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Factors affecting the rate of oxidation and resultant discolouration of tetracyclines contained in endodontic medicaments and irrigants
Author(s) -
Bennett Z. Y.,
Walsh L. J.
Publication year - 2015
Publication title -
international endodontic journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.988
H-Index - 119
eISSN - 1365-2591
pISSN - 0143-2885
DOI - 10.1111/iej.12323
Subject(s) - chemistry , ascorbic acid , nuclear chemistry , tetracycline hydrochloride , chloride , strontium chloride , magnesium , calcium , inorganic chemistry , tetracycline , strontium , biochemistry , organic chemistry , food science , antibiotics
Aim To determine the effect of p H , oxygen levels and ions on tetracycline oxidation and resultant discolouration. Methodology Solutions of demeclocycline hydrochloride or doxycycline hyclate were prepared and exposed to different p H conditions, pure oxygen or carbon dioxide, ascorbic acid or various ions (from calcium chloride, calcium nitrate, strontium chloride, magnesium chloride, zinc chloride, and bismuth nitrate). Subsequently, they were exposed to intense visible blue light (470 ± 15 nm) for 24 h. Colour change was monitored using standardized digital photography. Parametric statistical analysis employing the W ilcoxon matched‐pairs signed‐rank test was performed to compare the mean change in different colour channels, assessing the discolouration effect of the modified conditions. Results An acidic p H reduced discolouration, whilst alkaline p H increased it. A higher oxygen tension resulted in more discolouration, as did the presence of calcium, strontium, and bismuth ions, all of which bind to tetracyclines. Conversely, zinc and magnesium ions had a mild photoprotective effect. Ascorbic acid, an anti‐oxidant, reduced the level of discolouration. Conclusions The tendency of these tetracyclines to undergo photo‐oxidation is increased by common variables present in the clinical environment. There are potential benefits from using photoprotectors and anti‐oxidants in these materials, to reduce the possibility of discolouration.