Fracture Characteristics of Commercial PEEK Dental Crowns: Combining the Effects of Aging Time and TiO2 Content.

Polyetheretherketone (PEEK) is an emerging thermoplastic polymer with good mechanical properties and an elastic modulus similar to that of alveolar bone. PEEK dental prostheses for computer-aided design/computer-aided manufacturing (CAD/CAM) systems on the market often have additives of titanium dioxide (TiO2) to strengthen their mechanical properties. However, the effects of combining aging, simulating a long-term intraoral environment, and TiO2 content on the fracture characteristics of PEEK dental prostheses have rarely been investigated. In this study, two types of commercially available PEEK blocks, containing 20% and 30% TiO2, were used to fabricate dental crowns by CAD/CAM systems and were aged for 5 and 10 h based on the ISO 13356 specifications. The compressive fracture load values of PEEK dental crowns were measured using a universal test machine. The morphology and crystallinity of the fracture surface were analyzed by scanning electron microscopy and an X-ray diffractometer, respectively. Statistical analysis was performed using the paired t-test (α = 0.05). Results showed no significant difference in the fracture load value of the test PEEK crowns with 20% and 30% TiO2 after 5 or 10 h of aging treatment; all test PEEK crowns have satisfactory fracture properties for clinical applications. Fracture surface analysis revealed that all test crowns fractured from the lingual side of the occlusal surface, with the fracture extending along the lingual sulcus to the lingual edge, showing a feather shape at the middle part of the fracture extension path and a coral shape at the end of the fracture. Crystalline analysis showed that PEEK crowns, regardless of aging time and TiO2 content, remained predominantly PEEK matrix and rutile phase TiO2. We would conclude that adding 20% or 30% TiO2 to PEEK crowns may have been sufficient to improve the fracture properties of PEEK crowns after 5 or 10 h of aging. Aging times below 10 h may still be safe for reducing the fracture properties of TiO2-containing PEEK crowns.

Influence of Aging on the Fracture Characteristics of Polyetheretherketone Dental Crowns: A Preliminary Study.

Although polyetheretherketone (PEEK) is becoming more widely used in dentistry applications, little is known about how aging will affect this material. Therefore, this study aimed to investigate the influence of an aging treatment on fracture characteristics of PEEK dental crowns. Additionally, the impact of the addition of titanium dioxide (TiO2) into PEEK was examined. Two types of commercial PEEK discs were used in this study, including TiO2-free and 20% TiO2-containing PEEK. The PEEK dental crowns were fabricated and aging-treated at 134 °C and 0.2 MPa for 5 h in accordance with the ISO 13356 specification before being cemented on artificial tooth abutments. The fracture loads of all crown samples were measured under compression tests. Results demonstrated that adding TiO2 enhanced the fracture load of PEEK crowns compared to TiO2-free PEEK crowns before the aging treatment. However, the aging treatment decreased the fracture load of TiO2-containing PEEK crowns while increasing the fracture load of TiO2-free PEEK crowns. The fracture morphology of TiO2-containing PEEK crowns revealed finer feather shapes than that of the TiO2-free PEEK crowns. We concluded that adding TiO2 increased the fracture load of PEEK crowns without aging treatment. Still, the aging treatment influenced the fracture load and microscopic fracture morphology of PEEK crowns, depending on the addition of TiO2.

Blood Coagulation on Titanium Dioxide Films with Various Crystal Structures on Titanium Implant Surfaces.

