A couple of things to do for dental plaque

Besides flossing, colloidal silver is really good for eliminating plaque - especially if combined with brushing. Utopia Silver makes a colloidal silver skin and scalp bar which also contains aloe, plant minerals and other goodies and one of their customers wrote in one day to tell them that he had used the bar to brush his teeth with and that it removed his plaque and helped clear up gum problems.  Since posting his message, many others have tried it and verified what he said.   I suspect the same might be true for oil of oregano.

While I am not sure what it might do for plaque itself, a wonderful followup would be liquid Co-enzymeQ10 (CoQ10).  It apparently is great for healing gums and is also wonderful for the heart.  See:

http://curezone.com/forums/fm.asp?i=1945005#i

and

http://www.naturalnews.com/035846_CoQ10_health_longevity.html