Effect of a Collagen Crosslinker on Dentin Post-Sequential Chemical Application

Objectives: Chemical sequences, such as those used in root canal treatment, result in an alteration of the dentin ultrastructure and its properties. Collagen crosslinking may improve the mechanical properties of dentin. The objective of this study was to determine the elastic modulus of dentin treated with a crosslinker after the application of different chemical sequences and to qualitatively analyse the dentin surfaces with scanning electron microscopy (SEM).
Methods: Dentin beams (n = 180) and dentin blocks (n = 12) were obtained from freshly extracted third molars and divided into 2 groups: Group 1, Sodium hypochlorite (NaOCl) – ethylenediamine tetraacetic acid (EDTA); Group 2, NaOCl – EDTA – NaOCl. Specimens were subdivided into subgroup A, application of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide coupled with N-hydroxysuccinimide (EDC/NHS) crosslinker (6 h), subgroup B, no crosslinker. The elastic modulus of the dentin beams was analysed by the 3-point bending test, while the dentin blocks were observed under SEM. The elastic modulus data was statistically analyzed using one-way ANOVA (P = 0.05).
Results: The mean elastic modulus of the NaOCl-EDTA and NaOCl-EDTA-NaOCl specimens was 16.89 ± 4.6 and 8.02 ± 3.0 MPa respectively. Application of the crosslinker significantly increased the elastic modulus of NaOCl-EDTA-NaOCl treated dentin (20.37 ± 4.4 MPa) (P < 0.05), while it had no significant influence on NaOCl-EDTA treated dentin (15.5 ± 3.0) (P >0.05). SEM revealed an increase in the density of the fibres on the dentin surface in Group 1A (NaOCl-EDTA + EDC/NHS), while the surface of group 2B (NaOCl-EDTA-NaOCl; no crosslinker) showed degraded collagen fibres. Specimens of group 2A (NaOCl-EDTA-NaOCl + EDC/NHS) showed an increase in the sub-surface collagen density, indicating crosslinking.
Conclusions: The results of our study highlighted that the improvement in the elastic modulus of dentin treated with crosslinker (EDC/NHS) depends on the sequence of chemical application, and the resultant surface characteristics.