Russel Gitalis and IBBME UofT

October 16, 2019 @ 12:30 pm – 1:00 pm
Red Seminar Room
Donnelly Building

Event Name: Graduate Seminar Series: Clinical Stream

Graduate Seminar Series for the Institute of Biomaterials and Biomedical Engineering (IBBME). This day is for clinical stream presenters.

Location: Red Seminar Room – Donnelly Building

Presentation Title: Human neutrophils degrade methacrylate resins, tooth dentin and resin-dentin interfaces
Background: Cholesterol esterase-like (CE) activity from saliva and esterase from cariogenic bacteria hydrolyze ester linkages of dental methacrylate resins. Matrix metalloproteinase-like (MMP) activities from dentin and bacteria can degrade collagen in demineralized tooth dentin. Overtime the above enzymatic activities can degrade and compromise methacrylate resin composite restorations, allow for oral fluids and bacteria to penetrate into the gaps between the restorative and the tooth, and lead to recurrent decay and early failure of the restoration. Human neutrophils in the oral cavity contain factors that are hypothesized to have CE and MMP activities that contribute to the degradation of methacrylate resin composites and dentinal collagen.
Objectives: To measure the CE and MMP activities from human neutrophils and their ability to degrade dental methacrylate composite and dentinal collagen.
Methods: Neutrophils’ CE and MMP activities were measured using nitrophenyl-esters or fluorimetric MMP substrates, respectively. Neutrophils’ degradation of composite and dentinal collagen was quantified by measuring release of a universal 2,2-Bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bisGMA)-derived composite degradation byproduct, bishydroxy-propoxy-phenyl-propane (BisHPPP), or a collagen degradation by-product, hydroxyproline, respectively using ultra performance liquid chromatography, UV spectroscopy and mass spectrometry. Analysis of variance (ANOVA) in conjunction with a post-hoc Tukey’s honestly significant difference (HSD) test was used to measure statistical significance.
Results: Neutrophils’ CE activity (15.1±3.1units/107 neutrophils) was stable for 48 hours and increased the release of bisHPPP from bisGMA monomer compared to control after 24 (11.49±1.05μg/107 neutrophils vs 0.08±0.06μg/mL) and 48 (23.36±1.19μg/107 neutrophils vs 0.09±0.02μg/mL) hours (p<0.05). Neutrophils degraded polymerized resin composite and produced higher amounts of bisHPPP than buffer control after 48 hours of incubation (0.196±0.040μg/cm2/107 neutrophils vs 0.043±0.008μg/cm2) (p<0.05). Neutrophils show generic MMP (0.085±0.047µmol/min/107 neutrophils), gelatinase, MMP-2 (0.064±0.030µmol/min/107 neutrophils) and MMP-9 (0.099±0.018µmol/min/107 neutrophils), and collagenase, MMP-1 (0.014±0.003µmol/min/107 neutrophils) and MMP-8 (0.004±0.001µmol/min per 107 neutrophils) activities that were stable or increased over the first 24 hours (p<0.05). Neutrophils degraded demineralized dentin more than buffer-only groups, shown by scanning electron micrographs and by producing higher amounts of hyrdoxyproline (15.32±1.23μg/107 neutrophils vs 0.03±0.04μg/mL)(p<0.05).
Conclusions: The ability of neutrophils to degrade both dental composite and tooth dentin, suggest neutrophil’s potential role in root caries, and in recurrent carries by accelerating the degradation of resin-dentin interfaces, and compromising the longevity of the restoration.
Significance: Understanding the specific enzymatic activities from neutrophils and their degradative potential towards resin composites and tooth dentin could help in the development of new materials with anti-enzymatic activities to increase the longevity of dental restorations.
Supervisor Name: Dr. Yoav Finer
Year of Study: 2
Program of Study: MASc

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