Assessment of strategies for the formation of stable suspensions of titanium dioxide nanoparticles in aqueous media suitable for the analysis of biological fluids.

Due to their omnipresence in consumer products, there is a growing concern about the potential effects of nanoparticles on human health. Toxicological assessment and NP end-product studies require proper quantification of these materials in biological fluids. However, their quantifications in these media require stable predispersed NP solutions in aqueous media to enable the fortification in the matrices of interest or the preparation of calibration standards. In this study, a sample preparation scheme was developed by studying various dispersion media (polyvinylpyrrolidone and polyethylene glycol) and sonication strategies (bath and ultrasonic probe) to ensure homogeneous dispersion of titanium dioxide nanoparticles. Optimization of the various parameters was performed using SRM NIST 1898 NP reference material, composed of rutile and anatase phases. Number-based size distribution for titanium dioxide NPs was determined by dynamic light scattering and single-particle inductively coupled plasma mass spectrometry to evaluate the procedure efficiency. Changes in mean size and most frequent size distribution were also studied to determine if the agglomeration of nanoparticles occurs at the various dispersion conditions tested. Among the different dispersion parameters tested herein, the use of polyvinylpyrrolidone combined with a sonication process generated by a probe leads to a significant improvement in terms of suspension efficiency and stability over 72 h. The dispersion efficiency of the proposed methodology was assessed by single-particle inductively coupled plasma mass spectrometry with spiked biological fluids such as urine and blood. Graphical abstract.

PEEK versus titanium cages in lateral lumbar interbody fusion: a comparative analysis of subsidence.

OBJECTIVE: The authors have provided a review of radiographic subsidence after lateral lumbar interbody fusion (LLIF) as a comparative analysis between titanium and polyetheretherketone (PEEK) cages. Many authors describe a reluctance to use titanium cages in spinal fusion secondary to subsidence concerns due to the increased modulus of elasticity of metal cages. The authors intend for this report to provide observational data regarding the juxtaposition of these two materials in the LLIF domain. METHODS: A retrospective review of a prospectively maintained database identified 113 consecutive patients undergoing lateral fusion for degenerative indications from January to December 2017. The surgeons performing the cage implantations were two orthopedic spine surgeons and two neurosurgeons. Plain standing radiographs were obtained at 1-2 weeks, 8-12 weeks, and 12 months postoperatively. Using a validated grading system, interbody subsidence into the endplates was graded at these time points on a scale of 0 to III. The primary outcome measure was subsidence between the two groups. Secondary outcomes were analyzed as well. RESULTS: Of the 113 patients in the sample, groups receiving PEEK and titanium implants were closely matched at 57 and 56 patients, respectively. Cumulatively, 156 cages were inserted and recombinant human bone morphogenetic protein-2 (rhBMP-2) was used in 38.1%. The average patient age was 60.4 years and average follow-up was 75.1 weeks. Subsidence in the titanium group in this study was less common than in the PEEK cage group. At early follow-up, groups had similar subsidence outcomes. Statistical significance was reached at the 8- to 12-week and 52-week follow-ups, demonstrating more subsidence in the PEEK cage group than the titanium cage group. rhBMP-2 usage was also highly correlated with higher subsidence rates at all 3 follow-up time points. Age was correlated with higher subsidence rates in univariate and multivariate analysis. CONCLUSIONS: Titanium cages were associated with lower subsidence rates than PEEK cages in this investigation. Usage of rhBMP-2 was also robustly associated with higher endplate subsidence. Each additional year of age correlated with an increased subsidence risk. Subsidence in LLIF is likely a response to a myriad of factors that include but are certainly not limited to cage material. Hence, the avoidance of titanium interbody implants secondary solely to concerns over a modulus of elasticity likely overlooks other variables of equal or greater importance.

Comparison of the Efficiency of Two Novel Guided Bone Regeneration Devices in the Rabbit Calvarial Model.

