For every clinician effect of cement thickness on crown retention is a big suspense. Dental crowns are having various roles like restoration of oral function, esthetics, occlusal equilibrium as an important aspect of dental treatment. Increased human life longevity and awareness has led to an augmentation in dental treatment needs. Crowns are prescribed regularly in day to day practice as a part of treatment plan. Majority of partially edentulous patients turning to dental clinics today exert more emphasis on fixed prosthesis as compared to removable prosthesis because of several benefits of fixed prosthesis. Retention of crown is one of the most important properties of crown for execution of proper function of crown. Die spacer application is done as one of the laboratory procedure during fabrication of crown.Die spacer thickness affects the retentive property of crown as that space is occupied by cementing material. I carried out the study to determine the effect of various die spacer thickness on crown retention. This book explains association between die spacer thickness and crown retention in a simplified manner.