 The aim of this randomized clinical trial study is to compare the longevity of ART using high viscosity GIC and conventional treatment using composite resin in posterior primary teeth. As secondary outcomes, cost-efficacy and patients self-reported discomfort will also be tested. Children aging between 3 to 6 years old presenting at least one occlusal andor occlusal-proximal cavity will be randomly assigned in two groups according to the dental treatment - ART with high viscosity GIC experimental group or composite resin restoration control group -, which will be performed at dental care trailer located in a Educational Complex in BarueriSP, Brazil. The unit of analysis for randomization will be the child. A number of 240 teeth presenting occlusal cavities and 188 teeth presenting occlusal-proximal cavities were set after sample size calculation. The groups will still be stratified according to childrens caries experience. The primary outcome will be the restorations longevity, which will be assessed after 6, 12, 18 and 24 months by two examiners through clinical examination of treatment according to Frencken and Holmgren 2001 criteria for occlusal cavities and Roeleveld et al. 2006 criteria for occlusal-proximal ones. The time spent during the dental treatment and all materials used will be considered for estimating the cost-efficacy of each treatment. The individuals discomfort will be also measured after each dental procedure using the Facial Scale of Wong-Baker. 