Evaluation of the Influence of Acid Etching Technique on Surface Roughness and Fracture Strength of Heat-Pressed Lithium-disilicate Veneers

Abstract

Background Metal-free ceramic veneers exhibit many desirable properties. However, low fracture strength is a major disadvantage. The success of the veneers depends on optimal tooth preparation and intaglio surface preparation techniques for bonding porcelain substrates to the tooth to ensure clinical success. This study was conducted to evaluate the influence of acid etching technique on surface roughness and fracture strength of veneers. Methods The in vitro study was conducted on maxillary central incisors that were prepared to receive the veneers; the specimens were divided into two groups—group A and group B. The intaglio surface of veneer in both groups was etched with 4.6 % of the hydrofluoric acid solution for 30 seconds, in group B specimens were further treated with 33% sodium hypochlorite solution treatment following which the surface roughness was measured and calculated with scanning electron microscope at a magnification of 3000X and profilometer, respectively. The fracture strength of the specimens in both groups was determined by subjecting the tooth with veneer to a universal testing machine; the force was applied until the fracture occurred. Results There was a significant difference observed in the surface roughness, fracture strength, and bond strength of the heat-pressed lithium-disilicate veneers treated solely with hydrofluoric acid and samples treated with hydrofluoric acid and phosphoric acid. Conclusion Optimizing porcelain surfaces before treatment with various adhesives and luting resins requires an understanding of the involved substrates and materials, as well as a logical and systematic methodology in their manipulation. The intaglio surface of the veneers treated with hydrofluoric acid followed with phosphoric acid has no significant difference observed in the properties of the veneers but has better bonding with the tooth structure.