Purpose: To evaluate the effects of a new active collagenase inhibitor, Pirocton Olamine (PO), on acid demineralization in dentin and to investigate possible mechanisms of the inhibitory effects.
Methods: Demineralized bovine dentin sections were cyclically exposed to one of the test solutions containing PO (0-0.33%) and NaF (0.07%) for 3 minutes, then to a Clostridium histolyticum (Ch-collagenase) collagenase solution for 16 hours and finally to an acetate buffer solution for 6 hours for further demineralization within a single day. This cyclic treatment was repeated three times for 3 days. Changes in the mineral loss and lesion depth were quantified by transverse microradiography, and the extent of the degradation by the collagenase in the collagen matrix was measured by microscopic observation after the completion of the 3-day cyclic treatments. Possible mechanisms of PO inhibitory effects on collagen matrix degradation were tested by incubating PO with one of the substances (Ch-collagenase, bovine tendon collagen pieces, zinc2+ (acetate) which is essential ion for collagenolytic activity) at 37 degrees C. Following 1 hour incubation, the incubated solutions were filtrated and PO concentrations (unbound to the substances) in the filtrates were spectroscopically measured.
Results: With increasing PO concentrations, the inhibition rates of collagen matrix degradation and the mineral loss were increased. Moreover, there was a positive statistical correlation between mineral loss and collagen matrix degradation, demonstrating that preservation of the collagen matrix would contribute to inhibiting acid demineralization. While the spectroscopic measurements indicated that PO possessed binding to these substances, PO exerted its inhibitory action primarily on the collagenolytic activity.