Attempts to alter the genetically expected caries activity in rats by manipulation of the oral flora

Abstract

Inoculation of the mouths of Harvard caries-resistant rats with faeces from caries-active Harvard caries-susceptible rats, Hunt-Hoppert caries-susceptible rats or sialoadenectomized Harvard caries-resistant rats had relatively little accelerating influence on the dental caries activity of the Harvard resistants. Small increases in dental caries experience were observed in some inoculated groups and none in others. Inoculation of the mouths of Hunt-Hoppert caries-resistant rats with faeces from caries-active Harvard or Hunt-Hoppert caries-susceptible rats led to modest increases in caries activity. These levels of caries activity in 250 days approached those expected for caries-susceptible rats in 80 days. These data indicate that the caries-resistance of the Hunt-Hoppert rats can be overcome more readily by the transmission of appropriate micro-organisms than the caries-resistance of Harvard rats. The caries activity of Harvard caries-susceptible rats can be reduced dramatically by the continuous administration of 0.05% penicillin in the diet. The feeding of this penicillin-supplemented diet for the first 14–28 days only of an experiment led to significant reductions in caries activity over a normal caries assay period. The use of the supplemented diet as infrequently as 1, 2 or 3 days per week also led to significant decreases in dental caries experience. Depression of the oral flora of Harvard caries-susceptible females during the reproductive cycle by either penicillin administration or by the extraction of all molars did not lead to dramatic reductions in dental caries activity among their offspring.