Behind Amor Blunt Trauma Lung and Liver Strains From Indenter Loading Via Finite Element Modeling.

To determine behind armor blunt trauma (BABT) injury criteria, experiments have been conducted by launching blunt projectiles at live swine at velocities up to 65 meters per second (m/s) using one type of indenter design. To ensure the generalizability of the developed injury criteria, additional tests with different indenter designs are needed. The objectives of this study were to evaluate the kinematics and injury parameters from two indenter designs using human body finite element modeling.

Adverse effects of COVID-19 pandemic on a multicenter randomized controlled trial.

Objective: Describe the effects of the COVID-19 pandemic on subject enrollment in a multicenter randomized controlled trial.

Study Design: We assessed the number of eligible infants approached and consented for enrollment over five separate epochs including baseline, peak pandemic, and gradual but incomplete recovery.

Result: The pandemic had a major effect on ability to approach parents for consent.

Transforaminal lumbar interbody fusion with a silicon nitride cage demonstrates early radiographic fusion.

Background: Degeneration of the lumbar spine is common in aging adults and reflects a significant morbidity burden in this population. In selected patients that prove unresponsive to non-surgical treatment, posterior lumbar fusion (PLF) surgery, with or without adjunctive transforaminal lumbar interbody fusion (TLIF) can relieve pain and improve function. We describe here the radiographic fusion rates for PLF versus TLIF, using an intervertebral spinal cage made of silicon nitride ceramic (chemical formula SiN).

Antifungal activity of polymethyl methacrylate/SiN composites against Candida albicans.

Previous studies using gram-positive and -negative bacteria demonstrated that hydrolysis of silicon nitride (SiN) in aqueous suspensions elutes nitrogen and produces gaseous ammonia while buffering pH. According to immunochemistry assays, fluorescence imaging, and in situ Raman spectroscopy, we demonstrate here that the antipathogenic surface chemistry of SiN can be extended to polymethylmethacrylate (PMMA) by compounding it with a minor fraction (~8 vol.%) of SiN particles without any tangible loss in bulk properties.

Silicon nitride: a potent solid-state bioceramic inactivator of ssRNA viruses.

Surface inactivation of human microbial pathogens has a long history. The Smith Papyrus (2600 ~ 2200 B.C.

Activity and Mechanism of Action of the Bioceramic Silicon Nitride as an Environmentally Friendly Alternative for the Control of the Grapevine Downy Mildew Pathogen .

Downy mildew of grapevine, caused by (Berk. and Curt.) Berl.

Two-year results of a double-blind multicenter randomized controlled non-inferiority trial of polyetheretherketone (PEEK) versus silicon nitride spinal fusion cages in patients with symptomatic degenerative lumbar disc disorders.

Background: During lumbar spinal fusion, spacer cages are implanted to provide vertebral stability, restore sagittal alignment, and maintain disc and foraminal height. Polyetheretherketone (PEEK) is commonly used by most spine surgeons. Silicon nitride (SiN) is a less well-known alternative although it was first used as a spacer in lumbar fusion over 30 years ago.

Surface functionalization of PEEK with silicon nitride.

Surface roughness, bioactivity, and antibacterial properties are desirable in skeletal implants. We hot-pressed a mix of particulate sodium chloride (NaCl) salt and silicon nitride (β-SiN) onto the surface of bulk PEEK. NaCl grains were removed by leaching in water, resulting in a porous PEEK surface embedded with sim15 vol% β-SiNparticles.

Clinical outcomes for lumbar fusion using silicon nitride versus other biomaterials.

Background: In lumbar fusion surgery, intervertebral spacer cages made of silicon nitride (SiN) ceramic are an available option among other biomaterials. While the surface chemistry of SiN is known to favor bone fusion, large-scale clinical studies attesting to its efficacy are lacking. This multicenter retrospective study compared lumbar fusion outcomes for SiN cages to previously reported data for other cage materials.

3D-additive deposition of an antibacterial and osteogenic silicon nitride coating on orthopaedic titanium substrate.

