265 results on '"Chow LC"'
Search Results
2. THEORETICAL AND EXPERIMENTAL INVESTIGATION OF DYNAMIC CHARACTERISTICS OF SAND COLUMN
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SHEN, RY, primary, CHOW, LC, additional, and PINNINGTON, RJ, additional
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- 2024
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3. A PRACTICAL METHOD TO INCREASE DAMPING ON INDUSTRIAL MACHINERY USING SAND GRANULAR MATERIAL
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CHOW, LC, primary and PINNINGTON, RJ, additional
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- 2024
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4. INVESTIGATION OF THE DAMPING TREATMENTS SUITABLE FOR HIGH TEMPERATURE APPLICATIONS
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CHOW, LC, primary and PINNINGTON, RJ, additional
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- 2024
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5. ACOUSTIC FATIGUE ENDURANCE TEST OF SPF-DB TITANIUM COUPON SPECIMENS AND PANEL STRUCTURE
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CHOW, LC, primary and CUMMINS, RJ, additional
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- 2024
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6. SONIC FATIGUE CERTIFICATION OF AIRBUS AIRCRAFT
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CHOW, LC, primary and CUMMINS, RJ, additional
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- 2024
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7. Predicting bone scan positivity in non-metastatic castration-resistant prostate cancer
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Moreira, DM, Howard, LE, Sourbeer, KN, Amarasekara, HS, Chow, LC, Cockrell, DC, Hanyok, BT, Pratson, CL, Aronson, WJ, Kane, CJ, Terris, MK, Amling, CL, Cooperberg, MR, Liede, A, and Freedland, SJ
- Subjects
Biomedical and Clinical Sciences ,Clinical Sciences ,Oncology and Carcinogenesis ,Urologic Diseases ,Cancer ,Prostate Cancer ,Clinical Research ,Aging ,Aged ,Aged ,80 and over ,Biomarkers ,Tumor ,Bone Neoplasms ,Bone and Bones ,Humans ,Male ,Neoplasm Grading ,Odds Ratio ,Prognosis ,Prostate-Specific Antigen ,Prostatic Neoplasms ,Castration-Resistant ,Sensitivity and Specificity ,Urology & Nephrology ,Clinical sciences ,Oncology and carcinogenesis - Abstract
BackgroundTo evaluate PSA levels and kinetic cutoffs to predict positive bone scans for men with non-metastatic castration-resistant prostate cancer (CRPC) from the Shared Equal Access Regional Cancer Hospital (SEARCH) cohort.MethodsRetrospective analysis of 531 bone scans of 312 clinically CRPC patients with no known metastases at baseline treated with a variety of primary treatment types in the SEARCH database. The association of patients' demographics, pathological features, PSA levels and kinetics with risk of a positive scan was tested using generalized estimating equations.ResultsA total of 149 (28%) scans were positive. Positive scans were associated with younger age (odds ratio (OR)=0.98; P=0.014), higher Gleason scores (relative to Gleason 2-6, Gleason 3+4: OR=2.03, P=0.035; Gleason 4+3 and 8-10: OR=1.76, P=0.059), higher prescan PSA (OR=2.11; P
- Published
- 2015
8. New 'light' for one-world approach toward safe and effective control of animal diseases and insect vectors from leishmaniac perspectives
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Chang KP, Kolli BK, Batchu RB, Chen HW, Chow LC, Elliott RD, Head J, Fan CK, Hung CH, Ji DD, Lun ZR, MANNA, LAURA, Matsumoto Y, Ng DKP, de Oliveira C, Melo S, Ozbel Y, Özbilgin A, Reinolds J, Sanijoba C, Shiao SH, Shih NY, Tsai CW, Vicente MG, Barrè C, Volf P, Wu YL, Yu CL, Zhou X.N., Chang, Kp, Kolli, Bk, Batchu, Rb, Chen, Hw, Chow, Lc, Elliott, Rd, Head, J, Fan, Ck, Hung, Ch, Ji, Dd, Lun, Zr, Manna, Laura, Matsumoto, Y, Ng, Dkp, de Oliveira, C, Melo, S, Ozbel, Y, Özbilgin, A, Reinolds, J, Sanijoba, C, Shiao, Sh, Shih, Ny, Tsai, Cw, Vicente, Mg, Barrè, C, Volf, P, Wu, Yl, Yu, Cl, and Zhou, X. N.
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0301 basic medicine ,Protozoan Vaccines ,Insecticides ,Mosquito Control ,Cell Survival ,medicine.medical_treatment ,030106 microbiology ,Photodynamic therapy ,Review ,Biology ,Photosensitizers ,03 medical and health sciences ,Antigen ,Mosquito ,Immunity ,medicine ,Animals ,Leishmania ,Drug Carriers ,Photosensitizing Agents ,Viral Vaccine ,Vaccination ,biology.organism_classification ,3. Good health ,Microbicides for sexually transmitted diseases ,030104 developmental biology ,Infectious Diseases ,Parasitology ,Immunology ,Photodynamic insecticide ,Photodynamic vaccination - Abstract
Light is known to excite photosensitizers (PS) to produce cytotoxic reactive oxygen species (ROS) in the presence of oxygen. This modality is attractive for designing control measures against animal diseases and pests. Many PS have a proven safety record. Also, the ROS cytotoxicity selects no resistant mutants, unlike other drugs and pesticides. Photodynamic therapy (PDT) refers to the use of PS as light activable tumoricides, microbicides and pesticides in medicine and agriculture. Here we describe “photodynamic vaccination” (PDV) that uses PDT-inactivation of parasites, i.e. Leishmania as whole-cell vaccines against leishmaniasis, and as a universal carrier to deliver transgenic add-on vaccines against other infectious and malignant diseases. The efficacy of Leishmania for vaccine delivery makes use of their inherent attributes to parasitize antigen (vaccine)-presenting cells. Inactivation of Leishmania by PDT provides safety for their use. This is accomplished in two different ways: (i) chemical engineering of PS to enhance their uptake, e.g. Si-phthalocyanines; and (ii) transgenic approach to render Leishmania inducible for porphyrinogenesis. Three different schemes of Leishmania-based PDV are presented diagrammatically to depict the cellular events resulting in cell-mediated immunity, as seen experimentally against leishmaniasis and Leishmania-delivered antigen in vitro and in vivo. Safety versus efficacy evaluations are under way for PDT-inactivated Leishmania, including those further processed to facilitate their storage and transport. Leishmania transfected to express cancer and viral vaccine candidates are being prepared accordingly for experimental trials. We have begun to examine PS-mediated photodynamic insecticides (PDI). Mosquito cells take up rose bengal/cyanosine, rendering them light-sensitive to undergo disintegration in vitro, thereby providing a cellular basis for the larvicidal activity seen by the same treatments. Ineffectiveness of phthalocyanines and porphyrins for PDI underscores its requirement for different PS. Differential uptake of PS by insect versus other cells to account for this difference is under study. The ongoing work is patterned after the one-world approach by enlisting the participation of experts in medicinal chemistry, cell/molecular biology, immunology, parasitology, entomology, cancer research, tropical medicine and veterinary medicine. The availability of multidisciplinary expertise is indispensable for implementation of the necessary studies to move the project toward product development.
