate the effect of the thickness of relining material in relation to denture base on the transverse strength of acrylic resin denture base, and to study the effect of surface treatment by methyl methacrylate on the transverse strength of acrylic resin denture base. The main study was done by preparing 320 samples and divided into two parts to study the mechanical properties of samples representing a denture base cured by water bath and other group cured by microwave curing technique, and then the effect of relining by the two curing methods and the effect of surface treatment were evaluated. Analysis of variance (ANOVA) and Duncan's multiple range tests were used for statistical analysis. Results: of this study showed that the different thickness of relining material in relation to denture base had no significant difference on the transverse strength of the relined denture base. The transverse strength and tensile bonding strength of the relined samples were significantly improved (P=0.05) by monomer surface treatment for 180 seconds. Conclusions: Transverse and tensile strength of the acrylic resin denture base were affected by relining. Microwave curing method gave better mechanical properties of the relined acrylic resin denture base. A BHatim NA, AL-Omari AW Al -Rafidain Dent J Vol. 13, No2, 2013 Surface treatment and bonding of relined denture base Al -Rafidain Dent J Vol. 13, No2, 2013

Aims: Heat cured acrylic resin is the material of choice for construction of complete dentures due to its desirable properties, although it has some disadvantages as its susceptibility to fracture. Several methods and materials are used to reinforce acrylic resin denture base. One of these methods is reinforcement by using fibers. In this study, visible light cure fiber frame work is used as reinforcement material and compared with reinforcement with glass fiber. Materials and methods: in this study, 128 samples were prepared for evaluation of transverse strength, impact strength, surface hardness, and residual monomer tests. The samples were divided into four groups 8 sample for each group; control group without reinforcement, reinforcement by using visible light cure fiber frame work, random glass fiber reinforcement, and mesh glass fiber reinforcement. Results: the results of this study showed that visible light cure fiber frame work system significantly increase the transverse strength and impact strength of the heat cured acrylic resin, and it didn't affect the surface hardness and amount of residual monomer of heat cured acrylic resin. Conclusions: visible light cure fiber frame work system increase acrylic resin denture base resistance to fracture.