Phosphoric acid concentration affects dentinal MMPs activity
Abstract
Objectives
To
evaluate whether the concentration of phosphoric acid (PA) has an
effect on the proteolytic activity of sound human demineralized dentin.
It is hypothesized that the activity of matrix-bound and extracted
enzymes depends on the PA concentration used to demineralize dentin.
Methods
One-gram
aliquots of mid-coronal human dentin powder were demineralized with
1 wt%, 10 wt% and 37 wt% PA. Concentrations of released calcium were
measured for each set of demineralization. Extracted MMP-2 was
immunologically identified by western blot and its activity was
determined by conventional gelatin zymography. Analysis of released
hydroxyproline (HYP) and in situ zymography were performed to evaluate the activity of insoluble, bound-matrix enzymes.
Results
The
amount of released calcium from dentin powder treated with 37 wt% PA
was significantly higher (p ≤ 0.05) than that obtained by dentin
demineralization with 10 wt% and 1 wt% PA. Expression and activity of
endogenous enzymes, extracted from or bound to dentin matrix, were
detected for all samples regardless of the PA concentration. However,
the expression and activity of extracted MMP-2 were significantly higher
when dentin was treated with 10 wt% PA (p < 0.05), followed by 1 wt%
and 37 wt% PA. Similarly, the highest concentration of released HYP
(i.e. meaning higher percentage of collagen degradation) and the highest
activity in in situ zymography were observed when dentin samples were treated with 10 wt% PA (p < 0.05).
Conclusions
It was confirmed that
PA does not denature endogenous enzymes of dentin matrices, but it may
somehow modulate the expression and activity of these enzymes in a
concentration-dependent manner.
Clinical significance
Endogenous
proteases have been identified and suggested to be responsible for the
digestion of dentin matrix when activated by the acidic components of
dental adhesives. Proteolytic activity of dentinal MMPs showed to be
dependent on phosphoric acid concentration. The clinically-used
concentration (37%) does not inhibit MMPs activity, but slows it.
Comments