Magnetic and in vitro heating properties of implants formed in situ from injectable formulations and containing superparamagnetic iron oxide nanoparticles (SPIONs) embedded in silica microparticles for magnetically induced local hyperthermia

The biological and therapeutic responses to hyperthermia, when it is envisaged as an anti-tumor treatment modality, are complex and variable. Heat delivery plays a critical role and is counteracted by more or less efficient body cooling, which is largely mediated by blood flow. In the case of magnetically mediated modality, the delivery of the magnetic particles, most often superparamagnetic iron oxide nanoparticles (SPIONs), is also critically involved. We focus here on the magnetic characterization of two injectable formulations able to gel in situ and entrap silica microparticles embedding SPIONs. These formulations have previously shown suitable syringeability and intratumoral distribution in vivo. The first formulation is based on alginate, and the second on a poly(ethylene-co-vinyl alcohol) (EVAL). Here we investigated the magnetic properties and heating capacities in an alternating magnetic field (141 kHz, 12 mT) for implants with increasing concentrations of magnetic microparticles. We found that the magnetic properties of the magnetic microparticles were preserved using the formulation and in the wet implant at 37 degrees C, as in vivo. Using two orthogonal methods, a common SLP (20 Wg(-1)) was found after weighting by magnetic microparticle fraction, suggesting that both formulations are able to properly carry the magnetic microparticles in situ while preserving their magnetic properties and heating capacities. (C) 2010 Elsevier B.V. All rights reserved.

Raman scattering and photoluminescence analysis of silicon on insulator structures obtained by single and multiple oxygen implants

An analysis of silicon on insulator structures obtained by single and multiple implants by means of Raman scattering and photoluminescence spectroscopy is reported. The Raman spectra obtained with different excitation powers and wavelengths indicate the presence of a tensile strain in the top silicon layer of the structures. The comparison between the spectra measured in both kinds of samples points out the existence in the multiple implant material of a lower strain for a penetration depth about 300 nm and a higher strain for higher penetration depths. These results have been correlated with transmission electron microscopy observations, which have allowed to associate the higher strain to the presence of SiO2 precipitates in the top silicon layer, close to the buried oxide. The found lower strain is in agreement with the better quality expected for this material, which is corroborated by the photoluminescence data.

Characteristics and outcome of 27 elbow periprosthetic joint infections: results from a 14-year cohort study of 358 elbow prostheses.

Elbow arthroplasty is increasingly performed in patients with rheumatic and post-traumatic arthritis. Data on elbow periprosthetic joint infection (PJI) are limited. We investigated the characteristics and outcome of elbow PJI in a 14-year cohort of total elbow arthroplasties in a single centre. Elbow prosthesis, which were implanted between 1994 and 2007 at Schulthess Clinic in Zurich, were retrospectively screened for infection. PJI was defined as periprosthetic purulence, the presence of sinus tract or microbial growth. A Kaplan-Meier survival method and Cox proportional hazard analysis were performed. Of 358 elbow prostheses, PJI was identified in 27 (7.5%). The median patient age (range) was 61 (39-82) years; 63% were females. Seventeen patients (63%) had a rheumatic disorder and ten (37%) had osteoarthritis. Debridement and implant retention was performed in 78%, followed by exchange or removal of the prosthesis (15%) or no surgery (7%).The relapse-free survival (95% CI) was 79% (63-95%) after 1 year and 65% (45-85%) after 2 years. The outcome after 2 years was significantly better when patients were treated according to the algorithm compared to patients who were not (100% vs. 33%, p <0.05). In 21 patients treated with debridement and retention, the cure rate was also higher when the algorithm was followed (100% vs. 11%, p <0.05). The findings of the present study suggest that the treatment algorithm developed for hip and knee PJI can be applied to elbow PJI. With proper patient selection and antimicrobial therapy, debridement and retention of the elbow prosthesis is associated with good treatment outcome.