BACKGROUND: Creating a secluded large space using guided bone regeneration (GBR) is a novel osteogenesis technique used in the prevention of premature membrane exposure complications. However, this technique is not considered clinically feasible. OBJECTIVES: This study aimed to compare the outcome of the insertion of two novel GBR devices in a rabbit calvarial model in terms of mode of action, simplicity, and amount of new space and bone gained. MATERIALS AND METHODS: The expansible GBR (EGBR) device, composed mainly of a titanium plate, silicone membrane, and activation screw, was inserted beneath the periosteum in the calvarial area of eight rabbits. The smart GBR (SGBR) device, composed of silicone sheets and Nitinol strips, were inserted beneath the periosteum in the calvarial area of another 10 rabbits. Half of each group was sacrificed 2 months after surgery, and the other half was sacrificed after 4 months. RESULTS: Histological and microradiographical analysis showed that, at 2 months, the EGBR device achieved a mean space gain of 207.2 mm3, a mean bone volume of 68.2 mm3, and a mean maximum bone height of 1.9 mm. Values for the same parameters at 4 months were 202.1 mm3, 70.3 mm3, and 1.6 mm, respectively. The SGBR device had significantly higher (P < 0.05) mean space gain (238.2 mm3; 239.5 mm3), bone volume (112.9 mm3, 107.7 mm3), and bone height (2.7 mm; 2.6 mm) than the EGBR device at 2 and 4 months, respectively. CONCLUSION: Both devices proved to be effective in augmenting bone vertically through the application of GBR and soft tissue expansion processes. However, the SGBR device was more efficient in terms of mode of action, simplicity, and amount of bone created in the new space.

Lanthanum-containing hydroxyapatite coating on ultrafine-grained titanium by micro-arc oxidation: a promising strategy to enhance overall performance of titanium.

Titanium is widely used in biomedical materials, particularly in dental implants, because of its excellent biocompatibility and mechanical characteristics. However, titanium implant failures still remain in some cases, varying with implantation sites and patients. Improving its overall performance is a major focus of dental implant research. Equal-channel angular pressing (ECAP) can result in ultrafine-grained titanium with superior mechanical properties and better biocompatibility, which significantly benefits dental implants, and without any harmful alloying elements. Lanthanum (La) can inhibit the acidogenicity of dental plaque and La-containing hydroxyapatite (La-HA) possesses a series of attractive properties, in contrast to La-free HA. Micro-arc oxidation (MAO) is a promising technology that can produce porous and firmly adherent hydroxyapatite (HA) coatings on titanium substrates. Therefore, we hypothesize that porous La-containing hydroxyapatite coatings with different La content (0.89%, 1.3% and 1.79%) can be prepared on ultrafine-grained (~200-400 nm) titanium by ECAP and MAO in electrolytic solution containing 0.2 mol/L calcium acetate, 0.02 mol/L beta-glycerol phosphate disodium salt pentahydrate (beta-GP), and lanthanum nitrate with different concentrations to further improve the overall performance of titanium, which are expected to have great potential in medical applications as a dental implant.

Optimization of Bi2O3, TiO2, and Sb2O3 doped ZnO-based low-voltage varistor ceramic to maximize nonlinear electrical properties.

In ZnO-based low voltage varistor, the two essential features of microstructure determining its nonlinear response are the formation Bi-enriched active grain boundaries as well as a controlled ZnO grain size by secondary spinel-type phases. Besides, the microstructure and phase composition are strongly affected by the dopant concentration during sintering process. In this study, the optimal dopant levels of Bi2O3, TiO2, and Sb2O3 to achieve maximized nonlinear electrical property (alpha) were quantified by the response surface methodology (RSM). RSM was also used to understand the significance and interaction of the factors affecting the response. Variables were determined as the molar ratio of Bi2O3, TiO2, and Sb2O3. The alpha was chosen as response in the study. The 5-level-3-factor central composite design, with 20 runs, was used to conduct the experiments by ball milling method. A quadratic model was established as a functional relationship between three independent variables and alpha. According to the results, the optimum values of Bi2O3, TiO2, and Sb2O3 were obtained 0.52, 0.50, and 0.30, respectively. Under optimal conditions the predicted alpha (9.47) was calculated using optimal coded values from the model and the theoretical value is in good agreement with the value (9.43) obtained by confirmation experiment.

Would CoCr rods provide better correctional forces than stainless steel or titanium for rigid scoliosis curves?