- Published
- 2016
9. Letters To the Editor
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Chow Lc, Gerald L. Vogel, and Takagi S
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Chemistry ,Amorphous calcium phosphate ,General Dentistry ,Nuclear chemistry - Published
- 1998
10. Remineralization of demineralized enamel via calcium phosphate nanocomposite.
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Weir MD, Chow LC, Xu HH, Weir, M D, Chow, L C, and Xu, H H K
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Secondary caries remains the main problem limiting the longevity of composite restorations. The objective of this study was to investigate the remineralization of demineralized human enamel in vitro via a nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP). NACP were synthesized by a spray-drying technique and incorporated into a dental resin. First, caries-like subsurface enamel lesions were created via an acidic solution. Then, NACP nanocomposite or a commercial fluoride-releasing control composite was placed on the demineralized enamel, along with control enamel without a composite. These specimens were then treated with a cyclic demineralization/remineralization regimen for 30 days. Quantitative microradiography showed typical enamel subsurface demineralization before cyclic demineralization/remineralization treatment, and significant remineralization in enamel under the NACP nanocomposite after the demineralization/remineralization treatment. The NACP nanocomposite had the highest enamel remineralization (mean ± SD; n = 6) of 21.8 ± 3.7%, significantly higher than the 5.7 ± 6.9% for fluoride-releasing composite (p < 0.05). The enamel group without composite had further demineralization of -26.1 ± 16.2%. In conclusion, a novel NACP nanocomposite was effective in remineralizing enamel lesions in vitro. Its enamel remineralization was 4-fold that of a fluoride-releasing composite control. Combined with the good mechanical and acid-neutralization properties reported earlier, the new NACP nanocomposite is promising for remineralization of demineralized tooth structures. [ABSTRACT FROM AUTHOR]
- Published
- 2012
11. Novel CaF(2) nanocomposite with high strength and fluoride ion release.
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Xu HH, Moreau JL, Sun L, Chow LC, Xu, H H K, Moreau, J L, Sun, L, and Chow, L C
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Secondary caries and restoration fracture remain common problems in dentistry. This study tested the hypothesis that combining nano-CaF(2) and glass fillers would yield nanocomposites with high mechanical properties and F release. Novel CaF(2) nanoparticles (56-nm) were synthesized via spray-drying and incorporated into resin. F release increased with increasing the nano-CaF(2) content, or with decreasing pH (p < 0.05). F-release rates at 70-84 days were 1.13 microg/(cm(2) x day) and 0.50 microg/(cm(2) x day) for nanocomposites containing 30% and 20% nano-CaF(2), respectively. They matched the 0.65 microg/(cm(2) x day) of resin-modified glass ionomer (p > 0.1). The nanocomposites had flexural strengths of 70-120 MPa, after 84-day immersion at pH 4, pH 5.5, and pH 7. These strengths were nearly three-fold that of resin-modified glass ionomer, and matched/exceeded a composite with little F release. In summary, novel CaF(2) nanoparticles produced high F release at low filler levels, thereby making room in resin for reinforcement glass. This yielded nanocomposites with high F-release and stress-bearing properties, which may help reduce secondary caries and restoration fracture. [ABSTRACT FROM AUTHOR]
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- 2010
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12. Computer-aided detection (CAD) of lung nodules in CT scans: radiologist performance and reading time with incremental CAD assistance.
- Author
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Roos JE, Paik D, Olsen D, Liu EG, Chow LC, Leung AN, Mindelzun R, Choudhury KR, Naidich DP, Napel S, Rubin GD, Roos, Justus E, Paik, David, Olsen, David, Liu, Emily G, Chow, Lawrence C, Leung, Ann N, Mindelzun, Robert, Choudhury, Kingshuk R, and Naidich, David P
- Abstract
Objective: The diagnostic performance of radiologists using incremental CAD assistance for lung nodule detection on CT and their temporal variation in performance during CAD evaluation was assessed.Methods: CAD was applied to 20 chest multidetector-row computed tomography (MDCT) scans containing 190 non-calcified > or =3-mm nodules. After free search, three radiologists independently evaluated a maximum of up to 50 CAD detections/patient. Multiple free-response ROC curves were generated for free search and successive CAD evaluation, by incrementally adding CAD detections one at a time to the radiologists' performance.Results: The sensitivity for free search was 53% (range, 44%-59%) at 1.15 false positives (FP)/patient and increased with CAD to 69% (range, 59-82%) at 1.45 FP/patient. CAD evaluation initially resulted in a sharp rise in sensitivity of 14% with a minimal increase in FP over a time period of 100 s, followed by flattening of the sensitivity increase to only 2%. This transition resulted from a greater prevalence of true positive (TP) versus FP detections at early CAD evaluation and not by a temporal change in readers' performance. The time spent for TP (9.5 s +/- 4.5 s) and false negative (FN) (8.4 s +/- 6.7 s) detections was similar; FP decisions took two- to three-times longer (14.4 s +/- 8.7 s) than true negative (TN) decisions (4.7 s +/- 1.3 s).Conclusions: When CAD output is ordered by CAD score, an initial period of rapid performance improvement slows significantly over time because of non-uniformity in the distribution of TP CAD output and not to a changing reader performance over time. [ABSTRACT FROM AUTHOR]- Published
- 2010
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13. Strong nanocomposites with Ca, PO(4), and F release for caries inhibition.
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Xu HH, Weir MD, Sun L, Moreau JL, Takagi S, Chow LC, Antonucci JM, Xu, H H K, Weir, M D, Sun, L, Moreau, J L, Takagi, S, Chow, L C, and Antonucci, J M
- Abstract
This article reviews recent studies on: (1) the synthesis of novel calcium phosphate and calcium fluoride nanoparticles and their incorporation into dental resins to develop nanocomposites; (2) the effects of key microstructural parameters on Ca, PO(4), and F ion release from nanocomposites, including the effects of nanofiller volume fraction, particle size, and silanization; and (3) mechanical properties of nanocomposites, including water-aging effects, flexural strength, fracture toughness, and three-body wear. This article demonstrates that a major advantage of using the new nanoparticles is that high levels of Ca, PO(4), and F release can be achieved at low filler levels in the resin, because of the high surface areas of the nanoparticles. This leaves room in the resin for substantial reinforcement fillers. The combination of releasing nanofillers with stable and strong reinforcing fillers is promising to yield a nanocomposite with both stress-bearing and caries-inhibiting capabilities, a combination not yet available in current materials. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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14. Effects of calcium phosphate nanoparticles on Ca-PO4 composite.
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Xu HH, Weir MD, Sun L, Takagi S, Chow LC, Xu, H H K, Weir, M D, Sun, L, Takagi, S, and Chow, L C
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Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized for the first time. The objectives of this study were to incorporate DCPA nano-particles into resin for Ca-PO(4) release to combat dental caries, and to investigate the filler level effects. Nano-DCPA and nano-silica-fused silicon nitride whiskers at a 1:1 ratio were used at filler mass fractions of 0-75%. The flexural strengths in MPa (mean +/- SD; n = 6) of DCPA-whisker composites ranged from (106 +/- 39) at 0% fillers to (114 +/- 23) at 75% fillers, similar to (112 +/- 22) of a non-releasing composite (TPH) (p > 0.1). The composite with 75% fillers in a NaCl solution (133 mmol/L, pH = 7.4, 37 degrees C) yielded a Ca concentration of (0.65 +/- 0.02) mmol/L and PO(4) of (2.29 +/- 0.07) mmol/L. Relationships were established between ion-release and DCPA volume fraction V(DCPA): Ca = 4.46 V(DCPA)(1.6,) and = 66.9 V(DCPA)(2.6). Nano-DCPA-whisker PO(4) composites had high strength and released high levels of Ca-PO(4) requisite for remineralization. These new nano-composites could provide the needed combination of stress-bearing and caries-inhibiting capabilities. [ABSTRACT FROM AUTHOR]
- Published
- 2007
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15. Nano DCPA-whisker composites with high strength and Ca and PO(4) release.
