الفهرس 
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Abstract
Background: Removal of tooth structure via cavity preparation has been shown to weaken teeth and increase their susceptibility to fracture. One of the most important factors for maintaining the tooth is the type of restorative material used on it. The finite element analysis has become an increasingly powerful approach to predict stress and strain within structures in a realistic situation that cannot be solved by conventional linear static models. There are a handful of studies that have measured the stress in restored primary molars, especially when restored with preformed crowns. Purpose: The aim of this study was to evaluate the stress distribution in normal teeth structure and restorations at different preparation design with different restorative material such as stainless steel crown, zirconia crown and amalgam. Materials and Methods: Six sound or initial caries human primary mandibular second molar were used in this study. The teeth were divided into three main groups: group I (Restored with Amalgam), group II (Restored with stainless steel crown), group III (Restored with Zirconia crown). Each of these groups were also divided into two subgroups, Subgroup A (Class II Cavity with MOD extension), Subgroup B (pulpotomy with MO cavity extension). CBCT images were taken from that restored teeth to create finite element model for each tooth. These models were exported to ANSYS software and subjected to an average simulated bite force of 245 N. Results: Regarding to the final restoration material, the amalgam recorded lowest value of von Mises stress then zirconia and SSC under different force directions and cavity designs. Regarding to the tooth structure, the dentin structure receive the highest von Mises stress with amalgam than SSC and the lowest von Mises stress value with zirconia under different force directions and cavity designs. Conclusion: The SSC and zirconia crowns distribute occlusal stresses significantly, which helps in minimizing possible breakages and protecting the underlying tooth structures.