STUDY DESIGN: Comparative in vitro, biomechanical study. OBJECTIVE: Compare the effect of rod curvature and material properties on rod flattening and correctional forces. SUMMARY OF BACKGROUND DATA: Traditional methods of correction for large progressive deformities involve 3-dimensional correction, performed with an attempt to reach a balanced correction in all planes, spinal instrumentation, and fusion. Increasing attention to the transverse plane correction has developed after the introduction of segmental pedicle screws into the treatment of idiopathic scoliosis. Approximation of the spine (pedicle screws or hooks) to the rods remains the heart of many deformity procedures. Therefore, it is crucial that the instrumentation used provide and maintain the initial correction of the spinal deformity while minimizing potential intraoperative failures. METHODS: Two experiments were performed using 80 rods made from 4 different materials namely: stainless steel (SS), titanium (Ti), cobalt chromium (CoCr), and ultrahigh strength stainless steel (UHSS). Half of the rods were contoured to 20 degrees, whereas the reaming contoured to 30 degrees. Half of the rods were approximated to a synthetic spine models to measure the flattening of the rods when approximated to highly rigid spine. The other half was used to measure the correctional forces produced by each rod type and curvature. RESULTS: For the 20-degree pre-bend rods, Ti was the best in maintaining its original shape followed by UHSS, SS, and CoCr of 90%, 77%, 62.5%, and 54.4%, respectively. The 30-degree pre-bend showed exactly a similar trend with 80.7% for Ti, 71% for UHSS, 54.6% for SS, and 48.1% for the CoCr rods. For 30-degree pre-bend CoCr and UHSS rods, the intraoperative reduction forces were almost 42% and 10% higher than the Ti and SS rods, respectively. The correctional force produced by the Ti 30-degree pre-bend rod was approximately 67% that of a CoCr and UHSS rods. CONCLUSIONS: CoCr and UHSS rods have the ability to produce the highest correction forces, however, both can plastically deform in a very rigid curves. Therefore, it is critical to have sense of the quality of the bone fixation as well as the curve flexibility when selecting for appropriate rod size material and contouring the rod to the desired shape.

Bone quality affects stability of orthodontic miniscrews.

The objective of this study was to evaluate the effect of bone-miniscrew contact percentage (BMC%) and bone quality and quantity on orthodontic miniscrew stability and the maximum insertion torque value (ITV). Orthodontic miniscrews of five different dimensions and several bovine iliac bone specimens were used in the evaluation. Miniscrews of each dimension group were inserted into 20 positions in bovine iliac bone specimens. The experiment was divided into three parts: (1) Bone quality and quantity were evaluated using cone-beam computed tomography (CBCT) and microcomputed tomography. (2) The 3D BMC% was calculated. (3) The ITVs during miniscrew insertion were recorded to evaluate the stability of the orthodontic miniscrews. The results indicated that longer and thicker miniscrews enabled higher ITVs. CBCT was used to accurately measure cortical bone thickness (r = 0.939, P < 0.05) and to predict the bone volume fraction of cancellous bone (r = 0.752, P < 0.05). BMC% was significantly influenced by miniscrew length. The contribution of cortical bone thickness to the ITV is greater than that of cancellous bone structure, and the contribution of cortical bone thickness to BMC% is greater than that of cancellous bone structure. Finally, the higher is BMC%, the greater is the ITV. This study concludes that use of CBCT may predict the mechanical stability of orthodontic miniscrews.

A watertight acrylic-free titanium recording chamber for electrophysiology in behaving monkeys.

Neurophysiological recording in alert monkeys requires the creation of a permanent aperture in the skull for repeated insertion of microelectrodes. Most laboratories use polymethyl methacrylate to attach a recording chamber over the skull opening. Here, we describe a titanium chamber that fastens to the skull with screws, using no polymethyl methacrylate. The gap between the base of the chamber and the skull is filled with hydroxyapatite, forming a watertight gasket. As the chamber base osseointegates with the skull, the hydroxyapatite is replaced with bone. Rather than having a finite lifetime, the recording chamber becomes more firmly anchored the longer it is in place. It has a small footprint, low profile, and needs little maintenance to control infection. Toilette consists of occasional application of betadine to clean the scalp margin, followed by application of neomycin, polymyxin, and bacitracin ointment. Antibiotic is also placed inside the chamber to suppress bacterial proliferation. Thickening of the dura within the chamber can be prevented by regular application of mitocycin C and/or bevacizumab, an antibody against vascular endothelial growth factor. By conducting an e-mail survey, this protocol for chamber maintenance was compared with procedures used in 37 other vision research laboratories. Refinement of appliances and techniques used for recordings in awake monkeys promises to increase the pace of scientific discovery and to benefit animal welfare.

