Experimental gingivitis in immunized dogs

The present experiment was performed to study the clinical and histopathological features of developing gingivitis in eight dogs, of which four were repeatedly immunized with plaque antigens prior to the start of a defined plaque accumulating period. The dogs were, after weaning, fed a soft diet but also twice daily subjected to meticulous tooth cleaning. When they were 10 months old and their gingiva were in excellent health, all tooth cleaning procedures were terminated and dental plaque was allowed to accumulate for 4 weeks. Clinical examinations and gingival biopsy sampling were performed during this period. The biopsies were analyzed morphometrically.
In the injected dogs the levels of specific serum antibodies, as determined by an immunoradiometric assay (IRMA), were raised 3–4 fold. No antibody increase was observed in the controls. After the termination of the tooth-cleaning period, the immunized dogs seemed to accumulate dental plaque at the same rate as non-immunized controls. The gingiva of the immunized animals reacted to initial plaque formation with symptoms such as redness, swelling and bleeding in a manner very similar to the controls. The degree of gingival exudation and the size of the gingival connective tissue lesion was, however, less pronounced in the immunized dogs compared to the non-immunized controls.
The results indicate that raised immunity to plaque antigens may have a protective function in the dento-gingival tissues during the development of plaque induced gingivitis.