"Those bugs, the Lactobacillus acidophilus, that the dental scientists charge with causing a tooth to decay, are found in everybody's mouths; but, when food is correct the tissues are immuned. ... Why is it, then, that the rate of tooth decay varies from zero (as in certain Deaf Smith County families) to above 95 per cent? Not the bacteria count in the patient's mouth, but the food he has lived upon makes the difference. The mouth must be correct when the food is correct. When the mouth is correct, the bacteria do no damage."
Dr. George W. Heard in his book Man versus Toothache
The other quotes on that page, and the whole site, are also worth reading.