Self-Etching Glass-Ceramic Primer vs. Universal Adhesives: Bond Strength to Lithium-Disilicate

Objectives: The established standard technique to prepare glass-ceramic restorations for adhesive cementation recommends hydrofluoric acid (HF) etching prior to silanization. To eliminate the use of potentially toxic HF, a new HF-free self-etching glass-ceramic primer, Monobond Etch&Prime (MBEP), was developed to etch and prime glass-ceramics in one step.
This study compares bond-strength to lithium-disilicate (LD2; e.maxCAD, Ivoclar-Vivadent) of MBEP to a state-of-the-art ceramic primer and several universal adhesives.
Methods: Shear bond strength (SBS, N=5) to LD2 was investigated using the following material combinations.

Group: Etchant; Primer/Adhesives; Cement; Manufacturer
MBEP: No HF; Monobond Etch&Prime ; Multilink Automix; Ivoclar Vivadent
MBP: 5% HF; Monobond Plus; Multilink Automix; Ivoclar Vivadent
OXTR: 5% HF; Optibond XTR; NX-3; Kerr
ABU: 5% HF; AllBond Universal; DuoLink; BISCO
SBU: 5% HF; Scotchbond Universal; Relyx Ultimate; 3M ESPE

LD2-surfaces were wet-ground followed by HF-etching (20s, 5%HF) for all groups, except for MBEP, which does not require HF-etching. Prepared surfaces were then treated with either a primer or an universal adhesive according to manufacturer’s instructions. Afterwards the system-cement was applied in a single increment using an Ultradent-SBS-jig. Samples were light-cured for 20sec or 40sec for OXTR (Bluephase-Style, 1200mW/cm², Ivoclar-Vivadent) and stored in water for 24h@37°C or thermocycled 10’000-times at 5-55°C (30sec dwell-time; 10’000TC).
Results: For results see table below.

Initial SBS (24h) of MBEP to LD2 was significantly higher than all other groups tested, whereby the SBS values of universal adhesives were lower than MBP & MBEP. Exposure of these samples to aging (TC) showed to a similar trend (MBEP = MBP ≥ SBU > AU >OXTR). Moreover, pre-test-failures for OXTR were observed.
Conclusions: MBEP offers a promising HF-free alternative to the commonly combination of HF & primer or HF & universal adhesives, ensuring high bond-strength and bond longevity.