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Effect of low-viscosity resin-based composite on the microleakage of cervical restorations.

PURPOSE
To investigate the effect of a low-viscosity resin-based composite (LVC) liner on the microleakage of cervical resin-based composites bonded with new adhesive systems.


METHODS
180 wedge-shaped cervical cavities on bovine incisors were treated with AQ Bond (all-in-one), ABF (experimental two-step self-etching primer containing antibacterial monomer) or Clearfil SE Bond (two-step self-etching primer) systems according to the manufacturers' instructions. Half of the treated cavities in each adhesive system were lined with an LVC (Protect Liner F) and filled with a hybrid resin-based composite (Clearfil AP-X). Ten specimens from each group were immersed in 0.5% basic fuchsin solution immediately after finishing the restorations. The specimens to be subjected to thermocycling (5-60 degrees C, 15 seconds dwell time, 5,000 cycles) or to flexural load cycling (approximately 0.5 mm labio-lingual displacement at the incisal edge, 10,000 cycles, 1 Hz) prior to immersion in the dye solution were also prepared. The teeth were sectioned through the center of the restorations and the degrees of dye penetration were scored. The data were analyzed with the Mann-Whitney U-test or the Kruskal-Wallis test (P < 0.05).


RESULTS
The use of the LVC liner significantly improved marginal sealing of AQ Bond. However, the LVC liner could not prevent the deterioration in the marginal integrity caused by thermocycling or flexural load cycling. In the case of ABF, the use of the LVC liner showed a trend toward less microleakage. For Clearfil SE Bond, the LVC liner prevented the deterioration in the marginal seal caused by thermocycling.