Resin Cements Bonded on Different Treated Non-precious and Semi-precious Metal-alloys

With self-etch resin cements becoming more popular, some dentists may be tempted to use them to bond Maryland bridge. Objective: To compare the shear bond strength of a self-etch versus a total-etch resin cements when bonded to enamel and metal-alloy treated surfaces. Methods: Flat enamel (E) surfaces (n=15/group), non-precious metal-alloy (Np) disks (n=15/group), semi-precious metal-alloy (Sp) disks (n=15/group) were mounted in cold-cure acrylic rings. Cylinders (d=2.38mm x h=3.0mm) of Clearfil Esthetic Cement & DC Bond Kit (C) and RelyX Unicem (R) resin cements were bonded to enamel and to metal-alloy prepared surfaces (sandblast (SB), SB + sulfuric acid (SA) or SB + tin deposition (T)), polymerized, stored (H₂O, 37°C, 24hours) and thermocycled (500 cycles). Samples were tested individually in an Instron Universal Testing machine (1mm/min). Statistical analysis was done using a T-test comparison followed by a post hoc multiple comparisons (p£0.05). Results:

Bond strength MPa	Enamel	Non-precious metal-alloy		Semi-precious metal-alloy
	(Mean  ±  sd)	(Mean  ±  sd)		(Mean  ±  sd)
Resin Cements		SB	SB + SA	SB	SB + T
Clearfil Esthetic Cement	33.97 ±  17.18a	25.21 ±  14.66a, b	34.11 ±  15.57a	34.60 ±  14.86a	18.43 ±  10.83b
RelyX Unicem	10.48 ±  11.23b	15.96 ±  3.37b	18.90 ±  9.55b	11.41 ±  10.53c	10.08 ±  7.68c

For each group, values with same superscript are not significantly different. Results on enamel showed that the total-etch resin cement (C) had a statistically significant higher bond strength (33.97±17.18 MPa) than the self-etch resin cement (R) (10.48±11.23 MPa) (p£0.05). In the Sp group, a thin layer of tin added on the sandblasted metal surface reduced the bond strength significantly with the C resin cement (p£0.05). Conclusion: The total-etch resin cement (C) showed a statistically significant higher bond strength than the self-etch resin cement (R) on enamel and on three (Np-SB+SA; Sp-SB; Sp-SB+T) of the four metal-alloy surface groups.