Does dental ceramics’ post-etching cleaning influence its surface chemical composition and durability of adhesive bonding?
Asst. Prof. Barbara Łapińska1, Dr. Agata Szczesio-Włodarczyk2, Dr. Aleksandra Zimon3, Prof. Jerzy Sokołowski1, Prof. Małgorzata Iwona Szynkowska-Jóźwik3, Assoc. Prof. Jacek Rogowski3
1 Department of General Dentistry, Medical University of Lodz, ul. Pomorska 251, 92-213 Lodz, Poland,
2 University Laboratory of Materials Research, Medical University of Lodz, Pomorska 251, 92-213 Lodz, Poland,
3 Institute of General and Ecological Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland
Objectives
Adhesive cementation of all-ceramic prosthetic restorations fabricated glass ceramics involves hydrofluoric acid etching of ceramic surface. Despite rinsing the etchant from ceramic surface with water spray, some debris can still be present on the surface, potentially influencing the durability of adhesive bonding. Hence additional cleaning was proposed, using orthophosphoric acid or ultrasonic cleaning with different media. The study aimed to evaluate the influence of post-etching cleaning of dental ceramic surface on its chemical composition and durability of adhesive bonding.
Materials and Methods
Samples of three different ceramics: leucite-reinforced (LGC), lithium disilicate (LS2) and zirconia-reinforced lithium silicate (ZLS) were fabricated, flat-polished and ultrasonically cleaned. The surface was sandblasted, followed by hydrofluoric acid etching for 60, 20 or 30 seconds, respectively. The etchant was rinsed off the surface using air-water spray (control) and additional cleaning was performed: ultrasonic cleaning in water/ethanol, orthophosphoric acid cleaning followed or not by ultrasonic cleaning in water/ethanol. After cleaning, the adhesive bonding was performed, and the samples were subjected to artificial ageing (6000 thermal cycles, 5-55°C). Shear bond strength (SBS) was tested. The surface was examined in SEM, whereas changes in surface chemical composition were evaluated using TOF-SIMS method.
Results
For LGC ceramics, the highest SBS was noted after cleaning with orthophosphoric acid followed by ultrasonic cleaning in ethanol, whereas this method resulted in the lowest SBS for both LS2 and ZLS ceramics. For LS2, all cleaning methods resulted in higher SBS than in control group, with the highest values after ultrasonic cleaning in ethanol. In the case of ZLS ceramics, the highest SBS was achieved after cleaning with orthophosphoric acid. High SBS after cleaning was correlated with low concentration of fluoride on the surface as noted by TOF-SIMS.
Conclusions
Post-etching cleaning of the ceramic surface influenced the adhesive bond strength, whereas the choice of the most effective cleaning method is material specific.