Root-filled teeth are weakened by loss of strategic tooth structure through restorative procedures and caries, rather than by the endodontic procedures. Therefore, prompt restoration is required to minimise coronal leakage and the risk of tooth fracture. However, restorability should be confirmed before root canal treatment begins, by removing caries and existing restoration to evaluate the residual tooth structure. Based on the remaining tooth structure, the restoration is planned to maximise the longevity of root-filled teeth as a functional unit. This review considers risk factors for survival of root-filled teeth and principles of restoration, rather than detailed techniques, including direct and indirect restorations.