Method: The composites tested were: flowable-Venus Bulk Fill (VBF) and Surefil SDR (SDR), medium viscous-Venus (VD) and Spectrum TPH3 (SP). The depth of cure was defined via measuring the Vickers microhardness of cylindrical specimens (n=5) at several consecutive depths up to 7mm. The linear polymerization shrinkage was calculated by the deflective disc method (n=5). The internal adaptation was examined through observation by optical microscope of sections of 5mm-deep class I restorations in four groups of teeth restored with different techniques by means of the combination of flowable and conventional composites. The percentage of total (TDML) and highest (MDML) debonded marginal length relative to the total length of tooth-composite interface, the maximum gap width (MGW) of the MDML and the median width of the marginal gap (mGW) were calculated.
Result: VBF and SDR were polymerized at depth higher than 7mm whereas SP and VD sufficiently polymerized up to 4 and 3 mm, respectively. SDR and VBF presented higher dimension change than SP and VD. Among SDR and VBF and among SP and VD no statistically significant differences were observed in both properties (p<0.05). No statistically significant differences were found in the internal adaptation of the several filling techniques, in terms of TDML and MDML. When VBF was placed in bulk, wider gaps were observed than in case where it was used as liner.
Conclusion: The flowable bulk filling composites presented higher depth of cure and polymerization shrinkage that the conventional composites. The overall internal adaptation in class I restorations was independent of the filling procedure in terms of flowable and conventional composite combinations.