Preservation of structural specificity in free gingival grafts. Long-term histological observations in man.

Most of the previous histological studies devoted to free gingival grafts in humans were limited to the description of the various phases of healing between the graft and the subjacent tissues. The present long-term study illustrates the histological findings 1 to 36 months after grafting along the zone of passage between graft and surrounding tissues. In the transitional zone between graft and alveolar mucosa it was found that the structural characteristics of the palatal mucosa, with its dense network of collagen fibres and its orthokeratinized superficial layer were conserved even after an interval of time as long as 16 months. These features contrasted with the loose network of collagen fibres and the presence of numerous elastic fibres in the alveolar mucosa. As for the transitional zone between graft and gingiva the findings confirmed that these two types of mucosa are similar, except that the gingival epithelium showed, in epon embedded sections, a layer of parakeratinization, as opposed to the dense layer of orthokeratin found on the grafted palatal epithelium. A constant feature in the present investigation was the change in orientation of the collagen fibres along the zones of healing, both between graft and alveolar mucosa and between graft and gingiva.