الفهرس 
IntrodllctionOnly 14 pages are availabe for public view
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Abstract
Dentin-bonded allceramic crowns become a daily practice in the dental office. Allceramic crowns have the advantages of high esthetic quality and biocompatibility. However low fracture resistance and poor marginal fit still a common disadvantage among allceramic restorations. Several modifications in ceramic materials, fabrication techniques and adhesive luting agents were introduced in the dental market to improve strength properties and marginal fit of allceramic crowns. In this invitro study fracture resistance, marginal fit, internal fit and microleakage of Cerec 3 CADCAM and laboratory fabricated Duceram LFC crowns were evaluated. Ninetyone sound maxillary premolars were used in this study. Unprepared 7 premolars were used as a control group. The other 84 premolars were prepared for allceramic crowns. The prepared teeth were divided into 3 groups. Each group of 28 teeth for each ceramic material. Three ceramic materials were used (ProCAD and Vita Mark II) machinable ceramic and Duceram LFC. Furthermore each group was divided into two subgroups. Each subgroup of 14 teeth for each bonding procedure. Fiftysix CADCAM crowns (28 Vita Mark II and 28 ProCAD) were fabricated using Cerec 3 CADCAM system. While 28 Duceram LFC crowns were laboratory fabricated. Fortytwo crowns (14 of each ceramic material) were placed on their respective prepared natural teeth. Marginal fit was measured at preselected four points (mid, buccal, palatal, mesial and distal) using a stereomicroscope. Crowns were bonded to their respective prepared teeth with two different bonding procedures. First procedure by etching the fitting surface of each crown with 4.9% HF acid. Following that samples were cleaned in an ultrasonic bath containing distilled water then dried. After that Mirage ABC silane coupling agent was applied. Second procedure by cleaning the fitting surface of each crown using 65% aqueous solution of phosphoric acid. Following that samples were cleaned in an ultrasonic bath containing distilled water then dried. After that Porcelain Liner M was applied. Finally Mirage ABC dentin adhesive and Superbond C&B luting agent were used for cementation. One hour after cementation, the bonded samples were stored in water bath at 37 0C for 24 hours. Following that 42 samples, which were used for evaluating the marginal fit, were thermalcycled for 1500 cycles. Immersed in 50 % aqueous solution of silver nitrate for 1 hour. Then washed in distilled water and exposed to fluorescent light for 3 hours. Samples were embedded in transparent acrylic resin, sectioned and examined for internal fit and dye penetration at ceramic/cement and tooth/cement interface.