Sources of variability in rat caries studies: microbial infection and caging procedure.

Two sources of variability in rat caries experiments have been investigated: infection with two S mutans strains and two types of caging. Results indicated that strain 6715 was more virulent than was strain 10449 when 24-day-old rats were orally infected with the organism under standardized conditions. Caging of rats (2 per cage) in stainless steel, raised bottom cages resulted in higher level of caries than in plastic tubs (3 per cage) with hardwood bedding. Infection and caging conditions are two of the factors which may contribute to variability in caries pattern and severity in experimental rats.