Interpositional "Grafting" with autogenous bone and coralline hydroxyapatite

The lack of bone mass associated with relatively high muscle attachments and insufficient vestibular depth complicates the prosthetic restoration of the atrophic mandibular alveolar ridge. Alloplasts and autogenous bone grafts have been used to augment the atrophic alveolar ridge with variable results. Onlay bone grafts tend to resorb while alloplastics may become infected and resorb underlying bone. The concept of interpositional bone grafting has certain theoretical advantages. It has been postulated that preservation of the integrity of the mucosa-periosteum-cortex relationship of the repositioned bone and maintenance of its morphological form and osseous architecture will minimize resorption of the transposed basal bone. An animal study was designed to test the validity of this concept. The vascularization, revascularization, and bone healing associated with interpositional autogenous bone grafts and implants of coralline hydroxyapatite were investigated in nine adult mongrel dogs. The mandibular posterior teeth were extracted and an enbloc resection of the alveolar bone which encased the extracted teeth was accomplished to simulate mandibular atrophy. Eight weeks later through an intraoral approach an autogenous cortico-cancellous iliac bone graft was placed in the edentulous area; a 2 cm. × 1 cm. × 1 cm. hydroxyapatite implant was placed on the contralateral side. The animals were sacrificed immediately, at 3 days, and 1, 2, 4, 12, 24, 28, and 40 weeks. Radiographic, microangiographic, and histological studies indicated that the lingual mucoperiosteum in the mandible provided an adequate vascular pedicle for superior repositioning of mandibular basal bone in a single stage. There was early consolidation and remodelling of the grafted bone and implant with minimal alteration of the morphological form and architecture of the repositioned bone. The results of this animal study support the concept of interpositional bone grafting to augment the atrophic mandibular alveolar ridge. The promise of coralline hydroxyapatite was favourable and awaits further ongoing comparative studies with bone grafts.