Conclusions .
Airborne-particle abrasion and tribo-chemical silica coating are the pre-treatment methods with more evidence in the literature .
Increased adhesion could be expected after physico-chemical conditioning of zirconia .
Surface contamination has a negative effect on adhesion .
There is no evidence to support a universal adhesion protocol
Background .
Reliable bonding between resin composite cements and high strength ceramics is difficult to achieve because of their chemical inertness and lack of silica content that makes etching impossible .
The purpose of this review is to classify and analyze the existing methods and material s suggested to improve the adhesion of zirconia to dental substrate by using composite resins , in order to explore current trends in surface conditioning methods with predictable results .
Methods .
Effects of some chemical surface modifications on resin zirconia adhesion.
OBJECTIVES To evaluate the effects of various chemical surface modifications on adhesion between zirconia and resin adhesive . MATERIAL AND METHODS Pre-sintered zirconia discs were sectioned from commercial cylindrical blocks and polished with abrasive papers under running tap water . All the discs were r and omly divided into five study groups according to the methods of surface treatment , including : the  control group ( fully sintered , without any modification ) , group S ( fully sintered and s and blasted with silica coated alumina particles ) , group HN ( fully sintered and etched with a blend of mineral acid solution at 100 ° C for 25 min ) , group HF ( fully sintered and etched with 48 % hydrofluoric acid solution at 100 ° C for 25 min )  , and group Si ( coated with silica particles and then fully sintered ) .  The mean value of surface roughness was evaluated before further treatment . Resin stubs ( 3.6 mm in diameter and 3 mm in height ) were adhered and light cured on each zirconia disc after the application of a silane coupling agent . In each group , all the sample s were further divided into three subgroups with each n=12 , one for the measurement of initial adhesion strength ( shear bond ) value and the other two were tested after thermal cycling for 10,000 and 20,000 cycles , respectively . The results were analyzed with two-way ANOVA and Turkey HSD ( p<0.05 ) . XRD technique was utilized in the examination of zirconia surface crystallinity . The morphological appearance of zirconia surface after surface treatment was observed with SEM . RESULTS The control group showed the lowest initial shear bond strength ( SBS ) value ( 16.8 ± 2.4 MPa ) and did not survive the aging treatments . All the investigated surface treatments improved resin zirconia bond strength significantly , the group S displaying the highest initial value of 25.1 ± 2.7 MPa . However , the highest resistance to the aging effects of thermal cycling was found in group Si . It was further shown in the XRD examination that only the grit-blasting caused the crystalline transformation from tetragonal phase to monoclinic phase ( T → M ) . On the other h and , such a phase transformation could not be detected in all the other four groups . SIGNIFICANCE Resin zirconia adhesion could be effectively improved by both HF etching and silica coating on zirconia surface , without leading to a T → M crystalline phase transformation
Conclusions .
Airborne-particle abrasion and tribo-chemical silica coating are the pre-treatment methods with more evidence in the literature .
Increased adhesion could be expected after physico-chemical conditioning of zirconia .
Surface contamination has a negative effect on adhesion .
There is no evidence to support a universal adhesion protocol
Background .
Reliable bonding between resin composite cements and high strength ceramics is difficult to achieve because of their chemical inertness and lack of silica content that makes etching impossible .
The purpose of this review is to classify and analyze the existing methods and material s suggested to improve the adhesion of zirconia to dental substrate by using composite resins , in order to explore current trends in surface conditioning methods with predictable results .
Methods .