Interface Characterization Between a CaSi Cement and Biological Hydroxyapatite

The objective was to characterize the crystal structure and to determine the lattice parameters of mineral compounds growing inside the dentinal tubules at the dentin/ Biodentin^TMinterface.

Method:

A human molar was prepared with an occlusal cavity and filled with the CaSi cement and then stored at room temperature.

Neutron diffraction was used to characterize the crystal structures of biological HAP, compounds of the cement before and after setting, and as a function of time, the crystal structure of mineral compounds growing during one year at the interface.

Rietveld analysis was used to determine the crystal structures and the lattice parameters of biological apatite, cement components and new mineral compounds according to the pattern registered during 427 days.

Result:

The observed peaks in the pattern difference correspond to an additional contribution from the interface. This regenerated material has the same hydroxyapatite structure (monoclinic P 2 ₁/b space group) with very similar lattice parameters. These parameters are: a=9.4337(2) Å, b= 18.9364(2) Å, c= 6.909(1) Å and α =b= 90°; g= 120.009°.

Conclusion:

Previous studies have demonstrated the presence of “mineral tags” and/or “mineral infiltration zone”. Neutron diffraction methodology allows affirming the presence of a new hydroxyapatite regenerated material with lattice parameters which are close to but different from biological HAP.