Table 6 showed Vickers hardness numbers (VHN
) measured at different areas on the typical specimens, where [H.sub.S], [H.sub.N], and [H.sub.C] were VHN
obtained at surface and near surface at various depths, respectively.
Investment 120321.526 4 30080.381 18.581 < .001 Depth 3480275.573 5 696055.155 429.962 < .001 Interaction 75599.325 20 3779.966 2.335 .002 Error 202359.629 125 1618.877 Total 18294443.51 155 Table 6--Mean, standard deviation and contrast of Vickers hardness (VHN
Table 1: Composition of composite test samples Sample Composition Hardness No No(VHN
) 1 Al7075 alloy+2% of 84 Zircon+3% [Al.sub.2][O.sub.3] 2 Al7075 alloy+2% of 99 3 Al7075 alloy+2% of 91 Zircon +7% [Al.sub.2][O.sub.3] 4 Al7075 alloy+2% of 110 Zircon +9% [Al.sub.2][O.sub.3] Table 2: Hardness Values of test samples Al Zircon Aluminium Samples 7075 (%) Oxide (%) (%) Sample 1 95 2 3 Sample 2 93 2 5 Sample 3 91 2 7 Sample 4 89 2 9 Table 3: Tensile Strength Values of test samples Sample Composition Tensile Elongation % No.
The values measured at the top were considered as 100% and the values measured at 4mm distance were expressed as percentage of the value and were obtained from the following equation:%VHN=bottom VHN/TOP VHN
Filtek Z250 had the highest VHN
(97.6 +- 2.8 MPa), while the lowest value was recorded with Tetric EvoCeram (55.3 +- 2.9 MPa).
Although Chlorhexidine was shown to cause a statistically significant increase in the bond strength of adhesive materials to root dentine38, the mild increase or decrease of VHN
in this study found to be significant and could be attributed to the localized in dentine microhardness13.
Figure 1 shows that after the first immersion in cola drink for 2 minutes, 3 times per day for 3 days, the microhardness values sharply decreased by a mean of 120 VHN
; a 33% reduction from baseline which was highly significant (p < 0.01).
On one quadrant, the baseline (0 day) Vickers hardness number (VHN
) was measured and the remaining 3 quadrants were used for microhardness assessment after the various immersion periods of 2 days, 7 days and 21 days.
For each sample, 3 indentations were performed and the mean VHN
value was recorded.
Table-III: Means (SD) for Vickers micro-hardness (VHN
) values among study groups before and after ageing using ANOVA and Tukey multiple comparisons test.
The hardness for this section of the in-service operation specimen was 453 VHN
in comparison to 452 VHN
for the specimen with first treatment.
This study evaluated the cytotoxicity, microhardness (VHN
), surface roughness (Ra), and surface morphology of RMGICs with the addition of benzalkonium chloride (BC), cetylpyridinium chloride (DP), hexadecyltrimethylammonium bromide (CE), or silver nanoparticles (AgNP).