Purpose: To evaluate the bond strength to machinable glass ceramic using conventional silane and multipurpose primer after different surface treatments to composite build up.
 Materials and methods: A total of 64 lithium disilicateIPS e.max CADceramicspecimens with dimension(12Ⅹ10Ⅹ3) were fabricated using milling technology, thespecimens were equally divided into 4 main groups (n=16) according to the method of surface treatment as follows. In Group I: polished, Group II: Acidulated phosphate fluoride (APF) application, Group III: Hydrofluoric acid (HF) application, Group IV:Monobond Etch & Prime (MEP) application. Each main group was further equally subdivided into 2 subgroups (n=8) according to methods of chemical bonding. Subgroup (A):Conventional silane.Subgroup (B):Multipurpose primer.Composite resin cylinder (Master fill) were fabricated and cemented to the treated specimens by multistep adhesive resin cement. All bonded specimens were stored in water bath for 5 months and subjected to 10000 thermal cycles. Shear bond strength (SBS) test was performed afterwards. Scanning Electron Microscope (SEM) was used for specimens examination
.Results: The statistical analysis were done using two-way ANOVA and serial one-way ANOVAs followed by Post Hoc Tukey-HSD test at α =(0.05). Application of multipurpose primersignificantly increased SBS (P=0.001). The highest SBS mean value (14.8 ± 2.2 MPa) was obtained for APF followed by Monobond Etch & Prime with conventional silane (14.7 ± 2.8 MPa)On the other hand,APF with conventional silane showed the lowest SBS mean value(4.6 ± 2.0MPa). There was statistically significant difference between polished and APF considering conventional silane and multipurpose primer, and no statistically significant difference was reported between HF and Etch & Prim for conventional silane and multipurpose primer.
Conclusions: Multipurpose primershowed superior bond strength in comparison to conventional silanewhen used for conditioning of lithium disilicateIPS e.max CADceramics.