This systematic review sought to quantitatively answer the question as to whether, in tooth cavities of the same size, type of dentition and follow-up period, resin-modified glass-ionomer (GIC) restorations, when compared to conventional GIC restorations, offer a significant caries preventive effect, as measured by the absence of caries lesions at the margin of restorations. Six databases were searched for articles in English, Portuguese or Spanish until 07 May 2009. Four articles were accepted and 22 separate datasets extracted. The difference between both types of material were computed as relative risk (RR) with 95% confidence interval (CI). No meta-analysis was undertaken due to aspects of clinical/methodological heterogeneity. The results of the extracted datasets ranged between RR 0.90 (95% CI 0.81-1.01) and 1.08 (95% CI 0.71-1.63; p > 0.05) indicating no difference in the caries preventive effect between both types of materials. Further high-quality randomized control trials are needed in order to confirm these results.