The effect of flexural load cycling on the microleakage of cervical resin composites

Although several in vitro studies have attempted to investigate the microleakage of Class V resin composites under loading, the effect of load cycling on marginal seal is still unclear. This may be due to the fact that axial loads were applied to the specimens. This study investigated the effect of flexural loads on marginal sealing of cervical resin composites. One hundred and fifty cervical wedge-shaped cavities were restored with Clearfil Photo Bond, Clearfil Liner Bond 2, Scotchbond Multi-Purpose with 10% maleic acid, Scotchbond Multi-Purpose with 35% phosphoric acid or Mac-Bond 2 according to the manufacturers' instructions. After the restorations were finished, 10 specimens from each group were immersed in 0.5% basic fuchsin solution to examine microleakage. Prior to dye solution immersion, 20 specimens were subjected to flexural load cycling (1 mm labio-lingual or linguo-labial displacement at the incisal edge, 10,000 cycles, 1 cycle/second). The data were analyzed using the Kruskal-Wallis test and the Mann-Whitney U-test (p<0.05). When the flexural loads were not applied, both the incisal and apical margins showed good marginal sealing, regardless of the adhesive system used. Labio-lingual loading significantly deteriorated the marginal integrity at the incisal enamel margins, except for those restored with Clearfil Photo Bond. However, only Clearfil Photo Bond demonstrated a significant increase in microleakage along the apical dentin margins. Linguo-labial loading had no significant effect on the marginal seal.