Shear Bond Strength Of Two Self-Adhesive Resin Cements To Zirconia

Objective: To compare the immediate and aged shear bond strength values of 2 commercially-available self-adhesive resin cements to zirconia: one utilizing silica-coating and silanation as zirconia surface treatment, and the other containing a phosphate monomer, eliminating the need for a separate primer.

Method:

Sixty resin-composite rods (2.5mm in diameter and 3mm in length) were fabricated from a nano-optimized resin-composite (Tetric EvoCeram) using a Teflon mold then light polymerized with an LED light (Bluephase-G2). Zirconia plates (10X10X4mm) were sectioned from yttria-stabilized full-contour zirconia puck  (DiaZir), sintered, then mounted in  autopolymerizing acrylic-resin custom tray material (Bosworth Fastray). Composite rods were cemented to the zirconia plates using 2 different cements. Surface treatment of zirconia followed manufacturers’ instructions for each cement (Table 1)

	SpeedCEM	RelyX-Unicem
Mechanical Surface treatment	Airborne-particle abrasion (50µ-Al2O3, 1-bar).	Silica-coating (30µ silica-modified Al2O3).
Chemical surface treatment	None	Silane coupling agent.

Specimens were light polymerized and divided into 3 groups for each cement:

1-Immediate: specimens were loaded to failure immediately after preparation. 2-24hr: specimens were stored in an incubator for 24hrs before loading. 3-Aged: specimens were stored in an incubator for 60 days and received 10,000 thermocyles (5-55, 15 seconds dwell time) before loading. Specimens were loaded to failure in a universal loading machine (Instron) and the data analyzed using 2-way ANOVA (alpha=0.05).

Result:

Shear bond strength values are listed in Table-2. Bond strength for both cements was highest at 24-hrs and lowest in the immediate groups. There was no statistically-significant difference between the cements at any group level.

	SpeedCEM	RelyX-Unicem
Immediate	20.8±2.1a	16.8±3a
24hr	30.3±6.6b	31.9±4.6b
Aged	25.6±2.9c	22.8±3.5c

Groups assigned different superscripts are significantly different(P<0.05).

Conclusion:

Both cements had comparable bond strength to zirconia. MDP-containing SpeedCEM established a durable bond to full-contour zirconia without the need for a special surface treatment providing a more practical cementation choice.