Compressive properties of different types of dental composites

Method: Four different restoratives: Surefil SDR (SDR) (posterior bulk-fill flowable base, Dentsply), Tetric N Ceram Bulk Fill (TBF)( hybrid composite, Ivoclar Vivadent), Tetric N ceram (TNC) (nano-hybrid composite, Ivoclar Vivadent), Filtek Z 550 (FK) (Nano hybrid composite, 3M ESPE) were used in this study. 60 cylindrical shaped specimens were fabricated with a 3mm diameter and 6mm height (n=10). Specimens of the test groups are as follows:

1. SDR group (6mm SDR) (inserted 4mm and cured, 2mm and cured respectively)
2. SDR+FK1 group (inserted 4mm SDR and cured, 2mm FK inserted and cured respectively)
3. SDR+FK2 group (inserted 2mm SDR and cured, 2mm FK inserted and cured, 2mm FK inserted and cured respectively)
4. TBF group (inserted 4mmTBF and cured, 2mm TBF and cured respectively)
5. TNC group (inserted incrementally)
6. FK group (inserted incrementally)

Compressive tests were performed at 1mm/min crosshead speed with an international testing machine (Shimadzu AG-5 KN; Shimadzu Corp, Tokyo, Japan).The results were statistically analysed using the SPSS Statistics 22 for Windows (one way ANOVA, post hoc Tamhane’s T2 test) at a significance p<0.01.

Result: There were statistically significant differences between the tested groups (p: 0.001, p<0.01). The highest compressive strength was observed for FK group (223,80±41,34 MPa) and significantly higher than the other groups. SDR+FK1 group also showed significantly higher compressive strength values from the TBF group and TNC group. There were no statistically significant differences between other tested groups (p>0.05). 

Conclusion: Applying thicker layer of posterior bulk-fill flowable base composite under 2mm conventional nano-hybride composite showed similar compressive strength values obtained from conventional nano-hybride composite group.