B. Sonny Bal

SINTX Technologies

Ceramic materials have played an important role in the development of modern total hip replacements. Following the introduction of the modular low-friction total hip (THA) in the 1960s, subsequent improvements have addressed the various failure modes for this prosthetic implant. Over the past two decades, clinical practitioners have generally moved...

Medical-grade masks and N95 respirators containing non-woven fibers are designed to prevent the spread of airborne diseases. While they effectively trap respiratory droplets and aerosols, they cannot lyse entrapped pathogens. Embedded antimicrobial agents such as silver, copper, zinc, iodine, peptides, quaternary ammonium salts, or nanoparticles ha...

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 f...

Most structural bioceramics are comprised of metallic oxides such as alumina and zirconia. They are generally considered to be completely bioinert, but a non-oxide ceramic, silicon nitride, achieves equivalent levels of mechanical reliability while being bioactive. Silicon nitride can not only stimulate cellular proliferation but it is also antipat...

Previous studies using gram-positive and -negative bacteria demonstrated that hydrolysis of silicon nitride (Si3N4) 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 che...

Surface inactivation of human microbial pathogens has a long history. The Smith Papyrus (2600 ~ 2200 B.C.) described the use of copper surfaces to sterilize chest wounds and drinking water. Brass and bronze on doorknobs can discourage microbial spread in hospitals, and metal-base surface coatings are used in hygiene-sensitive environments, both as...

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-Si3N4) onto the surface of bulk PEEK. NaCl grains were removed by leaching in water, resulting in a porous PEEK surface embedded with ~15 vol.% β-Si3N4 particles. Thi...

The performance, durability, and bio-integration of functional biomedical coatings can be enhanced by changing or improving their substrate properties. In this study, we applied silicon nitride powder-based laser claddings to various substrates and undertook an in vitro assessment of their osteoconductive and antibacterial properties. The substrate...

Downy mildew of grapevine, caused by Plasmopara viticola (Berk. and Curt.) Berl. and de Toni, is one of the most devastating diseases of grapevine, severely affecting grape and wine production and quality worldwide. Infections are usually controlled by the intensive application of synthetic fungicides or by copper-based products in organic farming,...

Poly-Ether-Ether-Ketone (PEEK) is a structural biopolymer with various biomedical applications, from spinal cages to dental prosthetics. Due its high chemical stability combined with good mechanical strength, PEEK is considered to be one of the most successful bio-inert polymers ever developed. In this work, a mixture of PEEK and β-Si3N4 was used t...

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 (Si3N4) is a less well-known alternative although it was first used as a spacer in lumbar fusion...

Introduction Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the COVID-19 pandemic, remains viable and therefore potentially infectious on several materials. One strategy to discourage the fomite-mediated spread of COVID-19 is the development of materials whose surface chemistry can spontaneously inactivate SA...

Functional coatings are commonly applied to biomaterials in order to improve their properties. In this work, polyethylene was coated with a silicon nitride (Si3N4) powder using a pulsed laser source in a nitrogen gas atmosphere. Several analytical techniques were used to characterize the functionalized surface of the polymer, including Raman spectr...

Zirconia is the most common ceramic used in dental implants. Even if it possesses both mechanical strength and esthetics, its intrinsic bio-inertness often results in a lack of biological integration. On the other hand, Si3N4 has been proved to be bio-active and to be able to easily osteointegrate. In this work, a Si3N4 powder-based laser-cladding...

Background: In lumbar fusion surgery, intervertebral spacer cages made of silicon nitride (Si3N4) ceramic are an available option among other biomaterials. While the surface chemistry of Si3N4 is known to favor bone fusion, large-scale clinical studies attesting to its efficacy are lacking. This multicenter retrospective study compared lumbar fusi...

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) polymorphi...

Background: Intervertebral spacers made of silicon nitride (Si3N4) are currently used in cervical and thoracolumbar fusion. While basic science data demonstrate several advantages of Si3N4 over other biomaterials, large-scale clinical results on its safety and efficacy are lacking. This multicenter retrospective study examined outcomes for anterio...

A 3D-additive manufacturing approach produced a dense Si3N4 ceramic coating on a biomedical grade commercially pure titanium (cp-Ti) substrate by an automatic laser-sintering procedure. Si3N4 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...

Alumina (Al2O3) ceramic implants do not stimulate osteoblasts in vivo. Surface alterations targeted at changing the chemistry or topography have been proposed to enhance the bioactivity of alumina. This surface modification is intended to improve oxide bioceramic’s ability to integrate with the biological environment and, in particular, to rapidly...

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 differenti...

