Statement of problem: The clinical success of the ceramic restoration system that is strongly bonded to the tooth structure in order to prevent microleakage, marginal fracture, discoloration, and secondary caries. Which do types of cements and surface treatment considerably influence. Purpose: This study investigated the shear bond strength between three all ceramic systems (CAD-CAM CEREC type, The VM7( VITADURVEST) powder, and IPS Empress II) treated by air abrasion and hydrofluoric acid, then cemented to tooth structure by two types of adhesive resin cements.
Material and methods: Ninety freshly extracted human lower third molar teeth were used. Each tooth was free of caries or restorations. Teeth were embedded into autopolymerizing resin limited to their cervical line using dental surveyor. The occlusal third of the molars was grounded using diamond stones under water coolant to make dentin discs with smooth and flat surface. Ceramic discs with 5mm diameter and 3mm thickness of three types of all ceramics and two types of chemically cured resin cements were used.All specimens were randomly divided into three groups of 30 teeth each
according to the ceramic used. Each group are divided into three subgroup(n=10). The bonding surfaces of each ceramic discs of each subgroup are treated with one of the following: 9% hydrofluoric acid, Airborne particle abrasion with 50 μm grain sized aluminum oxide particles and Air abraded with 50 μm grain sized aluminum oxide particles and etched in 9% hydrofluoric acid .The ceramic disks were bonded to the flattened molars using one of the two types of the resin cement used in this study. All samples were mounted on a computer controlled materials testing machine with a load cell of 5
KN and their data were recorded using computer software. Results: The results of the present study showed the following mean loads at fracture: the Cerec type (7.56+1.96 N), VM7 (6.21+0.99 N) and Empress II (6.96+1.72 N) .ANOVA and Tukey's post-hoc test showed that the differences between these all ceramics types were statistically nonsignificant
(p>0.05). However the CAD-CAM Cerec blocs gave the highest mean of  shear bond strength .on the other hand, Statically analysis of the results showed that the differences between the three types of surface treatment were statistically significant (p<0.05). Hydrofluoric acid etching produced the highest mean shear bond strength. Panavia dental adhesive is better than Dyract cem plus as it produced higher mean shear bond strength values in all cases of this study. Conclusions: The three types of All ceramic used in this study have no clear effect in the Shear bond strength of ceramic to tooth structure, Hydrofluoric acid etching produced the higher mean shear bond strength than air abrasion(AA) with aluminum oxides, and according to this study Panavia dental adhesive is better than Dyract cem plus in Shearbond strength.