Background: Titanium (Ti) is one of the most popular implant materials, and its surface titanium dioxide (TiO2) provides good biocompatibility. The coagulation of blood on Ti implants plays a key role in wound healing and cell growth at the implant site; however, researchers have yet to fully elucidate the mechanism underlying this process on TiO2. Methods: This study examined the means by which blood coagulation was affected by the crystal structure of TiO2 thin films (thickness < 50 nm), including anatase, rutile, and mixed anatase/rutile. The films were characterized in terms of roughness using an atomic force microscope, thickness using an X-ray photoelectron spectrometer, and crystal structure using transmission electron microscopy. The surface energy and dielectric constant of the surface films were measured using a contact angle goniometer and the parallel plate method, respectively. Blood coagulation properties (including clotting time, factor XII contact activation, fibrinogen adsorption, fibrin attachment, and platelet adhesion) were then assessed on the various test specimens. Results: All of the TiO2 films were similar in terms of surface roughness, thickness, and surface energy (hydrophilicity); however, the presence of rutile structures was associated with a higher dielectric constant, which induced the activation of factor XII, the formation of fibrin network, and platelet adhesion. Conclusions: This study provides detailed information related to the effects of TiO2 crystal structures on blood coagulation properties on Ti implant surfaces.

Klebsiella pneumoniae bacteremia revisited: Comparison between 2007 and 2017 prospective cohorts at a medical center in Taiwan.

BACKGROUND: Community onset K. pneumoniae bacteremia (KPB) is a major problem in Taiwan for decades. We aimed to revisit the role of virulent genotype K1/K2 and possible predisposing factors, compared to our published 2007 cohort. METHODS: All adult patients with monomicrobial KPB during 2017 at a medical center in Taiwan were prospectively enrolled. We genotyped the major K types of K. pneumoniae strains, and analyzed the role of prior use of antibiotic or proton pump inhibitor (PPI). RESULTS: A total of 213 cases were enrolled. Compared to our previous 2007 study (n = 231), there was a higher percentage of patients with community onset bacteremia (75% vs. 60%, p = 0.003). The overall mortality rate was lower in 2017 (23% vs. 32%, p = 0.02), while the rates of antimicrobial resistance (all classes) were higher in 2017. There were 40 cases of liver abscesses in 2017 (19%), with an overall mortality rate of 7.5%. The prevalence of K1 was similar (16% in 2017 vs. 19% in 2007), but the prevalence of K2 decreased significantly (7% in 2017 vs. 17% in 2007, p = 0.001). After excluding 39 cases without data of recent medication use, 48 of 174 (28%) of patients had received a PPI within 90 days. Patients with recent PPI use had more complicated underlying illnesses, higher antimicrobial resistance, and higher in-hospital mortality, but was negatively associated with liver abscess (4% vs. 24%, p = 0.002). Of patients with community-acquired bacteremia, 51% used antibiotics within 90 days. After excluding 37 patients received antibiotics within 14 days before the detection of bacteremia, patient with antibiotic use within 15-90 days had higher Pittsburgh bacteremia scores (4.5 vs. 2.7, p = 0.04), creatinine levels, and frequency of recent surgery, but was not associated with liver abscess (21% vs. 31%, p = 0.33). DISCUSSION: In summary, after a decade, community onset KPB is still prevalent (1.3 case per 1000 emergency department visit). K1 remains to be the dominant genotype. The association of prior ampicillin/amoxicillin or PPIs use for liver abscess is not confirmed.

Vancomycin-loaded oxidized hyaluronic acid and adipic acid dihydrazide hydrogel: Bio-compatibility, drug release, antimicrobial activity, and biofilm model.

BACKGROUND: Prosthesis infection is a difficult-to-treat situation. Hydrogel is a novel biomaterial, which can be applied by simply spraying or by coating on implants before surgery and can be easily mixed with antibiotics. METHODS: In order to evaluate the potential use of antibiotic-loaded hydrogel, we incorporated vancomycin into oxidized hyaluronic acid (HA) and adipic acid dihydrazide and evaluated the drug release and antimicrobial activity against methicillin-resistant Staphylococcus aureus (ATCC 29213). RESULTS: The average release percentage of vancomycin on day 3 was about 86%. The antibiotic-loaded gel was biocompatible with mesenchymal stem cell, MC3T3, and L929 cell lines. The in vitro inhibition zones of vancomycin-loaded hydrogel [500X minimal inhibition concentration (MIC), 50X MIC, 10X MIC, and blank hydrogel] were 21, 13, 9, and 5 mm, respectively. In the Ti6Al4V implant biofilm model, 0.01-1% vancomycin-loaded gel exhibited significant anti-biofilm activity, measured by the MTT assay. CONCLUSIONS: Vancomycin could be loaded onto oxidized HA and adipic acid dihydrazide, which exhibited excellent drug release and in vitro antimicrobial activity with minimal cell toxicity.

