Ultrastructural study of induced keratinization in sulcular gingival epithelium in rhesus monkeys.

Gingival sulcular epithelium--which in primates normally does not keratinize--can be induced to undergo keratinization by prolonged intensive antibacterial therapy. Three months before biopsy the teeth of two adult male rhesus monkeys were scaled and polished, and for 5 days the monkeys were given intravenous injections of 75 mg Achromycin daily. Their teeth were subsequently subjected to daily cleaning and polishing. The presumably in-situ-keratinized sulcular epithelium was examined by transmission electron microscopy. It was also compared with oral gingival epithelium from the same two animals and with oral and sulcular epithelium from a rhesus monkey that had not been exposed to local or systemic antibacterial therapy. The results confirmed earlier histological studies, which have shown that under the conditions described the sulcular epithelium becomes parakeratinized. In addition, several other ultrastructural changes were observed, some of which suggest that the treatment given may result in the formation of a more efficient permeability barrier in the sulcular area. The possible clinical significance of such a barrier is briefly discussed.