Effect of Addition of Zinc Oxide on Color Stability of a Calcium Silicate–Based Cement Containing Bismuth Oxide in the Presence of Blood and Sodium Hypochlorite Publisher

Summary: Can adding ZnO to OrthoMTA improve color stability? Research suggests it reduces discoloration in dental cements exposed to NaOCl and blood. Findings highlight its potential use. #Dentistry #MaterialsScience

Khoshkhounejad M ; Shokouhinejad N ; Sarraf P ; Mirisiahi M
Source: International Journal of Dentistry Published:2026

Abstract

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), while no significant color change was observed in the saline subgroups (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. Copyright © 2026 Mehrfam Khoshkhounejad et al. International Journal of Dentistry published by John Wiley & Sons Ltd.