Does Bulk-fill Composites Reduce Cervical Microleakage in Class II Restorations?

Objectives: The objective of the present study was to assess the microleakage and tooth structure deflection of class II MOD cavities using bulk-fill composites.
Methods: Seventh-two human third-molars received a class II MOD cavity preparation, with margins in cementum. Samples were 3D-scanned using 3shape D2000 scanner, followed by restorations (ADM–Admira Xtra Fusion; FBP–Filtek Bulk Fill Posterior; FBF–Filtek Bulk Fill Flowable; SDR–Surefill SDR Flow; TBF–Tetric Evo Ceram Bulk Fill; XB–Xtra Base; XF–Xtra Fill; Z3F–Filtek Z350XT Flowable; Z3XT–Filtek Z350XT). Samples were stored in 37°C deionized water in absence of light. After 24 hours, a new 3D-scan was performed and images were superimposed to assess tooth structure deflection. After 7 days, restorations were finished and polished. Ten-thousand thermal cycles were performed (5-55°C) followed by surfaces’ sealing with a double layer of red nail varnish exposing 1mm around restorations’ cervical margins. µCT scans were performed before and after immersion in 50% ammoniacal silver nitrate overnight. Bidimensional/tridimensional microleakage analyses were performed.
Results: Tooth deflection was similar for all groups. ADM and XF presented the lowest values, while XB and TBF generated the highest values. The mean difference between the lowest and the highest values was about 12 microns. Considering 2D infiltration, all high viscosity composites showed lower infiltration length. The lowest infiltration length was observed for Z3XT, with a significant difference with XF when comparing the high viscosity composites. Z3F, generated the highest values. Regarding 3D infiltration, all high viscosity composites showed lower infiltration, with ADM and TBF generating the lowest values. Z3F generated the highest infiltration. A strong correlation could be observed between 2D and 3D infiltrations (p=0.0001). No correlation was observed between tooth structure deflection and bidimensional or tridimensional infiltration.
Conclusions: Bulk-fill composites showed similar microleakage results while allowing faster restorative protocol.