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 w...

The surfaces of silicon nitride (β-Si3N4) 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 m...

It is easy to capture and share clinical photographs and x-ray images using modern smartphones. This technology affords health-care providers the ability to rapidly collaborate and facilitate care for their patients. This improvement, however, has increased concerns regarding patient privacy and the safeguarding of protected health information. Hea...

Due to the favourable combination of mechanical strength and fracture toughness, silicon nitride has been applied as a load-bearing bioceramic, in particular for implants used in spinal fusion surgery. Only recently it has been observed that the supposedly inert surface of silicon nitride is actually bioactive: a slow, but not negligible, pH contro...

The following research is aimed at understanding the influence of Zirconia-Toughened Alumina (ZTA) and Silicon Nitride (Si 3 N 4 ) on Ultra-High Molecular Weight Polyethylene (UHMWPE) acetabular liners. Bioceramic femoral heads were systematically tested against UHMWPE in controlled environment according to static/load-free coupling in hydrothermal...

In vitro and in vivo studies have recently shown that silicon nitride (Si3N4) is an osseoconductive and potential osseoinductive biomaterial. Even though the amount of bone mineral produced by Si3N4 was inferior when compared to commercial Bioglass, it strongly stimulated the production of extracellular matrix and collagen tissues. Consequently, th...

Over the next two decades, strong demographic demand for arthroplastic devices coupled with decreased efficacy of antibiotics are predicted to result in an exponential increase in the number of periprosthetic joint infections (PJI). Advanced strategies are therefore required to improve the local peri-implant immune response and curb the pathogenic...

Back Cover: Silicon nitride (Si3N4) is a bioceramic with unique surface chemistry, friendly to cells and adverse to bacteria. A 15vol.% Si3N4 particulate dispersion into polyetheretherketone (PEEK) proved capable to translate such a unique biochemical behavior to a polymer‐matrix composite, which also became X‐ray translucent and retained a modulus...

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. Altho...

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 custo...

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. Bacteria exposed to silica glass substrates were used as a...

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 cer...

* Electronic communication has become pervasive throughout modern health care and has dramatically increased accessibility to health information. * Tools such as personal short message service (SMS), or text, communication provide instantaneous information and have changed the management of patient care. * Breach of privacy is a major concern, part...

Background: MRI in the evaluation of end-stage knee joint osteoarthritis (OA) is usually unnecessary when radiographic and clinical evidence of gonarthrosis is clear. The purpose of this study was to assess the prevalence of MRI scans ordered in patients with radiographically obvious gonarthrosis and to examine the characteristics of health care p...

Polycrystalline silicon nitride (Si3N4), sintered with the addition of minor fractions of yttrium and aluminum oxides (i.e., Y2O3 and Al2O3), possesses uniquely adjustable surface chemistry that results in improved cell metabolism and enhanced bone formation. Building upon previous in vitro mineralization studies using osteosarcoma cells, this stud...

While silicon nitride (Si3N4) is an antimicrobial and osseosintegrative orthopaedic biomaterial, the contribution of surface topography to these properties is unknown. Using a methicillin-resistant strain of Staphylococcus aureus (MSRA), this study evaluated Si3N4 implants in vitro via scanning electron microscopy (SEM) and colony forming unit (CFU...

Statement of significance: This research studies osseointegration processes comparing results from explanted PEEK and Si3N4 spinal spacers. Data show that the formation of hydroxyapatite on silicon nitride bio-ceramic surfaces happens with a peculiar mechanism inside the human body. Silicon and nitrogen were incorporated inside the bony tissue str...

Bioactive glass scaffolds have been used to heal small contained bone defects, but their application to repairing structural bone is limited by concerns about their mechanical reliability. In the present study, the addition of an adherent polymer layer to the external surface of strong porous bioactive glass (13–93) scaffolds was investigated to im...

The application of bioactive coatings onto orthopaedic appliances is commonly performed to compensate for the otherwise bioinert nature of medical devices and to improve their osseointegration. Calcium phosphates, hydroxyapatite (HAp), and bioglasses are commercially available for this purpose. Until recently, few other inorganic compounds have bee...

A clear discrepancy between predicted in vitro and actual in vivo surface phase stability of BIOLOX®delta zirconia-toughened alumina (ZTA) femoral heads has been demonstrated by several independent research groups. Data from retrievals challenge the validity of the standard method currently utilized in evaluating surface stability and raise a serie...

While the reciprocity between bioceramics and living cells is complex, it is principally governed by the implant’s surface chemistry. Consequently, a deeper understanding of the chemical interactions of bioceramics with living tissue could ultimately lead to new therapeutic strategies. However, the physical and chemical principles that govern these...

