[Effect of disinfectant solutions on surface roughness of heat cure denture base acrylic resins]

During infection control process, disinfection of prosthesis is important. But disinfecting method can cause some changes on dentures surface. The aim of this study was to evaluate the effect of disinfectant agents on surface roughness of denture base materials. In this study two chemical disinfectants [sodium hypochlorite 0.5%, glutaraldehyde 2%] and two dentures resin materials [Acropars, Meliodent] were used. 40 acrylic resin samples were made. Changes from baseline for surface roughness at four different times [10 minutes, 30 minutes, 24 hours and 7 days] were recorded. ANOVA and Duncan and T-test analysis compared the mean surface roughness of the groups. Mean variation of surface roughness for Acropars resin in sodium hypochlorite and glutaraldehyde at 24 hours and 7 days was significant [P<0.001]. This variation for Meliodent resin 7 days after immersion in hypoclorite 0.5% was significant [P<0.001]. Mean variation of surface roughness for Meliodent resin in glutaraldehyde was not significant for the time of the study. Mean surface roughness difference among Meliodent and Acropars resin in glutaraldehyde and sodium hypochlorite after 10 minutes and 24 hours was significant [P<0.001]. The difference between these two acrylic resin after 7 days in gluteraldehyde was also significant [P<0.001]. Result of this study indicated sodium hypochlorite 0.5% and glutaraldehyde 2% can be used on Acropars only up to a period of 30 minutes. Sodium hypochlorite 0.5% can be used on Meliodent for 24 h. However gluteraldehyde 2% can be used for a longer period

[Antifungal and antibacterial effect of eucaliptus oil added to tissue conditioner]

Contamination of soft denture lining materials and tissue conditioners with microorganisms is a common clinical problem. The aim of the study was to determine the effect of adding eucalyptus [E] oil to viscogel tissue conditioner against bacterial and fungal growth on it. In this experimental study MIC [Minimum Inhibitory Concentration] of E. oil against Candida albicans and Staphylococcus aureus was determined, then experimental specimen disks [diameter, 15mm, thickness: 2mm] with the amount of 1MIC, 2MIC and without E. oil were fabricated under aseptic conditions. The samples were divided to 11 groups; each group contained 5 samples. One group was considered as control. The samples immersed into 1 ml of saline. After 24 hours 1ml of bacterial or fungal suspension with BHI broth medium was added. The growth of microorganisms was investigated after another 24 hours. This test was done for the samples at the concentration of 2 MIC of E. oil. The data were analyzed with Fisher's exact test. The samples which were mixed with 1 MIC of E. oil showed antimicrobial effect in comparison with the controls [P= 0.024] after 72 hours. Samples of 2 MIC didn't show a significant inhibitory effect against S. aureus [P=0.08] after 24 and 48 hours, but this effect was significant against C. albicans after 24h [P=0.024] and 48h in comparison with control samples [P=0.004]. Addition of Eucaliptus oil significantly reduced the growth of microorganisms. The study showed that Eucaliptus oil leached out of tissue conditioner in 72 hours which is too short for clinical usage

[Evaluation of disinfecting effect of 0.5% sodium hypochlorite and 2% glutaraldehyde on heat-cure acrylic resin]

Disinfection of dental prostheses is important, so determining an appropriate disinfectant and the effective time for disinfection is necessary. The aim of this study was to evaluate of the disinfecting effect of 0.5% Sodium hypochlorite and 2% Glutaraldehyde on heat cure acrylic resin contaminated by two types of bacteria. In this experimental and In vitro study 90 acrylic resin samples, 6mmx17mm, were made using Acropars acrylic resin. The sterilized samples were divided into two groups. One group was exposed to a microbial suspension containing Streptococcus viridance and the other was exposed to a microbial suspension containing Bacillus subtilis. Two negative controls not contaminated with barteria were considered. Two samples from each group were used as the positive controls and were not disinfected. Each group was divided into two subgroups. The subgroups were immersed in either 2% glutaraldehyde or 0.5% sodium hypochlorite. After 30 min, 2h and 4h, seven samples were removed from each solution and transferred to individual tubes containing Brain Heart Inpusion [BHI] culture medium. The tubes were incubated for 24h at 37°C and then examined for turbidity. A sample of each tube was plated onto blood agar plate and the results were observed after 24h. Statistical analysis was made by Chi-Square tests [Fisher's exact test] and Kendalls tau-b. The difference between 3 time interval in all samples for hypochlorite solution [P=0.057] was not significant but it was significant for glutaraldehyde [P=0.021], Comparing 3 time intervals in the samples contaminated with Bacillus subtilis for hypochlorite solution [P=0.032] and glutaraldehyde [P=0.014] showed significant difference. The analysis was not made for Streptococcus viridance because all the results were negative. The difference between the disinfecting ability of the solutions after 30 min [P=1] and 2h [P=0.266] was not significant. The results indicate that both disinfecting solutions eliminated Streptococcus viridance after 30min but could not eliminate Bacillus subtilis until 4h immersion time. Within the number of the samples in this study there was no difference between the disinfecting ability of 0.5% sodium hypochlorite and 2% glutaraldehyde

