Post-etching cleaning influences the resin shear bond strength to CAD/CAM lithium-disilicate ceramics

Abstract

The hydrofluoric acid (HF) is able to promote selective dissolution of the glassy phase in silica-based ceramic. However, the etching leaves insoluble silica-fluoride salts in the surface that affects negatively the bond, affirming the need of a post-etching cleaning.

Evaluate the shear bond strength (SBS) of composite resin to CAD/CAM lithium-disilicate ceramics after different post-etching cleaning and silane treatments.

Twenty-four 2?mm-thick slices of IPS e.max CAD?(Ivoclar Vivadent, AG, Schann,?Liechtenstein) were crystallized, embedded in acrylic resin, polished and cleaned in an ultrasonic bath. Each specimen was etched with 5% HF for 20?s, rinsed for 60?s, and treatment was completed using surface cleaning and silanization. The cleaning methods were: AW—air/water spray; UB—ultrasonic bath; PA—37% phosphoric acid; and ST—steam cleaning. The cleaned surface received: E—no silane treatment; E/S—silane application for 20?s, air drying for 20?s and hot drying (60?°C) for 20?s; E/S+—silane application for 60?s, air drying for 20?s, hot air drying (60?°C) for 20?s, rinsing with boiling water for 15?s and hot air drying for 20?s. Cylinders of composite resin (n?=?12) (Z100, 3M-ESPE, Saint Paul, MN, USA) were bonded using an adhesive resin (Optibond FL adhesive, Kerr?Corp, Orange, CA, USA). SBS testing was carried out after 24?h of storage in water. Samples for each post-etching cleaning regimen were analyzed by SEM.

According to two-way ANOVA (Bonferroni-corrected post hoc tests, p?<?0.05), the SBS was significantly influenced by the post-etching cleaning, with UB yielding the highest SBS (21?MPa for E/S); other post-etching cleaning regimens showed lower SBS values (12–17?MPa). The type of silane application was not significantly different. The SEM analysis showed a cleaner ceramic surface for UB when compared to the other groups.

Etching lithium disilicate ceramics following by ultrasonic bath cleaning and regular application of a silane is recommended.