Effect of Photocuring vs. Autocuring on Properties of Resin Cements

Objective: To evaluate the effect of photocuring vs. chemical (auto) curing on mechanical properties of contemporary self-etching (SE) resin cements.  Methods:  Seven SE resin cements were tested: A. Embrace (Pulpdent); B. Monocem (shofu); C. BisCem (Bisco); D. G-cem (GC); E. Multilink Sprint (Ivoclar); F. Multilink Automix (Ivoclar); G. RelyX Unicem (3M ESPE).  Flexural strength (FS) and Elastic modulus (EM) were determined on bar-shaped specimens (2 x 2 x 25 mm). Compressive strength (CS) was measured on cylinderical specimens (6 x 4mm). Specimens were formed by placing the mixed cements into Teflon molds. Ten specimens in each group were photopolymerized using a Triad curing unit (Dentsply) for one minute. Another 10 specimens/group were tested after chemical auto-curing for 5 minutes. Specimens were placed in distilled water inside an incubator (37C⁰ ) for 24h. Testing was performed in an Instron Testing machine (0.5 mm/min). Data was analyzed using ANOVA and multiple comparison.  Results:   Mean CS, FS, EM and (SD) are shown below:

Test	Cement	A	B	C	D	E	F	G
CS (MPa)	Photo	236.3 (44)	267 (22)	204 (15)	211 (17)	198.5 (11)	300 (22)	204 (14)
	Auto	214 (21)	225 (35)	205.5 (24)	200 (15)	188.8 (8)	309 (17)	184.6 (11)
FS (MPa)	Photo	88.4 (13.4)	75 (13.7)	91 (16)	77 (12)	99 (18)	116.9 (6)	80.6 (11.6)
	Auto	42 (10)	53 (16.5)	71 (13)	59 (9.3)	75 (19)	100.8 (8)	62.6 (8.2)
EM (GPa)	Photo	2.7 (0.5)	2 (0.4)	6.8 (0.6)	7.7 (1.2)	6.3 (0.4)	6.3 (0.3)	6.9 (0.8)
	Auto	0.9 (0.3)	1.1 (0.4)	5.4 (0.9)	5.5 (0.5)	3.6 (1.3)	5.4 (0.3)	0.8 (0.4)

Conclusion:  ANOVA revealed that both cement type and curing method had a significant effect (P=0.000) on all properties tested. Photocuring proved higher mechanical properties than autocuring (P=0.000).