Curing mode and aging affect monomer conversion of resin cements

OBJECTIVES: To evaluate the effects of curing protocol and aging on degree of conversion (DC%) of dual-cured resin-cements. METHODS: Dual-cure resin-cements were mixed, light-cured (LC) immediately (Control) and DC (FTIR/ATR) determined after 5 and 15 min. Experimental samples were either allowed to self-cure (SC, dark) for 10 min and then light-activated with DC determined after SC/10min and 5 min after LC (EX1); or allowed to SC only for 15 min (EX2). DC was re-measured after aging the products for 12 weeks@37^oC. Five specimens (0.5 mm thick) were prepared for each condition and light-cured at 500 mW/cm²/as per manufacturer's instructions. RESULTS: ANOVA and Tukey test revealed significant influence of curing mode and aging (p<0.05). Mean DC%(SD):

condition    material	Control		EX1		EX2
	LC-5min	LC-15min † ‡	SC-10min	LC-5min	SC-15min
VARIOLINK(Ivoclar)	57.2(1.5)	*53.6(0.8)	*6.2(1.9)	54.6(3.5)	*19.9(2.9) ‡
Aged	54.9(2.1)	59.1(0.9)	2.5(1.8)	56.6(1.1)	1.3(0.4) ‡
CALIBRA (Dentsply)	45.9(1.7)	49.3(2.9)	*35.3(2.9)	*43.5(0.2) †	*40.5(0.9)
Aged	45.7(0.4)	47.7(0.4)	7.8(0.7)	49.2(0.3)	24.8(0.4) ‡
DUOLINK (Bisco)	49.4(0.3)	*53.8(3.3)	*47.7(2.1)	56.0(1.2)	*54.3(2.2)
Aged	52.2(1.6)	60.6(1.2)	44.7(1.6)	57.6(1.2)	47.6(1.0) ‡
PANAVIA F (Kuraray)	*36.3(1.8)	43.4(2.2)	1.3(0.7)	*36.2(1.4) †	*7.1(1.9) ‡
Aged	29.8(3.0)	40.9(4.1)	3.1(1.4)	42.8(1.2)	3.1(1.3) ‡
BISCEM (Bisco)	48.8(0.2)	*54.6(0.4)	32.0(0.9)	*50.5(0.4)	*35.1(0.2) ‡
Aged	50.2(1.5)	61.1(1.2)	29.5(4.5)	59.3(2.9)	29.5(4.7) ‡

* Indicates significant differences between fresh vs. aged per condition; † ‡ = indicates significant difference in final cure from control LC-15 min.

In general, DC increased with time after light-curing. Delaying light-activation for 10 min caused slight alterations in the final DC regardless of aging for some products. Aging dramatically affected the self-curing capability of the dual-cure cements and some did not present sufficient self-curing ability regardless of aging. CONCLUSION: DC was significantly affected by curing mode and aging of dual-cure resin cements. Some products did not properly cure without light-activation.

 SUPPORT: CAPES-Brazil; Bisco, Inc