This in vitro study aimed to evaluate the internal and marginal adaptation of crowns produced from partially crystallized and fully crystallized lithium disilicate CAD-CAM blocks using direct view and the silicone replica method. The mandibular first molar was used as an abutment. A total of twenty crowns (n = 10) were produced using milling CAD-CAM. The direct viewing technique was used to measure the marginal gap. The measurement of internal adaptation was conducted using the silicone replica technique. Following the subsequent glazing procedure, all crowns underwent another round of measurements. The paired samples t-test was used to compare two related continuous variables. The study revealed that the mean value of the marginal gap of the partially crystallized block is significantly higher than the fully crystallized block both before and after the glazing process. A statistically significant difference was found before and after glazing of the partially crystallized block in the marginal gap values. The fully crystallized crowns showed better marginal gap values than the partially crystallized ones. No change was observed before and after the glaze in the fully crystallized block. The recommended limit of 120 µm for the marginal gap of lithium disilicate CAD-CAM crowns was never exceeded.