Mechanical stability - University of Missouri, Kansas City, USA

Some patients and clinicians have become concerned about using Bis-GMA-based restorative materials due to the fact that it is a bis-phenol A (BPA)-derived monomer. To satisfy this concern, several restorative materials based on alternative monomers have been developed. Heraeus Kulzer invented the filling materials Venus Pearl and Venus Diamond which are based on a patented TCD-urethane chemistry. The development of this innovative new chemistry was driven by the inherent limitations of the Bis-GMA resin and a need for higher mechanical properties as well as lower shrinkage stress.

Due to the fact that fractures and secondary caries are still the main reasons for failure of restorations,¹ materials which may possess the above pre-conditions that reduce these failures were designed.

The following study by the University of Missouri, Kansas City, USA highlights the good mechanical properties of Venus Diamond and its TCD-urethane chemistry in comparison to two other composites.

Objective

The aim of this study was to evaluate the flexural strength properties of two commercially-available UDMA-based universal composites compared to a Bis-GMA-based universal composite.

Material and methods

Beam specimens (n = 10/material) of Filtek™ Supreme XTE Universal Restorative (Bis-GMA), Gradia Direct X (UDMA) and Venus Diamond (UDMA) were incubated for 24 hrs in H2O at 37°C prior to a 3-point bend test to measure flexural properties. An SEM qualitative fractography of representative specimens was done to characterise filler morphology and identify differences in the failure fracture as a function of material.

Results

All three materials differed significantly (p < 0.05) from one another in terms of flexural strength. Flexural moduli of Filtek Supreme XTE Universal Restorative and Venus Diamond were not significantly different statistically (9.34 ± 0.49 GPa and 9.40 ± 0.68 GPa). Gradia Direct X showed higher elasticity (5.02 ± 0.12 GPa). From the SEM analysis, Filtek Supreme XTE Universal Restorative had round, uniform fillers with fracture occurring through the resin. Gradia Direct X included irregularly shaped filler particles as well as some large pre-polymerised resin particles with fracture failure at the interface between pre-polymerised resin filler particles and resin. Venus Diamond included smaller round particles and large jagged particles with fracture through resin as well as through larger filler particles.

Conclusion

Based on flexural properties, Venus Diamond appears to be a viable universal alternative to Bis-GMA universal composites such as Filtek Supreme XTE Universal Restorative, while the lower properties of Gradia Direct X could be a concern for a universal material. Additional evaluations are needed to ensure flexural properties are optimal for the intended material application.

Comment

This study again confirms the high mechanical strength Venus Diamond features. It can be used universally for posterior and anterior restorations.

Source notes

Hooper P, Wing Lee J, Walter M: Flexural Property Comparison of UDMA-Based and Bis-GMA-Based Composites. J Dent Res Vol 95 (Spec Iss A, #0641, 2016. (www.iadr.org). The study was abbreviated and summarised, commented and all diagrams and titles have been established by Heraeus Kulzer. Venus is a registered trademark of Heraeus Kulzer.

References

1. Bernardo M, Luis H, Martin MD, Leroux BG, Rue T, Leitão J, DeRouen TA: Survival and reasons for failure of amalgam versus composite posterior restorations placed in a randomized clinical trial. JADA, 2007, 138 (6): 775–783.