جستجوی مقالات مرتبط با کلیدواژه « acrylic resin » در نشریات گروه « پزشکی »

Adding nanoparticles as filler aims to improve the mechanical properties of acrylic resin and reduce the incidence of fracture in them. This study aimed to investigate the effect of adding zirconium oxide and titanium oxide nanoparticles to acrylic resin on its flexural strength.

Methods and Materials:

 In this in-vitro study, surface modification of ZrO2 and TiO2 nanoparticles have been done by combining with silane coupling agent (trimethoxysilylpropyl methacrylate), and 25 samples of acrylic resin with 2.5*10*65 mm dimensions have been made. 5 groups were divided into control, 1 and 5% TiO2, 1 and 5% ZrO2. Flexural strength was evaluated by universal testing machine. Data were analyzed by One-Way ANOVA and Tukey's post hoc test. P < 0.05 was considered as statistically significant.

A significant increase in the flexural strength of acrylic resin modified with 1% zirconium oxide compared to the control sample was observed, with an average difference of 22.082 MPa (p<0.001). The difference in bending strength was significant between the control group and the groups containing nanoparticles (p<0.05). The highest and lowest bending strengths were found in the groups with 1% zirconium oxide, averaging 98.53±2.77 MPa, and 5% titanium oxide, averaging 61±1.52 MPa, respectively. There was a significant difference in flexural strength between the 1% and 5% zirconium oxide groups, with an average of 15.98 MPa (p<0.001). Additionally, there was no significant difference in flexural strength between the 1% and 5% titanium oxide groups, with an average of 4.16 MPa (p=0.06).

Based on the findings, ZrO2 nanoparticles improve and TiO2 nanoparticles weaken the flexural strength of acrylic resin. Also, by increasing the concentration of nanofiller, the mechanical properties of acrylic resin are weakened.

Dimensional stability of removable dentures in various disinfecting agents is considered an important and necessary property. The purpose of this study is to evaluate the dimensional stability of two types of heat-cured acrylic after immersion in distilled water, ozonated water and sodium hypochlorite solution.

In this in-vitro study, 60 disk-shaped samples were made, including 30 samples of Acropars heat cure acrylic resin and 30 samples of Pro Base heat cure acrylic resin. 30 samples of each acrylic were divided into three subgroups (n=10): 1) Immersion for 8 hours in distilled water (control group). 2) immersion for 8 hours in 1% sodium hypochlorite and 3) immersion for 8 hours in ozonized water. After every 8 hours, the solutions were changed and all samples were placed in disinfectant solutions for 16 weeks. Before and after immersion in each of the environments, the diameter of the samples was measured with an accurate micrometer with an accuracy of 1 micron. Finally, the obtained data were analyzed through appropriate statistical tests.

Results showed that the dimensional changes of Pro Base heat cure acrylic resin by immersion in any of the 1% sodium hypochlorite solutions, ozonated water and, distilled water are not significant, and the dimensional changes of Acropars (Iranian) acrylic resin are not also significant in each of these solutions. Therefore, both disinfectant solutions are suitable for disinfection of dentures.

After 16 weeks of immersion, the change in dimensions of heat cure acrylic resins in ozonated water is clinically acceptable, and according to the confirmation of the appropriate disinfection property of ozonated water in previous research and further studies, it can be suggested to the patients as a suitable disinfectant for disinfection of dentures.

Poly methyl methacrylate (PMMA) is still the most commonly used material in prosthetic dentistry. However, there are problems with the mechanical properties of this type of material including low flexural strength. Addition of nanoparticles into the polymer is one way to improve the mechanical properties of acrylic resin. In the present study, the effect of silicon dioxide (SiO2) nanoparticles addition into the heat-cured acrylic resin in different concentrations was investigated. Because of the controversy had been observed in previous articles, the aim of this study was to investigate the mechanical properties of PMMA/SiO2 nanoparticle obtained from different percentages of SiO2.

In this in-vitro study, acrylic resin specimens containing 0, 1, 3 and 5% silicon dioxide (SiO2) were prepared. The specimens were placed inside the gypsum molds and placed under pressure for three times. The mold cured in boiling water for 30 min. A trimmer was used to remove the additives. Sandpapers with 180, 320 and 600 grains of silicon-carbide were used for final finishing and polishing. Finally, the flexural strengths were measured using a universal testing machine. Data were finally analyzed by ANOVA and Tukey tests at a significant level of 5% using SPSS software.

The mean flexural strengths and standard deviations of control group, 1% filler, 3% filler, and 5% filler, were 57.24±8.30, 69.98±7.26, 60.16±9.18, and 61.59±9.28 MPa, respectively. After comparing significant values between each group with the control group, a significant difference was observed between the control and 1% filler group (P=0.021). However, no significant difference was observed between 3 and 5% fillers with the control group or each other. The significant differences (P-value) between 3% filler and control group were 0.892 and between 5% filler and control group was 0.975.

The results of the present study showed that the use of low percentage of silicone dioxide (SiO2) nanofiller could improve the flexural strength of poly methyl methacrylate acrylic resin.

