Background: Morphological structure of dental enamel-cement border of the 7th tooth is of great interest to many dentists with various different meanings. Study of the border of the 7th tooth allows the visual description of the morphological structure of this region. Objectives: To highlight the structure of dental enamel-cement border as well as its application in the endodontic treatment. Subjects and methods: The team used screening electronic microscopy to investigate the morphology and structure of twenty, second molar of adults who are between 18 and 35 year old. These teeth were extracted due to dental correction or caries (on chewing face). The study was conducted on both non-demineralized and demineralized teeth. Results: There are 3 kinds of connection in the enamel-cement border area of second molar: cement covering enamel, enamel-mineralized peridental ligament there is a gap between enamel and cement without exposing dentine. The kind of cement covering enamel connection is characteristic for dental interior face. The kind of enamel-mineralized peridental ligament is characteristic for the proximal, distal and middle dental face, the kind of enamel and cement without exposing dentine is characteristic for external face. Conclusion: Research conducted on only a small amount of tooth No. 7, further studies should be carried out on other teeth to have a more accurate description. \r\n', u'\r\n', u'
Morphological structure ; dental ; enamel -cement border of 7th tooth

BACKGROUND: Currently, it is recognized that water polluted with toxic heavy metal ions may cause serious effects on human health. Therefore, the development of new materials for effective removal of heavy metal ions from water is still a widely important area. Melanin is being considered as a potential material for removal of heavy metal from water. METHODS: In this study, we synthesized two melanin-embedded beads from two different melanin powder sources and named IMB (Isolated Melanin Bead originated from squid ink sac) and CMB (Commercial Melanin Bead originated from sesame seeds). These beads were of globular shape and 2-3 mm in diameter. We investigated and compared the sorption abilities of these two bead materials toward hexavalent-chromium (Cr) in water. The isotherm sorption curves were established using Langmuir and Freundlich models in the optimized conditions of pH, sorption time, solid/liquid ratio, and initial concentration of Cr. The FITR analysis was also carried out to show the differences in surface properties of these two beads. RESULTS: The optimized conditions for isotherm sorption of Cr on IMB/CMB were set at pH values of 2/2, sorption times of 90/300 min, and solid-liquid ratios of 10/20 mg/mL. The maximum sorption capacities calculated based on the Langmuir model were 19.60 and 6.24 for IMB and CMB, respectively. However, the adsorption kinetic of Cr on the beads fitted the Freundlich model with R values of 0.992 for IMB and 0.989 for CMB. The deduced Freundlich constant, 1/n, in the range of 0.2-0.8 indicated that these beads are good adsorption materials. In addition, structure analysis data revealed great differences in physical and chemical properties between IMB and CMB. Interestingly, FTIR analysis results showed strong signals of -OH (3295.35 cm) and -C=O (1608.63 cm) groups harboring on the IMB but not CMB. Moreover, loading of Cr on the IMB caused a shift of broad peaks from 3295.35 cm and 1608.63 cm to 3354.21 cm and 1597.06 cm, respectively, due to -OH and -C=O stretching. CONCLUSIONS Taken together, our study suggests that IMB has great potential as a bead material for the elimination of Cr from aqueous solutions and may be highly useful for water treatment applications.
Adsorption ; Chromium ; chemistry ; Kinetics ; Melanins ; chemistry ; Waste Disposal, Fluid ; methods ; Water Pollutants, Chemical ; chemistry ; Water Pollution, Chemical ; prevention & control ; Water Purification ; methods