Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics

Abstract

The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM-Vita Mark II-Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey's test. Only the factor "HF concentration" was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.

Effect of Cleaning Protocol on Bond Strength between Resin Composite Cement and Three Different CAD/CAM Materials

“…For lithium disilicate ceramic or glass ceramics in general, the cleaning with phosphoric acid is a well-tested method that shows positive results on bond strength values [ 18 ]. The common approach to bond lithium disilicate restorations includes etching with 5–9.5% hydrofluoric acid for 20–30 s in order to create a micro retentive increased surface with a high number of functional silane groups.…”

“…After etching of glass ceramics using hydrofluoric acid, the surface is often cleaned with phosphoric acid. This method has been tried and tested and leads to good bond strength values [ 18 ]. In contrast to these outcomes, there are theories that cleaning zirconia restorations with phosphoric acid can negatively affect the bond strength to resin composite cements [ 19 ].…”

Influência do tempo de condicionamento do ácido hidrofluorídrico na adesão protética de cerâmicas vítreas: uma revisão sistemática

“…As cerâmicas vítreas são consideradas materiais restauradores de escolha na odontologia, devido à sua biocompatibilidade, além das propriedades mecânicas e estéticas semelhantes aos dentes naturais (Mokhtarpour et al, 2017;Moura et al, 2020;Puppin-Rontani et al, 2017;Thiesen et al, 2019), possibilitando maior preservação dentária e durabilidade (Sudré et al, 2020). A denominação "vítrea" é atribuída aos materiais que apresentam em sua composição estrutural uma concentração de silicato acima de 15% (Fonzar et al, 2020), exemplificados pelas cerâmicas feldspáticas, reforçadas com leucita, infiltradas por polímero, de silicato de lítio reforçado por zircônia e dissilicato de lítio (Veríssimo et al, 2019).…”

“…A denominação "vítrea" é atribuída aos materiais que apresentam em sua composição estrutural uma concentração de silicato acima de 15% (Fonzar et al, 2020), exemplificados pelas cerâmicas feldspáticas, reforçadas com leucita, infiltradas por polímero, de silicato de lítio reforçado por zircônia e dissilicato de lítio (Veríssimo et al, 2019). Essas cerâmicas são indicadas para restaurações inlays, onlays, coroas unitárias, laminados e próteses fixas (Moura et al, 2020;Veríssimo et al, 2019).…”

“…A longevidade dos materiais cerâmicos está relacionada a uma adequada adesão (Wong et al, 2017), uma vez que, problemas clínicos oriundos de falhas adesivas podem ser observados, como cárie marginal, falhas cervicais, além de fraturas das restaurações (Moura et al, 2020). O protocolo considerado padrão ouro para o tratamento de superfície de cerâmicas vítreas envolve o condicionamento ácido com Ácido Hidrofluorídrico (HF) (Monteiro et al, 2018), o qual é responsável pela dissolução da matriz vítrea, com a exposição da fase cristalina.…”