Surface Structure and Chemical Composition of Hydrofluoric Acid-Etched Lithium Disilicate Ceramic After Application of Different Cleaning Methods of Saliva Contamination Removal

Background. The effective removal of saliva contamination from HF-etched inner surface of ceramic restoration, after try-in procedure, is essential to ensure the reliable bond interface between ceramic and resin cement. Ceramic surface cleaning protocols may affect, to some degree, the retentive surface structure and change its chemical composition, influencing indirectly ceramic-resin cement bond strength. Objectives. Analysis of changes in surface structure and chemical composition of lithium disilicate ceramics after applying different cleaning procedures on pre-etched ceramic surface. Material and Methods. Specimens of lithium disilicate ceramics, IPS e.max Press (R) (Ivoclar Vivadent), were formed as discs of 5 mm in diameter, in heat-press technique. Surface of ceramic specimens were polished, sandblasted with 50 mu aluminium oxide and etched with 9% hydrofluoric acid (HF) for 20 s. Following rinsing off the etchant, specimens were contaminated with saliva and water-sprayed afterwards. Next, specimens were divided into groups of 10, depending on surface cleaning method, which included cleansing with phosphoric acid, re-etching with HF, using Ivoclean (R) universal cleaning paste or without any additional cleaning. Control group were specimens without saliva contamination. Ceramic samples' surface were examined using Scanning Electron Microscopy with Energy Disperse Spectrometer (SEM-EDS) system allowing to determine changes in their morphology and chemical composition. Results. 9% HF acid etching of ceramics resulted in increasing the surface area. EDS analysis of ceramic surfaces showed no changes in chemical composition after using all tested methods of removing saliva contamination from lithium disilicate ceramic surface. Conclusions. Using phosphoric acid, re-etching with HF, Ivoclean universal cleaning paste or water spray may be found effective in the removal of contamination from HF-etched lithium disilicate ceramic surface.