Vitamin C - be sure you are getting your daily dose.  It helps the body repair and maintain connective tissue, and its antioxidant effects are important to help fight against periodontal disease.  A large 2010 study found that people who consumed less than the recommended daily dose of vitamin C (60 mg or about one orange) were 1.5 times more likely to develop severe gingivitis than those who consumed more than 180 mg each day.  (It should be noted that smoking also depletes your vitamin C resources.)  As residents (or snow-birds) of Florida where oranges are plentiful all year round, we have no excuse for not getting our daily "C"!