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Xu HHK, Sun L, Weir MD, Antonucci JM, Takagi S, Chow LC, Peltz M, Xu, H H K, Sun, L, Weir, M D, Antonucci, J M, Takagi, S, Chow, L C, and Peltz, M
- Abstract
The main challenges facing composite restorations are secondary caries and bulk fracture. The objective of this study was to develop nano DCPA (dicalcium phosphate anhydrous)-whisker composites with high strength and Ca and PO(4) ion release to combat caries. Flexural strength for the nano DCPA-whisker composites at a nano DCPA:whisker mass ratio of 1:2 ranged from (148 +/- 9) MPa to (167 +/- 23) MPa, significantly higher than the (103 +/- 32) MPa of an inlay/onlay commercial control composite without Ca-PO(4) release. The nano DCPA-whisker composite released PO(4) to a concentration of (1.95 +/- 0.13) mmol/L and Ca of (0.68 +/- 0.05) mmol/L. Compared with previous conventional Ca- and PO(4)-releasing composites, the nano DCPA-whisker composites had strengths two-fold higher, and released comparable or higher levels of Ca and PO(4). In conclusion, combining nano-DCPA with whiskers yielded novel composites that released high levels of Ca and PO(4) requisite for remineralization. These high-strength composites may provide a unique combination of stress-bearing and caries-inhibiting capabilities. [ABSTRACT FROM AUTHOR]
- Published
- 2006
16. The sonographic features of papillary thyroid carcinomas: pictorial essay.
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Jun P, Chow LC, Jeffrey RB, Jun, Peter, Chow, Lawrence C, and Jeffrey, R Brooke
- Published
- 2005
17. Multidetector-row CT urography in clinical practice.
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Saket RR and Chow LC
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The authors review the rapid progress in the development and implementation of computed tomographic urography (CTU) for detailed evaluation of the urinary tract in patients presenting with painless hematuria. With improved spatial resolution afforded with multidetector CT, CTU has the potential to replace the need for excretory urography in many cases. Optimization of CTU techniques continues in order to resolve several remaining limitations of this approach. [ABSTRACT FROM AUTHOR]
- Published
- 2004
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18. Effect of a low-fluoride-content, two-component rinse on fluoride uptake and on de--and remineralization of enamel lesions: an in vitro study.
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Takagi S, Liao H, Chow LC, Takagi, S, Liao, H, and Chow, L C
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The effect of calcium (Ca) concentrations and added ethanol on fluoride (F) depositions by experimental two-component rinses, each consisting of a Ca-containing and an F-containing component, was evaluated in an in vitro system. Among the tested rinses, a 3 mmol/l F two-component rinse with 200 mmol/l Ca and 10% v/v ethanol was found to produce the greatest F deposition relative to the F concentration in the rinse. Specifically, this rinse produced an F deposition that was about 7 times greater than a conventional 13.2-mmol/l sodium fluoride (NaF) rinse. In a second experiment, an in vitro pH cycling model was used to evaluate the potential anti-caries effects of 4 rinses: (1) placebo rinse (no F), (2) 13.2-mmol/l NaF rinse, (3) 52.6-mmol/l NaF rinse, and (4) the 3-mmol/l F two-component rinse in a 7-day in vitro pH cycling model. The changes in lesion mineral contents, delta(DeltaZ), as assessed by quantitative microradiographic measurements, were as follows [mean +/- standard deviation, n = 10]: (1) 72.5+/-10.2 microm, (2) 43.4+/-5.6 microm, (3) 17.3+/-10.2 microm and (4) 45.3+/-5.2 microm. These results showed that the 3-mmol/l F two-component rinse produced the same (p>0.05) protection against demineralization as did the 13.2-mmol/l NaF rinse which had 4 times the fluoride content. The results suggest that it is possible to formulate an effective low-F two-component rinse. [ABSTRACT FROM AUTHOR]
- Published
- 2001
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19. Iron burden and endocrine complications in transfusion-dependent thalassemia patients In Sarawak, Malaysia: a retrospective study.
- Author
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Chow LC, Lee BS, Tang SO, Loh EW, Ng SC, Tan XY, Ahmad Noordin MN, Ong GB, and Chew LC
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- Humans, Male, Retrospective Studies, Female, Malaysia epidemiology, Adult, Child, Adolescent, Young Adult, Middle Aged, Prevalence, Aged, Iron metabolism, Endocrine System Diseases epidemiology, Endocrine System Diseases etiology, Thalassemia therapy, Thalassemia complications, Thalassemia epidemiology, Blood Transfusion statistics & numerical data, Iron Overload etiology, Iron Overload epidemiology
- Abstract
Introduction: Thalassaemia is one of the major health problems in Malaysia. With safe blood transfusion regime, the lifespan of patients with transfusion-dependent thalassaemia (TDT) has improved but at the cost of a higher risk of developing endocrine disorders. It is crucial for us to monitor the iron overload to prevent end organ damage. This study aims to evaluate the iron burden and prevalence of endocrinopathies in patients with TDT in Sarawak., Materials and Methods: This retrospective cohort study was conducted between January 2020 to June 2020 in six government hospitals in Sarawak. A total of 89 patients with TDT, aged 10 years and above, were recruited., Results: Out of the 89 patients, there were 54 males (60.7%) and 35 females (39.3%) with a median age of 21 years (range 10.0-65.0). Sixty-seven (75.3%) patients had betathalassaemia major and 15 (16.9%) patients had haemoglobin E beta-thalassaemia (HbE beta-thalassaemia), remaining seven patients had other genotypes. Thirty-one (34.8%) patients had mean serum ferritin 2500ng/ml and above, and 44 (66.6%) had liver iron concentration (LIC) ≥7mg/g. The prevalence of endocrine disorders in our cohort was 69.7%. The most common endocrinopathies were short stature (n=46, 51.7%), followed by hypogonadism (n=24, 26.9%), delayed puberty (n=23, 25.8%), hypothyroidism (n=10, 11.2%), diabetes mellitus (n=9, 10.1%), impaired glucose tolerance (n=6, 6.7%) and hypoparathyroidism (n=3, 3.3%). Endocrinopathies were significantly associated with age (p=0.01), age at initiating regular blood transfusion (p<0.01) and duration of regular blood transfusion (p<0.01)., Conclusion: Our data shows that the development of endocrinopathies in TDT can be time dependent. Early detection of endocrine-related complications and prompt treatment with iron chelation therapy are important to improve morbidity and mortality. A multidisciplinary approach with good patient-doctor collaboration is the key to improving patient care in our settings.
- Published
- 2024
20. Electron Paramagnetic Resonance Characterization of Sodium- and Carbonate-Containing Hydroxyapatite Cement.
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Karim ET, Szalai V, Cumberland L, Myers AF, Takagi S, Frukhtbeyn SA, Pazos I, and Chow LC
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- Carbonates, Durapatite, Electron Spin Resonance Spectroscopy methods, Free Radicals, Hydroxyapatites, Sodium
- Abstract
Ionizing radiation-induced paramagnetic defects in calcified tissues like tooth enamel are indicators of irradiation dose. Hydroxyapatite (HA), the principal constituent in these materials, incorporates a variety of anions (CO
3 2- , F- , Cl- , and SiO4 4- ) and cations (Mn2+ , Li+ , Cu2+ , Fe3+ , Mg2+ , and Na+ ) that directly or indirectly contribute to the formation of stable paramagnetic centers upon irradiation. Here, we used an underexploited synthesis method based on the ambient temperature setting reaction of a self-hardening calcium phosphate cement (CPC) to create carbonate-containing hydroxyapatite (CHA) and investigate its paramagnetic properties following γ-irradiation. Powder X-ray diffraction and IR spectroscopic characterization of the hardened CHA samples indicate the formation of pure B-type CHA cement. CHA samples exposed to γ-radiation doses ranging from 1 Gy to 150 kGy exhibited an electron paramagnetic resonance (EPR) signal from an orthorhombic CO2 •- free radical. At γ-radiation doses from 30 to 150 kGy, a second signal emerged that is assigned to the CO3 •- free radical. We observed that the formation of this second species is dose-dependent, which provided a means to extend the useful dynamic range of irradiated CHA to doses >30 kGy. These results indicate that CHA synthesized via a CPC cement is a promising substrate for EPR-based dosimetry. Further studies on the CHA cement are underway to determine the suitability of these materials for a range of biological and industrial dosimetry applications.- Published
- 2022
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21. A family of three with haemoglobin Cheverly: low oxygen saturation in stable patients.
