This info. I copied from another site.
Apple Cider Vinegar & Dental Enamel
We are grateful that Dr. Yong, a dentist from London, wrote to us recently elucidating the subject.
Dr. Yong writes, "Warning - Taking cider vinegar by sipping it during the day may very well help cure some of these allergies, however, it will ruin the enamel on the teeth to such an extent that it may be lost entirely. As a dentist I have seen the effects of regular acid intake whether it be carbonated water or a natural acid like lemon juice - yes very cleansing to the system, but a disaster in the mouth. It leads to very costly mouth rehabilitation which can cost thousands of pounds. The first thing patients will usually notice is yellowing of the teeth and sensitivity as the enamel is lost. I am very much into holistic medicine and am training as a homeopath so understand when people wish to look for alternatives to self cure, however be aware that regular intake of vinegars and other acids will have deleterious oral effects!"
Terri from Prospect, OR agrees: "I just want to let you know that I agree with the dentist. I started drinking vinegar water 3 years ago all day long like you, and my teeth start going bad, since then I drink a glass in the morning as tea and then brush my teeth no more problems with my teeth."
1. Never drink ACV straight.. always drink it well diluted with water.
2. Immediately rinse your mouth well with water after drinking ACV. Don't brush your teeth right away as that may grind the vinegar into the enamel.
3. Do not drink it in combination with anything sweet like honey, juice or Gatorade. We have the feeling the combination is lethal on the teeth.
4. Possibility: Drink ACV with a straw at the back of the throat slowly. The trick is to not let the liquid touch your teeth.
Thought this might be helpful.