The role of sulcular environment in controlling epithelial keratinization.

The influence of the sulcular environment on the keratinization of the outer surface gingival epithelium was tested in three young adult Rhesus monkeys. A total of 40 mucoperiosteal flaps were raised, and inverted so as to bring the outer surface epithelium in contact with the tooth, and were sutured. The experimental time intervals varied from 1 hour to 60 days. The monkeys received H3 thymidine 1 hour prior to sacrifice. The material was prepared for histologic and radioautographic evaluation. Results indicated that the outer surface epithelium changes its morphology to a nonkeratinized epithelium devoid of deep rete pegs when in close contact with the tooth, resulting in the anatomical characteristics normally seen in sulcular epithelium. It is concluded that the sulcular environment has the capability of controlling the keratinizing potential of the outer surface gingival epithelium. It is further suggested that the constant irritation of bacterial plaque and its products may be responsible for the premature desquamation of the sulcular epithelium which in turn might not allow its full differentiation.