Browsing by Author "Karczewski, Ashley"

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    Clindamycin-modified Triple Antibiotic Nanofibers: A Stain-free Antimicrobial Intracanal Drug Delivery System
    (Elsevier, 2018-01) Karczewski, Ashley; Feitosa, Sabrina A.; Hamer, Ethan I.; Pankajakshan, Divya; Gregory, Richard L.; Spolnik, Kenneth J.; Bottino, Marco C.; Biomedical Sciences and Comprehensive Care, School of Dentistry
    INTRODUCTION: A biocompatible strategy to promote bacterial eradication within the root canal system after pulpal necrosis of immature permanent teeth is critical to the success of regenerative endodontic procedures. This study sought to synthesize clindamycin-modified triple antibiotic (metronidazole, ciprofloxacin, and clindamycin [CLIN]) polymer (polydioxanone [PDS]) nanofibers and determine in vitro their antimicrobial properties, cell compatibility, and dentin discoloration. METHODS: CLIN-only and triple antibiotic CLIN-modified (CLIN-m, minocycline-free) nanofibers were processed via electrospinning. Scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), and tensile testing were performed to investigate fiber morphology, antibiotic incorporation, and mechanical strength, respectively. Antimicrobial properties of CLIN-only and CLIN-m nanofibers were assessed against several bacterial species by direct nanofiber/bacteria contact and over time based on aliquot collection up to 21 days. Cytocompatibility was measured against human dental pulp stem cells. Dentin discoloration upon nanofiber exposure was qualitatively recorded over time. The data were statistically analyzed (P < .05). RESULTS: The mean fiber diameter of CLIN-containing nanofibers ranged between 352 ± 128 nm and 349 ± 128 nm and was significantly smaller than PDS fibers. FTIR analysis confirmed the presence of antibiotics in the nanofibers. Hydrated CLIN-m nanofibers showed similar tensile strength to antibiotic-free (PDS) nanofibers. All CLIN-containing nanofibers and aliquots demonstrated pronounced antimicrobial activity against all bacteria. Antibiotic-containing aliquots led to a slight reduction in dental pulp stem cell viability but were not considered toxic. No visible dentin discoloration upon CLIN-containing nanofiber exposure was observed. CONCLUSIONS: Collectively, based on the remarkable antimicrobial effects, cell-friendly, and stain-free properties, our data suggest that CLIN-m triple antibiotic nanofibers might be a viable alternative to minocycline-based antibiotic pastes.
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    Effect of post-irradiation polymerization on selected mechanical properties of six direct resins
    (J-STAGE, 2022) Sochacki, Sabrina; Karczewski, Ashley; Platt, Jeffrey; Roberts, Howard W.; Biomedical Sciences and Comprehensive Care, School of Dentistry
    This study evaluated the post-irradiation mechanical property development of six resin composite-based restorative materials from the same manufacturer starting at 1 h post irradiation, followed by 24 h, 1 week, and 1 month after fabrication. Samples were stored in 0.2M phosphate buffered saline until testing. Flexural strength, flexural modulus, flexural toughness, modulus of resiliency, fracture toughness, and surface microhardness were performed at each time interval. Mean data was analyzed by Kruskal Wallis and Dunn's post hoc testing at a 95% level of confidence (α=0.05). Results were material specific but overall, all resin composite material mechanical properties were found to be immature at 1 h after polymerization as compared to that observed at 24 h. It may be prudent that clinicians advise patients, especially those receiving complex posterior composite restorations, to guard against overly stressing these restorations during the first 24 h.
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    Resin-based dental materials containing 3-aminopropyltriethoxysilane modified halloysite-clay nanotubes for extended drug delivery
    (Elsevier, 2021-03) Karczewski, Ashley; Kalagi, Sara; Viana, Ítallo Emídio Lira; Martins, Victor Mota; Duarte, Simone; Gregory, Richard L.; P Youngblood, Jeffrey; Platt, Jeffrey A.; Feitosa, Sabrina; Biomedical Sciences and Comprehensive Care, School of Dentistry
    OBJECTIVE: To synthesize and characterize a novel resin-based dental material containing 3-aminopropyltriethoxysilane (APTES) surface-modified halloysite-clay nanotubes (HNTs) for long-term delivery of guest molecules. METHODS: The optimal concentrations of HNT (10, 15, 20 wt.%) and silane (0, 2, 4 vol.%sil) to be incorporated into the resin-based materials were determined (15 wt.%HNT, 4 vol.%sil) after assessment of the mechanical properties (DC%, degree of conversion; FS, flexural strength; FM, flexural modulus; and UTS, ultimate tensile strength). The HNTsil-powder was loaded with chlorhexidine (CHX) to evaluate the effect of the silanization on drug release. Resin-discs were prepared for the following groups: RES (resin), HNT (resin+15 wt.%HNT), HNTsil (resin+15 wt.%HNT silanized), HNT-CHX (resin+15 wt.%HNT loaded with chlorhexidine), HNTsil-CHX (resin+15 wt.%HNTsil-CHX), and 0.2 vol.%CHX (resin+0.2 vol.%CHX solution). Specimens were stored in water for 1, 3, 5, 10, and 15 days at 37 °C. Aliquots from each time point and the final 15-day specimens were evaluated for the zone of inhibition (ZOI) against Streptococcus mutans. CHX release was analyzed using spectrophotometry at absorbance of 300 nm. Data were statistically analyzed (α = 0.05). RESULTS: All materials presented similar DC%. Reduced FS but increased FM was detected for 20 wt.%HNT-4%APTES. Groups with 15 wt.% and 20 wt.%HNT with/without APTES presented higher values of UTS. Agar diffusion data indicates that the HNTsil-CHX had a greater ZOI than all other groups over 15 days. HNTsil-CHX had the highest absorbance for day 1 but presented similar values to other groups every time point after. SIGNIFICANCE: Silanization of nanotubes followed by encapsulation of chlorhexidine is a promising technique for long-term delivery of guest molecules.