Objectives This study aimed to assess the color stability of a calcium silicate‐based cement containing bismuth oxide (OrthoMTA) following addition of zinc oxide (ZnO) in the presence of blood and sodium hypochlorite (NaOCl). Materials and Methods For this study, eight polymethyl methacrylate (PMMA) blocks, measuring 109 mm × 88 mm × 4 mm, were prepared. In each block, 12 holes (6 mm in diameter and 4 mm in depth) were created, yielding a total of 96 molds. OrthoMTA was mixed with distilled water and placed into 48 molds, while the remaining molds were filled with mineral trioxide aggregate (MTA) that had been mixed with 5 wt% ZnO powder. After setting, the color parameters were measured with a spectrophotometer. Then each group of specimens ( n = 48) were randomly assigned to four subgroups for exposure to blood, 2.5% NaOCl, 5.25% NaOCl, or saline ( n = 12). Subsequent color measurements were carried out, and the data were analyzed using one‐way and two‐way ANOVA, and independent t ‐tests (alpha = 0.05). Results The addition of ZnO to OrthoMTA significantly reduced the color change (∆ E ) in specimens exposed to blood, 2.5% NaOCl, and 5.25% NaOCl ( p 0.05). The saline subgroups demonstrated significantly lower ∆ E values than all other experimental subgroups ( p < 0.05), irrespective of ZnO addition. The blood subgroups exhibited the second lowest ∆ E values among all groups, which were significantly lower than in both NaOCl subgroups, regardless of ZnO addition ( p < 0.05). Conclusion Within the limitations of this in vitro study, the results indicate that the addition of 5 wt% ZnO powder to OrthoMTA reduced cement discoloration induced by exposure to NaOCl and blood.
Khoshkhounejad et al. (Thu,) studied this question.