Damage to tooth structure

Staining of tooth substance from root canal filling materials containing silver may occur. Kerr’s PCS contains silver particles, as did the original formula for AH26. Staining in the above tooth is because of rezorcin formalin root filling.
Bleaching agents may have a deleterious effect on dentin structure, increasing permeability and allowing for chemotaxins to penetrate and initiate resorptive processes.