The role of inflammation in the pathogenesis of gingival enlargement during the administration of diphenylhydantoin sodium in cats

In order to determine the role of gingival inflammation in the pathogenesis of the gingival enlargment seen in individuals taking diphenylhydantoin sodium (DPH), thirteen female and ten male adult mongrel cats were subjected to a coarse diet, irritating plastic bands around selected teeth, and a daily tooth brushing routine. Fourteen days after initiating the diet, bands, and brushing, 12 of the cats were randomly selected to receive a daily intramuscular injection, 10 mg/kg body weight, of DPH. The remaining cats received the equivalent amount of inert solvent. The maxillary quadrants containing banded teeth were not brushed whilst the maxillary quadrants containing no banded teeth were brushed daily. This combination produced grossly inflamed (banded) and non‐inflamed (non‐banded) maxillary quadrants in two groups of animals; one group receiving DPH, the other receiving vehicle only. The mandibular gingiva were not used in this study. It was possible to reproduce the clinical and histological appearance of DPH gingival enlargement in 11 of the 12 cats receiving DPH and whose gingiva were subjected to local irritation and no oral hygiene. Animals receiving DPH and oral hygiene care, but with no bands on adjacent teeth and thus no local irritation, showed no overt gingival enlargement. Analysis of the results reveals that in the presence of local irritants, producing inflammation, gingival enlargement develops after DPH administration. In the absence of irritants no enlargement occurs.