BACKGROUND: Although rats have been extensively used in periodontal research, pre-experimental periodontal inspection has not been given high priority in previous studies of experimental periodontal disease in rats. An inspection of 50 Sprague-Dawley rats, which were to be used in a model of experimental periodontal disease, revealed signs of periodontal disease in a considerable proportion of the animals. OBJECTIVES: The objectives of the present study were to describe disease progression, identify factors responsible for induction of periodontal disease and test a method for breeding of healthy rats. METHODS AND RESULTS: A longitudinal study revealed that 33% of rats, bred under the same conditions, showed signs of periodontal disease during, or shortly after, eruption of the molars. Regular diet caused significantly more horizontal bone loss (P = 0.0001) and significantly less periodontal bone support (P < 0.0001) than the same kind of diet with a smaller grain size. Wood chip bedding in the rats' cages significantly reduced periodontal bone support (P < 0.0001) compared to a wire mesh floor and a simultaneous use of regular diet and bedding decreased it even further (P = 0.0023). Finally, by using finely milled diet, a wire mesh floor and tap water, instead of conventional breeding methods of regular diet, bedding and acidic water, it was possible to breed rats with minimal signs of periodontal disease. CONCLUSIONS: The results of the present study emphasize the need for pre- experimental examination of rats. They also show that diet and bedding conditions have the potential of seriously influencing outcomes of studies of periodontal disease in rats.
BACKGROUND: Although rats have been extensively used in periodontal research, pre-experimental periodontal inspection has not been given high priority in previous studies of experimental periodontal disease in rats. An inspection of 50 Sprague-Dawley rats, which were to be used in a model of experimental periodontal disease, revealed signs of periodontal disease in a considerable proportion of the animals. OBJECTIVES: The objectives of the present study were to describe disease progression, identify factors responsible for induction of periodontal disease and test a method for breeding of healthy rats. METHODS AND RESULTS: A longitudinal study revealed that 33% of rats, bred under the same conditions, showed signs of periodontal disease during, or shortly after, eruption of the molars. Regular diet caused significantly more horizontal bone loss (P = 0.0001) and significantly less periodontal bone support (P < 0.0001) than the same kind of diet with a smaller grain size. Wood chip bedding in the rats' cages significantly reduced periodontal bone support (P < 0.0001) compared to a wire mesh floor and a simultaneous use of regular diet and bedding decreased it even further (P = 0.0023). Finally, by using finely milled diet, a wire mesh floor and tapwater, instead of conventional breeding methods of regular diet, bedding and acidic water, it was possible to breed rats with minimal signs of periodontal disease. CONCLUSIONS: The results of the present study emphasize the need for pre- experimental examination of rats. They also show that diet and bedding conditions have the potential of seriously influencing outcomes of studies of periodontal disease in rats.