Shear Bond Strength Between Dentin And Zirconia Or Lithium Disilicate

Objectives: Many studies have been reported to test the bond strength between resin cements and dentin, or between resin cements and indirect substrates, but few have been done to test the bond strength directly between dentin and indirect substrates. The purpose of this study was to measure resin cements’ shear bond strengths between dentin and indirect substrates (e.g. zirconia and lithium disilicate). 

 Methods: Three commercial resin cement systems were chosen for the study: Duolink SE system (Bisco), Multilink System (Ivoclar Vivadent), and RelyX UniCem2 (3M ESPE). Lithium disilicate (Emax) and zirconia ceramics were sectioned into 21 bars (2×2×10mm) each. The surface to be bonded (2×2 mm) of lithium disilicates was etched (25sec, 4%HF Porcelain Etchant). The zirconia surface to be bonded (2×2mm) was lightly sandblasted (0.3MPa, 10sec, 10mm distance) by alumina sand. Dentin was polished by 320-grit SiC paper and rinsed with water. According to manufacturer’s instructions, lithium disilicate (or zirconia) bars were bonded to dentin by one of the three resin cement systems in self-curing modes (37ºC, 15min). The shear bond strength was tested (n=7) on an Instron tester (crosshead speed 5mm/min) after storage in de-ionized water (37ºC, 24 hours). The data were analyzed statistically by one-way ANOVA and Tukey Tests (p<0.05).

 Results: The test results are shown in the table below. For each row, means with different letters are statistically different at p < 0.05.

Average Bond Strength, MPa (Standard Deviation)	Duolink SE	Multilink	UniCem2
Zirconia-Dentin	20.6(2.1)a	16.9(3.8)b	1.6(0.5)c
Lithium Disilicate-Dentin	23.1(5.0)A	15.2(4.1)B	7.2(2.7)C

 Conclusions: Duolink SE system had significantly higher bond strength than Multilink System and RelyX UniCem2 (p<0.05). UniCem2 is the more convenient system, but provided the lowest bond strength (lower than 10MPa).