Objective: The purpose of this study was to evaluate two glass-ionomer cements placed in the occlusal surfaces of permanent molar teeth, using two cavity preparation methods. Method and materials: Three dentists placed 149 restorations for 68 patients in a hospital clinic. Atraumatic restorative treatment or conventional cavity preparation methods were used for two encapsulated, high-strength conventional glass-ionomer cements: Fuji IX GP and Ketac-Molar. Non-gamma 2 amalgam alloy was used in conventional preparations for comparison. Results: The restorative procedures were uneventful, but cavity preparations made with atraumatic restorative treatment hand instruments took approximately twice as long as did conventional rotary instrumentation. After 30 months, only one glass-ionomer cement restoration had failed. Both glass-ionomer cements showed high early losses of sealant material, but caries was not detected in the exposed fissures. Both glass-ionomer cements also showed relatively high restoration wear. At 30 months, the mean cumulative net occlusal wear was 119 ± 12 mm for Fuji IX GP and 96 ± 13 mm for Ketac-Molar; the difference was not statistically significant. Color matching improved significantly by 6 months; there was no significant difference in color match between the two glass-ionomer cements by 12 months. Minor surface tarnishing and marginal discrepancies were present in the amalgam restorations and increased with time. Conclusion: The occlusal restorations performed satisfactorily over periods of up to 30 months. However, the continued deterioration of the cements requires longer-term studies to be undertaken.