Surface microhardness of three thicknesses of mineral trioxide aggregate in different setting conditions

OBJECTIVES: This study aimed to compare the surface microhardness of mineral trioxide aggregate (MTA) samples having different thicknesses and exposed to human blood from one side and with or without a moist cotton pellet on the other side. MATERIALS AND METHODS: Ninety cylindrical molds with three heights of 2, 4, and 6 mm were fabricated. In group 1 (dry condition), molds with heights of 2, 4, and 6 mm (10 molds of each) were filled with ProRoot MTA (Dentsply Tulsa Dental), and the upper surface of the material was not exposed to any additional moisture. In groups 2 and 3, a distilled water- or phosphate-buffered saline (PBS)-moistened cotton pellet was placed on the upper side of MTA, respectively. The lower side of the molds in all the groups was in contact with human blood-wetted foams. After 4 day, the Vickers microhardness of the upper surface of MTA was measured. RESULTS: In the dry condition, the 4 and 6 mm-thick MTA samples showed significantly lower microhardness than the 2 mm-thick samples (p = 0.003 and p = 0.001, respectively). However, when a distilled water- or PBS-moistened cotton pellet was placed over the MTA, no significant difference was found between the surface microhardness of samples having the abovementioned three thicknesses of the material (p = 0.210 and p = 0.112, respectively). CONCLUSIONS: It could be concluded that a moist cotton pellet must be placed over the 4 to 6 mm-thick MTA for better hydration of the material. However, this might not be necessary when 2 mm-thick MTA is used.

study of DNA methylation of bax gene promoter in breast and colorectal carcinoma cell lines

The Bcl-2 protein family members have known as essential controllers of mitochondrial pathway of apoptosis. Bax is a proapoptotic member of Bcl-2 protein family, which is well known to play crucial roles for apoptosis control. bax has been implicated as potential tumor suppressor in certain solid tumors such as breast and colorectal carcinoma. DNA methylation of promoter associated CpG islands has known as a common mechanism for gene inactivation in tumor cells. The Methylation Specific PCR [MSP] has used to find the methylation profile of the bax gene promoter CpG islands in colorectal and breast cancer cell lines. We have not detected any kind of "CpG islands hyper methylation" in promoter region of the bax gene in T47D, MCF7 [as ER positive], MDA-MB-231 and MDA-MB-468 [as ER negative] breast carcinoma-derived cell lines and colorectal cancer cell lines H29 and Caco II. It seems that CpG island methylation could not play the main role in down-regulation of bax gene in breast and colon cancers