Off-Stoichiometric Reactions at the Cell-Substrate Biomolecular Interface of Biomaterials: In Situ and Ex Situ 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. Phenomenological studies of retrievals have clarified the final effect of bone formation, but have left the chemical interactions at the cell-material interface uncharted. Accordingly, the knowledge of the intrinsic material properties relevant for osteoblastogenesis and osteoinduction remains incomplete. Here, we systematically monitored in vitro the chemistry of mesenchymal cell metabolism and the ionic exchanges during osteoblastogenesis on selected substrates through conventional biological assays as well as via in situ and ex situ spectroscopic techniques. Accordingly, the chemical behavior of different bioceramic substrates during their interactions with mesenchymal cells could be unfolded and compared with that of biomedical titanium alloy. Our goal was to clarify the cascade of chemical equations behind the biological processes that govern osteoblastogenic effects on different biomaterial substrates.

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. Bacteria exposed to silica glass substrates were used as a control. S. epidermidis, a major cause of periprosthetic infections, was screened to obtain a precise time-lapse knowledge of its molecular composition and to mechanistically understand its interaction with different substrates. At the molecular level, the structure of proteins, lipids, nucleic acid, and aromatic amino acids evolved with time in response to different substrates. In combination with statistical validation and local pH measurements, a chemical lysis mechanism was spectroscopically observed in situ on the Si3N4 substrates. Utilization of FTIR in this study avoided fluorescence noise which occurred while probing the ZTA samples with Raman spectroscopy in a companion paper. The substrate-driven dynamics of polysaccharide and peptide variations in the bacterial cell wall, peculiar to Si3N4 bioceramics, are elucidated.

Radiological study on mandibular ramus asymmetry in young population.

BACKGROUND: The aim of this study was to estimate the prevalence of ramus asymmetries related to age and gender in a young population and the influence of growth spurt on ramus asymmetry. MATERIALS AND METHODS: The study consisted of 776 panoramic radiographs of individuals aged 9 to 21 years (335 males and 441 females). Individuals were divided into two groups with respect of linear growth spurt as age 12 in females and age 14 in males. The first group consisted of females aged between 9 and 11 and males between 9 and 13. The second group consisted of females aged between 12 and 21 and males between 14 and 21. Bilateral ramus heights on each radiograph were measured. A panoramic software programme was used to measure the ramus heights. Quantitative data was tested by Student's t test. Qualitative data was tested by χ2 test. The intraclass correlation coefficient was calculated for the magnitude error of the measurement. RESULTS: The mean of ramus asymmetry was found to be 2.90% ± 2.58%. Significant differences between the right and left ramus height ratios were observed (p < 0.01). There was a high prevalence (10.8%) of ramus asymmetry, which did not correlate with the age and gender of the patients. CONCLUSIONS: This study revealed a high prevalence of ramus asymmetry in 9-21- -year-old population. Within the limitations of this study, it can be concluded that ramus asymmetry should be carefully evaluated in all ages for the potential relation with temporomandibular dysfunctions and also for orthodontic anomalies.

Silicon Nitride Bioceramics Induce Chemically Driven Lysis in Porphyromonas gingivalis.

Organisms of Gram-negative phylum bacteroidetes, Porphyromonas gingivalis, underwent lysis on polished surfaces of silicon nitride (Si3N4) bioceramics. The antibacterial activity of Si3N4 was mainly the result of chemically driven principles. The lytic activity, although not osmotic in nature, was related to the peculiar pH-dependent surface chemistry of Si3N4. A buffering effect via the formation of ammonium ions (NH4(+)) (and their modifications) was experimentally observed by pH microscopy. Lysis was confirmed by conventional fluorescence spectroscopy, and the bacteria's metabolism was traced with the aid of in situ Raman microprobe spectroscopy. This latter technique revealed the formation of peroxynitrite within the bacterium itself. Degradation of the bacteria's nucleic acid, drastic reduction in phenilalanine, and reduction of lipid concentration were observed due to short-term exposure (6 days) to Si3N4. Altering the surface chemistry of Si3N4 by either chemical etching or thermal oxidation influenced peroxynitrite formation and affected bacteria metabolism in different ways. Exploiting the peculiar surface chemistry of Si3N4 bioceramics could be helpful in counteracting Porphyromonas gingivalis in an alkaline pH environment.

Medical and legal considerations in managing patients with musculoskeletal tumors.

At some point in their careers, many orthopaedic surgeons will have to navigate the legal system as it pertains to medical malpractice. An orthopaedic surgeon will find it helpful to review information on the basic legal elements of medical malpractice law along with suggestions on how he or she can assist the legal defense team if a lawsuit is filed. Surgeons who face litigation within the context of managing patients with musculoskeletal tumors should be aware of the common pitfalls in managing these patients. Knowledge of complementary strategies can provide good patient care and reduce legal risks when caring for patients with musculoskeletal neoplasms.

Improved radiographic outcomes with patient-specific total knee arthroplasty.

Patient-specific guides can improve limb alignment and implant positioning in total knee arthroplasty, although not all studies have supported this benefit. We compared the radiographs of 100 consecutively-performed patient-specific total knees to a similar group that was implanted with conventional instruments instead. The patient-specific group showed more accurate reproduction of the theoretically ideal mechanical axis, with fewer outliers, but implant positioning was comparable between groups. Our odds ratio comparison showed that the patient-specific group was 1.8 times more likely to be within the desired +3° from the neutral mechanical axis when compared to the standard control group. Our data suggest that reliable reproduction of the limb mechanical axis may accrue from patient-specific guides in total knee arthroplasty when compared to standard, intramedullary instrumentation.