EDX assessment of metalloproteinases influence on artificial root lesions

Objective: The observation that MMP-8 incubation of coronal dentin altered its remineralization pattern suggests a possible interference of MMPs in the progression of dentin lesions. This study aimed at investigating whether the presence of matrix metalloproteinase (MMP)-8 and -9 would influence the remineralization of artificial root lesions, with and without mechanical wear. The hypothesis to be tested was that MMP-8 and -9 collagenolytic activities would contribute to tissue loss, thus reducing dentin remineralization. Methods: Human root segments were inserted in a composite resin block and isolated with nail polish, except the cervical area. The segment blocks were then immersed in demineralizing solution. Next, Group A was not brushed and Group B was subjected to machine-controlled brushing, simulating mechanical wear. After demineralization and/or brushing, the specimens were immersed in remineralizing solution containing HEPES buffer (G1 - Control), tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) (G2), activated MMP-8 and MMP-9 (G3) and activated MMP-8, MMP-9 and TIMP-2 (G4), respectively. Ca2+, P, Mg2+ concentrations were determined through Energy Dispersive X-Ray (EDX), providing spatially controlled mineral lesion profiles. Results: EDX analysis indicated that, when the samples were demineralized and remineralized, the brushed samples demonstrated significantly higher Ca2+ content (p <0.05) Student-Newman-Keuls Method (SNK) in the immediate surface. For the non-brushed specimens, Ca2+ content at 20 mm decreased in the presence of TIMPs (p <0.05) (SNK). In the brushed samples, higher Ca values were observed in samples incubated with MMPs at 50mm (significantly different from control, p<0.05). Conclusion: MMPs and TIMPs yielded slight alterations in the mineral content of artificial root lesions. It is possible that, when not inhibited by TIMPs, MMPs may have degraded the completely demineralized collagen in the root surface, allowing for better recalcification in the deeper areas. This phenomenon was also facilitated by the brushing procedure.

Funding: Academy of Finland(#111724); CAPES(# 3799/05-0)