In rats, atropine, propranolol and clonidine all affected saliva and increased the risk of tooth decay (J Dent Res, 1989; 68: 1739-45; Arch Oral Biol, 1993; 38: 853-61; Caries Res, 2000; 34: 194-200). Although this may not apply to people, rats do respond to the same cavity-promoting/inhibiting factors as do humans (Townsend Lett Doc, 2005; 263: 16). Drugs similar to atropine include antihistamines such as Benedryl, and some antidepressants (such as Elavil and Aventyl). Propranolol and clonidine are antihypertensives.
If you are taking any of these, you might consider switching to other drugs or reducing the dose. Brushing more often, snacking less and avoiding sugar in your diet will also help.