There are more problems related to chewing gum than just cavities. However, chewing gum does actually stimulate the production of saliva and salivary flow. This is good because saliva is a natural buffering agent that helps keep teeth clean and healthy by rinsing them and neutralizing some of the acids produced by bacteria. Those acids are what erode enamel and lead to cavities.
People who don't produce an adequate amount of saliva should start to chew gum regularly; it will boost their saliva production. However, they should try to find a sugarless gum, like Eclipse or Trident. It's a common misconception that the saliva you produce will wash away the sugar in gum.
Not hardly. If you chew gum with sugar in it, you need to chew for twenty minutes or more in order to produce enough saliva to wash away a significant amount of the sugar residue. Even then, it's a good idea to brush your teeth afterwards. Again, if you're going to chew a lot of gum, the best thing you can do is choose a sugarless gum. Orthodontists also believe that moderate to excessive gum chewing might lead to jaw problems. If you experience headaches or jaw pain from chewing gum, you might want to cut back or pay a visit to your doctor.