Objectives: The purpose of this study is to compare the mechanical properties (compressive strength (CS) and diametral tensile strength (DTS)) of four different restorative materials: conventional glass ionomer (Fuji IX), ClearFil AP-X, Filtex Z350-XT, and Cention N. Materials and methods: Specimens (n = 80) were prepared from Fuji IX, ClearFil AP-X, Filtex Z350-XT, and Cention N for testing compressive strength and DTS. Statistical analysis: Results obtained were subjected to one-way ANOVA and Tukey's post hoc test at significance (p < 0.001). Results: There were significant differences among restorative materials tested. ClearFil AP-X exhibits the highest mechanical properties (CS and DTS) and least values were obtained by the Fuji IX. Conclusion: Strength is one of the most important criteria for the selection of a restorative material. Stronger materials better resist deformation and fracture, presenting more equitable stress distribution, greater probability, and greater stability of clinical success.