Current developments of dental adhesives aim for multi-substrate systems. So-called “universal adhesives” claim to facilitate adhesion to all clinically relevant surfaces. Due to the hitherto only vaguely described adhesion mechanism between such adhesives and silicate ceramics, the longevity of adhesion to this important substrate has to be investigated by robust bond strength methods. This study compares tensile bond strength (TBS) of two universal-adhesives and one dedicated state-of-the-art ceramic primer to lithium-disilicate.
Methods:
The following adhesive / cement systems were studied:
1) Scotchbond Universal (SBU) / RelyX Ultimate (RXU); (3M ESPE)
2) Optibond XTR (OTR) / NX3; (Kerr).
3) Monobond Plus (MBP) / Multilink Automix (MLAM); (Ivoclar Vivadent)
SiC-polished (600 grit) and HF-etched (Ceramic Etching Gel; Ivoclar Vivadent) lithium-disilicate slabs (emax; Ivoclar Vivadent) were treated with adhesive or primer, following manufacturer instructions. A composite-filled PMMA-cylinder (diameter = 3.2 mm) was placed on the conditioned surface using the system-associated cement and light-cured at 1200 mW/cm2 for 40s. The samples were aged for 24h in water at 37°C or by 10.000 thermocycles (TC) at 5-55°C, before testing tensile-bond-strength using a Z010 universal-testing-machine (Zwick-Roell).
Results:
|
TBS [MPa] |
||
SBU/RXU |
OTR/NX3 |
MBP/MLAM |
|
24h |
23.7±1.9(a) |
24.1±14.3(a) |
53.7±7.8(b) |
TC |
8.5±5.9(c) |
0.8±0.0(d) |
50.2±10.0(b) |
(same letters denominate statistical equivalence)
Conclusions:
Universal adhesives give significantly lower 24h-TSB to lithium-disilicate compared to the state-of-the-art primer. TC led to a further drastic drop of the TBS of universal adhesives, whereas the ceramic-primer was not affected.