فهرست مطالب homayoun alaghehmand

Zinc oxide (ZnO) and graphene oxide (GO) nanoparticles (NPs) have antimicrobial properties. The present study was undertaken to evaluate the effects of incorporating these NPs and their chemical and physical blends on abrasion, translucency, and microhardness of flowable composite resin.

In the present in vitro study, flowable composite resin samples (Grandio Flow, VOCO, Germany) were evaluated in 5 groups and the sample size was 10 for each group of each experiment (n = 10) as follows: Group 1, without NPs; Group 2, with ZnO NPs; Group 3, with GO NPs; Group 4, containing a physical mixture of GO and ZnO; and Group 5, containing a chemical mixture of GO and ZnO NPs. In all the groups, 1 wt% of the NPs were incorporate into flowable composite resin. Abrasion, translucency, and microhardness of the samples were evaluated. Data were analyzed with analysis of variance, followed by post hoc Tukey’s tests at the level of significance of P < 0.05.

In Groups 2, 4, and 5 (all the groups containing ZnO), a significant decrease in abrasion and microhardness of flowable composite resin was observed compared to the control group. Incorporation of NPs in all the groups resulted in a significant decrease in translucency compared to the control group.

Incorporation of NPs into flowable composite resin resulted in a decrease in translucency. The microhardness was reduced in groups containing ZnO, but the abrasion was also reduced in these groups. The incorporation of GO did not significantly alter the abrasion and microhardness of the composite resin.

The use of dental ceramics has increased due to their beauty and biocompatibility. The aim of this study was to evaluate the effect of hydrofluoric acid concentration and etching time on microtensile bond strength (μTBS) of the Enamic and Suprinity ceramics. In this in vitro study, two hydrofluoric acid (HFA) concentrations of 5% (A) and 10% (B) were used at the time of 20, 60 and 120 seconds (s) on the Suprinity and  Enamic ceramics of CAD/CAM. The etched surfaces were impregnated with silane coupling agent as well as priming and Clearfil SE bond. Then, the Panavia F 2.0  resin cement was applied on the ceramic surfaces and light-cured. There were groups of EA20, EA60, EA120, EB20, EB60, EB120 for Vita Enamic and SA20, SA60, SA120, SB20, SB60, SB120 for Vita Suprinity. The μTBS between resin cement and porcelains was measured with universal testing machine. Mode of failure was observed under the stereo microscope at 40x magnification. Data were analyzed using ANOVA and Chi-square. The μTBS was significantly different between EB20 and EB60 (p=0.008), EB120 and EB20 (p=0.005), SA120 and SB120 (p=0.013), EA120 and EB120 (p=0.002) as well as EA60 and EB60 (p=0.44). In both ceramics, different concentrations and etching times had significant effect on the mean of μTBS (p=0.016). In both ceramics, the time had no effect on the failure mode. For Suprinity ceramic, the HFA concentration had effect on the failure mode (P=0.028). The best surface treatment for Suprinity ceramic is 120 s with 5% HFA and for Enamic is 20 s with 10% HFA, which create the highest bond strength.

Studies have suggested that sodium fluoride (NaF) has an inhibitory effect on the activity of endogenous matrix metalloproteinase enzymes. This study assessed the effect of a fluoride-containing adhesive on microtensile bond strength (µTBS) over time.
Material & In this experimental study, 36 extracted third molars were used to evaluate the µTBS of a 5th generation adhesive modified by NaF. The exposed dentin surfaces were abraded and built up using composite resin. Then, the specimens were randomly divided into three groups of 12 teeth based on the type of adhesive used: Solobond M with no inhibitor (control); Solobond M with 5,000 ppm NaF; and Solobond M with 10,000 ppm NaF. The µTBS and failure mode of specimens were evaluated after 24-hour and 3-month storage in distilled water. Data were analyzed using ANOVA and Tukey’s test. P<0.05 was considered as significant level. The control group demonstrated a lower µTBS than the experimental groups after 24 hours and 3 months (p<0.05). The µTBS was higher in adhesive with 5,000 ppm NaF than in control group after 3 months (p<0.05). The group with 10,000 ppm NaF had the highest µTBS after 24 hours and 3 months (p<0.05). The fluoride-containing adhesives showed significantly higher bond strength values than the original adhesive without fluoride after 24-hour and 3-month storage in distilled water, leading to the improvement of resin-dentin bonds

The aim of this study was to compare the discoloration potential of calcium-enriched mixture (CEM) cement, white mineral trioxide aggregate (WMTA) and calcium hydroxide (CH), after placement in pulp chamber. Methods and Materials: Access cavities were prepared in 40 intact maxillary central incisors. Then, a 2×2 mm box was prepared on the middle third of the inner surface on the buccal wall of the access cavity. The specimens were randomly assigned into four groups; the boxes in the control group were left empty, in groups 1 to 3, the boxes were filled with CH, WMTA and CEM cement, respectively. The access cavities and the apical openings were sealed using resin modified glass ionomer (RMGI). The color measurement was performed with a spectrophotometer at the following intervals: before (T0), immediately after placement of the filling material (T1), one week (T2), 1 month (T3), 3 months (T4) and 5 months (T5) after filling of the box and finally immediately after removing the material from the boxes (T6). Color change (ΔE) values were calculated using the sample Kolmogorov-Smirnov test to determine the normal distribution of data, followed by ANOVA, repeated measured ANOVA and post-hoc Tukey’s tests. All materials led to clinically perceptible crown discoloration after 1 week. The highest ΔE value belonged to WMTA group. Discoloration induced by CEM cement was not significantly different from CH or the control group (P>0.05). CEM cement may be the material of choice in the esthetic region, specifically pertaining to its lower color changing potential compared to WMTA.

