Influence of curing units on one-step self etch adhesives

Objectives: To determine the effect of different curing units on microshear bond strength to enamel using one-step self-etch adhesives. The tested hypothesis was that curing unit type affects the bond strength of adhesives.

Methods: One-hundred and eighty human molars were used. Teeth were randomly divided in three main groups, according to the adhesive system used (n=60): Scotchbond Universal (3M ESPE); G-BOND (GC Corporation) and MTB-200 (Kuraray). Each adhesive system was applied according to manufacturer's instructions. Each group was divided in three subgroups according to the type of curing unit used (n=20): Bluephase-LED (Ivoclar Vivadent), VALO-LED (ULTRADENT) and Elipar 2500-halogen (3M ESPE). A composite (Filtek Supreme Z250- 3M ESPE) build-up was created on the bonded enamel surface, and immediately tested for microshear bond strength testing. Specimens were loaded to failure, and data statistically-analyzed by one-way Anova and Tukey's post-hoc test (p<0.05).

Results: Microshear values are reported in Table 1. G-bond showed lower bond strength than the other adhesives with all the tested curing units. Curing unit type did not affect MTB-200, while Scotchbond Universal polymerized with Bluephase showed the highest values.

Table 1: Means (MPa ±SD) of microshear bond strength of the tested adhesives.

	Scotchbond Universal	MTB-200	G-BOND
Bluephase	23.2(±2.0)e	19.4(±2.9)bcd	15.2(±2.8)a
VALO	20.4(±1.9)cd	18.5(±1.8)bc	15.7(±2.2)a
Curing unit 2.500	20.6(±1.7)d	18.1(±1.9)b	15.5(±1.9)a

Same superscript letters indicate no statistical difference (p>0.05).

Conclusions: The tested hypothesis was partially accepted since microshear bond strength varied according to adhesive type and was affected by curing unit only when Scotchbond Universal was used.

Supported, in part, by grants: FIRB RBAP1095CR and PRIN 2009SAN9K5 and 2009FXT3WL from MIUR, Italy.