In Pediatric practical dentistry, beside the great variety of direct dental restoration materials the dentist must take into account several factors such as morpho-structural particularities of temporary teeth, the clinical situation, physician performance, behavioural features of children and last but not least the quality of the chosen material. Thus, we investigated the behavior of glass ionomers cements in occlusal stress by determining their mechanical properties. The study aims to determine the vertical compressive strength values, which is one of the mechanical properties of filling materials, the strength of materials being useful in the research of occlusal forces exerted on the future restorations. We had used two glass ionomer cements and a resin modified glass ionomer cement, which then we have tested them to obtain comparative data of the resistance for vertical compression.