Introduction: Traditionally, internal tooth bleaching was performed using sodium perborate slurries. These are banned in some areas for potential carcinogenic effects. More recently, highly concentrated hydrogen peroxide gels have been used, which may cause dentin degradation. Consequently, the search for ideal internal tooth bleaching agents is still on. This study compared pure ROS-releasing granules regarding their liberation of oxidizing species, pH induction, bleaching of blood-stained dentin, and effects on mechanical dentin properties. Materials and methods: The ROS-releasing granules under investigation were sodium perborate, carbamide peroxide, and sodium percarbonate in aqueous suspension (4:3, wt/wt). The bleaching efficacy of these suspensions was compared in blood-stained human dentin ( Results: Granules release between 21.5% and 35.2% (wt/wt) of H Conclusions: Sodium perborate granules in aqueous suspension combined good de-staining properties with limited untoward effects on dentin integrity. Further studies are required to identify alternative compounds with a lesser general health concern.