Chitosan Effect on Hardening Dynamics of Calcium Phosphate Cement: Low-Field NMR Relaxometry Investigations

Abstract

Calcium phosphate cements are used in dentistry and orthopedics to repair and reconstruct bone defects. The properties of these bone cements can be improved by introducing additives into their composition. One favorable additive is chitosan, which can be beneficial but can also cause considerable damage if it has a high load, thus, limiting its clinical applicability and performance. That is why understanding chitosan’s role in cement composition is an important issue when developing new materials. The present work uses low-field nuclear magnetic resonance (NMR) relaxometry to investigate the effect introduced by the addition of chitosan on the hardening process of calcium phosphate cement. Two samples, prepared with and without chitosan, were comparatively investigated during the first six minutes of hardening. The liquid evolution inside these samples was monitored using transverse relaxation time distributions. It demonstrated an acceleration effect on the hardening dynamics introduced by the presence of chitosan. Furthermore, it was shown that even after one hour of hardening, there were still unreacted monomers inside the bone cement and their amount was reduced in the presence of chitosan.

The Influence of Chitosan on Water Absorption and Solubility of Calcium Phosphate Cement

“…The echo trains depicted in Figure 1 indicate a slower hardening process in the case of the C1 sample (Figure 1a) as compared with C2 sample (Figure 1b), which contains chitosan. This observation for longer hardening times is analogous with the previous results on similar samples for shorter evolution times [30]. It is also observed that for both samples, the polymerization process is not completely finalized even after one hour, and this may affect both the absorption and solubility dynamics.…”

“…Two samples made of calcium phosphate cements, denoted C1 and C2, respectively, were investigated, with the composition comprehensively discussed in our previous work [30]. The samples have the same solid-liquid ratios and identical quantity of liquid components and chemical initiation system.…”

“…Transverse relaxation measurements were performed at 35 Celsius using a low-field NMR instrument operating at 20 MHz proton resonance frequency (Minispec MQ20, Bruker, Heidelberg, Germany) and the well-known Carr-Purcell-Meiboom-Gill (CPMG) radiofrequency pulse sequence [30]. The CPMG pulse sequence generates a train of spin echoes separated by an echo time interval.…”

“…Note, however, that knowledge of the relaxivity constant is necessary if obtaining the absolute pore sizes is envisaged. The main advantages of NMR relaxometry investigations over other techniques are that the samples do not require prior preparation, and information can be extracted not only about the dynamics of water molecules but also about the evolution of porous structures [29,30].…”

Calcium Phosphate Loaded Biopolymer Composites—A Comprehensive Review on the Most Recent Progress and Promising Trends

“…Obviously, for biomedical or clinical applications it is crucial that their mechanical properties meet the required strict standards. Taking this into account, the toughening of these types of composites is crucial and many research groups have focused on this area, with good and promising achievements [87][88][89]. The strength of composites is also dependent on their pore size and distributions For example, Iqbal et al [90] produced dicalcium phosphate dihydrate (DCPD) composite scaffolds with different DCPD concentrations (0-50 wt%), and reported that the increasing DCPD content resulted in higher crystallinity and reduction in pore size and distribution, observing mainly entwined and closed porosity.…”