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The aim of this study was to evaluate the influence of addition of CaF2 powder to Biodentine™ to improve the biological properties without compromising the manipulative and mechanical properties.
Different concentration of CaF2 (2 &10 wt. %) was added to the Biodentine™ capsules and compared to a control unmodified Biodentine™. All the experimental groups were characterized using ESEM with EDX and XRD.
The different experimental groups was evaluated regarding their setting time and compressive strength to assess the manipulative and mechanical properties. The cement in-vitro bioactivity was assessed through combined evaluation of ion leaching, pH changes and apatite forming ability over different time intervals (1, 14 and 28 days) after storage in HBSS. Furthermore, the antibacterial effect of the different experimental groups was tested over different time intervals of storage in HBSS.
Regarding the setting time, it was evaluated according to the ISO (6867-2012) for root canal sealer. Both initial and final setting times were evaluated using Gilmore needle. For the compressive strength testing, the cement was evaluated following the ISO (9917-1) for water based cements test method.
For in-vitro bioactivity, the prepared cements discs were prepared according to the manufacturer’s instructions and stored in HBSS at 37◦ C. The discs were collected at different time intervals (1, 14 and 28 days). The discs surface was scanned using ESEM in conjunction with EDX elemental analysis. Meanwhile, the HBSS was collected and its pH was measured using pH meter and the calcium and fluoride leaching were evaluated using both ion chromatography and ICP-MS. Afterwards, the same discs were re-immersed in fresh HBSS till the next scheduled time interval for the same evaluation process repetition. After the final evaluation (28days) the discs were crushed into powder for XRD analysis of the crystalline phases formed.
The antibacterial behavior was evaluated using disc diffusion method immediately after setting and after storage in HBSS for 14 and 28 days.
The results of this study revealed a significant decrease in the initial setting time of Biodentine™ with increasing concentration of CaF2. The final setting was also decreased with addition of different concentrations of CaF2. The compressive strength results showed statistically insignificant difference between the different experimental groups. These results denote that addition of CaF2 enhanced the manipulative properties without compromising the mechanical properties of Biodentine™.
The pH evaluation of the HBSS revealed a potent alkalizing effect of the different experimental groups with significantly increased pH for the same group over the different time intervals. This extended alkalizing effect of the different experimental groups provide a favorable medium for mineralization and healing of the hard tissue as well as antibacterial potential.
Calcium ion leaching results revealed a significant increase between the different experimental groups with increasing CaF2 concentration. The amount of the released calcium ion was decreased significantly with time. The F10 group could maintain highest levels of calcium ion release over different time intervals.
The fluoride ion leaching results showed significant difference between F2 and F10 groups with higher amount of fluoride release over the different time intervals recorded for the F10 group.
The combined ESEM – EDX analysis revealed formation of calcium phosphate layer over the different experimental groups. The homogeneity and thickness of this layer increased with decreasing Ca/P ratio on increasing immersion time in HBSS. The F2 group showed the most homogenous surface layer. The XRD analysis of the discs after 28days revealed peaks of calcium silicate, calcium hydroxide, calcium carbonate in addition to calcium fluoride denoting continuous hydration process with remaining core of unreacted crystals ready for further hydration.
The disc diffusion disc test revealed significantly larger inhibition zones around Biodentine™ discs with increasing concentration of CaF2. The long term assessment antibacterial potential revealed failure of the different experimental groups to inhibit the bacterial growth.
Within limitations of this study it can be concluded that
1. Addition of CaF2 can enhance the manipulative properties without compromising the mechanical properties of Biodentine™
2. The overall in-vitro bioactivity of the CaF2 modified Biodentine™ was enhanced through higher amount of calcium and fluoride release with formation of calcium phosphate surface layer.
3. The immediate antibacterial activity of Biodentine™ against streptococcus mutans was enhanced with addition of CaF2.
1. Addition of CaF2 to Biodentine™ as it can shorten the setting time and enhance its bioactivity.
2. The long term antibacterial effect of Biodentine™ needs further investigation with different methodologies and different bacterial strains.