Influence of Light on Bonding of Dual-cure Resin to Ceramic

Objective: To measure and compare shear bond strength of three dual-cure composite resin cements; EXP (experimental cement), PAF (Panavia F 2.0, Kuraray), and MAM (Multilink Automix, Ivoclar Vivadent) to leucite reinforced feldspathic ceramic (Ivoclar Vivadent) with (WLI) and without light irradiation (W/OLI).

Method: Forty square blocks (10 x 10 x 3 mm) were prepared for each cement group from the ceramic material (total n=120).The top surfaces of blocks were acid etched with hydrofluoric acid (4.8%) for 60 seconds. Cylindrical composite samples (2.1 mm in diameter, 3 mm in height) were prepared and  bonded to the ceramic  surfaces with one of the study cements in a special alignment apparatus, where a load of 1000 g was applied for 10 minutes. Half of the specimens were light cured, while the other half was prepared and kept in a darkroom without light exposure. The light-cure specimens were irradiated for 40 s from three sides for a total of 120 s. The specimens were stored in deionized water at 37⁰ C for 24 h and thermocycled for 10,000 cycles between 5 to 60⁰C with 60 s dwell time. Shear bond strengths were determined at a cross-head speed of 0.5 mm/minute. Shear forces were converted to MPa by dividing the failure load by the bonding area. Data were analyzed with ANOVA and Tukey's HSD test. Result:

CEMENTS	Bond strength [Mpa]±SD
	WLI	W/OLI
PAF	13.9±4.5a	9.6±4.0be
MAM	10.4±4.1b	10.8±4.1bd
EXP	17.9±4.5c	6.4±2.9e

EXP showed the highest bond strength values after light irradiation. However, bond strength was significantly less for PAF and EXP when cements were not lightcured (p<0.05), Bond strength did not change for MAM with or without light curing. *Means with same letter are not different

Conclusion: Self-curing capacity of dual-cure resin cements significantly affects their bonding performance to ceramic surface.