Effect of post-etching cleaning methods on surface micromorphology and shear bond strength of composite resin cement to feldspathic ceramic blocks

Statement of the problem: Silica-based ceramics, such as feldspathic porcelain are widely introduced as laminate veneers and inlays/onlays due to their excellent esthetic properties. The success in achieving the right bonding protocol is the challenge which contributes to the restorations longevity.
Objectives: This study aimed to evaluate the effect of post etching surface cleaning protocol on the surface micromorphology and shear bond strength of resin cement composite to feldspathic ceramic blocks.
Materials and Methods: A total of sixty discs (fifty for the mechanical test and 5 for each scanning microscopic method) of feldspathic ceramic blocks (VITA MARKII) were prepared and etched with 9.5% hydrofluoric acid for 90 seconds the discs then randomly divided into five groups (N=10) HF not subjected to any cleaning step after HFl etching. The HHU group 37% phosphoric acid postetched for 30 seconds then immersed in ultrasonic bath for 5 minutes, the HHV group was postetched with 37% phosphoric acid for 30 seconds then vacuum dried, HV group was vacuum dried only. The HHUV group was postetched with 37% phosphoric acid for 30 seconds then immersed in ultrasonic bath for 5 minutes then vacuum dried. The surface of each disc was scanned for examination of the surface topography before and after surface treatments. Two different imaging techniques were used: scanning electron microscopy and laser confocal microscopy. Adhesive resin cement (NEXUS 3) was directly bonded to each ceramic disc using a special device providing the same thickness of the cement layer. All the samples were then subjected to shear bond strength tests. Statistical significances between groups were analyzed using one-way ANOVA and (SNK) multiple comparison tests.
Results: The results of the shear bond strength showed that there is significant difference between (HF) group and both HV or HHV groups, while showed no significant differences with any other groups where the ultrasonic bath was used. Laser confocal microcopy 3D data analysis showed significant difference in the surface roughness depth between the groups what is subjected to Ultrasonic bath (HHUV and HHU) and the other three groups. the analysis shows significant difference as well between (HF group) and (HV and HHV groups). While was no significant difference between (HV and HHV) groups.
Clinical implication Finding an exact protocol of post etching cleaning is of a big importance nowadays with the increased shifting towards the conservatism and esthetic dentistry and laminate veneers solutions which success depends mainly on the long term bonding strength.