Suboptimal outcomes after closed reduction and internal fixation of displaced femoral neck fractures in middle-aged patients: is internal fixation adequate in this age group?

BACKGROUND: There have been many studies regarding nongeriatric femoral neck fractures (FNFs), which included patients of a wide age range (between 20 and 60 years old). We aimed to determine whether internal fixation provided acceptable outcomes for middle-aged patients with displaced FNFs, and identify predictors of successful internal fixation. METHODS: A total of 117 patients, aged 50-60 years and who underwent closed reduction and unilateral internal fixation using cannulated screws, were included. The outcomes were classified as either "complications" (varus malunion, femoral neck shortening, non-union/early collapse, avascular necrosis, or arthroplasty during the follow-up) or "optimal outcomes" (no complications). Patients with displaced FNFs (Garden stages III-IV, n = 69) were categorized according to whether they experienced acceptable or unacceptable reduction. We evaluated whether patients' clinical characteristics could predict optimal outcomes. RESULTS: Patients with displaced FNFs generally experienced complications (84.1%). Twenty-two percent of patients experienced optimal outcomes when acceptable reduction was achieved. Patients with unacceptable reductions experienced complications. Optimal outcomes were positively associated with Pauwels' type II fracture (OR: 8.67, p = 0.025) and negatively associated with excessive alcohol consumption (p = 0.045). CONCLUSIONS: Compared with the younger age group, complication rates are higher in middle-aged patients with displaced FNFs treated using cannulated screws. If internal fixation is to be used for a displaced FNF, patient selection is essential. Care must be taken to avoid selecting patients with excessive alcohol consumption, while successful internal fixation may be more likely for patients with Pauwels' type II fracture.

Evaluation of New Biphasic Calcium Phosphate Bone Substitute: Rabbit Femur Defect Model and Preliminary Clinical Results.

Autogenous bone grafting, used to repair bone defects, is limited and the donor site can experience complications. Compared to autogenous bone graft, artificial bones have different porosity, which might make them suitable alternatives to bone grafts. Here, two porous biphasic calcium phosphate bone substitutes, namely Bicera™ and Triosite™, are used in an animal study and clinical practice to find a suitable porosity for implantation. Bicera™ and Triosite™ consist of 60 wt% hydroxyapatite and 40 wt% ß-tricalcium phosphate, with the porosity of Bicera™ (82%) being higher than that of Triosite™ (70%). In the animal study, the implantation procedure was carried out on twenty-four female New Zealand rabbits. 12 weeks after implantation, the new bones were well infiltrated into the Bicera™ and Triosite™ bone grafts. In the clinical study, patients with comminuted fracture, fracture nonunion, or arthrodesis were included in the study of bone substitution with Bicera™. 27 patients underwent fracture fixation treatment. Bone healing of 22.22% (6/27) of patients happened within 3 months after the surgery, and that of 66.67% (18/27) of patients happened within 6 months. These results reveal that Bicera™ has good incorporation with host bone, and that new bone is able to grow within the porous structure, giving it high potential in the treatment of bone defects.

Clinical significance of postdecompression facet joint effusion after minimally invasive decompression for degenerative lumbar spinal stenosis.

