Effects of a mineralization-promoting peptide on the physical and chemical properties of mineral trioxide aggregate.

Mineral trioxide aggregate (MTA) has been used widely in dentistry due to its sealing ability and biocompatibility. Delayed setting time is one of the major limitations of MTA. Various additives have been studied to further improve the properties of MTA with varied degrees of success. In this study, we have investigated the effect of a calcium phosphate mineralization promoting-peptide (MPP3) on the physical and chemical properties of MTA in comparison with NaHPO. Based on the reported effects of MPP3 on calcium-phosphate mineralization reaction, our hypothesis was that MPP3 may also show beneficial effects on the calcium-silicate mineralization system of MTA. NaHPO was used for comparison since its setting accelerant effect on MTA has been well documented. The cements were prepared by mixing with distilled water, 0.40 mM MPP3 solution, 15% NaHPO solution, and a combination of MPP3 and NaHPO solution. Initial and final setting times were measured via Vicat needle. Microhardness values were measured via Vickers indenter at 1,3,7, and 28 days after hydration. Compressive strength after setting was measured via universal testing machine. Morphological and compositional analyses were performed via FESEM imaging, XRD and Raman spectroscopy. The microhardness data was evaluated via repeated-measures ANOVA. Setting time and compressive strength data were evasluated via one-way ANOVA. Initial setting time was reduced to ∼3 min in the NaHPO containing groups but remained at ∼5 min in the control and MPP3 groups. Final setting times were significantly reduced in all groups compared to the control group. The reduction in the final setting times in the NaHPO containing groups were significantly higher compared to the MPP3 group. Microhardness was significantly higher in the MPP3 group at all time points. No statistically significant difference in compressive strength was observed among the groups. FESEM analysis showed presence of ettringite crystals in the MPP3 group, and NaBiO crystals in the NaHPO containing groups. XRD analysis showed a broadening of peaks at 2θ = 32° in the NaHPO containing groups, possibly due to presence of NaBiO. Raman spectroscopy showed statistically higher ettringite content in the MPP3 containing groups. Our findings indicate that MPP3 is a beneficial additive to eliminate some of the drawbacks associated with MTA with no detrimental effects on mechanical properties and without resulting in phases that potentially cause discoloration, such as NaBiO. We propose that the reduced final setting time and increased microhardness by MPP3 may be associated with the increased ettringite content. Future studies, where wider range of MPP3 concentrations are studied may help elucidate and optimize the beneficial effects of MPP3 observed in this study.