Free radicals, superoxide dismutase activity and lipid peroxides in the gingiva of Dental University (ODU) plaque-susceptible (Sus) rats were estimated at the ages of 1,2,3,4,5,7 and 8 months, and were compared with those of control Wistar-kyoto rats. Low levels of hydroxyl radicals were noted in the anterior and posterior gingiva of ODU Sus rats at 2 and 5 month, but significantly increased in the anterior gingiva at 4 and 7 months and in the anterior and posterior gingiva at 7 and 8 months, compared to those of control rats. Levels of carbon centered radicals were significantly higher in the anterior gingiva at 2 months and in both the anterior and posterior gingiva at 3 months.
Superoxide dismutase activities were accelerated significantly at 2,4 and 5 months, and then were reduced at 8 months in the anterior gingiva. Otherwise, they were at low levels in the posterior gingiva at 1 and 2 months, were accelerated at 3 and 4 months, and reduced again at 7 and 8 months. Thiobarbituric acid reactive substances decreased transitorily at 7 months in both the anterior and posterior. These experimental results suggest that free radicals may be related to the pathogenesis and development of gingivitis in plaque susceptible ODU Sus rats.