STUDY DESIGN: A retrospective case series study. OBJECTIVE: To investigate the clinical significance of postdecompression facet effusion (PDFE) after microendoscopic decompressive laminotomy (MEDL). SUMMARY OF BACKGROUND DATA: The facet joint effusion noted on magnetic resonance imaging was considered as an indicator of degeneration of the facet joints and segmental instability. PDFE occurring after MEDL might imply postdecompression segmental instability. Its clinical significance has not yet been clarified. MATERIALS AND METHODS: From 2005 to 2010, 165 patients with degenerative lumbar spinal stenosis (average age: 64.5, average follow-up: 25.8 mo) who received MEDL were reviewed. We investigated the incidence of PDFE with preoperative and repetitive magnetic resonance imaging at 6 months postoperatively. The clinical data and treatment courses were reviewed. The treatment outcomes were evaluated with Oswestry Disability Index and Japanese Orthopedic Association scores. RESULTS: The incidence of PDFE was 17.0% (n=28), which was significantly higher in patients receiving multilevel decompression and patients with scoliosis or spondylolisthesis. The intensity of low back pain was similar between patients with and without PDFE, but "mechanical" low back pain was only noted in patients with PDFE. Of the 28 patients with PDFE, only 9 symptomatic patients required invasive treatment (5 facet joint steroid injection, 3 revision MEDL, and 1 spinal fusion). Although the postoperative Oswestry Disability Index and Japanese Orthopedic Association scores were significantly worse these 9 patients, the final outcomes were good. Progression of spondylolisthesis was noted in 2 patients without PDFE but no patients with PDFE during the follow-up period. CONCLUSIONS: The relatively high incidence of PDFE after MEDL suggests that injury to the integrity of facet joint is inevitable during decompression of the stenosis, even using minimally invasive techniques. However, the overall stability is well preserved with very rare progression of spondylolisthesis. Most patients with PDFE are asymptomatic. The prognosis of PDFE is very good. Spinal fusion is rarely indicated.

Chondrogenesis of human bone marrow mesenchymal cells by transforming growth factors ß1 through cell shape changes on controlled biomaterials.

The phenotypic responses of human bone marrow mesenchymal cells (hBMSCs) on different ratio of chitosan/polycaprolactone (PCL) blends were investigated in this study. The results showed that hBMSCs existed different morphology on chitosan/PCL blends due to the different adhesion characteristic of cell on neat PCL and neat chitosan. Interestingly, comparing to hBMSCs on neat PCL, hBMSCs aggregated to form spheroid and to express ascendant trend of transforming growth factor ß1, collagen type II, collagen type X, and Sox9 mRNA on the chitosan/PCL blended substrates with the decrease of PCL content. To confirm chondrogenesis of hBMSCs with spheroid on test substrates, Alcian Blue and Safranin O staining were used to detect the cartilaginous extracellular matrix (ECM). It revealed hBMSCs with spheroid on neat chitosan and 10 wt % PCL did turn to chondrogenic differentiation and synthesize cartilaginous ECM. Therefore, these findings provided new insights into the role of chitosan/PCL blended material could mediate the endogenous gene expression of hBMSCs to alter the phenotypic behavior through mediating the cell shape.

Modulation of gene expression and collagen production of anterior cruciate ligament cells through cell shape changes on polycaprolactone/chitosan blends.

Our previous study has illustrated that chitosan could enhance human anterior cruciate ligament (ACL) cells to exhibit a dramatic effect on increasing the gene expression of transforming growth factor beta1 (TGF-beta1), which is a specific gene for wound healing and collagen synthesis. However, human ACL cells could not adhere and proliferate well on chitosan. In order to overcome this drawback, we introduced polycaprolactone (PCL) into chitosan by the method of blending in this study. It was found that the morphology, viability and gene expression of human ACL cells on the chitosan/PCL blends could be effectively regulated. With the increase of PCL content in blends, human ACL cells presented more flatten shape, well-organized cytoskeleton, and higher proliferated ability. Compared to flatten shape, human ACL cells with round shape exhibited higher levels of mRNA expression of TGF-beta1 and collagen type III through 3-day culture period. Furthermore, these blended materials could upregulate protein synthesis of human ACL cells, which corresponded to their gene expressions. Therefore, it is possible to combine the advantages of chitosan and PCL to create a new blended material, which could control cellular morphologies specifically, and further to regulate the gene expression and protein production of cells for specific applications. We expected this concept, controlling the cell shape through biomaterial to modulate the behavior of cells, could provide a new vision for the material selection of ligament tissue engineering.

The phenotypic responses of human anterior cruciate ligament cells cultured on poly(epsilon-caprolactone) and chitosan.

