During post crown restoration, the preparation of the post canal can be fraught with difficulties resulting in widening, gouging and transportation of the post canal; sometimes with near root perforation. A technique is described to repair such iatrogenically damaged internal root canal walls using reinforcing resin composite and optic glass fibre posts. The root dentine, resin composite and glass fibres, having similar moduli of elasticity, will result in a repaired root with a ‘monolithic’ structure and possessing numerous desirable characteristics. This repair technique can easily be carried out in one sitting at the chairside thereby allowing the continued serviceability of the iatrogenically compromised root-filled tooth.