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The complementary techniques of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy have confirmed that alternate exposure of the teeth to the antibacterial agents sodium hypochlorite and the calcium-chelating agent EDTA (ethylene diaminetetracetic acid) deplete the organic content of dentine and so seriously degrade the teeth. C. Ramirez-Bommer, Kishor Gulabivala, José Antonio Poli de Figueiredo, and A. Young of the Unit of Endodontology, in the UCL Eastman Dental Institute at University College London hoped to characterize the changes in the chemical composition of dentine - the the inner structure and the bulk of the tooth which is not usually visible in the mouth - obtained from samples of extracted molars exposed to a common endodontic antibacterial treatment after root canal work. Qualitative measurements have been carried out previously, but this is the first time quantitative measurements have been used to investigate the physical and chemical changes caused by the treatment. The researchers used FTIR to record spectral lines for collagen, carbonate, and phosphate content and to compare the levels of these materials before and after treatment of the samples with sodium hypochlorite solution (2.5%) and EDTA. Sodium hypochlorite and EDTA are commonly used as an endodontic antibacterial treatment. The team found that the two solutions NaOCl and EDTA used alternately raised collagen or phosphate peaks in the dentine and that the effect depended strongly on the final solution used. The team found that the collagen peak at 1640 cm-1 when they exposed dentine particles to NaOCl and the 1010 peak cm-1 due to phosphate, both decreased after exposure to EDTA. They could use the relative phosphate-collagen peak heights to determine the fraction of phosphate lost from the dentine over time due to EDTA exposure. "Sodium hypochlorite depleted the surface organic content of dentine rapidly within the first two minutes [of exposure] and steadily thereafter exposing a phosphate-rich surface," the researchers say, "EDTA depleted the inorganic content continuously over a longer period of time, leaving a collagen-rich surface." The results indicate that used alternately, the solutions progressively degrade the dentine structure. "Dentine is made up of organic material which is dissolved by bleach and mineral material which is dissolved by EDTA," Gulabivala explains, "Using the two alternately, gradually erodes the structure from the exposed surface. Using just bleach, the surface erosion is self-limited and whilst the same should apply with EDTA, the results did not confirm this in the present study design." He adds that, "This is only a problem if dentists use these solutions at high concentration for long periods and alternate continually. In reality, EDTA is usually only used as a final wash by most dentists. The research showed that continual alternation, sometimes recommended, may not be a good idea." Related links:
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