The aim of this study is to examine the mechanical behavior of different types of composite resins (short fiber-reinforced composite, conventional high-fill hybrid composite and bulk-fill composite) used in the restoration of class II MOD cavities of primary molar teeth by the finite element analysis (FEA). Three three-dimensional tooth models were created in a computer environment. Model 1: tooth model without restoration (control group), Model 2: class II MOD cavity tooth model restored using composite resin (incremental technique), and Model 3: class II MOD cavity tooth model restored using composite resin (bulk technique). Subgroups were formed using the properties of different types of composite resins tested in the class II MOD cavity tooth model. To simulate the average bite force in a child with primary dentition, vertical static loading of 245 N was applied to each of the occlusal contact points of the models. The maximum von Mises stress values were calculated for the models. For all models, the von Mises stress values obtained in enamel were higher than those obtained in dentin. Similar von Mises stress values were obtained in all subgroups of Model 2. The lowest von Mises stress values transmitted to the dental tissues were obtained in Model 3.