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Chow LC, Puah SH, Tiong XT, Aloysious NS, Leong TS, and Chew LP
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- Humans, Oxygen, Pandemics, SARS-CoV-2, COVID-19, Hemoglobins, Abnormal analysis, Hemoglobins, Abnormal genetics
- Abstract
Haemoglobin (Hb) Cheverly is a rare, low oxygen affinity haemoglobinopathy. It is a result of point mutation at the 45 codon of the beta globin genes that leads to substitution of phenylalanine by serine. It is characterised by spuriously low peripheral oxygen saturation with normal arterial oxygen saturation. We describe a family of three with Hb Cheverly in Sarawak General Hospital, Malaysia. It was discovered through incidental finding during hospital admission for unrelated complaints. Laboratory testing revealed abnormal haemoglobin detected at the C window of the high performance liquid chromatography. Subsequent DNA analysis detected replacement of thymidine by cytosine at the beta globin genes. Hb Cheverly may or may not have clinical significance as most of the patients live a normal life; however, it is crucial for us to make early diagnosis to prevent unnecessary extensive investigations for hypoxaemia detected via pulse oximetry, especially in the midst of COVID-19 pandemic., Competing Interests: No conflict of interests declared.
- Published
- 2021
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22. Elevation of secondary metabolites production through light-emitting diodes (LEDs) illumination in protocorm-like bodies (PLBs) of Dendrobium hybrid orchid rich in phytochemicals with therapeutic effects.
- Author
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Yeow LC, Chew BL, and Sreeramanan S
- Abstract
Gas-chromatography-mass-spectrometry revealed the presence of various bioactive compounds with anticancer properties in protocorm-like-body (PLB) cultures of a Dendrobium hybrid orchid ( Dendrobium Enopi x Dendrobium Pink Lady). Pre-illumination of red fluorescent light lessened the stimulating effects of light-emitting diodes (LEDs) on secondary metabolites production among in vitro PLB cultures, possibly due to habituation. The highest flavonoid content of 16.79 μmol/ g of fresh weight (FW) was achieved under blue-red (1:1) LED for PLBs pre-treated with white LED for more than 3 subculture cycles. Phenolics content significantly reduced as PLBs pre-cultured under red fluorescent light for 2 subculture cycles were exposed to LED illuminations, where far red LED resulted in the lowest total phenolic content (18.85 μmol/ g FW). High intensity green LED (16.9 μmol/s) enhanced the accumulation of phenolics while amino acids such as L-leucine, glycine and proline exhibited no significant stimulating effect for secondary metabolites production., Competing Interests: The authors declare that there are no conflicts of interest., (© 2020 Published by Elsevier B.V.)
- Published
- 2020
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23. Droplet-vitrification of Aranda Broga Blue orchid: Role of ascorbic acid on the antioxidant system and genetic fidelity assessments via RAPD and SCoT markers.
- Author
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Khor SP, Yeow LC, Poobathy R, Zakaria R, Chew BL, and Subramaniam S
- Abstract
A droplet-vitrification cryopreservation protocol has been successfully developed for Aranda Broga Blue orchid hybrid using protocorm-like bodies (PLBs). However, maximum growth regeneration percentage was recorded at 5% only based on previous report. Thus, to improve growth recovery of cryopreserved PLBs, cryopreservation stages were supplemented with ascorbic acid, tested at 50, 100 and 150 mg/L. However, results demonstrated that exogenous ascorbic acid was not favorable in regeneration of cryopreserved explants (maximum value of 1.67 % with 50 mg/L ascorbic acid supplementation). Total soluble protein and various antioxidant enzyme activities such as catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX) were evaluated after each cryopreservation stages in conjunction with the application of exogenous ascorbic acid. Addition of antioxidant must be carefully evaluated and its application may not guarantee successful growth recovery. RAPD and SCoT molecular analysis confirmed the genetic stability of regenerated cryopreserved PLBs as no polymorphism was detected compared to control PLBs culture., Competing Interests: None., (© 2020 Universiti Sains Malaysia.)
- Published
- 2020
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24. Thrombosis and Bleeding as Presentation of COVID-19 Infection with Polycythemia Vera. A Case Report.
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Chow LC, Chew LP, Leong TS, Mohamad Tazuddin EE, and Chua HH
- Abstract
Coronavirus disease (COVID-19) has a wide spectrum of clinical manifestations. In this case report, we describe our first case of COVID-19 pneumonia that was complicated by cerebral venous thrombosis and bleeding in a patient with polycythemia vera. Madam A, a 72-year-old lady with polycythemia vera, ischemic stroke, hemorrhoids, diabetes mellitus, hypertension, and dyslipidemia was admitted to the hospital for COVID-19 pneumonia. She was treated with hydroxychloroquine and lopinavir/ritonavir as per hospital protocol. She continued taking hydroxyurea and aspirin for her treatment of polycythemia vera. Subsequently, she developed rectal bleeding when her platelet count was 1247 × 10
3 /μl, even though she was not on an anticoagulant. Her aspirin was withheld. One week later, she was readmitted to the hospital for cerebral venous thrombosis and her D-dimer was 2.02 μg/ml. She was commenced on a therapeutic dose of low molecular weight heparin. Following that, her D-dimer level showed a decreasing trend and normalized upon her discharge. Patients with polycythemia vera are prone to develop thrombotic and bleeding complications. Management of this group of patients has become more complex with COVID-19 infection. It is crucial for us to decide when to start an anticoagulant especially when there is a history of recent bleeding. We need to balance the risks of further bleeding versus potentially fatal thrombotic events. Studies have shown that D-dimer can be used as a clinical marker to predict thrombotic events in COVID-19 infection. Patients with COVID-19 infection and polycythemia vera will benefit from both pharmacological thromboprophylaxis and close monitoring for bleeding., Competing Interests: Conflict of InterestThe authors declare that they have no conflict of interest., (© Springer Nature Switzerland AG 2020, corrected publication 2020.)- Published
- 2020
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25. Correction to: Thrombosis and Bleeding as Presentation of COVID-19 Infection with Polycythemia Vera: a Case Report.
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Chow LC, Chew LP, Leong TS, Mohamad Tazuddin EE, and Chua HH
- Abstract
[This corrects the article DOI: 10.1007/s42399-020-00537-0.]., (© Springer Nature Switzerland AG 2020.)
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- 2020
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26. Iron oxide nanoparticle-calcium phosphate cement enhanced the osteogenic activities of stem cells through WNT/β-catenin signaling.
