Discoloration of White Mineral Trioxide Aggregate Immersed in Endodontic and Restorative Treatment-related Solutions

<p> Purpose: Tooth color change is sometimes caused by discoloration of white mineral trioxide aggregate (WMTA) used for direct pulp capping and perforation repair. However, a few studies have performed detailed analyses regarding its discoloration including color tone and penetration. Therefore, this study aimed to examine the discoloration pattern of WMTA treated with endodontic and restorative treatment-related solutions.</p><p> Methods: WMTA powders were mixed with distilled water (DW) in a 3 : 1 powder/liquid ratio. The mixture was placed inside polypropylene molds to form WMTA disks. These disks were treated with DW, sodium hypochlorite solution (NaClO), ethylenediaminetetraacetic acid solution (EDTA), hydrogen peroxide solution (H₂O₂), bonding agent (BOND), blood (BLOOD), typeⅠ collagen solution (COL1), and iodine solution (JG). After 1, 7, and 14 days, the disks were observed with a stereoscopic microscope and their color was analyzed by a spectrophotometer. Additionally, they were dissected at their center and the dissected surfaces were observed with the stereoscopic microscope. Additionally, bismuth oxide powders were also treated with DW, NaClO, BLOOD, and JG, and they were observed and analyzed similar to WMTA disks. Statistical analysis was carried out on the color values from five randomly chosen points in the images of MTA disks and bismuth oxide powders.</p><p> Results: MTA disks treated with DW, EDTA, H₂O₂, BOND, and COL1 showed the same color as before the treatment; however, disks immersed in NaClO, BLOOD, and JG revealed significant discoloration. While the discoloration was localized on the surface of the disks treated with BLOOD, it had penetrated the disks immersed in NaClO and JG. The discoloration was also observed in bismuth oxide powders treated with NaClO, BLOOD, and JG; however, its pattern was different between WMTA disks and bismuth oxide powders.</p><p> Conclusion: WMTA disks and bismuth oxide powders showed discoloration when they were treated with sodium hypochlorite solution, blood, and iodine solution; however, their discoloration pattern and penetrating level were different.</p>