Although many health practitioners will tell you that good health starts in the digestive system; good health also comes from having a healthy, clean mouth!
Dr. Weston A. Price was the pioneer of research into the effect that bad bacterias in the mouth can have on the health of the rest of the body, and proved time and time again that many chronic diseases such as heart disease, arthritis, cancerous tumours and many other systemic ailments had their roots (literally) in the mouth and teeth.
From the research that I have done into this issue; it appears that the two worst things you can do for the health of your mouth (and the rest of your body) is to have mercury amalgam fillings, and root canals therapy. Interestingly enough, cavities in the teeth come from the poor nutritional status of the whole body – not from the eating of sugar. Studies have been done that inject sugar into mice, and they develop cavities due to their poor state of health, rather than the sugar touching their teeth.
For more information, I suggest you read this article: Root Canal Cover-Up Exposed, and purchase Dr. Meinig’s book of the same name for a more detailed expose of the dangers which could be lurking in your mouth.