Background and Aims: The purpose of this in vitro study was to assess the effect of two different surface treatments on the contrast ratio of IPS Emax press ceramic submitted to ACCELERATED AGING.Materials and Methods: Ten ceramic (IPS Emax press) disks (10-mm diameter and 1.5-mm thick) were fabricated according to the manufacturer’s recommendations. The samples were randomly divided into 2 groups (n=5): polishing and glazing. Contrast ratio ware obtained with a spectrophotometer before and after ACCELERATED AGING. The contrast ratio (CR=Yb/Yw), defined as the ratio of illuminance (Y) of the test material when it is placed on the black background (Yb) to the illuminance of the same material when it is placed over a white background (Yw), was determined. The data were statistically analyzed by two-way analysis of variance (P<0.05).Results: All specimens of IPS Emax press ceramic showed significant increase in CR after 300-hour ACCELERATED AGING time (P=0.005). Polished samples showed significantly higher opacity compared with that of the glazed ones (P=0.018).Conclusion: Within the limitations of this study, it may be concluded that the glazed specimens showed more stability in their translucency than the polished specimens.

Introduction: Discoloration is one of the most common reasons for replacement of resin composites. The purpose of this study was to compare the color stability of three Methacrylate-based Resin Composites (Filtek Z250, Filtek Z250x, Filtek Z350xt) with Silorane-based Resin Composites (Filtek P90) after ACCELERATED Artificial AGING (AAA).Materials & Methods: In this in vitro study 56 composite discs were prepared (N=14). CIE L*a*b* parameters of each specimen were measured by a reflectance spectrophotometer after 24h and 384 h of AAA. Then Color change (DE) of each composite was calculated. Data were analyzed by one way ANOVA, Tukey and paired t-test at the significance level of 0.05.Results: DE values of Filtek Z250, Filtek Z250x, Filtek Z350xt and Filtek P90 were 7.77, 5.86, 8.95 and 8, respectively. One way ANOVA demonstrated a significant difference between DE values of composites (P˂0.001). Tukey’s test revealed that DE value of Filtek Z250xt was significantly lower than those of other composites (P˂0.05).Conclusion: Silorane and methacrylate based composites showed a color change more than the clinically acceptable level (DE˃3.3) after AAA. Filtek Z250xt showed the lowest color change and other composites showed relatively similar color change.

Vigor of seed often decreases under AGING conditions. This experiment aimed to evaluate germination indices and enzyme activity under ACCELERATED AGING condition in canola (Brassica napus). To accelerate AGING, seeds were imposed to different AGING periods of 0, 2, 4, 6 and 8 d at 41oC in sealed AGING boxes. Standard germination test was carried out at 20oC for 7 d in three replications of 50 seeds. Results showed that germination of deteriorated seed was reduced. Eight days deterioration had the most influence on the germination indices. The highest germination indices were attained under 0 d AGING. Also our results showed that catalase and ascorbate peroxidase activities decreased under ACCELERATED AGING.

The oil-impregnated dielectric papers are the main components of distribution transformer which govern its service time. Therefore, durability enhancement of this grade of paper will cause to extend transformers life. In this research, long fiber unbleached Kraft pulp and its mixture with bagasse soda pulp at the ratios of 20% to 80% were used to make oil-impregnated dielectric papers with the grammage of 60 g/m2. The effect of dicyandiamide impregnation and its content in the paper structure and thermal AGING were then assessed on dielectric properties and tensile strength of the insulation papers. The results showed that with increasing dicyandiamide content, the capacitance and tensile strength index decreased in comparison with untreated samples, but dielectric loss, insulation resistance, and breakdown voltage were improved. However, slight changes were observed in most dielectric properties during AGING, but dicyandiamide caused to prevent loss of the tensile strength of insulated papers. Generally it could be concluded that dicyandiamide acts efficiently in thermal stabilization of insulation paper exposed to aggressive conditions inside the oil-filled transformer.

Objectives: Color change of cements over time can be detected through translucent ceramic veneers, compromising the aesthetic appearance of restorations in the long-term. This study aimed to assess the color stability of ceramic laminate veneers cemented with self-adhesive resin cements after ACCELERATED AGING. Materials and Methods: In this study, 21 IPS e. max ceramic discs, measuring 8mm in diameter and 0. 7 mm in thickness, were fabricated and divided into three groups (n=7) for the application of Choice 2 total-etch light-cure resin cement, RelyX U200 dual-cure self-adhesive resin cement, and SpeedCEM self-cure self-adhesive resin cement. The ceramic discs in each group were cemented on the prepared facial surface of bovine teeth. The color parameters were assessed using a spectrophotometer. Subsequently, the samples were subjected to ACCELERATED AGING for 100 hours, and the color parameters were measured again. The data were analyzed using two-way repeated-measures analysis of variance (ANOVA) and Tamhane’ s post-hoc test (P<0. 05). Results: AGING significantly affected the ceramic laminate color parameters in all three groups (P<0. 05). SpeedCEM cement showed the lowest color stability (Δ E=4. 2) after AGING, and its color change was clinically unacceptable (Δ E>3. 5). The color change of the other two groups was clinically acceptable (1<Δ E<3. 5). Conclusion: The self-adhesive dual-cure cement showed color stability comparable to that of the total-etch light-cure cement for cementation of IPS e. max ceramic laminates. The color stability of both cements was superior to that of the self-adhesive self-cure cement.