Sugar Substitutes, Chewing Gum and Tooth Decay
While sugar by itself doesn’t harm enamel, everything changes when there is plaque bacteria involved. Sugar in chewing gum (and anything else that we eat) is fermented by plaque bacteria into acid, which then causes tooth decay.
The two main artificial sweeteners used chewing gum are xylitol and sorbitol. Plaque bacteria doesn’t ferment these sweeteners in the same way as sugar, so there is little or no decay-causing acid produced when chewing sugar-free gum.
Another benefit when we chew gum is that we produce a lot of saliva. Saliva neutralises acid in the mouth and contains factors that naturally strengthen our teeth.
This summary of a 1998 study by WM Edgar (Oral Biology Unit, School of Dentistry, University of Liverpool) explains more. http://www.ncbi.nlm.nih.gov/pubmed/9479811