effect of surface coating on softness of two kinds of tissue conditioners

One of the limitations of tissue conditioners [TC] is gradual hardening of the material in a short time period after insertion in the mouth, due to the loss of their viscoelastic properties. The aim of this study was to determine the softness of two different tissue conditioners with and without the Monopoly coating. In this experimental study, Acropars and Viscogel tissue conditioners were examined. Ten samples of each tissue conditioner were prepared, using 3x20 mm [hxd] aluminum cylindrical molds. Half of the samples in each group were coated with Monopoly coating. Samples were kept in a water bath at 37 degree C and the hardness of their surfaces was measured [in Shore-A] after 1, 3, 7, 14, and 28 days. The results were analyzed using t-test, Multivariant ANOVA and Tucky posthoc test. There were significant differences in hardness [P < 0.05], comparing, the coated and uncoated Acropars [p=0.000], the coated and uncoated Viscogel [p=0.000], the coated Acropars and uncoated Viscogel [p=0.000], the coated Acropars and coated Viscogel [p=0.036], and the uncoated Acropars and coated Viscogel [p=0.000] samples. It was found that the hardness of all of the samples increased with time. For both tissue conditioners, the hardness of samples with coating was higher than of those without coating. This indicates that the Monopoly coating does not protect the softness of these two tissue conditioners

comparison on dimensional changes of two irreversible hydrocolloid impression materials disinfected by immersion in sodium hypochlorite solution

One of the most important problems in disinfecting alginate impressions is the dimensional changes caused by hydrocolloid nature of alginate. The aim of this study was to determine and compare the dimensional changes of two irreversible hydrocolloid impression materials [Iralgin -Alginoplast] disinfected by immersion in sodium hypochlorite solution. One metal model consisting of one platform and two partial conical dies was made and 80 impressions were then prepared using two kinds of alginate impressions materials. The impressions were divided into four groups. In groups 1 and 3, impressions were first rinsed for 15 seconds and immersed in 0.525% sodium hypochlorite solution and finally were poured by type 111 dental stone. In groups 2 and 4, impressions made by these two materials were only rinsed by tap water for 15 seconds and kept in 10% moisture for another 10 minutes and then were poured by type III dental stone. Different dimensions of samples in four groups were measured by digital caliper and compared using variance analysis and Duncan tests. Diameters, heights and outer distances of all samples showed significant differences with the metal model [P=0.049], however; inner distances did not have any significant difference [P=0.269]. Moreover, significant differences, in diameter and height, were found between case and control groups. In all four groups, diameters and outer distances increased and heights decreased compared to the metal model which are in agreement with the similar studies. All such changes were estimated less in Iralgin than Alginoplast

[Comparing the effects of using standard die-spacer and shellac on the retention of fixed prosthesis]

The application of die- spacer to crown preparation dies prior to the fabrication of cast crowns is an acceptable procedure that improves the fit of the restorations. Previous studies have shown that the retention of the restoration will be improved, unchanged or reduced when an appropriate thickness of die- spacer is used. But in our country shellac is used instead of die- spacer. No study has compared the effect of using standard die-spacer and shellac on the retention of fixed prosthesis. This study compares the effect of using these two materials on the retention of fixed prosthesis. Ninety eight cast copings were fabricated on dies coated with die-spacer and shellac, cemented on the dies and removed using an Instron Universal Testing Machine. T-test showed that there is statistically significant difference between the mean force required to remove crowns relieved with die- spacer and relieved with shellac. With regard to some practical difficulties in application of shellac and the results of this study; it appears that application of die-spacer is better than shellac