Candidiasis is the most common fungal infection in oral cavity, usually caused by Candida albicans. Since one of the most common complications of denture wearing is denture stomatitis, presence of opportunistic microorganisms such as C. albicans and colonization of denture base by these microorganisms, the aim of this study was to compare the effects of three different methods of acrylic resin processing on adherence and colonization of C. albicans. In this experimental study, 60 square acrylic resin samples, measuring 10×10×10 mm3 (Ivoclar Vivadent, Liechtenstein) were processed with three methods of preparation: cold-cured [CC], heat-cured [HC] and injection-molded [IM]. Yeast suspensions were incubated on the surface of resin blocks for 40 minutes and then washed with 1 mL of sterile saline solution; 20 µL of this solution were inoculated on Sabouraud dextrose agar and incubated at 37 C. The colony counts were determined after 24 and 48 hours. At 60- and 120-minute intervals the colony counts were determined again. Data were analyzed with SPSS 20, using two-way ANOVA and paired t-test (α = 0.05). The method of preparation of acrylic resin (p value = 0.001) and duration of proximity of acrylic resin with the yeasts (p value < 0.001) were significant. The lowest colony counts were observed in the cold-cured method. In all these three methods and durations of proximity of acrylic resin and C. albicans, the colony counts at 48 hours were significantly higher than those at 24 hours (p value < 0.001). The acrylic resin preparation method affected the adhesion and colonization of C. albicans. Considering the lower colonization in cold-cured acrylic resin, it is the most appropriate acrylic resin, especially for those with poor oral hygiene or those susceptible to fungal infections.

Backgournd and aim: Transferring the implant position from the mouth to the definitive cast is one of the most critical steps in implant prosthodontics. The aim of the study was to compare The accuracy of casts obtained from three implant impression techniques.
In this experimental invitro study, One acrylic resin model with five implant analogs, was fabricated and three open tray techniques were tested: 1.non splinted (NS), 2.splinted with acrylic resin GC(S)& 3. Splinted, sectioned and rejoined with acrylic resin GC(SS). For each technique, five impressions with PVS (manoprane) were made. The positional accuracy of implant analogs on reference model and 15 casts, were evaluated using coordinate measuring machine. The statistical analysis of the data was performed with ANOVA and Duncan multiple range test.
there was a significant statistical difference (p≤0.01) between SS technique than NS and S techniques. And no significant differences were found between NS and S techniques.
Based on the results, the best accuracy of the definite casts was achieved when the impression copings were splinted with auto polymerized acrylic resin GC, sectioned and rejoined.

Using disinfectants for cleansing dentures is inevitable. Despite their favorable effect on reducing microorganisms, these chemical materials can cause undesirable effects on the surface of dentures. The aim of this study is to determine the effect of chemical disinfectant solutions on surface roughness of denture base materials. In this experimental in-vitro study, 50 acrylic resin specimens were fabricated from 2 different brands of Meliodent and Acropars. Samples were placed in four groups of solutions (sodium hypochlorite 0.5%, vinegar 2.5%, sodium bicarbonate 5% and Corega tabs). Control group was placed in normal tap water. Samples were evaluated for the initial and secondary surface roughness. One specimen from each group was coated in PVD procedure and was assessed with SEM. Data were analyzed using ANOVA and Post-hoc tests and multiple comparisons. The initial measurements revealed no significant difference between two acrylic materials regarding the studied features (P<0.4). The highest surface roughness in Meliodent group was observed in 0.5% sodium hypochlorite, which was significantly higher than other solutions (P<0.05). In Acropars group, the highest surface roughness was caused by 2.5% vinegar, which was significantly higher than other solutions (P<0.05). Corega tabs presented the least amount of surface roughness on both acrylic resin specimens (P<0.01). Results showed that the effect of disinfectant solutions on surface roughness of Meliodent acrylic is higher than Acropars and the least destructive effect was for Corega tabs. Usage of chlorinated solutions for disinfecting Meliodent acrylic and acidic solutions for Acropars is not recommended.

Several studies have evaluated the effect of microwave radiation on physical properties of acrylic resins. However، due to the recent introduction of heat-cure and cold-cure acrylic resins into the dental market and rapid popularity of cold-cure resins with less distortion in denture base، the present study sought to assess the effect of microwave disinfection on dimensional stability and flexural strength of two recently introduced heat-cure (Ivoclar) and cold-cure (FuturaGen) acrylic resins. In this laboratory study، acrylic models were fabricated of an edentulous maxillary model using Ivoclar and FuturaGen acrylic resins. Three reference points were marked on the model: two in the back and one in the front of the edentulous arch. These reference points were used for the measurement of dimensional stability in the anteroposterior and cross-arch dimensions. Ten specimens of each acrylic resin were not disinfected. Ten samples were subjected to two 3 min cycles of microwave disinfection with 600 watt power. Distances between the reference points were measured by a Profile Projector. To evaluate flexural strength، a metal mould measuring 64x10x3. 3 mm was used for the fabrication of resin specimens. Similar to what was done for dimensional stability testing، 10 specimens of each acrylic resin were not disinfected and 10 other samples were subjected to 3-point bending test after disinfection. Data were compared and statistically analyzed using Mann-Whitney U test. The mean difference in anteroposterior and cross-arch dimensions revealed that two cycles of microwave disinfection of Ivoclar and FuturaGen acrylic resins did not have a significant effect on their dimensional stability (P>0. 017). The mean and standard deviation of the flexural strength of FuturaGen acrylic resin before and after disinfection was 76. 86±16. 80 and 70. 18±8. 48، respectively. These values for Ivoclar acrylic resin were 85. 92±12. 23 and 81. 91±6. 59، respectively. Two cycles of disinfection with microwave did not cause a significant effect on flexural strength of the two understudy acrylic resins (P>0. 05). Two cycles of microwave disinfection had no negative effect on dimensional stability or flexural strength of FuturaGen and Ivoclar acrylic resins.