This in vitro study investigated repairs to glass ionomer cements (GIC) with a new GIC layer added after different time intervals (15 minutes, 24 hours, 6 days) and after different types of surface treatments. The results indicated: 1) GIC can be repaired with a new GIC layer added on with specific types of surface treatment. The shear bond strength created at the interface attained no less than 65% of the value for unrepaired specimens; 2) The surface treatment that best enhances the bond was either 20 seconds of etching with phosphoric acid or roughening the surface followed by acid etching. The latter showed higher values but not at a statistically significant level; 3) Both Ketac-Fil and Fuji II provided high bond strengths when the repair occurred on a newly set surface (15 minutes); 4) When Ketac-Fil and Fuji II specimens were repaired at 24 hours, shear bond strength was lower compared to the repair bond strength at 15 minutes and demonstrated less cohesive ability; 5) When 6-day-old specimens were repaired, Fuji II provided higher bond strength values than Ketac-Fil.