Current techniques for intra-coronal bleaching of stained root-filled teeth employ oxidative bleaching with hydrogen peroxide. However, it has been shown that hydrogen peroxide and hydroxyl radicals, the by-products of the bleaching process, diffuse from the pulp chamber to the outer root surface. The control of such diffusion may be of importance in minimizing the risk of invasive cervical resorption (ICR) which has been linked to intracoronal bleaching. A novel reductive-oxidative bleaching process using a thiourea and hydrogen peroxide regimen is proposed as a more effective and safer bleaching protocol. Also, other clinical considerations during the intra-coronal bleaching of root-filled teeth are discussed.