During preparation of a 38-year-old man for denture-making, a perforation of the pulp chamber floor was detected in the bifurcation area of tooth 46. Objectively, tooth 46 is immobile and has no periodontal pockets. X-ray shows completely filled root canals of tooth 46 without pathologic changes in their periapical area. In the bifurcation area of tooth 46, the apex of the interradicular septum is destroyed. What type of procedure is recommended in this case to retain the tooth?