A 3D-additive manufacturing approach produced a dense SiN ceramic coating on a biomedical grade commercially pure titanium (cp-Ti) substrate by an automatic laser-sintering procedure. SiN coatings could be prepared with thicknesses from the single to the tens of microns. A coating thickness, t = 15 ± 5 μm, was selected for this study, based on projections of homogeneity and scratching resistance.

Clinical outcomes for anterior cervical discectomy and fusion with silicon nitride spine cages: a multicenter study.

Background: Intervertebral spacers made of silicon nitride (SiN) are currently used in cervical and thoracolumbar fusion. While basic science data demonstrate several advantages of SiN over other biomaterials, large-scale clinical results on its safety and efficacy are lacking. This multicenter retrospective study examined outcomes for anterior cervical discectomy and fusion (ACDF) using SiN cages.

Burst Strength of BIOLOXdelta Femoral Heads and Its Dependence on Low-Temperature Environmental Degradation.

Zirconia-toughened alumina (ZTA) currently represents the bioceramic gold standard for load-bearing components in artificial hip joints. ZTA is long known for its high flexural strength and fracture toughness, both properties arising from a microscopic crack-tip shielding mechanism due to the stress-induced tetragonal-to-monoclinic (t→m) polymorphic transformation of zirconia. However, there have been concerns over the years regarding the long-term structural performance of ZTA since the t→m transformation also spontaneously occurs at the material's surface under low-temperature environmental conditions with a concomitant degradation of mechanical properties.

Enhanced bioactivity of SiN through trench-patterning and back-filling with Bioglass®.

Using a simple and innovative sandblasting process, disks of monolithic biomedical silicon nitride (β-SiN) were texturized with a matrix of regular, discrete square trenches with a total depth in the range of hundreds of microns. The process consisted of sandblasting SiN substrates through a stainless-steel wire-mesh (150 or 200 μm) using abrasive silicon carbide powders (α-SiC, ∼40 μm) under 1,034 kPa (150 psi) of gas pressure. The depth of the porosities could be controlled varying both the treatment time and the distance from the surface.

The role of nitrogen off-stoichiometry in the osteogenic behavior of silicon nitride bioceramics.

The surface chemistry of silicon nitride plays an important role in stimulating osteoblasts to proliferate and produce bone tissue with improved efficiency. This property, which is advantageous in spinal fusion surgery has a chemical origin and is a direct consequence of the cleavage of covalent SN bonds in an aqueous environment. Building upon a wealth of published research on the stimulation of osteoblastic activity by silicon, the aim of this paper is to explore the role of nitrogen and, more specifically, the N/Si atomic ratio on the osteogenic response of SiN.

Off-Stoichiometric Reactions at the Cell-Substrate Biomolecular Interface of Biomaterials: and Monitoring of Cell Proliferation, Differentiation, and Bone Tissue Formation.

The availability of osteoinductive biomaterials has encouraged new therapies in bone regeneration and has potentially triggered paradigmatic shifts in the development of new implants in orthopedics and dentistry. Among several available synthetic biomaterials, bioceramics have gained attention for their ability to induce mesenchymal cell differentiation and successive bone formation when implanted in the human body. However, there is currently a lack of understanding regarding the fundamental biochemical mechanisms by which these materials can induce bone formation.

In situ molecular vibration insights into the antibacterial behavior of silicon nitride bioceramic versus gram-negative Escherichia coli.

Gram-negative bacteria represent a substantial fraction of pathogens responsible for periprosthetic infections. Given the increasing resistance of such bacteria to antibiotics, significant efforts are nowadays paid in developing new biomaterial surfaces, which offer resistance against bacterial adhesion and/or possess inherent antibacterial effects. Non-oxide silicon nitride (SiN) bioceramic in its polycrystalline form is a biomaterial with inherent antibacterial properties.

Bioglass functionalization of laser-patterned bioceramic surfaces and their enhanced bioactivity.