Effect of the Glenosphere Position and Size on Reverse Shoulder Prostheses Mobility

Introduction: Several methods have already been proposed to improve the mobility of reversed prostheses (lateral or inferior displacement, increase of the glenosphere size). However, the effect of these design changes have only been evaluated on the maximal range of motion and were not related to activities of daily living (ADL). Our aim was thus to measure the effect of these design changes and to relate it to 4 typical ADL. Methods: CT data were used to reconstruct a accurate geometric model of the scapula and humerus. The Aequalis reversed prosthesis (Tornier) was used. The mobility of a healthy shoulder was compared to the mobility of 4 different reversed designs: 36 and 42 mm glenospheres diameters, inferior (4 mm) and lateral (3.2 mm) glenospheres displacements. The complete mobility map of the prosthesis was compared to kinematics measurement on healthy subjects for 4 ADL: 1) hand to contra lateral shoulder, 2) hand to mouth, 3) combing hair, 4) hand to back pocket. The results are presented as percentage of the allowed movement of the prosthestic shouder relative to the healthy shoulder, considered as the control group. Results: None of the tested designs allowed to recover a full mobility. The differences of allowed range of motion among each prosthetic designs appeared mainly in two of the 4 movements: hand to back pocket and hand to contra lateral shoulder. For the hand to back pocket, the 36 had the lowest mobility range, particularly for the last third of the movement. The 42 appeared to be a good compromise for all ADL activities. Conclusion: Reverse shoulder prostheses does not allow to recover a full range of motion compared to healthy shoulders, even for ADL. The present study allowed to obtain a complete 3D mobility map for several glenosphere positions and sizes, and to relate it to typical ADL. We mainly observed an improved mobility with inferior displacement and increased glenosphere size. We would suggest to use larger glenosphere, whenever it is possible.

Photopolymerizable hydrogels for implants: Monte-Carlo modeling and experimental in vitro validation.

Photopolymerization is commonly used in a broad range of bioapplications, such as drug delivery, tissue engineering, and surgical implants, where liquid materials are injected and then hardened by means of illumination to create a solid polymer network. However, photopolymerization using a probe, e.g., needle guiding both the liquid and the curing illumination, has not been thoroughly investigated. We present a Monte Carlo model that takes into account the dynamic absorption and scattering parameters as well as solid-liquid boundaries of the photopolymer to yield the shape and volume of minimally invasively injected, photopolymerized hydrogels. In the first part of the article, our model is validated using a set of well-known poly(ethylene glycol) dimethacrylate hydrogels showing an excellent agreement between simulated and experimental volume-growth-rates. In the second part, in situ experimental results and simulations for photopolymerization in tissue cavities are presented. It was found that a cavity with a volume of 152  mm3 can be photopolymerized from the output of a 0.28-mm2 fiber by adding scattering lipid particles while only a volume of 38  mm3 (25%) was achieved without particles. The proposed model provides a simple and robust method to solve complex photopolymerization problems, where the dimension of the light source is much smaller than the volume of the photopolymerizable hydrogel.

Polyethylene wear in anatomic and reversed shoulder prostheses

Purpose: Polyethylene wear is a recurrent problem in joint arthroplasty. Small debris particles are also associated to inflammation reaction of the surrounding bone, eventually leading to the failure of the bound between the implant and the host bone, and implant loosening. The goal of this study was thus to estimate the volume of polyethylene wear of a reversed prosthesis, and compare it to an anatomic prosthesis, during one year of activities of daily living. Material and Methods: A numerical musculoskeletal model of the glenohumeral joint was used for this comparative study. The reversed (RP) and anatomic (AP) Aequalis prostheses were positioned in the numerical model. Eight levels of abduction were considered. Their daily frequency was estimated from in-vivo recorded data on healthy volunteers during activities of daily living. One year of use was simulated to predict the linear and volumetric wear. The volumetric wear was the difference of volume between the original and worn component. Results: With the AP, the contact pattern on the glenoid surface moved rapidly from the inferior to the superior side during the first 30 degrees of abduction, and then went back to the inferior side. With the RP, the contact pattern on the humeral cup surface remained at the inferior side. Contact pressure was 20 times lower with the RP than with the AP. One year of use produced a maximum linear wear of 0.2 mm with the AP, and 0.13 mm with the RP. However, the volumetric wear was 8.4 mm3 with the AP, but reached 44.6 mm3 with the RP. Conclusion: Polyethylene particles are a matter of concern with AP. Infiltration of these particles within the bone-implant interface can induce a implant loosening. This problem should not be underestimated with RP. It might be associated to a higher level of humeral stem loosening reported with RP. The long term survival of RP might be improved by using a highly cross-linked polyethylene, which has a better abrasion resistance but lower plastic resistance.

