Manufacturing and performance evaluation of medical radiation shielding fiber with plasma thermal spray coating technology.

Lead, which has been used for radiation shielding in medicine, is currently sought to be replaced by an eco-friendly shielding material. Therefore, it should be replaced with shielding materials possessing excellent processability and radiation shielding performance similar to that of lead. In this study, a new process technology was developed focusing on the processability of tungsten, a representative eco-friendly shielding material. It is difficult to reproduce the shielding performance when using the method of coating nonwoven fabrics with a liquid using tungsten powder on a polymer material, which is adopted to ensure the flexibility of the shielding fabric. To address this, tungsten powder was sprayed on the fabric using a plasma thermal spray coating process and coated to a thickness of 0.2 mm to evaluate the shielding performance. Compared to standard lead with a thickness of 0.2 mm, the shielding efficiency differed by approximately 15%. Since the developed process can maintain the amount of injection in an area, it is possible to ensure the reproducibility of the shielding performance and automated process for mass production. This approach is economically feasible as it does not entail the mixing of polymer materials; hence, it can be used for preparing radiation shielding clothing for medical institutions.

Double-layered fiber for lightweight flexible clothing providing shielding from low-dose natural radiation.

Natural and medical radiation are the most frequent sources of daily low-dose radiation exposure for the general public, but these radiation levels are generally acceptable. Among various occupations, aviation crew members and medical workers are exposed to high levels of radiation from scattered rays. This study focused on developing clothing for shielding aviation crew members from natural radiation during air travel. Materials were selected considering their radiation-shielding properties. A tungsten double-layered composite yarn and a polyethylene terephthalate (PET) fiber fabric containing BaSO4 were manufactured. The characteristics and shielding performances of the products were analyzed. Prototypes of a protective scarf (for shielding the thyroid gland) and apron (for shielding the torso) for flight attendants were produced. A lightweight fabric was produced that neither restricts the movement of the wearer nor causes them skin discomfort. The shielding performances of the tungsten composite and PET fiber fabrics containing BaSO4 were 0.018 mmPb and 0.03 mmPb, respectively, demonstrating low-dose shielding that may be useful for protecting aviation crew members from scattered rays. The characteristics of the developed fibers are comparable to those of materials used in clothing production; therefore, low-dose radiation-shielding clothing could be manufactured for use in aviation, medical, and other industries.

Effect of Hydrogen Dioxide Treatment on the Osteogenic Potential of Duck-beak Bone-derived Natural Bioceramic Microparticles.

BACKGROUND/AIM: As an alternative material to the autogenous bone, duck-beak bone particle for bone substitute have been attracting great attention due to their biological properties. To deliver the most favorable outcome of medical treatment, it is essential to study the effect of various processing methods of the duck-beak bone. In this study, we compared the two deproteinizing agents for manufacturing duck-beak bone. Group 1 was treated by a conventional chemical agent (ethylenediamine) and Group 2 by hydrogen dioxide (H2O2). In vitro and in vivo experiments were conducted in parallel to compare the cytocompatibility and osteogenic capability between two processing methods. For in vitro tests, human adipose-derived mesenchymal stem cells (hAD-MSCs) were planted onto each sample and their attachment and growing were evaluated. For in vivo biocompatibility and osteogenic properties, the samples were applied on the critical-sized calvarial bone defect of rats. Group 2 showed significantly higher cell attachment but Group1 showed slightly higher cell proliferation. In in vivo tests, all groups have shown biocompatibility and increased level of osteogenic potential. However, Group 2 had significantly higher bone regeneration (p<0.05). This experiment confirmed that H2O2 can be an optimal processing method for duck-beak bone particle.

Osteogenic Evaluation of Porous Calcium Phosphate Granules with Drug Delivery System Using Nanoparticle Carriers.

Novel porous biphasic calcium phosphate (BCP) granules incorporated with drug-releasing poly(lactic-co-glycolic acid) (PLGA) nanoparticles were developed as a drug delivery platform for bone regeneration. The charge interaction between the BCP and PLGA nanoparticle surfaces was manipulated to create this combination system. Spherical BCP granules with open micro-channels and PLGA nanoparticles loaded with dexamethasone (DEX) as a model drug were fabricated using a liquid nitrogen method and standard emulsion method, respectively. Polyethyleneimine was coated on the DEX-loaded PLGA nanoparticle surfaces, resulting in a net positively charged surface. Such modified nanoparticles were immobilized physically on the negatively charged BCP granule surfaces. An in vitro evaluation of MG 63 cells cultured for 1 and 2 weeks on the BCP granules containing DEX-loaded PLGA nanoparticles showed greater cell proliferation, differentiation, and a more extensively connected-tissue network than those cultured on the BCP granules alone. This innovative platform for bioactive molecule delivery more potently induced osteogenesis in vitro, which might be exploited in implantable bioceramic bone graft materials for stem cell therapy or improved in vivo performance.

