The black layer on the teeth of betel chewers: a light microscopic, microradiographic and electronmicroscopic study.

Ten teeth of betel chewing P'wo Karen, a hilltribe group of northern Thailand, were available for this morphologic study. The structural composition of the black layer on these teeth was studied by light microscopy, microradiography and by electronmicroscopy. Principally, the black layer on the teeth of betel chewers was identical with subgingival calculus which had been colored by specific polyphenols contained in the betel nut. However, a pellicle-like layer forming initially on enamel crystals was also observed. From the morphologic aspect of the black layer a specific anticariogenic property cannot be attested. Further studies on the chemical composition of this black layer may elucidate its probable anticariogenic and its carcinogenic properties relative to oral submucous fibrosis.