Administration, Oral, Animals, Antibodies, Bacterial, Bacterial Proteins, Bacterial Vaccines, Dental Caries, Dose-Response Relationship, Drug, Germ-Free Life, Immunoglobulin A, Secretory, Membrane Glycoproteins, Peyer's Patches, Rats, Rats, Inbred F344, Saliva, Salmonella typhimurium, Spleen, Streptococcal Infections, Streptococcus sobrinus, Vaccines, Synthetic