Drug delivery from hydroxyapatite-coated titanium surfaces using biodegradable particle carriers.

The goal of this study was to develop a functional titanium (Ti) implant loaded with bioactive molecules using biodegradable polymeric particles as drug delivery carrier for dental applications. In this study, dexamethasone (DEX)-loaded poly(lactic-co-glycolic acid) (PLGA) particles were electrostatically immobilized on a Ti disc surface coated with hydroxyapatite (HA) nanocrystals using a low temperature high speed collision (LTHSC) method. Resorbable blasting media (RBM) Ti discs (S1), HA-Ti discs (S2), and HA-Ti discs treated with DEX-loaded PLGA particles (S3) were fabricated in this study as sample discs. To facilitate surface immobilization, PLGA particles were coated with polyethyleneimine (PEI) to produce a positive surface charge. This modification of PLGA particle surfaces, allowed DEX-loaded PLGA particles to be immobilized on negatively charged S2 disc surface. It was found that DEX-loaded PLGA particles were well dispersed and immobilized onto the S3 disc surfaces. Release profile studies of DEX from S3 discs in a 4-week immersion study indicated an initial burst release followed by sustained release. In vitro evaluation of bone marrow derived mesenchymal stem cells (BMSCs) cultured for 1 and 2 weeks on S3 discs showed greater BMSC differentiation than on S1 or S2 discs, demonstrating that this innovative delivery platform potently induced BMSC differentiation in vitro, and suggesting that it could be exploited for stem cell therapy purposes or to enhance in vivo osteogenesis. In addition, the results of the present study shows that various bioactive molecules that promote bone regeneration can be efficiently incorporated onto HA-Ti surfaces using biodegradable polymeric particles.

Drug-loaded porous spherical hydroxyapatite granules for bone regeneration.

Porous spherical hydroxyapatite (HAp) granules, which are not only can be used for bone void filler, but also drug delivery systems, were prepared using a liquid nitrogen method. Various pore and channel structures of spherical granules were obtained by adjusting the ratio of water to HAp powder and the amount of sodium chloride (NaCl). By using the water to powder ratio at 2.0 ml/g and the amount of NaCl at 15 wt% by powder, the spherical granules have optimal pore volume, micro-channel structure and strength to handle as well as the ability to work as a drug delivery system. When the NaCl content was 15 wt%, the micro-channel structure was changed, but the pore volume was maintained. For the drug release test, dexamathasone (Dex) was loaded as a model drug on the prepared HAp granules by the immersion method, and the drug release behavior was curved by a UV/vis spectrophotometer. As a result, different drug release behavior was observed according to micro-channel structural differences. Therefore, it was concluded that the NACl could be applied as the pore and micro-channel structure control agent. Porous spherical HAp granules, which were fabricated by a liquid nitrogen method, show potential as bone void filler with the ability of controlled drug release.

Comparative study between resorbable and nonresorbable plates in orthognathic surgery.

PURPOSE: The purpose of the present study was to evaluate the clinical application of resorbable and nonresorbable plates for correction of facial asymmetry. PATIENTS AND METHODS: A total of 272 patients who had undergone orthognathic surgery were enrolled. The site of osteotomy was fixed using a nonresorbable plate in group I (n = 152) and using a resorbable plate in group II (n = 120). The postoperative complications included postoperative anterior open bite, infection, temporomandibular joint dysfunction, and postoperative relapse. The incidence of all complications was examined. RESULTS: The surgical outcome was successful in 269 patients (98.89%). Of the 152 patients with a titanium plate, 13 (8.6%) developed complications. Of the 120 patients with a resorbable plate, 22 (18.3%) developed complications. A greater degree of postoperative open bite and a trend toward relapse were observed in patients' cases in which an absorbable fixation plate was used. Postoperative infection occurred in patients with an absorbable fixation plate. CONCLUSION: On the basis of these data, we have concluded that an absorbable fixation plate should be used instead of a titanium fixation plate in indicated patients.

