Apart from the properties of the ceramic material itself, the fitness of the crown restoration, whether marginal or internal,plays a very important role in the long-term success of the restoration, affecting the retention and strength of the restoration. This book is focusing on the recent development in ceramic materials including the translucent zirconia, lithium disilicate, zirconia-reinforced lithium silicate, and resin-ceramic hybrid material,and the techniques used for the measurement of marginal and internal fitness of crown restoration. The authors concentrated on the use of the of silicone replica technique for the measurement of the marginal and internal fitness including the basic concepts of the technique and its advantages.