Biodentine

10
2.2 - Density and Porosity
The mechanical resistance of calcium silicate based materials is also dependant on their
low level of porosity. The lower the porosity, the higher the mechanical strength. The
superior mechanical properties of Biodentine were determined by the low water
content in the mixing stage. Two different methods confirmed the low porosity of
Biodentine.
First a mercury intrusion porosimetry method was used. Mercury, the only known liquid
really suitable for porosimetry type measurements, can be forced into pores. The
pressure required to intrude mercury into a pore is determined by the pore diameter. The
samples were prepared under the same conditions as those used for CS measurements.
Measurements were carried out on fourteen 28-day-old cylinders, dried at 40°C in a
primary vacuum for 12 days to eliminate residual water. The porous volume and the
distribution of pore diameters were determined by mercury intrusion porosimetry
(Autopore III, Micromeritics Instruments Corporation, Norcross, USA).
Material Porous characteristics
Dens. g/cm3 Pore V.cm3/g Porosity %
PMTA 1.882(0.002) 0.120(0.002) 22.6 (0.2)
FUJI IX 2.320(0,002) 0.033(0.002) 7.2 (0.2)
BIODENTINE 2.260(0.002) 0.031(0.002) 6.8 (0.2)
As expected, Biodentine exhibits lower porosity than ProRoot ® MTA. The density and
the porosity of Biodentine and Fuji IX are equivalent.
Electrical Resistance Measurements
An alternative method to illustrate the hardening process is to examine the mobility of
ions which depend of the pore size and number of pores during setting by
electrochemical analysis. Impedance spectroscopy technique leads to the increase of
the electrical resistance along with the porosity reduction (Fig.2) (Golberg et al., 2009).
Fig. 2: Electrical resistance (Ω) versus time (hours)
during setting of Biodentine
This shows that even
after the initial setting of
Biodentine, the
material continues to
improve in terms of
internal structure towards
a more dense material,
with a decrease in
porosity.
Biodentine is an
evolutive material which
improves its mechanical
properties with time.