Journal of American Science 2010;6(11) http://www.americanscience.org editor@americanscience.org 264 Margin Assessment and Fracture Resistance of Adhesively Luted Ceramic Crowns Jylan F. ElGuindy 1 , Dina H. Mostafa *2 and Mona A. El Agroudi 1 1 Fixed Prosthodontics Department and 2 Biomaterials Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. * dinamostafa@hotmail.com Abstract: Objectives: The aim of this study was to investigate the effect of different adhesive systems on the vertical marginal gap distance and the fracture resistance of lithium disilicate based crowns. Methods: Forty premolars were prepared to receive forty e-max crowns. The crowns were divided into 4 groups (N=10 each) according to the adhesive luting systems. Group (U): using RelyX Unicem resin cement (self-adhesive system). Group (V): Variolink II (total-etch system). Group (GU) and group (GV): application of G-bond (self-etch) on dentin preceded previously used adhesive systems. A stereomicroscope was used to record the vertical marginal gap distance before and after cementation. The crowns were subjected to cyclic loading and fracture resistance test. Data were statistically analyzed using One-way Analysis of Variance (ANOVA) SPSS 15.0. A scanning electron microscope was used to qualitatively examine the dentin/resin interface. Results: Groups (GU) (67.6 ± 5.8 μm) and (GV) (68 ± 6.4 μm) recorded the significantly lowest vertical marginal gap, followed by group (V) (82 ± 6.8 μm). Group (U) showed the highest marginal inaccuracy (114 ± 6.4 μm). Group (GU) recorded the significantly highest fracture resistance (2840.5 ± 3.8 N), followed by group (GV) (2411.3 ± 3.3 N) and group (V) (2365.8 ± 3.6 N). Group (U) showed the lowest results (2270.9 ± 3.4 N). Conclusions: Ceramic restorations luted with total-etch system offer better vertical marginal gap distance and fracture resistance than restorations luted with self-adhesive system. Treatment of the dentin surface prior to the application of the bonding system is efficient. [Journal of American Science. 2010;6(11):264-273]. (ISSN: 1545-1003). Keywords: Adhesives, marginal gap, fracture resistance, all-ceramics 1. Introduction Success of any indirect dental restorations depends on many factors among them the cementation techniques and procedures. Dental cement must act as a barrier against microleakage, holding the tooth and restoration together mechanically and/or chemically. The behavior of the cement and bonding systems is complex and partly depends on the properties and quality of the component parts of each system. 1 An ideal dental adhesive should be able to wet, infiltrate dentin and provide a durable bond between the unhomogenicity of enamel and dentin and the restoration. 2 The permeability of dentin to adhesive agents depends on the resin infiltration of both dentinal tubules and intertubular dentin, however, resin infiltration into intertubular dentin can occur only if the mineral phase of dentin is removed by acid conditioners. 3 Knobloch et al 2007, reported a résumé of the modification done through the bonding agent generations. 4 Total-etch technique including dry and wet techniques, rely on etching the dentin and removal of the smear layer. This technique involves a separate etch and rinse step followed by priming and application of the bonding resin, it is said to be a time consuming technique. 5 Self-etching technique rely on etching the dentin using non rinse acidic monomers that simultaneously condition and prime, in one step, incorporating the smear layer within the hybrid layer so that it becomes one single layer. 6 RelyX Unicem (3M ESPE, Seefeld, Germany) the self-adhesive, universal resin cement without surface pretreatment has been introduced. It is based on a novel initiation technology using new monomer and filler. The organic matrix consists of newly developed multifunctional phosphoric acid methacrylate, which, can react with the basic fillers in the luting cement and the hydroxyapatite of the hard tooth tissue. This cement quickly neutralizes during the curing process, to switch from a hydrophilic to a hydrophobic state. This unique switch allows the material to adapt to the tooth structure while in the hydrophilic state, yet provide for ongoing dimensional stability with the restoration after converting to the hydrophobic matrix. 7 Today operators have the choice between water based and resin based cements, which can be used with or without adhesives.