Comparison of the microleakage in class II bulk-fill restorations and different filling techniques: An “in vitro study”

Objective: The aim of this study is to evaluate the microleakage at the interproximal horizontal margin in Class II restorations realized using four different types of composite resin: SDR® (Dentsply, Dentsply Sirona Italy – Piazza dell’Indipendenza, 11, 00185 Rome RM), Xtra-base® (VOCO, VOCO GmbH – 27457 Cuxhaven, Germany), Ceram-X™ (Dentsply, Dentsply Sirona Italy – Piazza dell’Indipendenza, 11, 00185 Rome RM), GrandioSO®(VOCO, VOCO GmbH – 27457 Cuxhaven, Germany). Additionally, two of these (SDR® and Xtra-base®) were used following a bulk fill technique following the producer’s instructions, while the other two (Ceram-X™ and GrandioSO®) were used following the traditional incremental technique. Methods: A total of 20 freshly extracted human teeth, either molar or premolars, were selected. They were randomly divided in four groups, one for each material: for each tooth, two Class II cavities, one mesial and one distal, were realized in order to be reconstructed with the material assigned to each tooth. In total, each group had five teeth and 10 restorations made, for a total of 40 restorations. After restoration, the teeth were covered with nail polish except for a 2mm-wide area which included the interproximal horizontal margin, and the apexes were sealed using Dyract®Seal sealer (Dentsply, Dentsply Sirona Italy – Piazza dell’Indipendenza, 11, 00185 Rome RM). The samples were then thermocycled at 55°C for 500 cycles and immersed in a solution of 0.2% Fuchsin dye for 24 hours. They were then sectioned mesiodistally and examined using an optical microscope (Leica DMS 1000) at a magnification of 20x: the microleakage was assessed by measuring the dye penetration through the floor of the restoration and scored using the Demarco scale (Demarco 2001). A Kruskal-Wallis Test and six Mann-Whitney tests were then performed to investigate whether or not the difference between the results in the different groups was statistically significant. Results: In this study, the best performance was observed in Group 2 (Xtra-base® VOCO; Bulk Fill technique) since no signs of microleakage were noticed. In Group 1 (SDR® Dentsply; Bulk Fill technique) the worst performance was observed: five samples showed no infiltration, while the other five showed a score of 2. In group 3 (Ceram-X™ Dentsply; Incremental technique.) six samples showed a score of 0, two samples a score of 1 and two samples a score of 2. In group 4 (GrandioSO®VOCO; Incremental technique) seven samples showed a score of 0, while one sample showed a score of 1 and two samples showed a score of 2. The Kruskal-Wallis test, however, did not reveal any statistically significant difference. Six different Mann-Whitney tests (one for each pair of groups, every combination possible) confirmed these results by not showing statistically significant differences between the different composites and techniques. Conclusion: Within the natural limitations of an in-vitro study, there is no statistically significant difference in terms of microleakage scores, even after thermocycling, between four different composite resins (Xtra-base® VOCO, SDR® Dentsply, Ceram-X™ Dentsply, GrandioSO®VOCO) two of which used with a bulk fill technique (Xtra-base® VOCO, SDR® Dentsply) and two with an incremental technique (Ceram-X™ Dentsply, GrandioSO®VOCO), as per the manufacturer’s instructions. These results encourage the design of clinical studies which could highlight differences between the performance of these composites through time when subjected not only to intra-oral temperature variation, but to occlusal forces, pH variations and plaque accumulation too