Comparison of titanium and biodegradable miniplates for fixation of mandibular fractures.

PURPOSE: The purpose of the present study was to compare the use of biodegradable miniplates and titanium miniplates for the fixation of mandibular fractures. PATIENTS AND METHODS: BioSorb FX biodegradable plates and screws and titanium miniplates were used in 91 patients (65 males and 26 females; age range 11 to 69 years) for the treatment of mandibular fractures. The clinical and radiographic findings were recorded at 1, 3, 6, and 12 months after surgery. RESULTS: The overall complication rate was 4.41%. In the biodegradable plate group, infection occurred in 2 cases (4.26%) and was resolved by incision and drainage and antibiotics. In the titanium plate group, infection occurred in 1 case and plate fracture in 1 case (4.56%). The fractured plate was removed, and a new titanium miniplate was applied using a trocar. The infection was resolved with antibiotics. No adverse tissue reactions, malocclusions, or malunions occurred during the observation period. CONCLUSIONS: Our results have shown that the rate of morbidity is very low with the use of biodegradable plates and titanium plates, suggesting that biodegradable and titanium plates have the potential for successful use in the fixation of mandibular fractures.

Evaluation of peri-implant tissue in nonsubmerged dental implants: a multicenter retrospective study.

OBJECTIVES: The objective of this study was to evaluate the peri-implant's hard and soft tissue response associated with the 1-stage, nonsubmerged, endosseous dental implant. STUDY DESIGN: A multicenter retrospective clinical evaluation was performed on 339 nonsubmerged implants placed in 108 patients at 5 clinical centers between January 2003 and December 2007. RESULTS: After a mean follow-up period of 30 months, the mean crestal bone resorption in 339 implants was 0.43 mm. The survival and success rates were observed to be 99.1% and 95.1%, respectively. The mean calculus, inflammatory, and plaque indices were 0.13, 0.37, and 0.73, respectively, and the mean width of buccal keratinized mucosa was observed to be 2.43 mm. CONCLUSION: The short- to intermediate-term evaluation of the 1-stage, nonsubmerged, endosseous implant yields relatively high survival and success rates.

Vertical distraction osteogenesis using a titanium nitride-coated distractor.

OBJECTIVES: The purpose of this study was to examine the effect of using a titanium nitride (TiN)-coated vertical distractor on osseointegration after implantation. STUDY DESIGN: Four adult mongrel dogs, weighing 9-10 kg, were used in this study. The lower premolars were extracted, and vertical distraction was performed after 10 weeks using 8 distraction devices (left, 4 titanium; right, 4 nitrified). A 7-day latency period was allowed before distraction began. The distraction device was activated at a rate of 0.5 mm twice a day for 5 days. After completing distraction, the device was removed after a consolidation period of 6 weeks and 24 implants were installed. The dogs were killed after 4 or 8 weeks. Histologic examinations were performed. RESULTS: The implant success rate was 100% in all of the study groups. Direct bone contact was achieved, and there were no significant differences between the control and experimental groups in the implantation area. CONCLUSION: The results suggested that the nitrified distraction device does not negatively affect osseointegration in the vertical distraction osteogenesis; therefore, it has the advantageous potential to substitute for the conventional distractor.

Evaluation of peri-implant tissue response according to the presence of keratinized mucosa.

OBJECTIVES: The purpose of this study was to evaluate the responses of peri-implant tissue in the presence of keratinized mucosa. STUDY DESIGN: A total of 276 implants were placed in 100 patients. From the time of implant placement, the average follow-up observation period was 13 months. The width of keratinized mucosa was compared and evaluated through the gingival inflammation index (GI), plaque index (PI), the pocket depth, mucosal recession, and marginal bone resorption. RESULTS: The GI, PI, and pocket depth in the presence or absence of the keratinized gingiva did not show statistically significant differences. However, mucosal recession and marginal bone resorption experienced statistically significant increases in the group of deficient keratinized mucosa. Based on implant surface treatments, the width of keratinized gingiva and crestal bone loss did not show a significant difference. CONCLUSION: In cases with insufficient keratinized gingiva in the vicinity of implants, the insufficiency does not necessarily mediate adverse effects on the hygiene management and soft tissue health condition. Nonetheless, the risk of the increase of gingival recession and the crestal bone loss is present. Therefore, it is thought that from the aspect of long-term maintenance and management, as well as for the area requiring esthetics, the presence of an appropriate amount of keratinized gingiva is required.