Background. The authors compare the incidence of recurrent caries around two glass ionomer restorative materials and one amalgam material. Methods. The authors placed 111 restorations in nine xerostomic patients. Patients were given oral hygiene instructions and fluoride gel to use daily. The authors evaluated the restorations clinically and with photographs and impressions at six months, one year and two years according to criteria for marginal adaptation, anatomical form, caries in adjacent tooth structure and caries at the cavosurface margin. The authors divided patients into users and nonusers of fluoride. Results. At the two-year recall appointments, the authors evaluated 95 (86 percent) of the 111 restorations. They analyzed two-year data using an analysis of variance for repeated measures and Fisher's post hoc test. The study results showed no significant differences among materials in regard to caries at the cavosurface margin among fluoride users. However, among fluoride nonusers, patients with amalgam restorations had a significantly higher incidence of caries at the cavosurface margins than did patients with either of the two glass ionomer restorations. The authors found no statistically significant difference between restorations with regard to marginal integrity or anatomical form. However, one patient exhibited failure of glass ionomer restorations owing to material loss. Conclusions. Less caries developed at the margins of glass ionomer restorations compared with amalgam restorations in xerostomic patients who did not routinely use a neutral topical sodium fluoride gel. Clinical Implications. Fluoride-releasing materials may reduce caries surrounding restorations in high-risk patients who do not routinely use topical fluoride. Patients who routinely used topical fluoride gel did not develop recurrent caries, and clinicians should encourage the use of fluoride gel on a daily basis.