Browsing by Author "Platt, J.A."

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    Beam Profile Influence on Polymerization Characteristics of Resin-Matrix Composites
    (Office of the Vice Chancellor for Research, 2016-04-08) Al-Zain, A.O.; Ong, V.; Eckert, G.J.; Megremis, S.; Platt, J.A.
    The objective of this study was to quantify the homogeneity of the beam of light radiated from each of two different light-curing units (LCUs) using beam profiling, and then evaluate the relationship between these beam profiles and polymerization patterns of a resin-matrix composite (RMC). Beam profile and irradiance measurements of one light-emitting diode (LED) and one quartz-tungsten-halogen (QTH) curing unit were collected using a beam-profiler-system and a MARC-RC resin calibrator, respectively. The camera-based beam-profiler-system (BGP-USB-SP620 with 50-mm-lens, Ophir-Spiricon) combined radiant-power-values from an irradiance-probe (cosine-corrector/spectrometer-assembly) to measure beam-homogeneity (the distribution of irradiance-values across the light-beam) for each curing-unit. A mapping approach was used to investigate the polymerization pattern of nano-hybrid RMC samples (5×5×2mm) at various depths utilizing both micro-Raman-spectroscopy (degree-of-conversion, DC) and ethanol softening (cross-link-density, CLD), which was determined using automated-microhardness testing after exposure to ethanol. Two-sample t-tests with unequal-variances were used to compare the LCUs for differences in irradiance (mW/cm2) and radiant-exposure (J/cm2). Comparisons among polymerization by depths with-respect-to LCU were made using paired t-tests and two-sample t-tests as appropriate for the specific depths. The effects at each depth of location on the sample and LCU were tested using mixed-model ANOVA. The LED demonstrated inhomogeneity and significantly higher irradiance values compared to the QTH. Both LCUs demonstrated variations in DC (62-74%) and percent Knoop hardness number (KHN) reduction (33-49%) at different depths and locations. A gradual decrease in KHN occurred from top to bottom in the RMC cured with QTH unlike the LED. A gradual decrease in CLD was exhibited in both LCUs. This study showed that the beam-profile-inhomogeneity of QTH and LED curing-units resulted in localized differences in DC, KHN and CLD of RMC samples at specific depths and locations. However, adequate polymerization of the RMC was achieved at all points when using the LED LCU.
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    Bioactive nanofibrous scaffolds for regenerative endodontics
    (SAGE, 2013-11) Bottino, M.C.; Kamocki, K.; Yassen, G.H.; Platt, J.A.; Vail, M.M.; Ehrlich, Y.; Spolnik, K.J.; Gregory, R.L.; Endodontics, School of Dentistry
    Here we report the synthesis, materials characterization, antimicrobial capacity, and cytocompatibility of novel antibiotic-containing scaffolds. Metronidazole (MET) or Ciprofloxacin/(CIP) was mixed with a polydioxanone (PDS)polymer solution at 5 and 25 wt% and processed into fibers. PDS fibers served as a control. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), tensile testing, and high-performance liquid chromatography (HPLC) were used to assess fiber morphology, chemical structure, mechanical properties, and drug release, respectively. Antimicrobial properties were evaluated against those of Porphyromonas gingivalis/Pg and Enterococcus faecalis/Ef. Cytotoxicity was assessed in human dental pulp stem cells (hDPSCs). Statistics were performed, and significance was set at the 5% level. SEM imaging revealed a submicron fiber diameter. FTIR confirmed antibiotic incorporation. The tensile values of hydrated 25 wt% CIP scaffold were significantly lower than those of all other groups. Analysis of HPLC data confirmed gradual, sustained drug release from the scaffolds over 48 hrs. CIP-containing scaffolds significantly (p < .00001) inhibited biofilm growth of both bacteria. Conversely, MET-containing scaffolds inhibited only Pg growth. Agar diffusion confirmed the antimicrobial properties against specific bacteria for the antibiotic-containing scaffolds. Only the 25 wt% CIP-containing scaffolds were cytotoxic. Collectively, this study suggests that polymer-based antibiotic-containing electrospun scaffolds could function as a biologically safe antimicrobial drug delivery system for regenerative endodontics.