The ultrastructure of the gingival epithelium in smokers''melanosis

The ultrastructural morphology of melanocytes and keratinocytes was studied in clinically pigmented and non-pigmented gingival tissue from smokers and non-smokers. No differences were found between clinically pigmented lesions in smokers and non-smokers. In contrast, clinically non-pigmented tissue of smokers contained significantly more melanin-loaded keratinocytes as compared to that of non-pigmented non-smokers. In tissue of smokers and pigmented non-smokers melanocytes contained well melanized melanosomes (stages III and IV) as compared to non-pigmented tissue of non-smokers where stage II melanosomes dominated.
It was concluded that tobacco smoking may be a causative factor in melanin pigmentation of the oral mucosa and that smoking activates the epithelial melanin unit in a non-specific way. The hypothesis was put forward that in the oral mucosa melanin plays a role as a binder of toxic products such as free radicals and polycyclic compounds. In this way the epithelial melanin unit serves a protective function and prevents tissue damage.