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Xia Y, Guo Y, Yang Z, Chen H, Ren K, Weir MD, Chow LC, Reynolds MA, Zhang F, Gu N, and Xu HHK
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- Bone Regeneration drug effects, Bone and Bones drug effects, Cell Differentiation drug effects, Chitosan chemistry, Dental Cements chemistry, Dental Pulp drug effects, Dental Pulp metabolism, Humans, Stem Cells metabolism, Tissue Engineering methods, Tissue Scaffolds chemistry, Wnt Proteins metabolism, beta Catenin metabolism, Bone Cements chemistry, Bone Cements pharmacology, Calcium Phosphates chemistry, Ferric Compounds chemistry, Nanoparticles chemistry, Osteogenesis drug effects, Signal Transduction drug effects, Stem Cells drug effects
- Abstract
Calcium phosphate cement (CPC), functionalized with iron oxide nanoparticles (IONP), is of great promise to promote osteoinduction and new bone formation. In this work, the IONP powder was added into the CPC powder to fabricate CPC + IONP scaffolds and the effects of the novel composite on bone matrix formation and osteogenesis of human dental pulp stem cells (hDPSCs) were explored. A series of CPC + IONP magnetic scaffolds with different IONP contents (1%, 3% and 6%) were fabricated using 5% chitosan solution as the cement liquid. Western blotting and RT-PCR were used to analyze the signaling pathway. The IONP incorporation substantially enhanced the performance of CPC + IONP, with increases in both mechanical strength and cellular activities. The IONP addition greatly promoted the osteogenesis of hDPSCs, elevating the ALP activity, the expression of osteogenic marker genes and bone matrix formation with 1.5-2-fold increases. The 3% IONP incorporation showed the most enhancement among all groups. Activation of the extracellular signal-related kinases WNT/β-catenin in DPSCs was observed, and this activation was attenuated by the WNT inhibitor DKK1. The results indicated that the osteogenic behavior of hDPSCs was likely driven by CPC + IONP via the WNT signaling pathway. In conclusion, incorporate IONP into CPC scaffold remarkably enhanced the spreading, osteogenic differentiation and bone mineral synthesis of stem cell. Therefore, this method had great potential for bone tissue engineering. The novel CPC + IONP composite scaffolds with stem cells are promising to provide an innovative strategy to enhance bone regenerative therapies., (Copyright © 2019 Elsevier B.V. All rights reserved.)
- Published
- 2019
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27. Is now the right time to abolish breast cancer screening in Hong Kong?
- Author
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Chow LC
- Subjects
- Attitude to Health, Breast Neoplasms mortality, Breast Neoplasms prevention & control, False Positive Reactions, Female, Hong Kong, Humans, Technology Assessment, Biomedical, Breast Neoplasms diagnostic imaging, Early Detection of Cancer ethics, Early Detection of Cancer methods, Mammography ethics, Unnecessary Procedures
- Published
- 2018
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28. Calcium phosphate cements for bone engineering and their biological properties.
- Author
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Xu HH, Wang P, Wang L, Bao C, Chen Q, Weir MD, Chow LC, Zhao L, Zhou X, and Reynolds MA
- Abstract
Calcium phosphate cements (CPCs) are frequently used to repair bone defects. Since their discovery in the 1980s, extensive research has been conducted to improve their properties, and emerging evidence supports their increased application in bone tissue engineering. Much effort has been made to enhance the biological performance of CPCs, including their biocompatibility, osteoconductivity, osteoinductivity, biodegradability, bioactivity, and interactions with cells. This review article focuses on the major recent developments in CPCs, including 3D printing, injectability, stem cell delivery, growth factor and drug delivery, and pre-vascularization of CPC scaffolds via co-culture and tri-culture techniques to enhance angiogenesis and osteogenesis., Competing Interests: The authors declare no conflict of interest.
- Published
- 2017
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29. Effect of calcium phosphate nanocomposite on in vitro remineralization of human dentin lesions.
- Author
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Weir MD, Ruan J, Zhang N, Chow LC, Zhang K, Chang X, Bai Y, and Xu HHK
- Subjects
- Calcium Phosphates, Cariostatic Agents, Humans, Tooth Demineralization, Tooth Remineralization, Composite Resins, Dentin, Nanocomposites
- Abstract
Objective: Secondary caries is a primary reason for dental restoration failures. The objective of this study was to investigate the remineralization of human dentin lesions in vitro via restorations using nanocomposites containing nanoparticles of amorphous calcium phosphate (NACP) or NACP and tetracalcium phosphate (TTCP) for the first time., Methods: NACP was synthesized by a spray-drying technique and incorporated into a resin consisting of ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM). After restoring the dentin lesions with nanocomposites as well as a non-releasing commercial composite control, the specimens were treated with cyclic demineralization (pH 4, 1h per day) and remineralization (pH 7, 23h per day) for 4 or 8 weeks. Calcium (Ca) and phosphate (P) ion releases from composites were measured. Dentin lesion remineralization was measured at 4 and 8 weeks by transverse microradiography (TMR)., Results: Lowering the pH increased ion release of NACP and NACP-TTCP composites. At 56 days, the released Ca concentration in mmol/L (mean±SD; n=3) was (13.39±0.72) at pH 4, much higher than (1.19±0.06) at pH 7 (p<0.05). At 56 days, P ion concentration was (5.59±0.28) at pH 4, much higher than (0.26±0.01) at pH 7 (p<0.05). Quantitative microradiography showed typical subsurface dentin lesions prior to the cyclic demineralization/remineralization treatment, and dentin remineralization via NACP and NACP-TTCP composites after 4 and 8 weeks of treatment. At 8 weeks, NACP nanocomposite achieved dentin lesion remineralization (mean±SD; n=15) of (48.2±11.0)%, much higher than (5.0±7.2)% for dentin in commercial composite group after the same cyclic demineralization/remineralization regimen (p<0.05)., Significance: Novel NACP-based nanocomposites were demonstrated to achieve dentin lesion remineralization for the first time. These results, coupled with acid-neutralization and good mechanical properties shown previously, indicate that the NACP-based nanocomposites are promising for restorations to inhibit caries and protect tooth structures., (Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)
- Published
- 2017
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30. Predicting Time From Metastasis to Overall Survival in Castration-Resistant Prostate Cancer: Results From SEARCH.
- Author
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Moreira DM, Howard LE, Sourbeer KN, Amarasekara HS, Chow LC, Cockrell DC, Pratson CL, Hanyok BT, Aronson WJ, Kane CJ, Terris MK, Amling CL, Cooperberg MR, and Freedland SJ
- Subjects
- Age Factors, Aged, Aged, 80 and over, Disease-Free Survival, Hospital Mortality, Hospitals, Veterans, Humans, Kallikreins metabolism, Male, Neoplasm Metastasis, Nomograms, Prostate-Specific Antigen metabolism, Prostatic Neoplasms, Castration-Resistant metabolism, Retrospective Studies, Survival Analysis, United States epidemiology, Prostatic Neoplasms, Castration-Resistant mortality
- Abstract
Objective: To identify the predictors of time from initial diagnosis of metastatic castration-resistance prostate cancer (mCRPC) to all-cause death within the Shared Equal Access Regional Cancer Hospital cohort., Patients and Methods: We performed a retrospective analysis of 205 mCRPC men. Overall survival was estimated and plotted using the Kaplan-Meier method. The uni- and multivariable overall survival predictors were evaluated with the Cox proportional hazards model. A nomogram was generated to predict overall survival at 1, 2, 3, and 5 years after mCRPC. Concordance index and calibration plot were obtained., Results: A total of 170 men (83%) died over a median follow-up of 41 months. In univariable analysis, older age, more remote year of mCRPC, nonblack race, greater number of bone metastasis, higher prostate-specific antigen (PSA) levels, shorter PSA doubling time, and faster PSA velocity at mCRPC diagnosis were significantly associated with shorter overall survival (all P < .05). In multivariable analysis, older age, more remote year of mCRPC, greater number of bone metastasis, higher PSA levels, and shorter PSA doubling time at mCRPC diagnosis remained significantly associated with shorter overall survival (all P < .05). On the basis of these variables, a nomogram was generated yielding a concordance index of 0.67 and good calibration., Conclusion: The use of clinical parameter such as age, disease burden, and PSA levels and kinetics can be used to estimate overall survival in mCRPC patients., (Copyright © 2016 Elsevier Inc. All rights reserved.)
