SIGNIFICANCE OF THE PERIOSTEUM IN ONLAY CRANIOFACIAL AUGMENTATION

In the quest for bioinert, easily applicable, and individually adaptab le alloplastic materials, hydroxyapatite (HA) has gained a new applica tion in onlay craniofacial augmentation. On the basis of clinical and experimental proof that intraosseous translocation of HA occurs after HA onlay augmentation, we conducted an animal study on 16 adult Goetti ngen minipigs in which HA, as blocks or granular, was implanted for a maximum time of 72 weeks. Our aim was to study the difference between periosteal and subperiosteal onlay augmentation of two different HA fo rms by comparing HA-bone interface on the intact frontal bone treated with a block form of HA versus granular HA, with special emphasis on t he periosteum. Within a few weeks after subperiosteal augmentation, su bimplant changes in the grafted bone became evident to such an extent that within 72 weeks the granules migrated into the frontal sinus. In contrast, in epiperiosteal HA onlay augmentation, no intraosseous migr ation of HA particles was observed, regardless of the type of HA impla nts. The HA particles were integrated within the connective tissue, an d the connective tissue infiltrated the interstitial spaces. For the m ost part, the location and the shape of the implant remained stable. T he periosteum assumed the function of a limiting membrane. We recommen d that epiperiosteal onlay augmentation with HA be performed only if p revious studies have proven that shape and location are stable. The pe riosteum should be preserved because it functions as a limiting membra ne, retaining the HA and preventing it from migrating into the subimpl ant bone.