Electron microscopic evidence of a cellular attachment between junctional epithelium and dental calculus

Following scaling, the gingiva of rhesus monkeys was maintained in a state of clinical normalcy by single daily intra‐oral swabs with 2 % chlorhexidine gluconate, supplemented by toothbrushing and interdental cleansing with toothpicks three times per week. Chance findings in 2 animals, one maintained for 3 months on this regimen, the other for only 3 weeks followed by a period of 12 days without oral hygiene, revealed that under these circumstances, the junctional epithelium is able to form an attachment to a calculus mass which contained morphologically recognizable bacterial cells. Electron microscopy revealed that this attachment was mediated through a dental cuticle, a basement lamina and hemidesmosomes. The ultrastructure of the epithelial attachment to calculus was indistinguishable from that which exists between junctional epithelium and various tooth surfaces. These results may be due to the inhibiting effect of chlorhexidine gluconate on plaque formation and possibly a concomitant lowering of the toxicity of calculus.