- Published
- 2017
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31. Rechargeable calcium phosphate orthodontic cement with sustained ion release and re-release.
- Author
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Zhang L, Weir MD, Chow LC, Reynolds MA, and Xu HH
- Subjects
- Adsorption, Calcium Phosphates chemical synthesis, Dental Cements chemical synthesis, Ions metabolism, Shear Strength, Water chemistry, Calcium Phosphates chemistry, Dental Cements chemistry
- Abstract
White spot lesions (WSL) due to enamel demineralization are major complications for orthodontic treatments. Calcium phosphate (CaP) dental resins with Ca and P ion releases are promising for remineralization. However, previous Ca and P releases lasted for only weeks. Experimental orthodontic cements were developed using pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA) at mass ratio of 1:1 (PE); and PE plus 10% of 2-hydroxyethyl methacrylate (HEMA) and 5% of bisphenol A glycidyl dimethacrylate (BisGMA) (PEHB). Particles of amorphous calcium phosphate (ACP) were incorporated into PE and PEHB at 40% filler level. Specimens were tested for bracket-enamel shear bond strength, water sorption, CaP release, and ion recharge and re-release. PEHB+40ACP had higher bracket-enamel bond strength and ion release and rechargeability than PE+40ACP. ACP incorporation into the novel orthodontic cement did not adversely affect the bracket-enamel bond strength. Ion release and re-release from the novel ACP orthodontic cement indicated favorable release and re-release patterns. The recharged orthodontic cement could release CaP ions continuously for four weeks without further recharge. Novel rechargeable orthodontic cement containing ACP was developed with a high bracket-enamel bond strength and the ability to be repeatedly recharged to maintain long-term high levels of CaP ion releases., Competing Interests: The authors Xu H, Zhang L, Weir MD. declares the U.S. Provisional Patent Application. Number: 62/1121,438 (2015).
- Published
- 2016
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32. Predictors of Time to Metastasis in Castration-resistant Prostate Cancer.
- Author
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Moreira DM, Howard LE, Sourbeer KN, Amarasekara HS, Chow LC, Cockrell DC, Hanyok BT, Aronson WJ, Kane CJ, Terris MK, Amling CL, Cooperberg MR, Liede A, and Freedland SJ
- Subjects
- Aged, Aged, 80 and over, Gonadotropin-Releasing Hormone agonists, Gonadotropin-Releasing Hormone antagonists & inhibitors, Humans, Male, Orchiectomy, Prognosis, Prostatic Neoplasms, Castration-Resistant therapy, Retrospective Studies, Time Factors, Prostatic Neoplasms, Castration-Resistant secondary
- Abstract
Objective: To investigate predictors of time to metastasis among men treated with androgen deprivation therapy for nonmetastatic prostate cancer who developed castration-resistant prostate cancer (CRPC) within the Shared Equal Access Regional Cancer Hospital cohort., Methods: This is a retrospective analysis of 458 nonmetastatic CRPC men. Metastases were detected in routine bone scans or other imaging tests. Predictors of time to metastasis were analyzed using proportional hazards model with CRPC as time zero., Results: A total of 256 (56%) men were diagnosed with metastatic disease over a median follow-up of 36 months. Metastasis-free survival was 79%, 65%, 52%, 47%, and 41% at 1, 2, 3, 4, and 5 years after CRPC, respectively. In multivariable analysis, Gleason score 8-10 (hazard ratio [HR] = 1.61; P = .026), receiving primary localized treatment (HR = 1.38; P = .028), higher prostate-specific antigen (PSA) levels at CRPC diagnosis (logPSA HR = 1.64; P < .001), and PSA doubling time ≤6 months (HR = 1.42; P = .040) were independently associated with shorter time to metastasis. Race, year of CRPC, age, and time from androgen deprivation therapy to CRPC were not associated with metastasis., Conclusion: Among nonmetastatic CRPC men, nearly 60% developed metastatic disease during the first 5 years, with most of the metastasis occurring within the first 3 years. Higher Gleason score, receiving primary treatment, higher PSA, and shorter PSA doubling time were independently associated with shorter time to metastasis. Therefore, these variables can be used to stratify patients according to metastasis risk., (Copyright © 2016 Elsevier Inc. All rights reserved.)
- Published
- 2016
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33. Novel rechargeable calcium phosphate dental nanocomposite.
- Author
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Zhang L, Weir MD, Chow LC, Antonucci JM, Chen J, and Xu HH
- Subjects
- Benzoates chemistry, Bisphenol A-Glycidyl Methacrylate chemistry, Composite Resins chemical synthesis, Elastic Modulus, Materials Testing, Methacrylates chemistry, Polyethylene Glycols chemistry, Polymethacrylic Acids chemistry, Calcium Phosphates chemistry, Composite Resins chemistry, Dental Caries prevention & control, Dental Materials chemistry, Nanocomposites chemistry
- Abstract
Objectives: Calcium phosphate (CaP) composites with Ca and P ion release can remineralize tooth lesions and inhibit caries. But the ion release lasts only a few months. The objectives of this study were to develop rechargeable CaP dental composite for the first time, and investigate the Ca and P recharge and re-release of composites with nanoparticles of amorphous calcium phosphate (NACP) to achieve long-term inhibition of caries., Methods: Three NACP nanocomposites were fabricated with resin matrix of: (1) bisphenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) at 1:1 mass ratio (referred to as BT group); (2) pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA) at 1:1 ratio (PE group); (3) BisGMA, TEGDMA, and Bis[2-(methacryloyloxy)ethyl] phosphate (BisMEP) at 2:1:1 ratio (BTM group). Each resin was filled with 20% NACP and 50% glass particles, and the composite was photo-cured. Specimens were tested for flexural strength and elastic modulus, Ca and P ion release, and Ca and P ion recharge and re-release., Results: NACP nanocomposites had strengths 3-fold of, and elastic moduli similar to, commercial resin-modified glass ionomer controls. CaP ion recharge capability was the greatest for PE group, followed by BTM group, with BT group being the lowest (p<0.05). For each recharge cycle, CaP re-release reached similarly high levels, showing that CaP re-release did not decrease with more recharge cycles. After six recharge/re-release cycles, NACP nanocomposites without further recharge had continuous CaP ion release for 42 d., Significance: Novel rechargeable CaP composites achieved long-term and sustained Ca and P ion release. Rechargeable NACP nanocomposite is promising for caries-inhibiting restorations, and the Ca and P ion recharge and re-release method has wide applicability to dental composites, adhesives, cements and sealants to achieve long-term caries-inhibition., (Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)
- Published
- 2016
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34. Injectable nanoamorphous calcium phosphate based in situ gel systems for the treatment of periapical lesions.
