Microleakage of Class II restorations and microtensile bond strength to dentin of low-shrinkage composites

To evaluate the microleakage of Class II cavities restored with experimental low-shrinking resin composites proposed for bulk filling and to measure their microtensile bond strength (microTBS) to dentin and compare to those of previously marketed low-shrinkage composites.

Class II cavities (7 mm occluso-gingival height, 2 mm mesio-distal depth of the box, 4 mm occlusal depth, 4 mm bucco-lingual width) were prepared in 50 molars and randomly divided into five groups (n = 10), according to the material: SureFil SDR flow (SDR), Filtek Silorane (FS) and experimental materials (G-aenial Flo bulk fill, GF; G-aenial Universal Flo bulk fill, GUF; GC Kalore bulk fill, GK). Microleakage was separately assessed at enamel and dentin margins by scoring the depth of silver-nitrate penetration. Twenty teeth divided into five groups (n = 4) were selected for microTBS testing. The same materials as for microleakage assessment were placed in bulk to mid-coronal dentin. Microtensile beams were loaded in tension, and microTBS at failure was calculated in MPa. Microleakage and microTBS data were analyzed by ANOVA on ranks, followed Dunn's post hoc test (P< 0.05).

Microleakage was not observed at the enamel interface in any of the groups. At the dentin interface, SDR recorded significantly higher microleakage than the other materials. microTBS of GF, GUF and GK did not differ among each other (33 +/- 12 MPa, 31 +/- 11 MPa, 30 +/- 9 MPa, respectively), while SDR (63 +/- 17 MPa) and FS (55 +/- 17MPa) achieved significantly higher microTBS values. No direct association between the sealing properties and the bond strength values was observed.