title: Assessment of color stability of white mineral trioxide aggregate angelus and bismuth oxide in contact with tooth structure.
abstract: BACKGROUND
  Dental discoloration with use of materials containing bismuth oxide has been reported. It is postulated that the discoloration is a result of chemical interaction of bismuth oxide with dentin. The aim of the study was to analyze dental color alteration and the chemical interaction of bismuth oxide with the main components present in composite (methacrylate) and in dentin (collagen).
  
  
  METHODS
  Fifty bovine teeth were prepared and filled with white mineral trioxide aggregate (MTA) Angelus, Portland cement (PC) with 20% zirconium oxide, or PC with 20% calcium tungstate and then sealed with composite. Triple antibiotic paste and unfilled samples were the positive and negative controls, respectively. The specimens were stored in separate flasks immersed in tap water at 37°C with ambient light blocked out. The color assessment was performed with a spectrophotometer at different intervals, namely before filling and 24 hours, 15 days, and 30 days after filling. The color change and the luminosity were calculated. The statistical analysis was performed by using nonparametric Kruskal-Wallis and Dunn tests (P < .05). The interaction of the bismuth oxide, zirconium oxide, and calcium tungstate with collagen and methacrylate was assessed by placing the materials in contact, followed by color assessment.
  
  
  RESULTS
  The analysis of color change values showed that all the materials presented color alteration after the evaluated periods. Statistically higher luminosity was verified for PC/20% zirconium oxide in comparison with white MTA Angelus (P < .05). The teeth filled with white MTA Angelus demonstrated a grayish discoloration with evident dentin staining. Bismuth oxide exhibited a color change when in contact with collagen.
  
  
  CONCLUSIONS
  The color of white MTA Angelus was altered in contact with dental structures. Collagen, which is present in dentin matrix, reacted with bismuth oxide, resulting in a grayish discoloration. The use of an alternative radiopacifier to replace bismuth in white MTA is indicated.
authors: Department of Restorative Dentistry, Dental Materials and Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil. Electronic address: marinangelica@usp.br.
authors: Marina Angélica
authors: MA
authors: Marciano
authors: Department of Restorative Dentistry, Dental Materials and Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil.
authors: Reginaldo Mendonça
authors: RM
authors: Costa
authors: Department of Restorative Dentistry, University of Malta, Msida, Malta.
authors: Josette
authors: J
authors: Camilleri
authors: Department of Restorative Dentistry, Dental Materials and Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil.
authors: Rafael Francisco Lia
authors: RF
authors: Mondelli
authors: Department of Restorative Dentistry, Dental Materials and Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil.
authors: Bruno Martini
authors: BM
authors: Guimarães
authors: Department of Restorative Dentistry, Dental Materials and Endodontics, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil.
authors: Marco Antonio Hungaro
authors: MA
authors: Duarte
mesh_terms: D000818:Animals; D001729:Bismuth / Q000737:chemistry / Q000494:pharmacology*; D017610:Calcium Compounds / Q000737:chemistry / Q000494:pharmacology; D002417:Cattle; D003094:Collagen / Q000187:drug effects; D003116:Color; D003188:Composite Resins / Q000737:chemistry; D003624:Darkness; D003738:Dental Cements / Q000494:pharmacology*; D003764:Dental Materials / Q000737:chemistry; D003804:Dentin / Q000187:drug effects*; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D010087:Oxides / Q000494:pharmacology*; D011897:Random Allocation; D012387:Root Canal Filling Materials / Q000494:pharmacology*; D017640:Silicates / Q000737:chemistry / Q000494:pharmacology; D013053:Spectrophotometry / Q000295:instrumentation; D013696:Temperature; D013997:Time Factors; D014075:Tooth Discoloration / Q000139:chemically induced*; D017973:Tungsten Compounds / Q000737:chemistry / Q000494:pharmacology; D014867:Water / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry / Q000494:pharmacology
chemical_list: D017610:Calcium Compounds; D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; C475480:MTA-Angelus; D008689:Methacrylates; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; D017973:Tungsten Compounds; C479082:natural flow composite resin; D014867:Water; D003094:Collagen; C018858:calcium tungstate; C033301:bismuth oxide; D015040:Zirconium; C028541:zirconium oxide; C031293:calcium silicate; D001729:Bismuth
keywords: Bismuth oxide; spectrophotometry; tooth discoloration; white MTA