- Author
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Mostafa AA, Zaazou MH, Chow LC, Mahmoud AA, Zaki DY, Basha M, Abdel Hamid MA, Khallaf ME, Sharaf NF, and Hamdy TM
- Subjects
- Animals, Anti-Inflammatory Agents, Non-Steroidal administration & dosage, Bone Substitutes administration & dosage, Bone Substitutes chemistry, Delayed-Action Preparations chemistry, Diffusion, Dogs, Hydrogels administration & dosage, Hydrogels chemical synthesis, Ibuprofen chemistry, Injections, Intralesional, Materials Testing, Molecular Conformation, Nanocapsules chemistry, Nanocapsules ultrastructure, Particle Size, Periapical Diseases pathology, Treatment Outcome, Calcium Phosphates administration & dosage, Calcium Phosphates chemical synthesis, Delayed-Action Preparations administration & dosage, Ibuprofen administration & dosage, Nanocapsules administration & dosage, Periapical Diseases drug therapy
- Abstract
Nonsurgical local treatment of a periapical lesion arising from trauma or bacterial infection is a promising innovative approach. The present study investigated the feasibility of developing injectable amorphous calcium phosphate nanoparticles (ACP NPs) and ACP NPs loaded with an anti-inflammatory drug; ibuprofen (IBU-ACP NPs) in the form of thermoreversible in situ gels to treat periapical lesions with the stimulation of bone formation. NPs were produced by a spray-drying technique. Different formulations of Poloxamer 407 were incorporated with/without the produced NPs to form injectable gels. A drug release study was carried out. A 3 month in vivo test on a dog model also was assessed. Results showed successful incorporation of the drug into the NPs of CP during spray drying. The particles had mean diameters varying from 100 to 200 nm with a narrow distribution. A drug release study demonstrated controlled IBU release from IBU-ACP NPs at a pH of 7.4 over 24 h. The gelation temperature of the injectable in situ gels based on Poloxamer 407 was measured to be 30 °C. After 3 months of implantation in dogs, the results clearly demonstrated that the inclusion of ACP NPs loaded with IBU showed high degrees of periapical bone healing and cementum layer deposition around the apical root tip.
- Published
- 2015
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35. In-situ hybridization of calcium silicate and hydroxyapatite-gelatin nanocomposites enhances physical property and in vitro osteogenesis.
- Author
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Chiu CK, Lee DJ, Chen H, Chow LC, and Ko CC
- Subjects
- 3T3 Cells, Animals, Biophysical Phenomena, Bone Regeneration, Gelatin chemistry, Male, Materials Testing, Mice, Microscopy, Electron, Nanocomposites ultrastructure, Osteogenesis, Rats, Rats, Sprague-Dawley, Siloxanes chemistry, Skull injuries, Skull physiopathology, Skull surgery, Spectroscopy, Fourier Transform Infrared, Tissue Scaffolds chemistry, X-Ray Diffraction, Bone Substitutes chemistry, Calcium Compounds chemistry, Durapatite chemistry, Nanocomposites chemistry, Silicates chemistry
- Abstract
Low mechanical strengths and inadequate bioactive material-tissue interactions of current synthetic materials limit their clinical applications in bone regeneration. Here, we demonstrate gelatin modified siloxane-calcium silicate (GEMOSIL-CS), a nanocomposite made of gelatinous hydroxyapatite with in situ pozzolanic formation of calcium silicate (CS) interacting among gelatin, silica and Calcium Hydroxide (Ca(OH)2). It is shown the formation of CS matrices, which chemically bonds to the gelatinous hydroxyapatite, provided hygroscopic reinforcement mechanism and promoted both in vitro and in vivo osteogenic properties of GEMOSIL-CS. The formation of CS was identified by Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction. The interfacial bindings within nanocomposites were studied by FTIR and thermogravimetric analysis. Both gelatin and CS have been found critical to the structure integrity and mechanical strengths (93 MPa in compressive strength and 58.9 MPa in biaxial strength). The GEMOSIL-CS was biocompatible and osteoconductive as result of type I collagen secretion and mineralized nodule formation from MC3T3 osteoblasts. SEM and TEM indicated the secretion of collagen fibers and mineral particles as the evidence of mineralization in the early stage of osteogenic differentiation. In vivo bone formation capability was performed by implanting GEMOSIL-CS into rat calvarial defects for 12 weeks and the result showed comparable new bone formation between GEMOSIL-CS group (20%) and the control (20.19%). The major advantage of GEMOSIL-CS composites is in situ self-hardening in ambient or aqueous environment at room temperature providing a simple, fast and cheap method to produce porous scaffolds.
- Published
- 2015
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36. Development of a novel fluorapatite-forming calcium phosphate cement with calcium silicate: in vitro and in vivo characteristics.
- Author
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Suzuki Y, Hayashi M, Yasukawa T, Kobayashi H, Makino K, Hirano Y, Takagi S, Chow LC, and Ogiso B
- Subjects
- Animals, Dental Cements, Materials Testing, Rats, Tensile Strength, X-Ray Diffraction, Apatites chemistry, Bone Cements chemistry, Calcium Compounds chemistry, Calcium Phosphates chemistry, Silicates chemistry
- Abstract
Aim of this study was to develop a novel fluorapatite-forming calcium phosphate cement (FA-CPC) with tricalcium silicate (TCS) for endodontic applications and to examine its in vitro and in vivo characteristics. The FA-CPC powder consisted of 62.8% CaHPO4, 30.8% CaCO3, and 6.4% NaF. One part of TCS was combined with 9 parts of FA-CPC powder (FA-CPC with TCS). A 1.5 M phosphate solution was used as cement liquid. Setting time (ST), diametral tensile strength (DTS), phase composition by X-ray diffraction (XRD), and cement alkalinity were analyzed. Cement biocompatibility was assessed using rat subcutaneous model. Cement ST was 10.3±0.6 min and DTS was 3.89±0.76 MPa. XRD patterns showed that highly crystalline apatitic material was the only significant phase present and pH value was approximate 11.0. FA-CPC with TCS demonstrated similar biocompatibility as that of mineral trioxide aggregate control. These results suggest that FA-CPC with TCS may be useful for endodontic applications.
- Published
- 2015
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37. Oral fluoride levels 1 h after use of a sodium fluoride rinse: effect of sodium lauryl sulfate.
- Author
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Vogel GL, Schumacher GE, Chow LC, and Tenuta LM
- Subjects
- Adult, Calcium analysis, Calcium pharmacokinetics, Cariostatic Agents pharmacokinetics, Cariostatic Agents therapeutic use, Dental Plaque chemistry, Dental Plaque metabolism, Female, Fluorides pharmacokinetics, Humans, Ion-Selective Electrodes, Male, Middle Aged, Saliva metabolism, Cariostatic Agents analysis, Fluorides analysis, Mouthwashes therapeutic use, Saliva chemistry, Sodium Dodecyl Sulfate pharmacology, Sodium Fluoride therapeutic use, Surface-Active Agents pharmacology
- Abstract
Increasing the concentration of free fluoride in oral fluids is an important goal in the use of topical fluoride agents. Although sodium lauryl sulfate (SLS) is a common dentifrice ingredient, the influence of this ion on plaque fluid and salivary fluid fluoride has not been examined. The purpose of this study was to investigate the effect of SLS on these parameters and to examine the effect of this ion on total (or whole) plaque fluoride, an important source of plaque fluid fluoride after a sufficient interval following fluoride administration, and on total salivary fluoride, a parameter often used as a surrogate measure of salivary fluid fluoride. Ten subjects accumulated plaque for 48 h before rinsing with a 12 mmol/l NaF (228 µg/g F) rinse containing or not containing 0.5% (w/w) SLS. SLS had no statistically significant effect on total plaque and total saliva fluoride but significantly increased salivary fluid and plaque fluid fluoride (by 147 and 205%, respectively). These results suggest that the nonfluoride components of topical agents can be manipulated to improve the fluoride release characteristics from oral fluoride reservoirs and that statistically significant change may be observed in plaque fluid and salivary fluid fluoride concentrations that may not be observed in total plaque and total saliva fluoride concentrations.
- Published
- 2015
- Full Text
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38. Müllerian duct anomalies: embryological development, classification, and MRI assessment.
