Fatigue Failure Load of Restored Premolars: Effect of Etching the Intaglio Surface of Ceramic Inlays With Hydrofluoric Acid at Different Concentrations

Abstract

The aim of this study was to evaluate the effect of etching, with different hydrofluoric acid concentrations at the intaglio surface of feldspathic ceramic inlays, on the fatigue failure load of restored premolars. A total of 60 upper premolars were embedded in plastic cylinders with acrylic resin (up to 3 mm below the cement-enamel junction) and prepared using a device specially designed for that purpose. Teeth were randomly assigned to three groups (n=20): HF1, HF5, and HF10 (etching with hydrofluoric acid for 60 seconds at concentrations of 1%, 5%, and 10%, respectively). Preparations were scanned and restorations were milled by a computer-aided design / computer-aided manufacturing system. The inner surfaces of the inlays were etched and received an application of a silane coupling agent; the dentin and enamel were treated appropriately for the luting system (RelyX ARC, 3M-ESPE). The restorations were cemented and the fatigue failure load (in N) was determined using the staircase method (10 Hz; 10 cycles in each step). The initial load (585.5 N) was applied on the slopes of the cusps (labial and palatal/lingual, simultaneously) through a cylinder attached to the test machine (Instron ElectroPuls E3000). The tested samples were analyzed under a stereomicroscope for failure analysis. Fatigue data were analyzed by one-way analysis of variance. There was no statistical difference among the fatigue failure loads (in N): HF1 (448.5±79.1), HF5 (360.7±55.4), and HF10 (409.5±121.1). Regarding the fracture mode, there was a predominance of interfacial fracture (50%), followed by cusp fracture (34.6%). It may be concluded that the etching with hydrofluoric acid at the tested concentrations (1%, 5%, and 10%) does not influence the fatigue failure load of feldspathic ceramic inlays cemented on premolars.

Effect of hydrofluoric acid and self-etch ceramic primers on the flexural strength and fatigue resistance of glass ceramics: A systematic review and meta-analysis of in vitro studies

“…Cementation can improve the mechanical behavior of brittle materials by diminishing flexure, improving stress distribution, and reducing tensile stresses on the intaglio surface opposite to the cusp contact [27] , [48] , [46] , [55] , [47] . Therefore, reducing radial flexural fractures.…”

Effect of different impression methods and ceramic materials on adaptation of inlays

“…For maximum longevity of these restorations, the bond between the tooth structure and allceramic inlays should be reliable, since this type of restoration is retained in the preparation mainly by the bond between different substrates (dentin / enamel and restorative material) [1] and the low mechanical friction that takes place. [2] Thus, the ceramic type should be taken into account for a proper cementation. Both, feldspathic and lithium disilicate ceramic have shown to be suitable for inlay restorations.…”