Titanium alloys as fixation device material for cranioplasty and its safety in electroconvulsive therapy.

Here, we report the case of a patient successfully treated by a series of electroconvulsive therapy (ECT) who had implanted skull fixation devices made of titanium alloy. The patient was a 57-year-old man with bipolar I disorder. He was hospitalized for the treatment of manic symptoms of bipolar I disorder with pharmacotherapy and ECT. He sustained a fall and hit his head hard on the ground. Acute subdural hematoma developed, and emergent surgery to remove the hematoma was carried out. Cranioplasty was performed using fixation devices made of titanium alloy (Ti 6Al-4V). In order to control his manic symptoms, a series of ECT was readministered from 1 week after surgery. No adverse effects occurred. Devices must be investigated and chosen very carefully for permanent implantation, especially in patients during a course of ECT.

Fractionation and characterization of particles simulating wear of total joint replacement (TJR) following ASTM standards.

Reactions of bone cells to orthopedic wear debris produced by the articulating motion of total joint replacements (TJRs) are largely responsible for the long-term failure of such replacements. Metal and polyethylene (PE) wear particles isolated from fluids from total joint simulators, as well as particles that are fabricated by other methods, are widely used to study such in vitro cellular response. Prior investigations have revealed that cellular response to wear debris depends on the size, shape, and dose of the particles. Hence, to have a better understanding of the wear-mediated osteolytic process it is important that these particles are well characterized and clinically relevant, both qualitatively, and quantitatively. In this study we have fractionated both ultra-high molecular weight polyethylene (UHMWPE) and Ti particles, into micron (1.0-10.0 µm), submicron (0.2-1.0 µm), and nanoparticle (0.01-0.2 µm) fractions, and characterized them based on the following size-shape descriptors as put forth in ASTM F1877: i) equivalent circle diameter (ECD), ii) aspect ratio (AR), iii) elongation (E), iv) roundness (R), and v) form factor (FF). The mean (± SD) ECDs (in µm) for micron, submicron, and nanoparticles of UHMWPE were 1.652 ± 0.553, 0.270 ± 0.180, and 0.061 ± 0.035, respectively, and for Ti were 1.894 ± 0.667, 0.278 ± 0.180, and 0.055 ± 0.029, respectively. The values for other descriptors were similar (no statistically significant difference). The nanofraction particles were found to be more sphere-like (higher R and FF values, and lower E and AR values) as compared to larger particles. Future experiments will involve use of these well characterized particles for in vitro studies.

Surface polishing positively influences ease of plate and screw removal.

Difficulties removing temporary fracture fixation devices due to excessive bony on-growth results in extended surgical time leading to excessive blood loss, debris contamination and potentially refracture. Commercially available locking plates and screws are manufactured for clinics with a micro-rough surface, which contributes to the excessive bony on-growth reported. We have applied polishing technology to commercially pure titanium locking compression plates (LCP) and titanium-6%aluminium-7%niobium (TAN) plates and screws to assess if it can alleviate problems with strong bony overgrowth. Samples were implanted for 6, 12 and 18 months in a bilateral sheep tibia non fracture model and assessed for screw removal torque, percentage of bone contact and tissue-material response. Both electropolishing (p=0.001) and paste polishing (p=0.010) of TAN screws significantly reduced the mean torque required for removal compared to their micro-rough counterparts. This was accompanied by a trend for a lower percentage of bone contact for polished screws. This difference in bone contact was significant for paste polished TAN screws (p<0.001 parallel but not electropolished TAN screws (p=0.066). Ex vivo, soft tissue removal was much easier (approximately five minutes) for polished constructs, which was difficult and at least four times longer for standard micro-rough constructs. We suggest that polishing of locked plate/screw systems will improve ease of removal and reduce implant related removal complications encountered due to excessive strong bony on-growth while maintaining biocompatibility and implant stability. Future studies aim to assess the potential of this technology in the next level of complication, a fracture model.

Outcomes of interbody fusion cages used in 1 and 2-levels anterior cervical discectomy and fusion: titanium cages versus polyetheretherketone (PEEK) cages.

