30 September 2022

---

Second class restorations: which material between nano-hybrid composite and bulk-fill composite?

Lorenzo Breschi

---

Manufacturers are constantly introducing new compositions with different fillers and matrices, and several years ago they introduced bulk-fill composites. These materials promised time saving and higher layer thickness (up to 4-5mm). Some bulk-fill materials contain a new initiator – Ivocerin- which gives more translucency to the composite and allow the clinicians to place it in larger cavity with thickness layer increased and a shorter time for polymerization (10s).

Several studies have been conducted which reported good results for bulk-fill composites due to reduced polymerization shrinkage stress, adequate curing depth up to 4 mm, good bond strength, independent of the filling technique or cavity configuration.

Hoffmann and Kunzelmann conducted an in vivo study to investigate the behavior of four different combinations of composites: 1) the combination of a low-viscosity bulk-fill composite with 4 mm of thickness with a high viscosity bulk-fill capping layer of 2 mm of thickness; 2) a high viscosity bulk-fill composite applied in a layer of 4 mm; 3) high viscosity bulk-fill composite applied in layer of 2 mm of thickness; 4) a nanohybrid composite as control group in layer of 2 mm of thickness. The authors observed the restorations for 2 years. 




Materials and methods
The authors studied a low-viscosity (SDR), a high-viscosity bulk-fill (Tetric EvoCeram Bulk Fill) and a conventional nanohybrid composite (Tetric EvoCeram), they randomly assigned the materials to patients and performed 160 class-II cavities in 94 patients. Restorations were clinically examined at baseline (n = 160), after 12 (n = 150) and 24 months (n = 148) and evaluated according to eight selected FDI criteria scored 1-5: 1) surface lustre; 2) surface staining; 3) marginal staining; 4) color match and translucency; 5) esthetic anatomical form; 6) fracture of material and retention; 7) marginal adaptation; 8) postoperative sensitivity and tooth vitality  . In case of complete loss of the restoration or irreversible pulpitic symptoms, the restoration was rated as failure; repair was considered as relative failure.




Results
After 2 year of follow-up the results obtained by Hoffmann and Kunzelmann showed that the materials investigated had no significant differences regarding the FDI scores and failure rate during the entire follow-up. After 12 months, 7 failures and after 24 months a total of 8 failures were observed. After 2 years, Tetric EvoCeram Bulk Fill with a 4-mm layer thickness and SDR in combination with Tetric EvoCeram Bulk Fill with a 2-mm layer thickness exhibited a non-significant tendency towards increased hypersensitivity (FDI score 5) as compared to the reference material Tetric EvoCeram with a 2-mm layer thickness (p = 0.051; Kruskal-Wallis test).




Conclusion
The authors and their research group concluded that the 2- years outcome of the bulk-fill composites were comparable to nanohybrid traditional composites.




(Photocredit: Dott.ssa Federica Florenzano)




For further information: Bulk-fill Composites Compared to a Nanohybrid Composite in Class-II Cavities - A Two-year Follow-Up Study

Bulk-fill composites; nanohybrid composite; FDI criteria; viscosity; thickness