Prevalence of complications after the oral rehabilitation with implant-supported hybrid prostheses

Objectives: Assess the main problems referred by the patients and observed by the professionals after the bucodental rehabilitation with an implant-supported hybrid prothesis. Patients and Methods: A retrospective study was carried out in which there were 43 patients included who were visited in the Department of Oral Surgery and Orofacial Implantology of University of Barcelona Dental School for one year. An oral rehabilitation with an implant-supported hybrid prosthesis was made to those patients. The following variables were registered: age, gender, number of inserted implants, type of implant and principal problems produced by the hybrid prosthesis. Results: The rehabilitation with an implant supported hybrid prosthesis was only performed in 43 of 116 cases treated in one year (January, 2006 to January, 2007). They were 26 men and 17 women of ages between 37 and 74 years, being the rate age of 56,5 years. The main complication recorded was the mucositis, associated frequently with a difficulty to carry a correct oral hygiene and to an overextention of the tail of resin of the prosthesis. Other observed problems were the peri-implantitis, the break of the acrylic teeth and the loss of some of the prosthetic screws. Conclusions: The most frequent complication after the laying of an implant supported hybrid prosthesis was the mucositis, associated mainly with a prosthetic tail too long and to the consequent difficulty of carrying a correct oral hygiene. In spite of the high prevalence of observed complications, most of them were mild and resolved on subsequent visits.

Improved diagnosis of periprosthetic joint infection by multiplex PCR of sonication fluid from removed implants.

The microbiological diagnosis of periprosthetic joint infection (PJI) is crucial for successful antimicrobial treatment. Cultures have limited sensitivity, especially in patients receiving antibiotics. We evaluated the value of multiplex PCR for detection of microbial DNA in sonication fluid from removed orthopedic prostheses. Cases of PJI in which the prosthesis (or part of it) was removed were prospectively included. The removed implant was sonicated, and the resulting sonication fluid was cultured and subjected to multiplex PCR. Of 37 PJI cases (17 hip prostheses, 14 knee prostheses, 4 shoulder prostheses, 1 elbow prosthesis, and 1 ankle prosthesis), pathogens were identified in periprosthetic tissue in 24 (65%) cases, in sonication fluid in 23 (62%) cases, and by multiplex PCR in 29 (78%) cases. The pathogen was detected in 5 cases in sonication fluid only (Propionibacterium acnes in all cases; none of these patients had previously received antibiotics) and in 11 cases by multiplex PCR only (all of these patients had previously received antibiotics). After exclusion of 8 cases caused by P. acnes or Corynebacterium species, which cannot be detected due to the absence of specific primers in the PCR kit, sonication cultures were positive in 17 cases and multiplex PCR sonication cultures were positive in 29 cases (59% versus 100%, respectively; P < 0.01). Among 19 cases (51%) receiving antibiotics, multiplex PCR was positive in all 19 (100%), whereas sonication cultures grew the organism in 8 (42%) (P < 0.01). Multiplex PCR of sonication fluid is a promising test for diagnosis of PJI, particularly in patients who previously received antibiotics. With modified primer sets, multiplex PCR has the potential for further improvement of the diagnosis of PJI.