STUDY DESIGN: A prospective study was performed in case with cervical spondylosis who underwent anterior cervical discectomy and fusion (ACDF) with titanium or polyetheretherketone (PEEK) cages. OBJECTIVE: To find out which fusion cage yielded better clinical and radiographic results. SUMMARY OF BACKGROUND DATA: Although use of autogenous iliac-bone grafts in ACDF for cervical disc diseases remain standard surgical procedure, donor site morbidity and graft collapse or breakage are concerns. Cage technology was developed to prevent these complications. However, there is no comparison regarding the efficacy between titanium and PEEK cage. METHODS: January 2005 to January 2006, 53 patients who had 1 and 2-levels ACDF with titanium or PEEK cages were evaluated. We measured the rate and amount of interspace collapse, segmental sagittal angulations, and the radiographic fusion success rate. Odom criteria were used to assess the clinical results. RESULTS: The fusion rate was higher in the PEEK group (100% vs. 86.5%, P=0.0335). There was no significant difference between both groups in loss of cervical lordosis (3.2 + or - 2.4 vs. 2.8 + or - 3.4, P=0.166). The mean anterior interspace collapse (1.6 + or - 1.0 mm) in the titanium group was significantly higher than the collapse of the PEEK group (0.5 + or - 0.6 mm) (P<0.0001). The mean posterior interspace collapse was also higher in the titanium group (1.6 + or - 0.9 mm vs. 0.5 + or - 0.5 mm, P<0.0001). An interspace collapse of 3 mm or greater was observed in 16.2% of the patients in the titanium group, compared with zero patients in the PEEK group (P<0.0001). The PEEK group achieved an 80% rate of successful clinical outcomes, compared with 75% in the titanium group (P=0.6642). CONCLUSIONS: The PEEK cage is superior to the titanium cage in maintaining cervical interspace height and radiographic fusion after 1 and 2-levels anterior cervical decompression procedures.

Bending characteristics of polymethylmethacrylate columns, connecting bars of carbon fiber, titanium, and stainless steel used in external skeletal fixation and an acrylic interface.

OBJECTIVE: To (1) mechanically evaluate polymethylmethacrylate (PMMA) columns of various sizes and compare them to connecting bar materials (carbon fiber composite, titanium, stainless steel) and (2) compare the properties of an intact PMMA column to those of an acrylic interface. STUDY DESIGN: Experimental mechanical study. SAMPLE POPULATION: Experiment 1: 6 groups of 6 specimens each; experiment 2: 2 groups of 12 specimens each. METHODS: All specimens were tested in 3-point bending. Stiffness, yield strength, and ultimate strength values were calculated for each specimen. RESULTS: PMMA 1 columns (23.25 mm) compared favorably to titanium or stainless-steel bars. PMMA 3 columns (30.15 mm) and carbon fiber bars had similar yield strength but PMMA 3 columns were less stiff than carbon fiber bars. PMMA 3 columns had lower bending modulus and a higher variability in their mechanical properties than PMMA 1 or PMMA 2 (25.64 mm) columns. Acrylic interface specimens were less strong but as stiff as intact specimens. CONCLUSION: An acrylic interface was easily created and had acceptable biomechanical characteristics. CLINICAL RELEVANCE: PMMA 2 and PMMA 3 columns are not recommended for clinical use at this time. Further tests are needed to analyze an acrylic patch in a more clinically relevant loading model.

Mechanical Analysis of Notch-Free Pre-Bent Rods for Spinal Deformity Surgery.

STUDY DESIGN: Experimental study of spinal rod as per the American Society for Testing Materials (ASTM) F2193 methodology for static and dynamic four-point bending. OBJECTIVE: The hypotheses underlying this study were that the notch-free, curved rod would have a significantly higher ultimate load and fatigue strength compared with conventional notched curved rods. This study aimed to analyze the mechanical properties of notch-free curved rods compared with conventional notched rods. SUMMARY OF BACKGROUND DATA: The goal of instrumented spinal fusion in the management of spinal deformities is to realign the spine and maintain the correction and stability in order to obtain arthrodesis. Although rod curvature could play an important role, intraoperative contouring of the straight rod induces notches into the rod, leading to decreased fatigue strength. METHODS: Commercially produced titanium alloy (ϕ6.0 mm) and cobalt chromium alloy (ϕ5.5 mm) spinal rods were assessed by four-point bending tests in accordance with the ASTM F2193. RESULTS: Static four-point bending tests for the curved spinal rods showed that cobalt chromium alloy rods had significantly higher stiffness compared with titanium alloy rods. Notch-free cobalt chromium alloy rods had a significantly higher ultimate load than the conventional notched cobalt chromium alloy and titanium alloy rods. The dynamic four-point bending test showed that force/displacement at a minimum force at 2,500,000 cycles was larger in the notch-free cobalt chromium alloy rod than in the notched cobalt chromium alloy rod. CONCLUSION: The notch-free curved cobalt chromium alloy rod is likely to maintain its curvature after spinal deformity surgery with a decreased risk of breakage and could overcome the problems of the conventional notched rod such as breakage and spring-back. LEVEL OF EVIDENCE: N/A.

