ABSTRACT
INTRODUCTION: Matrix metalloproteinase (MMP) inhibition may improve endodontic treatment prognosis. The purpose of this study was to determine if zinc incorporation into experimental resin cements containing bioactive fillers may modulate MMP-mediated collagen degradation of dentin. METHODS: Human dentin samples untreated and demineralized using 10% phosphoric acid or 0.5 mol/L EDTA were infiltrated with the following experimental resins: (1) unfilled resin, (2) resin with Bioglass 45S5 particles (OSspray, London, UK), (3) resin with beta-tricalcium silicate particles (ßTCS), (4) resin with zinc-doped Bioglass 45S5, and (5) resin with zinc-doped ßTCS particles. The specimens were stored in artificial saliva (for 24 hours, 1 week, and 4 weeks) and submitted to radioimmunoassay to quantify C-terminal telopeptide. Scanning electron microscopy analysis was also undertaken on dentin samples after 4 weeks of storage. RESULTS: Collagen degradation was prominent both in phosphoric acid and EDTA-treated dentin. Resin infiltration strongly reduced MMP activity in demineralized dentin. Resin containing Bioglass 45S5 particles exerted higher and stable protection of collagen. The presence of zinc in ßTCS particles increases MMP inhibition. Different mineral precipitation was attained in dentin infiltrated with the resin cements containing bioactive fillers. CONCLUSIONS: MMP degradation of dentin collagen is strongly reduced after resin infiltration of dentin. Zinc incorporation in ßTCS particles exerted an additional protection against MMP-mediated collagen degradation. However, it did not occur in resin containing Bioglass 45S5 particles, probably because of the formation of phosphate-zinc compounds.
Subject(s)
Biocompatible Materials/chemistry , Calcium Phosphates/chemistry , Protective Agents/chemistry , Resin Cements/chemistry , Zinc Oxide/chemistry , Acid Etching, Dental/methods , Bisphenol A-Glycidyl Methacrylate/chemistry , Calcium Compounds/chemistry , Ceramics/chemistry , Collagen/ultrastructure , Collagen Type I/analysis , Composite Resins/chemistry , Dentin/enzymology , Dentin/ultrastructure , Edetic Acid/chemistry , Electron Probe Microanalysis , Glass/chemistry , Humans , Materials Testing , Matrix Metalloproteinase Inhibitors/chemistry , Methacrylates/chemistry , Microscopy, Electron, Scanning , Peptides/analysis , Phosphoric Acids/chemistry , Polyethylene Glycols/chemistry , Polymethacrylic Acids/chemistry , Polyurethanes/chemistry , Saliva, Artificial/chemistry , Silicates/chemistry , Time FactorsABSTRACT
We have applied fluorescence lifetime imaging (FLIM) to the autofluorescence of different kinds of biological tissue in vitro, including animal tissue sections and knee joints as well as human teeth, obtaining two-dimensional maps with functional contrast. We find that fluorescence decay profiles of biological tissue are well described by the stretched exponential function (StrEF), which can represent the complex nature of tissue. The StrEF yields a continuous distribution of fluorescence lifetimes, which can be extracted with an inverse Laplace transformation, and additional information is provided by the width of the distribution. Our experimental results from FLIM microscopy in combination with the StrEF analysis indicate that this technique is ready for clinical deployment, including portability that is through the use of a compact picosecond diode laser as the excitation source. The results obtained with our FLIM endoscope successfully demonstrated the viability of this modality, though they need further optimization. We expect a custom-designed endoscope with optimized illumination and detection efficiencies to provide significantly improved performance.
