Clinical Time Required and Internal Adaptation in Cavities restored with Bulk-fill Composites

The aim of this study was to compare the restorative time required and the internal adaptation after thermomechanical aging of class I restorations using either the conventional incremental technique or bulk-fill technique.

Cavities (Class I) were prepared on the occlusal surface of human third molars. 40 teeth were divided into four experimental groups according to the restorative technique (n = 10): G1 = 3 mm increment of Surefill SDR Flow + 1 mm Filtek P60; G2 = 3 mm increment of Filtek Bulk-Fill + 1 mm Filtek P60; G3 = Filtek P60 inserted with incremental technique; G4 = 3 mm increment of Filtek Z350 Flow XT + 1 mm increment of Filtek P60. The required restorative clinical time for each technique was marked. Specimens were submitted to thermomechanical loading (20,000 mechanical cycles-80 N/thermal cycling-5/55°C for 30 seconds). After, samples were sectioned, ratio of internal gaps to interface length (%) was recorded using dye-staining-gap technique. Data were submitted to analysis of variance (ANOVA) and Tukey's test (95% significance).

There was no significant difference in gap formation and none of the groups was completely gap-free. However, a significant reduction on required restorative clinical time was observed for G1 (167 ± 7 seconds), G2 (169 ± 4 seconds), and G4 (169 ± 8 seconds) when compared with G3 (204 ± 8 seconds).

No significant difference in gap formation was found among bulk-fill and conventional incremental restorative technique tested; however, the use of a bulk-fill composite reduced 20% of the required restorative clinical time.

None of the restorative techniques applied were able to prevent internal gap formation. The use of bulk-fill composite reduced the required clinical time to perform class I restorations.