Mechanical behavior of a titanium alloy scaffold mimicking trabecular structure.

BACKGROUND: Additively manufactured porous metallic structures have recently received great attention for bone implant applications. The morphological characteristics and mechanical behavior of 3D printed titanium alloy trabecular structure will affect the effects of artificial prosthesis replacement. However, the mechanical behavior of titanium alloy trabecular structure at present clinical usage still is lack of in-depth study from design to manufacture as well as from structure to mechanical function. METHODS: A unit cell of titanium alloy was designed to mimick trabecular structure. The controlled microarchitecture refers to a repeating array of unit-cells, composed of titanium alloy, which make up the scaffold structure. Five kinds of unit cell mimicking trabecular structure with different pore sizes and porosity were obtained by modifying the strut sizes of the cell and scaling the cell as a whole. The titanium alloy trabecular structure was fabricated by 3D printing based on Electron Beam Melting (EBM). The paper characterized the difference between the designs and fabrication of trabecular structures, as well as mechanical properties and the progressive collapse behavior and failure mechanism of the scaffold. RESULTS: The actual porosities of the EBM-produced bone trabeculae are lower than the designed, and the load capacity of a bearing is related to the porosity of the structure. The larger the porosity of the structure, the smaller the stiffness and the worse the load capacity is. The fracture interface of the trabecular structure under compression is at an angle of 45o with respect to the compressive axis direction, which conforms to Tresca yield criterion. The trabeculae-mimicked unit cell is anisotropy. Under quasi-static loading, loading speed has no effect on mechanical performance of bone trabecular specimens. There is no difference of the mechanical performance at various orientations and sites in metallic workspace. The elastic modulus of the scaffold decreases by 96%-93% and strength reduction 96%-91%, compared with titanium alloy dense metals structure. The apparent elastic modulus of the unit-cell-repeated scaffold is 0.39-0.618 GPa, which is close to that of natural bone and stress shielding can be reduced. CONCLUSION: We have systematically studied the structural design, fabrication and mechanical behavior of a 3D printed titanium alloy scaffold mimicking trabecula bone. This study will be benefit of the application of prostheses with proper structures and functions.

Biological impact of lead from halide perovskites reveals the risk of introducing a safe threshold.

Regulations currently in force enable to claim that the lead content in perovskite solar cells is low enough to be safe, or no more dangerous, than other electronics also containing lead. However, the actual environmental impact of lead from perovskite is unknown. Here we show that the lead from perovskite leaking into the ground can enter plants, and consequently the food cycle, ten times more effectively than other lead contaminants already present as the result of the human activities. We further demonstrate that replacing lead with tin represents an environmentally-safer option. Our data suggest that we need to treat the lead from perovskite with exceptional care. In particular, we point out that the safety level for lead content in perovskite-based needs to be lower than other lead-containing electronics. We encourage replacing lead completely with more inert metals to deliver safe perovskite technologies.

Osteogenic inducer sustained-release system promotes the adhesion, proliferation, and differentiation of osteoblasts on titanium surface.