The surfaces of silicon nitride (-SiN) and zirconia toughened alumina (ZTA) were patterned using a high-energy laser source, which operated at a wavelength of 1064 nm. The patterning procedure yielded a series regular, cylindrical cavities 500 and 300 μm in diameter and depth, respectively. These cavities were subsequently filled with bioglass mixed with different fractions of SiN powder (0, 5, and 10 mol.

A single center retrospective clinical evaluation of anterior cervical discectomy and fusion comparing allograft spacers to silicon nitride cages.

Background: Iliac crest autograft or allograft spacers have been traditionally utilized in anterior cervical discectomy and fusion (ACDF) to provide vertebral stabilization and enhanced osteogenesis. However, abiotic cages have largely replaced these allogenic sources due to host-site morbidities and disease transmission risks, respectively. Although devices made of polyetheretherketone (PEEK) or titanium-alloys (Ti) have gained wide popularity, they lack osteoinductive or conductive capabilities.

In vitro antibacterial activity of oxide and non-oxide bioceramics for arthroplastic devices: I. In situ time-lapse Raman spectroscopy.

Over the next two decades, a strong demographic demand for arthroplastic devices coupled with a decreased efficacy of antibiotics has been predicted to result in an exponential increase in the number of periprosthetic joint infections (PJIs). Advanced strategies are therefore required to improve the local peri-implant immune response and curb the pathogenic events of bacterial adhesion and biofilm formation. The use of biomaterials that autonomously counter infections is one approach to improve orthopedic outcomes.

Monitoring metabolic reactions in Staphylococcus epidermidis exposed to silicon nitride using in situ time-lapse Raman spectroscopy.

Staphylococcus epidermidis (S. epidermidis) is one of the leading nosocomial pathogens, particularly associated with periprosthetic infections of biomedical implants. Silicon nitride (Si3N4), a nonoxide biomaterial widely used in spinal implants, has shown bacteriostatic effects against both gram-positive and gram-negative bacteria; however, the physicochemical interactions between Si3N4 and bacteria yet remain conspicuously unexplored.

Incorporating Si N into PEEK to Produce Antibacterial, Osteocondutive, and Radiolucent Spinal Implants.

Polyetheretherketone (PEEK) is a popular polymeric biomaterial which is primarily used as an intervertebral spacer in spinal fusion surgery; but it is developed for trauma, prosthodontics, maxillofacial, and cranial implants. It has the purported advantages of an elastic modulus which is similar to native bone and it can be easily formed into custom 3D shapes. Nevertheless, PEEK's disadvantages include its poor antibacterial resistance, lack of bioactivity, and radiographic transparency.

In vitro antibacterial activity of oxide and non-oxide bioceramics for arthroplastic devices: II. Fourier transform infrared spectroscopy.

The metabolic response of Gram-positive Staphylococcus epidermidis (S. epidermidis) bacteria to bioceramic substrates was probed by means of Fourier transform infrared spectroscopy (FTIR). Oxide zirconia-toughened alumina (ZTA) and non-oxide silicon nitride (Si3N4) substrates were tested.

Evaluation of Environmental Sensors During Laboratory Direct and Indirect Head Exposures.

With the prevalence of traumatic brain injury (TBI) in the military and athletics, several commercial and military environmental sensors (ES) have been developed to quantify head impact exposures. The performance of five ES in controlled laboratory exposures from direct and indirect loadings, and the effect on impact protection and dynamic retention of the worn Advanced Combat Helmet (ACH) was evaluated. Direct impacts were conducted on a drop tower and indirect impacts used a mini-sled.

Oxide ceramic femoral heads contribute to the oxidation of polyethylene liners in artificial hip joints.

Experimental evidence demonstrates that a loss of stoichiometry at the surface of oxide bioceramic femoral heads enhances the oxidation rate of polyethylene acetabular liners in artificial hip joints. Contradicting the common notion that ceramics are bioinert, three independent experiments confirmed substantial chemical interactions between the ceramic femoral heads and their polyethylene counterparts. The experiments reported herein included hydrothermal tests, frictional tests, and hip-simulator experiments.