Aim: To evaluate fracture strength and change in structure of three types of ceramic crowns after debonding with Er,Cr:YSGG laser. Materials & Methods:A maxillary premolar tooth was prepared to receive an all-ceramic crown then duplicated into thirty resin dies.Dies were scanned with Omnicam intraoral scanner, and thirty ceramic crowns were milled with Cerec MCXL milling machine.Crowns were divided into three main groups according to their material type (n=10);group A (E-Max CAD),group B (Vita Enamic) and group C (InCoris TZI).Crowns were bonded to their dies using TheraCem adhesive resin cement.Each group was subdivided into two subgroups (n=5); subgroup 1:crowns were not subjected to laser and subgroup 2:crowns were subjected to laser.Subgroups (A2, B2, and C2) were debonded using Er,Cr:YSGG laser irradiation and rebonded again. Crowns were subjected to a load to fracture using a universal testing machine at a crosshead speed of 1 mm/min.Six rectangular specimens were milled from the three materials blocks. One specimen from each material was subjected to laser irradiation then all specimens were scanned using x-ray diffraction.Data were analyzed by one way ANOVA and paired t-test. Results:There was a statistically significant difference in mean fracture resistance between subgroups of group A and subgroups of group B.There was a non-statistically significant difference in mean fracture resistance between subgroups of group C. Conclusions: Er,Cr:YSGG laser debonding had a significant effect on the fracture resistance of the rebonded E-max CAD and Vita Enamic crowns and a non-significant effect on the rebonded InCoris TZI crowns fracture resistance