OBJECTIVE: Biomaterial can be locally applied to promote the osseointegration of dental implants. This study aimed to fabricate an osteogenic inducer (OI) sustained-release system and to evaluate its effects on the adhesion, proliferation, and differentiation of osteoblasts on titanium surfaces. METHODS: First of all, different contents of OI solution were added to the poly (lactic-co-glycolic acid) (PLGA) gel individually to investigate the best physical properties and drug-release rate. Moreover, osteoblasts were isolated from the calvaria of two-month-old New Zealand rabbits through sequential enzymatic digestion. Osteoblasts were seeded onto the surface of Ti disks (control group), Ti coated with PLGA gel (PLGA group), and Ti coated with the OI sustained-release system (PLGA+OI group). Cell adhesion was observed by scanning electron microscopy. Cell proliferation was analyzed by cell counting kit-8. Cell differentiation was tested by alizarin red staining, alkaline phosphatase (ALP) activity and osteogenic-related gene expression. RESULTS: The OI sustained-release system contained 15% OI solution had appropriate physical properties and drug-release rate. The osteoblasts in the PLGA+OI group were in a typical spindle shape with a considerable number indicating the promotion of adhesion and proliferation. The expression of early and late stage osteoblast differentiation genes in the PLGA+OI group were significantly higher than that of the control group and PLGA group at each time point. The PLGA group showed accelerated adhesion and differentiation but reduced proliferation compared with the control. CONCLUSION: The OI sustained-release system promotes the adhesion, proliferation, and differentiation of osteoblasts on titanium surfaces. This system is a cost-effective osteoconductive biomaterial that might be promising for use in dental implantation.

An in vivo evaluation of surface polishing of TAN intermedullary nails for ease of removal.

Fractures of the tibia and femoral diaphysis are commonly repaired by intra-medullary (IM) nailing. Currently IM nails are available in either electropolished stainless steel (SS) or in Titanium-Aluminium-Niobium (TAN). After healing, removal of the nails still is common but removal of TAN IM nails often has complications whereas SS IM nails of the same design are less often associated with problems. We believe the differences in removal are due to the ability of TAN to promote strong bone on-growth. We have previously shown in vivo that polishing cortical screws reduces removal torque and the percentage of bone-implant contact. Therefore, we postulate that bony on-growth onto IM nails can be reduced by means of surface polishing, for ease of removal. Here we aim to compare the pull-out forces for removal of standard TAN (TAN-S) compared to experimental paste polished TAN (TAN-PP) IM nails from a bilateral non-fracture sheep tibia model after 12 months implantation. Histological analysis was also performed to assess tissue on-growth to the nails. We show that polishing significantly reduces (p=0.05) the extraction force required for TAN IM nail removal. This effect in part is attributable to the distinct tissue-material reaction produced. For TAN-S nails direct bone contact was observed while for TAN-PP nails a fibrous tissue interface was noted. Since TAN is preferred over SS for IM nailing due to superior biocompatibility and mechanical properties, we believe these findings could be used to recommend changes to current surface technologies of intramedullary nails to reduce complications seen with nail removal especially in rapidly growing bone in children.

Load sharing and stabilization effects of anterior cervical devices.

STUDY DESIGN: Biomechanical human cadaveric cervical flexibility testing with direct load-sharing measurement. OBJECTIVE: To determine if the flexibility and load-sharing characteristics of a functional spinal unit were affected by anterior treatments for cervical pathologies. SUMMARY OF BACKGROUND DATA: With advancements in polymers, anterior cervical plates have used thermoplastics including recent designs from biodegradable polylactide acids. However, the difference in material properties between metal and polymer can be significant. METHODS: Thirteen cervical spine specimens were subjected to 5 treatments at C4-C5. Each treatment for each specimen was subjected to multidirectional flexibility testing. The third cycle was used for treatment comparisons. RESULTS: With the integrated load cell spacer, the mean range of motion for the functional spinal unit measured on average 104% + or - 40% normalized to the intact control. The mean biodegradable and titanium plate were 55% + or - 31% and 40% + or - 36%, respectively. Both plates exhibited statistically lower mean range of motions (P = 0.001 and P < 0.001) compared with spacers. The load transmitted through the interbody space was 54% + or - 20%, 43% + or - 20%, and 33% + or - 15% on average for the spacer, biodegradable, and titanium plate constructs, respectively. No statistically significant difference was detected between the biodegradable plate and spacer (P = 0.214). CONCLUSIONS: From this research, a biodegradable plate offers immediate postoperative stability significantly different than spacer alone treatments but with graft load sharing that is statistically no different. Thus, the intrinsic lower native material modulus of elasticity of biodegradable polymers has biomechanical implications. However, clinical evidence, particularly for long-term outcomes, will be required in understanding the efficacy of biodegradable polymers.