Acid Etching as Surface Treatment Method for Luting of Glass-Ceramic Restorations, part 1: Acids, Application Protocol and Etching Effectiveness

Abstract

AIM:The purpose of this review is to represent acids that can be used as surface etchant before adhesive luting of ceramic restorations, placement of orthodontic brackets or repair of chipped porcelain restorations. Chemical reactions, application protocol, and etching effect are presented as well.STUDY SELECTION:Available scientific articles published in PubMed and Scopus literature databases, scientific reports and manufacturers’ instructions and product information from internet websites, written in English, using following search terms: “acid etching, ceramic surface treatment, hydrofluoric acid, acidulated phosphate fluoride, ammonium hydrogen bifluoride”, have been reviewed.RESULTS:There are several acids with fluoride ion in their composition that can be used as ceramic surface etchants. The etching effect depends on the acid type and its concentration, etching time, as well as ceramic type. The most effective etching pattern is achieved when using hydrofluoric acid; the numerous micropores and channels of different sizes, honeycomb-like appearance, extruded crystals or scattered irregular ceramic particles, depending on the ceramic type, have been detected on the etched surfaces.CONCLUSION:Acid etching of the bonding surface of glass - ceramic restorations is considered as the most effective treatment method that provides a reliable bond with composite cement. Selective removing of the glassy matrix of silicate ceramics results in a micromorphological three-dimensional porous surface that allows micromechanical interlocking of the luting composite.

Current status on lithium disilicate and zirconia: a narrative review

“…For LS 2 , 20 s HF etching (at 5% concentration) is suggested, that is a shorter time than requested for feldspathic and leucite-based ceramics (generally 60 s). Higher HF concentrations (9-10%) and longer etching times have been shown to be too aggressive and can introduce relevant damages, not only to the surface but also to the internal microstructure of the material, negatively influencing mechanical performance (reduction of flexure strength), adhesion potential and long-term success of ceramic restorations, particularly when thickness is low [38][39][40][41]. Another system to create surface microirregularities is sandblasting LS 2 with aluminum oxide particles.…”

Contemporary Dental Ceramic Materials, A Review: Chemical Composition, Physical and Mechanical Properties, Indications for Use

“…In the third group - “resin-matrix ceramics” are included materials that have a polymer matrix, containing predominantly inorganic refractory compounds [ 7 ]. Different phases present in materials’ chemical composition affects the sensitivity of the ceramic material to the hydrofluoric acid when etching (as a surface treatment method before adhesive luting) to achieve stronger resin-ceramic bond [ 19 ].…”

“…Numerous micropores and channels of different sizes with irregular ceramic particles can be observed on the surface of VITA Mark II after surface etching with hydrofluoric acid; such a modified surface micromorphology is suitable for capturing of a composite luting cement [ 19 ] [ 22 ].…”

“…Randomly-oriented, densely distributed, elongated fine-grained lithium disilicate crystals, 1.5 µm in length, scattered with shallow irregularities become visible after dissolving the glassy matrix by etching the surface with hydrofluoric acid (HF) [ 19 ] [ 22 ] [ 30 ].…”

“…Dissolving of the glassy matrix using hydrofluoric acid before adhesive lutting of the restoration made up from zirconia-reinforced lithium silicate causes exposure of the homogeneously and densely arranged bean-like lithium silicate crystals [ 19 ] [ 22 ].…”