FTIR characterization of the setting reaction of biodentine™

To provide insight of the setting reactions of Biodentine™, a hydraulic calcium silicate cement, based upon observations using Fourier Transform Infra-Red (FTIR) spectroscopy.

FTIR spectra of components before and during the setting reaction were taken using the attenuated total reflectance (ATR) technique. Measurements over wavelengths 600-4000cm-1 were taken at regular intervals for two days.

FTIR spectrum of Biodentine™ powder revealed a number of peaks from 650 to 1100cm-1 and a plateau from 1400 to 1500cm-1, indicative of SiO and CO3-bonding, while the mixing fluid exhibited water peaks. Results following mixing displayed three distinct regimes; (i) incubation phase, during the first 35min, when minimal change occurred, (ii) rapid transitory stage, between 35 and 90min, when major changes occurred, and (iii) slow sustained reaction stage for remaining 45h. Incubation appears to be associated with the presence of CO3-peaks. The transition region indicates formation of CaOH and Jennite OH-peaks, anticipated intermediate reaction phases. At 90min, the end of second stage, CaOH and Jennite are replaced by a dominant Portlandite (Ca(OH)2)-peak and minor presence of Tobermorite, another anticipated intermediate phase, and water reduction. During the following 45h Portlandite and Tobermorite decline while the water peak increases.

FTIR can be used to follow the chemical reactions in dental cements and provides insight into the relatively slow setting reactions of hydraulic calcium silicate cements.