Dental discoloration caused by bismuth oxide in MTA in the presence of sodium hypochlorite.
OBJECTIVE
The aim of this research was to analyse the dental discolouration caused by mineral trioxide aggregate (MTA) induced by bismuth oxide and also assess the colour stability of other dental cements.


METHODS
Bismuth oxide, calcium tungstate and zirconium oxide were placed in contact with sodium hypochlorite for 24 h after which they were dried and photographed. Phase analyses were performed by X-ray diffraction (XRD) of radiopacifiers before and after immersion in sodium hypochlorite. Furthermore, teeth previously immersed in water or sodium hypochlorite were filled with MTA Angelus, Portland cement (PC), PC with 20 % zirconium oxide, PC with 20 % calcium tungstate and Biodentine. Teeth were immersed for 28 days in Hank's balanced salt solution after which they were sectioned and characterized using scanning electron microscopy (SEM) with energy-dispersive mapping and stereomicroscopy.


RESULTS
Bismuth oxide in contact with sodium hypochlorite exhibited a change in colour from light yellow to dark brown. XRD analysis demonstrated peaks for radiopacifier and sodium chloride in samples immersed in sodium hypochlorite. The SEM images of the dentine to material interface showed alteration in material microstructure for MTA Angelus and Biodentine with depletion in calcium content in the material. The energy-dispersive maps showed migration of radiopacifier and silicon in dentine.


CONCLUSIONS
MTA Angelus in contact with a tooth previously immersed in sodium hypochlorite resulted in colour alteration at the cement/dentine interface.


CONCLUSIONS
MTA Angelus should not be used after irrigation with sodium hypochlorite as this will result in tooth discoloration.
Department of Dentistry, Dental School of Bauru, University of São Paulo - USP, Bauru, SP, Brazil.
Marina Angélica
MA
Marciano
Department of Dentistry, Dental School of Bauru, University of São Paulo - USP, Bauru, SP, Brazil.
Marco Antonio Hungaro
MA
Duarte
Department of Restorative Dentistry, Faculty of Dental Surgery, Medical School, University of Malta, Msida, MSD 2090, Malta. josette.camilleri@um.edu.mt.
Josette
J
Camilleri
D017607:Aluminum Compounds / Q000737:chemistry; D001729:Bismuth / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry; D003738:Dental Cements / Q000737:chemistry; D004338:Drug Combinations; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D012973:Sodium Hypochlorite / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D014075:Tooth Discoloration / Q000139:chemically induced*; D017973:Tungsten Compounds / Q000737:chemistry; D014961:X-Ray Diffraction; D015040:Zirconium / Q000737:chemistry
D017607:Aluminum Compounds; D017610:Calcium Compounds; D003738:Dental Cements; D004338:Drug Combinations; D010087:Oxides; D017640:Silicates; D017973:Tungsten Compounds; C086631:mineral trioxide aggregate; C018858:calcium tungstate; C033301:bismuth oxide; D015040:Zirconium; D012973:Sodium Hypochlorite; C028541:zirconium oxide; D001729:Bismuth
Bismuth oxide; Characterization; Discolouration; Interface; Sodium hypochlorite