Survival of zirconia- and metal-supported fixed dental prostheses: a systematic review

Purpose: The aim of this review was to systematically evaluate and compare the frequency of veneer chipping and core fracture of zirconia fixed dental prostheses (FOPS) and porcelain-fused-to-metal (PFM) FDPs and determine possible influencing factors. Materials and Methods: The SCOPUS database and International Association of Dental Research abstracts were searched for clinical studies involving zirconia and PFM FDPs. Furthermore, studies that were integrated into systematic reviews on PFM FDPs were also evaluated. The principle investigators of any clinical studies on zirconia FDPs were contacted to provide additional information. Based on the available information for each FOP, a data file was constructed. Veneer chipping was divided into three grades (grade 1 = polishing, grade 2 = repair, grade 3 = replacement). To assess the frequency of veneer chipping and possible influencing factors, a piecewise exponential model was used to adjust for a study effect. Results: None of the studies on PFM FDPs (reviews and additional searching) sufficiently satisfied the criteria of this review to be included. Thirteen clinical studies on zirconia FDPs and two studies that investigated both zirconia and PFM FDPs were identified. These studies involved 664 zirconia and 134 PFM FDPs at baseline. Follow-up data were available for 595 zirconia and 127 PFM FDPs. The mean observation period was approximately 3 years for both groups. The frequency of core fracture was less than 1% in the zirconia group and 0% in the PFM group. When all studies were included, 142 veneer chippings were recorded for zirconia FDPs (24%) and 43 for PFM FDPs (34%). However, the studies differed extensively with regard to veneer chipping of zirconia: 85% of all chippings occurred in 4 studies, and 43% of all chippings included zirconia FDPs. If only studies that evaluated both types of core materials were included, the frequency of chipping was 54% for the zirconia-supported FDPs and 34% for PFM FDPs. When adjusting the survival rate for the study effect, the difference between zirconia and PFM FDPs was statistically significant for all grades of chippings (P = .001), as well as for chipping grade 3 (P = .02). If all grades of veneer chippings were taken into account, the survival of PFM FDPs was 97%, while the survival rate of the zirconia FDPs was 90% after 3 years for a typical study. For both PFM and zirconia FDPs, the frequency of grades 1 and 2 veneer chippings was considerably higher than grade 3. Veneer chipping was significantly less frequent in pressed materials than in hand-layered materials, both for zirconia and PFM FDPs (P = .04). Conclusions: Since the frequency of veneer chipping was significantly higher in the zirconia FDPs than PFM FDPs, and as refined processing procedures have started to yield better results in the laboratory, new clinical studies with these new procedures must confirm whether the frequency of veneer chipping can be reduced to the level of PFM. Int J Prosthodont 2010;23:493-502

BS-SEM evaluation of the tisular interactions between cortical bone and calcium-phosphate covered titanium implants

The improvement of the reliability of the contact between the osseous tissues and the implant materials has been tested by recovering the metallic implants with ceramic materials, usually calcium phosphates. In our study, the calcium phosphate recovering layers were deposited by means of a pulsed-laser deposition technique. Our aim was to to evaluate the tissue interactions established between cortical bone and titanium implants covered by five different layers, ranging from amorphous calcium phosphate to crystalline hydroxyapatite, obtained by altering the parameters of the laser ablation process. The surgical protocol of the study consisted in the simultaneous implantation of the five types of implants in both the tibial dyaphisis of three Beagle dogs, sacrificed respectively one, two and three months after the last surgical procedures. After the sacrifice, the samples were submitted to a scheduled procedure of embedding in plastic polymers without prior decalcification, in order to perform the ultrastructural studies: scanning microscopy with secondary and backscattered electrons (BS-SEM). Our observations show that both in terms of the calcified tissues appearing as a response to the presence of the different coatings and of time of recovering, the implants coated with crystalline calcium phosphate layers by laser ablation present a better result than the amorphous-calcium-phosphate-coated implants. Moreover, the constant presence of chondroid tissue, related with the mechanical induction by forces applied on the recovering area, strongly suggests that the mechanisms implied in osteointegration are related to endomembranous, rather than endochondral ossification processes