الفهرس 
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Abstract
The present study investigated the effect ErCr:YSGG laser on the debonding of all ceramic endocrown restorations. A total of 30 caries free human molar teeth were collected. All teeth were placed in epoxy resin by using a custom-made device.To standardize the preparation of all samples, decoronation of the teeth was done using a straight handpiece affixed to a surveyor and was done at a level 1mm above the cemento-enamel junction. Each abutment was scanned, and the copings were designed using interactive CAD software. An occlusal extension with an occlusal hole was added to the coping design to facilitate the coping removal during the test. Samples were then divided in to 2 groups: Group(A) (n=15):endocrowns subjected to ErCr:YSGG laser application. Group(B) (n=15): endocrowns not subjected to laser (control). After cementation of the samples, group A was subjected to ErCr:YSGG laser application while group B was not. Testing the samples: All samples were then subjected to thermocycling at 5000 cycles, then the cemented specimens were mounted in a jig attached to a universal testing machine to measure the retentive pull out tensile load of the material. A tensile mode of force was applied via materials testing machine at a crosshead speed of 5 mm/min up to pull out the coping until cement failure. The maximum pull out load was recorded automatically in Newton via the computer software connected to the testing machine. Mode of failure was examined using photos with scanning electron microscope. Results: A statistically significant difference was found between the load required to debond both groups. group A recorded 156.66±32.89 N for debonding, while a load of 258.14±63.43 N incase of group B.