One factor affecting the degree of polymerization is the type of light-curing device. The aim of this study was to compare the effects of LED and QTH light curing units on the surface hardness of composite and compomer. In this experimental study, 30 samples of composite and compomer were divided into 3 groups of 10 each. One-half of the subgroups in each group were cured with LED and the other half with Halogen light curing units (LCUs). 49 points on the surface were marked and then the hardness of these points was measured by using Vickers hardness test. The mean hardness of composites cured by using LED was more than the Halogen group but in compomer it was reversed and this difference was statistically significant (p<0.001). Z 250 composite had the highest level of hardness and the lowest hardness was related to the Heliomolar composite and had significant difference. (p<0.001) In the present study, the results indicated that LED light curing unit had great effect on the hardness of composites but in compomer, the QTH showed a better result.

Background and The use of bioactive glass-ceramics in medicine has been noticed because of their ability in directly connection to bony tissue and bone repairing. Chitosan is also nontoxic material and biologically is compatible with the capability of biodegradation. However, due to the minimally invasive nature of injectable systems and their ability to make scaffold in place of using, they can take the shape of bone defect and eliminate the need for fabricated implants. The aim of this study was evaluation of rat's connective tissue reaction to injectable glass-ceramic-chitosan nanocomposite; it looks to be a good substitute synthetic material in filling bone defects and its production is possible in Iran. In this animal study, 40 rats were divided into 5 groups of 8. Polyethylene tubes filled with glass-ceramic-chitosan nanocomposite as case group and the empty tube as control group were implanted in subcutaneous tissue of rats. Biopsy samples from case and control sites were histologically examined after 7, 15, 30, 60, and 90 days and the number of inflammatory cells and blood vessels were counted. T and analysis of variance (ANOVA) tests were used to examine differences at the significance level of P < 0.05. Overall, no significant differences in severity of inflammation and vessel counts were found between case and control groups on different days (P > 0.05 for all). It seems that injectable glass-ceramic-chitosan nanocomposite was biocompatible.

Previous researches showed that neutral soaps significantly increased bond strength and decreased microleakage of dentin bonding agents. The aim of this study was histopathological evaluation of the effect of sodium sulfonate application as neutral soap on the cat's dental pulp after an ideal composite restorative treatment.

Ten adult cats with 40 caries-free canine teeth were selected for the study. Class V cavities were prepared in the buccal surfaces of all the teeth. The teeth of the right quadrants were treated with composite, whereas the teeth of the left quadrants were primarily etched, after using of sodium sulfonate solution, they treated with composite. The first five cats were killed after one week and the other five cats after one month. The teeth were fixed, decalcified and after being sliced, paraffined blocks were made and microscopic slides were prepared and histologically evaluated.

The results of the histological evaluation showed that there were no statistically significant differences between the intensity of inflammation in the pulp of the teeth in the right and left quadrants after one week (p=1.000) and one month (p=0.773). However, there was significant difference after one week regarding predentin formation (p=0.017) and in the teeth of the left quadrants, the formation of predentin was more that the right quadrants, but no meaningful difference was observed after one month (p=0.203).

It seems that the sodium sulfonate in composite restorative treatments without fear of damage to the pulp can be used.

Low resistance of composite resins to abrasion is a primary concern in the application of these materials for posterior restorations which are prone to high occlusal loads. This study compared the wear resistance of three types of composites. In this laboratory experiment, five specimens of each of the three types of composites (z250, Heliomolar, Opallis) were prepared separately in brass molds. Composites were placed in 1-mm layers and were cured for 40 seconds. Using an abrasive device, Pedeb 1, with a chrome-cobalt abrasor, the specimens were abraded under a 20-MPa force, after 5000, 20000, 40000, 80000, 120000 abrasive rotations. Before and after all abrasion cycles, the specimens were weighed with an electronic balance with a precision of 10-4 g. The collected data were analyzed using paired samples statistics t-test and ANOVA analysis. All the specimens showed a reduction pattern from the initial weights to weights after 120000 abrasive rotations. With more abrasive rotations, greater weight reduction occurs and this is of statistical significance. ANOVA analysis showed no significant difference between the three types of composites; yet, the z250 and Heliomolar groups were associated with the least and the greatest amount of wear, respectively. In all specimens, significant weight reduction occurred after abrasion but there were no significant differences between the 3 types of composites.

The degree of polymerization depends on the type of light-curing unit. The aim of this study was to compare the hardness of composite resin cured by LED and Halogen light curing units. In this experimental study, 20 cylindrical samples of Tetric Ceram composite were prepared. Half of them were cured with Ultralume 2 LED and the other half with Astralis 7 Halogen light curing unit. In the depths of 0,1,2 and 3 mm from surface, one point in peripheral and one point in central portion were marked, then the hardness of these points was measured by Vickers test. The data was analyzed by a pvalue less than 0.05 considered as significant. The mean hardness of samples cured by LED was more than halogen group in different depths and this difference was statistically significant in peripheral points (p=.048) but this was not significant in central points (p=0.644). The mean hardness in both groups had a decreasing trend from surface to the deep parts in central and peripheral parts and this was more in the central parts. Composites cured by LED light curing unit showed more hardness in similar depths, besides the hardness of composites in central parts is more than the peripheral ones in both groups.