Publications by authors named "Juliana Ivancik"

5 Publications

  • Page 1 of 1

Mechanical properties of silicone based composites as a temperature insensitive ballistic backing material for quantifying back face deformation.

Forensic Sci Int 2018 Apr 31;285:1-12. Epub 2018 Jan 31.

U.S. Army Research Laboratory, 4600 Deer Creek Loop, Aberdeen Proving Ground, MD 21005, USA. Electronic address:

This paper describes a new witness material for quantifying the back face deformation (BFD) resulting from high rate impact of ballistic protective equipment. Accurate BFD quantification is critical for the assessment and certification of personal protective equipment, such as body armor and helmets, and ballistic evaluation. A common witness material is ballistic clay, specifically, Roma Plastilina No. 1 (RP1). RP1 must be heated to nearly 38°C to pass calibration, and used within a limited time frame to remain in calibration. RP1 also exhibits lot-to-lot variability and is sensitive to time, temperature, and handling procedures, which limits the BFD accuracy and reproducibility. A new silicone composite backing material (SCBM) was developed and tested side-by-side with heated RP1 using quasi-static indentation and compression, low velocity impact, spherical projectile penetration, and both soft and hard armor ballistic BFD measurements to compare their response over a broad range of strain rates and temperatures. The results demonstrate that SCBM mimics the heated RP1 response at room temperature and exhibits minimal temperature sensitivity. With additional optimization of the composition and processing, SCBM could be a drop-in replacement for RP1 that is used at room temperature during BFD quantification with minimal changes to the current RP1 handling protocols and infrastructure. It is anticipated that removing the heating requirement, and temperature-dependence, associated with RP1 will reduce test variability, simplify testing logistics, and enhance test range productivity.
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http://dx.doi.org/10.1016/j.forsciint.2018.01.014DOI Listing
April 2018

On the Mechanics of Fatigue and Fracture in Teeth.

Appl Mech Rev 2014 May 30;66(3):0308031-3080319. Epub 2014 Apr 30.

Department of Materials Science and Engineering, University of Washington , Seattle, WA 98195;

Tooth fracture is a major concern in the field of restorative dentistry. However, knowledge of the causes for tooth fracture has developed from contributions that are largely based within the field of mechanics. The present manuscript presents a technical review of advances in understanding the fracture of teeth and the fatigue and fracture behavior of their hard tissues (i.e., dentin and enamel). The importance of evaluating the fracture resistance of these materials, and the role of applied mechanics in developing this knowledge will be reviewed. In addition, the complex microstructures of tooth tissues, their roles in resisting tooth fracture, and the importance of hydration and aging on the fracture resistance of tooth tissues will be discussed. Studies in this area are essential for increasing the success of current treatments in dentistry, as well as in facilitating the development of novel bio-inspired restorative materials for the future.
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http://dx.doi.org/10.1115/1.4027431DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4240032PMC
May 2014

The importance of microstructural variations on the fracture toughness of human dentin.

Biomaterials 2013 Jan 3;34(4):864-74. Epub 2012 Nov 3.

Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250, USA.

The crack growth resistance of human dentin was characterized as a function of relative distance from the DEJ and the corresponding microstructure. Compact tension specimens were prepared from the coronal dentin of caries-free 3rd molars. The specimens were sectioned from either the outer, middle or inner dentin. Stable crack extension was achieved under Mode I quasi-static loading, with the crack oriented in-plane with the tubules, and the crack growth resistance was characterized in terms of the initiation (K(o)), growth (K(g)) and plateau (K(p)) toughness. A hybrid approach was also used to quantify the contribution of dominant mechanisms to the overall toughness. Results showed that human dentin exhibits increasing crack growth resistance with crack extension in all regions, and that the fracture toughness of inner dentin (2.2 ± 0.5 MPa·m(0.5)) was significantly lower than that of middle (2.7 ± 0.2 MPa·m(0.5)) and outer regions (3.4 ± 0.3 MPa·m(0.5)). Extrinsic toughening, composed mostly of crack bridging, was estimated to cause an average increase in the fracture energy of 26% in all three regions. Based on these findings, dental restorations extended into deep dentin are much more likely to cause tooth fracture due to the greater potential for introduction of flaws and decrease in fracture toughness with depth.
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http://dx.doi.org/10.1016/j.biomaterials.2012.10.032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3511669PMC
January 2013

Contributions of aging to the fatigue crack growth resistance of human dentin.

Acta Biomater 2012 Jul 3;8(7):2737-46. Epub 2012 Apr 3.

Department of Mechanical Engineering, University of Maryland Baltimore County, USA.

An evaluation of the fatigue crack resistance of human dentin was conducted to identify the degree of degradation that arises with aging and the dependency on tubule orientation. Fatigue crack growth was achieved in specimens of coronal dentin through application of Mode I cyclic loading and over clinically relevant lengths (0 ≤ a ≤ 2 mm). The study considered two directions of cyclic crack growth in which the crack was either in-plane (0°) or perpendicular (90°) to the dentin tubules. Results showed that regardless of tubule orientation, aging of dentin is accompanied by a significant reduction in the resistance to the initiation of fatigue crack growth, as well as a significant increase in the rate of incremental extension. Perpendicular to the tubules, the fatigue crack exponent increased significantly (from m=14.2 ± 1.5 to 24.1 ± 5.0), suggesting an increase in brittleness of the tissue with age. For cracks extending in-plane with the tubules, the fatigue crack growth exponent does not change significantly with patient age (from m=25.4 ± 3.03 to 22.9 ± 5.3), but there is a significant increase in the incremental crack growth rate. Regardless of age, coronal dentin exhibits the lowest resistance to fatigue crack growth perpendicular to the tubules. While there are changes in the cyclic crack growth rate and mechanisms of cyclic extension with aging, this tissue maintains its anisotropy.
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http://dx.doi.org/10.1016/j.actbio.2012.03.046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3367091PMC
July 2012

Evaluation of the structural behavior of three and four implant-supported fixed prosthetic restorations by finite element analysis.

J Prosthodont Res 2012 Apr 21;56(2):110-9. Epub 2011 Nov 21.

Bioengineering Research Group (GIB), Product Design Engineering Department, EAFIT University, Medellín, Colombia.

Purpose: There is much controversy about the minimum number of implants and maximum cantilever length in mandible prosthetic restoration. Finite elements analysis of three and four implant-supported prostheses was performed to determine the stresses in the superstructure, implants and cortical bone and, therefore, the failure prediction for each restoration.

Methods: An edentulous mandible was modeled from CT scan images. Two finite element models of three and four implant-supported prostheses with cantilever lengths of 10 and 15 mm were created. Occlusal loads in different parts of the superstructure were applied and shear and normal stresses were calculated.

Results: Two failure criteria were analyzed: the von Mises criterion for isotropic materials (superstructure and implants) and the Tsai-Wu criterion for transversely isotropic material (cortical bone). Both criteria predict failure in the three implant-supported prosthesis for all cases analyzed. The same applies for the four-implant prosthesis of 15 mm cantilever length. However, four implants and a cantilever length of 10mm passed the failure criteria and were considered safe.

Conclusions: The results from the patient analyzed showed that fixed support prostheses on three implants are not recommended from a structural point of view because they do not adequately support occlusal loads. Excessive stress in the superstructure and the cortical bone can be expected, which would anticipate the failure of the restoration. Fixed support prostheses on four implants with a cantilever length of 10mm properly resist occlusal loading.
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http://dx.doi.org/10.1016/j.jpor.2011.07.001DOI Listing
April 2012
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