The purpose of this study is to evaluate the phenotypic responses of human anterior cruciate ligament (ACL) cells on two biodegradable materials: poly(epsilon-caprolactone) (PCL) and chitosan. ACL cells cultured on PCL displayed phenotypes that were well spread with a developed cytoskeleton. In comparison, chitosan was not an appropriate substrate to support the attachment and spreading of ACL cells, which was attributed to the low fibronectin (FN) adsorption of chitosan. However, ACL cells cultured on chitosan exhibited a dramatic effect on increasing transcripts of transforming growth factor beta1 (TGF beta1) and collagen III. After coating FN on chitosan surface, cell morphology and the mRNA levels of all tested genes had the similar levels on PCL and FN-coated chitosan. This indicates the expression of TGF beta1 and collagen III mRNA of human ACL cells was seem to correlate closely with the adhesion behavior of human ACL cells and was influenced by the underlying substrate properties. Since an ideal scaffold used in ACL tissue engineering is not only for cell attachment but also for extracellular matrix deposition during ligament regeneration, chitosan may be considered as a scaffold for ACL tissue engineering, which can upregulate the expression of specific genes of matrix production and wound healing in human ACL cells to synthesize more quantity of FN and TGF beta1 proteins.

Designing a three-dimensional expanded polytetrafluoroethylene-poly(lactic-co-glycolic acid) scaffold for tissue engineering.

The purpose of this study was to design a three-dimensional expanded polytetrafluoroethylene (ePTFE)-poly(lactic-co-glycolic acid) (PLGA) scaffold for tissue engineering. To test the feasibility of this composite scaffold, a series of two-dimensional culture experiments were performed to investigate the behavior of anterior cruciate ligament (ACL) cells on the ePTFE and PLGA membranes. It was found PLGA provided a cell-favorable substrate for cell adhesion, migration, and growth, indicating PLGA is an ACL cell-conductive material. Conversely, poor adhesion and proliferation of ACL cells were observed on the ePTFE, even on the collagen-coated ePTFE. Therefore, the scaffold was not fabricated by coating PLGA on the ePTFE surface because it is difficult to coat anything on the extremely hydrophobic ePTFE surface. Instead, the ePTFE embedded in the PLGA matrix was prepared by immersing ePTFE scrim yarns into the PLGA solution, and then precipitating PLGA to form a three-dimensional construction with porous morphology. The role of ePTFE is regarded as a reinforcing constituent to improve the mechanical strength of porous PLGA matrix to provide early repair strength for tissue healing. However, porous PLGA matrix acts as a supportive environment for allowing cell adhesion, migration, and growth to guide the repair and regeneration of ligament tissue. To test this assumption, a preliminary animal experiment of rabbit ACL wound healing with this three-dimensional ePTFE-PLGA scaffold was performed. These results are very encouraging because such a new scaffold made of ePTFE scrim yarns embedded in PLGA may serve as ACL prostheses in the ligament tissue engineering.

Superior mesenteric artery syndrome complicating staged corrective surgery for scoliosis.

Superior mesenteric artery syndrome (SMAS) is a rare complication following correction of scoliosis with either nonoperative or operative methods. If the patient diagnosed with this syndrome is not managed timely and adequately, mortality may result. We report two cases of SMAS complicating staged corrective surgery for scoliosis using modern segmental derotation instrumentation system. The aim of this report is to highlight the clinical presentations, laboratory findings, radiologic features, and management of the syndrome. The first patient had the syndrome after two-staged scoliosis surgery with halo traction between two stages, and the second patient after three-staged scoliosis surgery with halo traction between the first and second surgeries. The first patient responded well to conservative treatment. However, the second patient failed to respond to conservative treatment and needed a gastrojejunostomy operation to bypass the duodenal obstruction. Clinicians treating post scoliosis surgery patients should always have a high index of suspicion for this potential life-threatening condition. Early diagnosis will enable a multidisciplinary team approach to be initiated early to provide optimal care for the patient. Nutritional and fluid supplementation is mandatory during conservative treatment. The duration for trial of conservative treatment should not exceed 1 week.