‫األهداف‬ : ‫ل‬ ‫األسٌبى‬ ‫حجز‬ ‫لوبدة‬ ‫الوسحىق‬ ‫إلى‬ ‫الوبء‬ ‫ًسبت‬ ‫على‬ ‫الوٍبٍ‬ ‫هي‬ ‫هخخلفت‬ ‫أًىاع‬ ‫حأثٍز‬ ‫حمٍٍن‬ . ‫وطر‬ ‫المواد‬ ‫ائ‬ ‫العمل‬ ‫ق‬ : ‫الذراست‬ ‫هذٍ‬ ‫فً‬ ‫خوس‬ ‫اسخخذام‬ ‫حن‬ ‫ة‬ ‫الوٍبٍ‬ ‫هي‬ ‫هخخلفت‬ ‫أًىاع‬ ( ‫البئز‬ ‫هبء‬ ‫و‬ ‫غٍزاالٌىًً‬ ‫الوبء‬ ‫الحٌفٍت،‬ ‫،هبء‬ ‫المىام‬ ‫رلٍك‬ ‫هالط‬ ، ‫الومطز‬ ‫الوبء‬ ) ‫هزجهب‬ ‫حن‬ ‫الخً‬ ‫األسٌبى‬ ‫حجز‬ ‫هبدة‬ ‫هي‬ ‫ًىعٍي‬ ‫هع‬ (plaster and stone) . ‫النتائج‬ : ‫الوسحىق‬ ‫إلى‬ ‫الوبء‬ ‫ًسبت‬ ‫فً‬ ‫هعٌىي‬ ‫اخخالف‬ ‫وجىد‬ ‫الٌخبئج‬ ‫أظهزث‬ ‫الذراست‬ ‫فً‬ ‫الوسخخذهت‬ ‫الوٍبٍ‬ ‫هي‬ ‫الوخخلفت‬ ‫األًىاع‬ ‫هع‬ ‫هزجهب‬ ‫عٌذ‬ ‫األسٌبى‬ ‫حجز‬ ‫لوبدة‬ . ‫االستنتاجات‬ : ‫الخً‬ ‫الوبء‬ ‫كوٍت‬ ‫إى‬ ‫الٌخبئج‬ ‫بٌٍج‬ ‫الوزج‬ ‫فً‬ ‫الوسخخذم‬ ‫الوبء‬ ‫ًىع‬ ‫حسب‬ ‫حخخلف‬ ‫الجبس‬ ‫هبدة‬ ‫هشخمبث‬ ‫ححخبجهب‬ . ‫الجبس‬ ‫هشخمبث‬ ‫إلٍهب‬ ‫ححخبج‬ ‫هبء‬ ‫ًسبت‬ ‫الل‬ ‫الٌخبئج‬ ‫أظهزث‬ ‫كوب‬ ‫المىام‬ ‫رلٍك‬ ‫الوالط‬ ‫اسخخذام‬ ‫عٌذ‬ ‫هً‬ .ABSTRACT Aims: To evaluate the effect of different water types on the water powder ratio of dental gypsum products. Materials and Methods: In this study five types of water (distilled, tab, slurry, de-ionized and well water) were used to be mixed with two types of dental gypsum products (plaster and stone). Results: Results showed a statistically significant difference at p ≤ 0.05 in water powder ratio of gypsum products when mixed with different types of water that used in this study . Conclusions: Water requirement of gypsum product varies in respect to the type of water used to be mixed with. The most pronounce decrease in water requirement of dental gypsum products was achieved with slurry water. Key words: types of water, water powder ratio and gypsum product.Taqa AA. Mohammed NZ. Alomari AW. The Effect of Different Water Types on The Water Powder

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.

Many attempts have been made enhancing properties of PMMA denture base material. Adding fillers to PMMA was a commonly used method to improve physical and mechanical properties. To estimate the effects of incorporating recycled polymethylmethacrylate with a different percentage with conventional heat-cured acrylic resin on some properties of heat-cured denture base resin. The recycled polymethylmethacrylate (Chaini-HK G) particles dissolved at (5%,10%,15%) was added to heat-cured polymethylmethacrylate (Spofadental, Czech Republic) polymer and mixed with a ratio of 2:1 with the polymethylmethacrylate monomer. A total number of specimens were 80, which divided into three experimental groups (5%, 10%, 15%) and control group. Each group have 20specimens. The surface hardness, water sorption, solubility and residual monomer of test groups measured as well as compared to that of control groups. Fourier transform infrared spectroscopy test (FTIR) was done for three experimental and control group. This study shows a statistically significant difference at (p<0.01) in the hardness of recycled polymethylmethacrylate incorporate material (10 %,15%) groups when compared with a control group; while recycled polymethylmethacrylate incorporated (5%) group show no significant difference, group with 15% shows the highest Vickers hardness value. The mean values of water sorption test solubility test and residual monomer were decreased with the increase of incorporating a percentage of recycled polymethylmethacrylate as compared to the mean value of the control group. The incorporation of recycled polymethylmethacrylate to heat acrylic resin at different percentage improves some of its properties.

Aims:To determine the effect of thermal cycling on the fitness accuracy of modified heat cured acrylic resin maxillary denture base. Materials and Methods: One hundred samples of heat cured acrylic resin maxillary denture base (Major base 2) were prepared and divided into two groups; Thermal cycling group and without thermal cycling group, each group contain; Control samples (10 samples of heat cured acrylic resin without additives) and modified samples (40 samples of heat cured acrylic resin with additives: 1% Chlorohexidine gluconate , 1.5% Nigella oil , 1.5% Thyme oil and 20% Plasticiz-er& caramel ). The thermal cycling employed in this study was 10 cycle per day at (5-55C°). The fitness accuracy measured after 70,300,900,1800 cycle at immersion periods of (1 week, 1,3,6 months) respectively. For fitness accuracy measurement , the surface area of the gap occurred between the posterior border of the maxillary denture base and the posterior margin of the stone cast were recorded by digital camera and measured with AutoCAD program . The collected data of fitness accuracy were subjected to the descriptive analysis(mean and standard deviation) , one way analysis of variance (ANOVA), 2 sample t-test and Duncan Multiple range test. Results: The fitness accuracy of thermal cycling group was less than that of without thermal cycling. For thermal cycling group, the highest value of fitness was achieved after 6 month of immersion for modified samples, while for control samples the highest value was achieved before immersion. Conclusion: Thermal cycling adversely affect the fitness accuracy of control and modified samples. The fitness accuracy of modified samples was better than that of control samples either with or without thermal cycling.

Aims : The aims of this study were to determine the effect of thickness and additives (Nigella Stavia oil and Thymol oil) on water sorption and solubility of heat cured acrylic resin denture base. Materials and Methods: Two types of heat cured acrylic resin Quayle dental resin and Major base2 were used. Two additive materials (0.5%) have been added to major base 2 which are(Nigella Stavia oil and Thymol oil). Water sorption and solubility of specimens were measured by mean of mass change in material after water saturation and dehydration. The specimens were prepared in three thicknesses (1mm, 2mm and 3mm). The effect of thickness on water sorption and solubility also has been measured. The data were analyzed using analysis of variance and Duncan's multiple range tests. Results: Increase thickness causes decrease in water sorption and solubility; Q.D has more water sorption and solubility than major acrylic resin. The two additives caused an increase in the water sorption and solubility of major acrylic resin denture base. Conclusions: The thickness and type of manufacturing materials added into acrylic resin played an important role in determining its water sorption and solubility.