δ‐Bismuth Oxide Responsible for Tooth Discolouration—A Laboratory Investigation

The δ-phase bismuth oxide formation led to the material darkening which will cause tooth discolouration in a clinical setting. Due to the phase changes, the material chemistry after the interaction is different from that of the material placed in the tooth. The by-products of the reaction have not been tested for use in patients. It is recommended to ban the use of bismuth oxide from dental materials and other clinical use due to its instability. The clinical guidance for endodontic treatment needs to be changed to reflect this.