Neutrophils and IgG at the host-plaque interface on children's teeth.

This study is part of an investigation aimed at discovering how subcontact area plaque, unlike corresponding embrasure plaque, survives the host response and enters the gingival crevice. Approximal gingival margin plaques incorporating these two sites were obtained from children's teeth and subjected to transmission electron and immunoelectron microscopy. The specimens were examined for the main components of the initial host response at the plaque-host interface, namely polymorphonuclear leukocytes and IgG. Both were found preferentially at the actual apical border of plaque, especially in embrasures. Some polymorphs showed evidence of phagocytosis. Most of those in contact with plaque showed lysosome and glycogen loss and occasional phagocytosis. It was concluded that at least one important mechanism by which chronic gingivitis and approximal caries are initiated, involves lack of polymorph activity apical to the contact area. Possible explanations include the stagnation of gingival fluid so that neutrophils do not reach the plaque, failure of neutrophils to adhere to tapering border plaque, lysis of polymorphonuclear leukocytes (PMN) or elaboration of antichemotactic or other factors inhibiting PMN function by the colonizers of the gingival crevice.