Renewed attention is being paid to biomaterials used in total hip arthroplasty (THA) given the continued clinical problems of osteolysis and aseptic loosening which result from the long-term wear of acetabular polyethylene (PE) bearing surfaces. One advantage of using ceramic femoral heads is low PE wear, presumably because of the ceramics' bioiner...

Silicon nitride (Si3N4) implants are used in spinal fusion surgery and are under development for use in other biomedical applications. The ability to create Si3N4 implants with anatomically relevant shapes and controllable architecture can be beneficial in these applications. In the present study, an aqueous paste composed of Si3N4 powder and sinte...

The chemical interaction of femoral heads with polyethylene liners is an important new area of research in total hip arthroplasty (THA) as a consequence of an unabating quest for elongated artificial joint lifetimes. It is a topic that goes beyond simple mechanical behavior or wear. It seeks to describe the prosthetic device as a whole by adding ch...

This chapter discusses the release of angiogenic ions (copper) and/or an osteogenic growth factor (bone morphogenetic protein-2) (BMP2) from bioactive silicate glass (13-93) scaffolds to accelerate healing of bone defects in vivo. The chapter states that allografts are costly, have unpredictable healing to bone due to donor variance and adverse imm...

This chapter examines the re-development of the microstructure of the uniform gridlike bioactive glass (13-93) scaffolds created in the previous studies in order to improve their flexural strength. Each model was composed of 13 alternating orthogonal layers of parallel filaments. The length and angle of the filaments and the spacing between the par...

Introduction: The ideal material for the manufacture of cervical fusion cages used in anterior cervical discectomy and fusion (ACDF) is undetermined. Spacers made of polyether-ether-ketone (PEEK) are commonly used, although metal and ceramic devices are also commercially available. This observational study compared outcomes of ACDF using two differ...

Background: Interbody cages used in spinal fusion surgery can subside into the adjacent vertebral bodies after implantation, leading to loss of spinal height, malalignment, and possible radicular symptoms. Several factors may contribute to cage subsidence. Methods: This in vitro investigation examined the possible contribution of substrate densi...

Perioperative and latent infections are leading causes of revision surgery for orthopaedic devices resulting in significant increased patient care, comorbidities, and attendant costs. Identifying biomaterial surfaces that inherently resist biofilm adhesion and bacterial expression is an important emerging strategy in addressing implant-related infe...

Understanding the intrinsic reason(s) for the enhanced tetragonal to monoclinic (t → m) polymorphic phase transformation observed on metal-stained surfaces of zirconia-toughened alumina (ZTA) requires detailed knowledge of off-stoichiometry reactions at the molecular scale. In this context, knowledge of the mechanism(s) for oxygen vacancy creation...

Exploitation of the toughening effect induced by polymorphic phase transformation of zirconia in zirconia-toughened alumina (ZTA) requires the composite being properly designed and carefully manufactured. A sound algorithm for predicting phase stability along with strict control over manufacturing steps are required in order to prevent possible in...

Femoral heads made from zirconia-toughened alumina (ZTA) are the most advanced bioceramic available for total hip arthroplasty. ZTA's superior mechanical properties result from the polymorphic transformation of its zirconia (ZrO2) phase in the presence of a propagating crack. In vitro derived activation energies predict that several human lifetimes...

Due to its remarkable stoichiometric flexibility and surface chemistry, hydroxyapatite (HAp) is the fundamental structural material in all vertebrates. Natural HAp's properties inspired an investigation into silicon nitride (Si3N4) to see if similar functionality could be engineered into this bioceramic. Biological and in situ spectroscopic analyse...

In this paper, an updated analytical model for the kinetics of the tetragonal to monoclinic (t → m) polymorphic transformation in ZTA composites for hip joints is proposed and discussed. The model builds upon the so-called Mehl-Avrami-Johnson (MAJ) description of transformation kinetics, which combines two overlapping processes: nucleation of monoc...

The effect of frictional sliding on the surface degradation of commercially available zirconia-toughened alumina (ZTA) femoral heads was studied using a pin-on-ball wear tester under three different lubricating conditions: dry, water, and squalene. Water and squalene were employed under boundary lubrication regimes. Despite the unique (non-standard...

The remarkable stoichiometric flexibility of hydroxyapatite (HAp) enables the formation of a variety of charged structural sites at the material’s surface which facilitates bone remodeling due to binding of biomolecule moieties in zwitterionic fashion. In this paper, we report for the first time that an optimized biomedical grade silicon nitride (S...