CHOICE OF BONE GRAFTING MATERIAL FOR ALVEOLUS
Survival of the donor tissue is an important aspect in bone grafting. Under optimal conditions, the osteogenic cells survive the surgical procedure. Johanson and Röckert (1961) proved in histological and micro-radiographical clinical and experimental studies, that cancellous autogenous bone grafts, harvested from either tibia or iliac crest, were transformed to the same structure as the surrounding palate. After six months it was not possible, micro-radiographically or morphologically, to distinguish a biopsy sample from the graft region from one taken from a normal palate at the same age. Furthermore, the architecture of the graft appears to adapt to the functional requirements.
The formation of new bone starts on the surface of the pre-existing trabeculae. Cancellous bone is more vascular, has more space, contains more bone regeneration and has better ingrowth of new bone from the adjacent bone segments. In principle, cancellous autografts heal primarily by osteogenesis, followed considerably later by resorption of the bone trabeculae in the transferred donor tissue.
Early establishment of nutrition to cortical bone cells requires restoration of flow through existing vessels or canaliculi and ingrowth of capillaries. A cortical graft will usually die and be replaced by invasion of bone cells originating from the recipient site. The metabolic turnover and remodelling/transformation of cortical bone are much slower than in cancellous bone, making re-establishment of the tooth-bearing function of the alveolar process in the cortical graft unfeasible.