Histology and Surface Ultrastructure of Early Healing After Gingival Augmentation

Objectives: The objective of the present study is the histological and surface ultrastructural evaluation of the early healing of augmented keratinized human mucosa, following the surgical placement of a xenogeneic collagen matrix.
Methods: Biopsies of full depth mucosa, including simultaneously original attached gingiva, augmented gingiva, and their separation zone were microsurgically harvested at baseline, at 7 and at 14 days, from 6 patients that underwent surgical augmentation of keratinized tissue by placement of a 3D xenogeneic collagen matrix, and were stained in Hematoxillin-Eosin, Masson-trichrome, picrosirius-red and Papanicolaou-trichrome. Low-vacuum scanning electron microscopy surface analysis was correlated with histology.
Results: Histological and SEM findings at 7 days indicated clearly visible separation zones; the newly-formed half of biopsies presented a well-structured, immature gingival tissue displaying per secundam healing characteristics, visible under a collagenic amorphous membrane-like structure thick of ab.100 microns, completely detached from the newly-formed mucosa. At 14 days, both histological and ultrastructural results showed an almost complete maturation process. At both time points, remnants of matrix were not detected within the newly-formed tissue.
Conclusions: The study suggests that the 3D-collagen matrix seems to be playing an indirect role in the early phase healing process, rather protecting the underlying tissue and allowing for the formation of the new epithelia. Histologically, newly-formed tissue is still under formation at one week but is mature at two weeks post-surgery. Sequenced histological protocoles with additional confirmatory SEM and immunohistochemical assessment could elucidate the fate of non-autologous grafts for gingival augmentation in early healing phases.