Influence of Surface Treatment of Contaminated Ceramics on Surface Free Energy and Resin Cement Bonding

Abstract

 Purpose: The purpose of this study was to examine the influence of saliva contamination and cleaning methods on the surface free energy of ceramics and resin cement bonding.
 Methods: Lithium disilicate glass-ceramic (IPS e. max CAD, EM) plates were used. All specimens were ground with 600-grit silicon carbide paper, and then hydrofluoric acid (Ceramic Etching Gel, CE) application was carried out. The cleaned samples were randomly divided into five groups as follows: Group 1 (control) : the specimens were not contaminated, Group 2 (SC) : after saliva contamination, the surface was rinsed with tap water, Group 3 (TE) : after saliva contamination, the surface was treated with phosphoric acid (Total Etch) for 30 s, Group 4 (IC) : after saliva contamination, the surface was treated with Ivoclean for 20 s, Group 5 (CE) : after saliva contamination, the surface was subjected to additional hydrofluoric acid application. The surface free energy of the ceramic surfaces and the bond strengths of resin cement were measured.
 Results: For all of the SC group treated surfaces, γ_S^d, γ_S^p, and γ_S^h values of the SC group decreased compared with the control. On the other hand, γ_S^p and γ_S^h values of the treated group increased substantially. The control and CE groups showed relatively higher bond strength, and no significant differences were found among these three groups under different storage conditions.
 Conclusion: The results of this study indicate that a thin layer of contaminants remains on the ceramic surface after exposure to saliva, significantly impeding the bonding of the resin cement and reducing the surface free energy. Hydrofluoric acid application is an effective method of removing the contaminants and creating an effective surface for resin cement bonding.