Aim: to evaluate which type of access cavities will not affect the tooth strength after preparation and canal preparation. Methodology: an extracted maxillary second premolar was scanned to make a finite model. Models were designed with two different canal preparations (30/.04 and 40/.04) and three different access cavity designs (conservative access cavity “CEC”, caries driven access cavity and traditional access cavity “TEC”) were generated. In order to simulate the normal masticatory force range, occlusal load of 50 N was applied. After applying the load to all models, finite element analysis was used to determine the maximum Von Mises stresses “vM” and life span of models