[ effect of porcelain veneer and coloring pigments on microtensile bond strength of a zirconia ceramic]

The bond strength between veneer ceramics and zirconia frameworks is the weakest component in the layered ceramics. Due to the possible effect of adding pigments to the core materials on the bond strength between core and veneer as well as the introduction of new ceramic materials in dentistry, the aim of this study was to compare the zirconia core-veneer microtensile bond strength using two ceramic veneers with or without coloring the core. In the experimental study, 12 disc-shaped specimens were fabricated using a manually aided design- manually aided manufactured [MAD/MAM] zirconia core [Zirkonzahn]. Two veneering ceramics of Ceram Kiss and Zirkonzahn ICE were also used to veneer the specimens. Half of the zirkonzahn discs were remained white and the others were colored by shade A2. Then, the discs were cut into microbars [30 for each group] and the microtensile bond strength of the core-veneer was calculated. The specimens were assessed using scanning electron microscopy [SEM] and the data were analyzed using two-way ANOVA and Student's t-test. Significant differences with respect to veneer layer were found [P<0.001]. No significant differences were seen among colored and uncolored cores [P=0.69]. According to the apparent effect of veneering ceramics on the core-veneer bond strength, careful selection of these agents is essential to achieve adequate bond strength between core and veneer to prevent delaminating and chipping failures of zirconia veneered restorations

Evaluation of solubility of modelling plastic in contiguity of ethanol and plasticizer

In patients with complete denture, some clinicians have used modelling plastic impression compound [MPIC] along tissue conditioner [TC] materials simultaneously. Little information is available on the composition of these materials and the interaction between them. The purpose of this study was to evaluate the influence of two components of MPIC on the structure and chemical composition of TC. In this experimental study, MPIC specimens were provided in 25x2 mm discs. Specimens were randomly divided into three groups and were immersed in ethanol 70%, plasticizer [dibutyl phthalate] and a mixture of them [ethanol 70% and dibutyl phthalate]. All of the discs were weighed with a digital balance before and 2, 4, 6 and 24 hours after immersion. Values were analyzed by non parametric Kruskal-Wallis [alpha= 0.05] and SPSS 16 for Windows [SPSS Inc., Chicago, IL] was used for statistical analysis. Statistical analysis indicated significant differences among all groups [p>.05]. Dibutyl phthalate [DBP] had high impact on the solubility of MP, while the mixture of dibutyl phthalate [DBP] and ethanol demonstrated the highest impact

Evaluation of various characteristics of Plastalgin alginate according to International ISO Standards and ADA specifications

Alginate is one of the most widely used impression materials in dentistry. Currently, a variety of alginates are available on the market. Quality control should be performed for all dental materials used in Iran. The aim of the present study was to evaluate several parameters of Plastalgin alginate [Made in France] according to the currently valid international standard for dental alginate impression materials. The studied parameters were: working time, setting time, compressive strength, permanent deformation and strain in compression. All factors associated with packaging were also evaluated. All tests were performed in accordane with ISO or ADA standards and 6 specimens were employed for each test. The working time of Plastalgin was within standard limits and the mean setting time was found to be 2 minutes and 28 seconds. The strain in compression, permanent deformation and mean compressive strength was 7/35%, 3/25% and 0/74 Mpa, respectively. Our findings did not confirm the information listed on the Plastalgin[R] packages. The investigated parameters were in accordance with ISO standards, except for permanent deformation. Our findings did not correspond with the information written on the packages. Further studies are required to determine the properties of this material

Comparison of some properties of four provisional restorations resin: Trim, Tempron, Acropars TRII and Duralay [Aria Dent]

Use of provisional restorations is one of the important phases in the treatment of patients who need fixed prosthesis. Some physical properties are required for these materials. The purpose of this study was the comparison of some physical properties of 4 kinds of resins: Trim, Tempron, Duralay [Aria Dent] and Acropars TRII. In this experimental study, transverse-strength [TS], setting time [ST], polymerization shrinkage [PS] and temperature rise [TR] during polymerization were tested. In transverse strength test, 5 samples of each resin were made. TS testing was done with an Instron testing machine. ST testing [5 samples in each group] was done with Gilmore needle. In PS test, 11 cylindric samples were prepared from each resin and the shrinkage was examined with digital micrometer [up to 24 hours]. In TR test, after mixing the powder and liquid of resins [8 samples in each group], the temperature rise was recorded with 10 seconds interval [up to 15 minutes]. Data were analyzed with one-way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance. In TS test, all samples of Trim were bent and no fracture was observed, while Tempron and Duralay showed no significant difference. Both Tempron and Duralay revealed high significant difference with Acropars TRII [P <0.01]. In ST test, the difference between groups was significant [P<0.01]. The lowest ST was observed in Acropars TRII [7 min], and the highest in Tempron [9.53 min]. In PS test, significant difference was observed between Trim and Acropars TRII [P<0.01]. PS was completed after 120 min in Tempron and Trim groups. However, PS continued to increase in other groups. In TR test, the difference between groups was significant [P<0.05]. Duralay showed the highest TR and the lowest was seen in Trim. In this study, Trim showed better properties than other studied groups. Acropars TRII had the lowest strength. The highest temperature rise was recorded for Duralay and Tempron, respectively

comparison flow of four impression compounds [green stick] with ADA standard

Statement of Problem: Low- fusing compound [type 1] is used for border molding and impressions. Flow and reproducibility of surface detail are two important characteristics of these materials. There are no valid data available comparing domestic and imported brands

Purpose: The Purpose of this study was to evaluate these two properties of four different products including Kerr [Kerr Manufacture MI 98174-2600], Harvard [Hoffman Harvard Dental GMb H Germany]; Kymia [Kymia dental company 713 Iran]; and Pishro [Pishro 72534 Iran]

Materials and Methods: All procedures were followed according to ADA and BS Standard. Total number of 48 samples were divided into 8 groups [6 in each group]. Twenty disks were fabricated for impression tests. The specimen dimensions were 40 mm [diameter] and 6mm [thickness]. Standard test blocks were used to test the specimens

Results: The Willcoxon test showed significant difference in flow rate between materials tested with the best result for Kerr [P<0.05]. Kerr flow was 85% and under 5% at 45°C and 37°C, respectively. There were great deviations from standards value at 45°C. For the rest of the samples at 37°C; except Kymia the flow rate for 3 materials [Kerr; Harvard Pishro] were almost acceptable. The impression test results revealed that only Kerr was able to record the details at 45°C

Conclusion: Kerr flow is exactly what ADA standards specify. But the flow rate for three materials exhibit a great distance from these standards. In impression test only Kerr was able to record the details