Browsing School of Dentistry by Author "Feldman, Steven G."
Developing a 3D-Printed Peri-Implantium Based Plaque Assay (2016)Feldman, Steven G.; Kim, Jeffrey J. (2016-03-23)Objectives: Currently, there is no consensus of how to best maintain dental implants. With over 2 million dental implants placed annually, there is an urgent need for objective ways to measure plaque removal from peri-implant surfaces. Here, we developed a cost effective, fast and accurate way to measure the effectiveness of various oral hygiene products to maintain health of the implant and surrounding oral tissues using a 3D printer. Methods: Digitizations of dentoform teeth and jaws provided the basis for 3D-printed custom models. Simulated gingiva and genuine dental implants were incorporated to maximize clinical relevance. Fabricated model teeth were analyzed for consistency of cusp heights, inter-cusp distance and mass. Mass was remeasured following water immersion. An artificial plaque substrate (APS) was applied to 3D-printed and porcelain surfaces to ensure consistent performance. A standard by which toothbrush mediated APS removal from the interproximal and subgingival areas was developed, with varying brushing angle, force and toothbrush design. Results: The 3D-printed models had higher dimensional accuracy than the resolution of the 3D printer (X/Y<400μm, Z<100μm). Immersion in water yielded an increase in mass that was correlated linearly with time (r2 = .9365) and could be reversed upon desiccation. APS behaved similarly on the 3D-printed surface as porcelain. Conclusions: Lack of commercially available dentoforms with accurate dental implant anatomy limited the ability to simulate implant systems in vitro. However, the advent of low-priced commercial grade 3D printers enables individuals to create such models rapidly and at low cost. We developed highly accurate, anatomically correct, 3D-printed dental implant model systems, which mitigated flaws in extant designs and devised a high-throughput method for assessing in vitro plaque removal that is superior to existing methods. In the future, digital model files can be included in an electronic library for rapid manufacturing of identical models anywhere in the world.
Tissue Lipid Analysis via MALDI Imaging (MALDI-IMS)Feldman, Steven G.; Scott, Alison June; Ernst, Robert K. (2013-04-11)Mammalian tissue contains a complex array of lipids and membrane components. Analysis is typically accomplished by one of many histological methods, such as Hematoxylin and Eosin (H&E) stain, immunohistochemistry (IHC) and in situ hybridization (ISH). However, a limitation of most techniques is a requirement for prior knowledge of the targets of interest. Mass spectrometry (MS) coupled assays are useful for their inherent speed and accuracy. Hyphenated MS techniques, such as MALDI-TOF MS (Matrix Assisted Laser Desorption Ionization-Time of Flight) have been developed for rapid analysis of complex biological samples. MALDI-TOF MS lends itself to tissue slices because it does not require pure samples and can offer de novo discovery of sample components. Here we show the coupling of this technique with histological staining for the investigation of lipids and their localization within mouse kidney tissue slices. This method is shown to be extensible through the incorporation of LIFT (MS/MS) wherein a specific peak of known molecular weight is exposed to a high energy laser which causes reliable and reproducible fragmentation based on bond energies within the molecule. As such, aspects of the target molecule from a class (eg phospholipids) down to side chains can be identified allowing the fullscale investigation of major tissue components. In a proof of concept study, pure standards of the major phospholipids phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were subjected to LIFT, to confirm structures. Subsequently, MALDI-IMS applied to tissue slices reveals abundant peaks in the range of predicted phospholipids. These results will be analyzed to confirm these tissue phospholipids. MALDI-TOF MS coupled with LIFT presents a novel way of looking at tissue without prior knowledge of its constituents as it allows for analysis in the absence of traditional reagents such as antibodies or nucleic acid probes.