Demineralization affects dentin collagen degradation

Objective:

This study evaluated the effect of phosphoric acid (PA) and ethylenediaminetetraacetic acid (EDTA) on the degradation of the dentin collagen matrix due to the activation of host-derived MMPs and cathepsins. The tested hypothesis was that the demineralizing agent has no influence on the degradation of collagen.

Method:

Dentin slabs 1.0±0.1 mm thick were obtained from human teeth and completely demineralized in two different acid mediums: PA, 10 wt% (pH=1) for 24h at 25°C or 0.5M EDTA, pH=7.4 for 28 days at 25°C. After demineralization the collagen slabs were cut in circular disks of 6.0±0.2 mm in diameter by means of a surgical biopsy punch. Collagen disks were stored in artificial saliva and complete medium (2.5mM CaCl₂, 0.05mM ZnCl₂, 5mM HEPES buffer, 0.3mM NaN₃, pH=7.4), and tested at increasing evaluation time-points. Collagen degradation was assayed quantitating ICTP and CTX fragments using an ELISA test. Additionally, the biaxial flexural modulus of elasticity of all tested specimens was performed.

Results:

Figure 1: Biaxial flexural modulus of elasticity (left panel) and release of ICTP collagen fragments (right panel).

Conclusions:

The tested hypothesis was rejected since significant differences were observed in the ICTP and CTX release in relation to the demineralizing procedure. EDTA demineralized specimens lost stiffness faster and had higher endogenous telopeptidase activity compared to PA-demineralized specimens. Additionally collagen degradation was correlated to the decrease of the mechanical properties of the dentin matrix.

Supported, in part, by grants: FIRB RBAP1095CR and PRIN 2009SAN9K5 and 2009FXT3WL from MIUR, Italy, R01DE015306 to DHP (PI), and #8126472 from the Academy of Finland to AT-M (PI).