Effect of Ultrasonic finishingon the Accuracyof FitandMicro leakageof Lithium Disilicate Crowns

Abstract

The current study evaluated the effect of ultrasonic finishing on marginal accuracy, internal fit and microleakage of empress e-max crowns fabricated by two methods. In this study, the teeth were divided into two groups according to the type of finish line as the following: Group (c): 20 upper central incisors with a deep chamfer finish line, of a 1mm width. Group (s): 20 upper central incisors with a shoulder finish line, of a 1mm width. Each group was divided according to the type of finishing tool into two subgroups: Subgroup (C I): Ten upper central incisors possessing a deep chamfer finish line were finished using low speed conventional finishing stones. Subgroup (C II): Ten upper central incisors possessing a deep chamfer finish line. The prepared teeth were finished all around using Satelec Perfect Margin chamfer (PM) ultrasonic Kit. Subgroup (S I): Ten upper central incisors possessing a shoulder finish line were finished using low speed conventional finishing stones. Subgroup (S II): ten upper central incisors possessing a shoulder finish line were finished all around for each side using a Satelec Perfect Margin Shoulder (PMS) ultrasonic Kit. The surface roughness was measured at the area of the finish lines of all prepared teeth surfaces to obtain a quantitative comparison of the two finishing protocols by using Stereo microscope. Electron microscopic scanning was done for evaluation of the morphologic and microstructural changes after finishing. Forty crowns were constructed using Empress e-max ceramic material using two techniques;