- Author
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Robbins JB, Broadwell C, Chow LC, Parry JP, and Sadowski EA
- Subjects
- Female, Humans, Cervix Uteri pathology, Embryonic Development physiology, Magnetic Resonance Imaging methods, Mullerian Ducts abnormalities, Uterus pathology, Vagina pathology
- Abstract
Müllerian duct anomalies (MDA) occur due to abnormal development of the uterus, cervix, and vagina, many times affecting a woman's ability to conceive and carry a pregnancy to term. The spectrum of possible abnormalities are related to the development of two separate Müllerian systems, which then fuse and subsequently undergo degeneration of the fused segments. This multiphasic development explains the multiple variations within the scheme of MDA classification. The purpose of this article is to review the embryologic development of the Müllerian ducts, relate the development to the most commonly used classification system, and review the magnetic resonance imaging (MRI) assessment of Müllerian duct anomalies. A brief review of the treatment options, as they relate to the imaging diagnosis, will be provided as well., (© 2014 Wiley Periodicals, Inc.)
- Published
- 2015
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39. A New Bioactive Polylactide-based Composite with High Mechanical Strength.
- Author
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Dong Q, Chow LC, Wang T, Frukhtbeyn SA, Wang F, Yang M, and Mitchell JW
- Abstract
A new bioresorbable polylactide/calcium phosphate composite with improved mechanical strengths and a more basic filler, tetracalcium phosphate (TTCP), was prepared by melt compounding. N-(2-aminoethyl)-3-aminoproplytrimethoxysilane (AEAPS) and pyromellitic dianhydride (PMDA) were used to improve the interfacial adhesion between TTCP and polylactide (PLA). While AEAPS improved the dispersion of TTCP in the matrix, PMDA might react with the terminal hydroxyl group of PLA and the amino group on the surface of AEAPS modified TTCP, which could further enhance the interfacial strength. The tensile strength was improved to 68.4 MPa for the PLA/TTCP-AEAPS composite from 51.5 MPa for the PLA/TTCP composite (20 wt% of TTCP). Dynamic mechanical analysis suggested that there was a 51 % improvement in storage modulus compared to that of PLA alone, when PMDA (0.2 wt% of PMDA) was incorporated into the PLA/TTCP-AEAPS composite (5 wt% of TTCP). Using this new bioresorbable PLA composite incorporated with a more basic filler for biomedical application, the inflammation and allergic effect resulted from the degraded acidic product are expected to be reduced.
- Published
- 2014
- Full Text
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40. Antibacterial activity and ion release of bonding agent containing amorphous calcium phosphate nanoparticles.
- Author
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Chen C, Weir MD, Cheng L, Lin NJ, Lin-Gibson S, Chow LC, Zhou X, and Xu HH
- Subjects
- Biofilms, Colony Count, Microbial, Saliva microbiology, Shear Strength, Anti-Bacterial Agents pharmacology, Calcium Phosphates analysis, Dental Bonding, Nanoparticles
- Abstract
Objective: Recurrent caries at the margins is a primary reason for restoration failure. The objectives of this study were to develop bonding agent with the double benefits of antibacterial and remineralizing capabilities, to investigate the effects of NACP filler level and solution pH on Ca and P ion release from adhesive, and to examine the antibacterial and dentin bond properties., Methods: Nanoparticles of amorphous calcium phosphate (NACP) and a quaternary ammonium monomer (dimethylaminododecyl methacrylate, DMADDM) were synthesized. Scotchbond Multi-Purpose (SBMP) primer and adhesive served as control. DMADDM was incorporated into primer and adhesive at 5% by mass. NACP was incorporated into adhesive at filler mass fractions of 10%, 20%, 30% and 40%. A dental plaque microcosm biofilm model was used to test the antibacterial bonding agents. Calcium (Ca) and phosphate (P) ion releases from the cured adhesive samples were measured vs. filler level and solution pH of 7, 5.5 and 4., Results: Adding 5% DMADDM and 10-40% NACP into bonding agent, and water-aging for 28 days, did not affect dentin bond strength, compared to SBMP control at 1 day (p>0.1). Adding DMADDM into bonding agent substantially decreased the biofilm metabolic activity and lactic acid production. Total microorganisms, total streptococci, and mutans streptococci were greatly reduced for bonding agents containing DMADDM. Increasing NACP filler level from 10% to 40% in adhesive increased the Ca and P ion release by an order of magnitude. Decreasing solution pH from 7 to 4 increased the ion release from adhesive by 6-10 folds., Significance: Bonding agents containing antibacterial DMADDM and remineralizer NACP were formulated to have Ca and P ion release, which increased with NACP filler level from 10% to 40% in adhesive. NACP adhesive was "smart" and dramatically increased the ion release at cariogenic pH 4, when these ions would be most-needed to inhibit caries. Therefore, bonding agent containing DMADDM and NACP may be promising to inhibit biofilms and remineralize tooth lesions thereby increasing the restoration longevity., (Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)
- Published
- 2014
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41. Effects of Inorganic Fillers on the Thermal and Mechanical Properties of Poly(lactic acid).
- Author
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Liu X, Wang T, Chow LC, Yang M, and Mitchell JW
- Abstract
Addition of filler to polylactic acid (PLA) may affect its crystallization behavior and mechanical properties. The effects of talc and hydroxyapatite (HA) on the thermal and mechanical properties of two types of PLA (one amorphous and one semicrystalline) have been investigated. The composites were prepared by melt blending followed by injection molding. The molecular weight, morphology, mechanical properties, and thermal properties have been characterized by gel permeation chromatography (GPC), scanning electron microscope (SEM), instron tensile tester, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). It was found that the melting blending led to homogeneous distribution of the inorganic filler within the PLA matrix but decreased the molecular weight of PLA. Regarding the filler, addition of talc increased the crystallinity of PLA, but HA decreased the crystallinity of PLA. The tensile strength of the composites depended on the crystallinity of PLA and the interfacial properties between PLA and the filler, but both talc and HA filler increased the toughness of PLA.
- Published
- 2014
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42. Immobilization of Xanthate Agent on Titanium Dioxide and Surface Initiated RAFT Polymerization.
- Author
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Lei Y, Wang T, Mitchell JW, and Chow LC
- Abstract
Surface modification of titanium dioxide (TiO
2 ) nanoparticle is essential to control its surface properties, thereby to enhance its cell penetration capability, reduce its cytotoxicity, or improve its biocompatibility. In order to graft polyvinyl acetate onto TiO2 nanoparticles, xanthate was chemically immobilized on the surface of TiO2 by acylation followed by nucleophilic substitution with a carbodithioate salt. Reversible addition fragmentation chain transfer polymerization was conducted to graft vinyl acetate onto the surface of TiO2 . Both the TiO2 -xanthate and TiO2 -polyvinyl acetate hybrids were characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The chemical immobilization of xanthate on the surface of TiO2 and the subsequent controlled polymerization provide useful insight for decoration and modification of TiO2 and other nanoparticles.- Published
- 2014
43. A calcium prerinse required to form calcium fluoride in plaque from a sodium fluoride rinse.
- Author
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Vogel GL, Tenuta LM, Schumacher GE, and Chow LC
- Subjects
- Adult, Calcium administration & dosage, Calcium Compounds administration & dosage, Calcium Compounds therapeutic use, Calcium Fluoride analysis, Cariostatic Agents administration & dosage, Cariostatic Agents analysis, Dental Plaque chemistry, Female, Fluorides analysis, Humans, Hydrogen-Ion Concentration, Lactates administration & dosage, Lactates therapeutic use, Male, Middle Aged, Mouthwashes administration & dosage, Sodium Fluoride administration & dosage, Sodium Fluoride analysis, Young Adult, Calcium therapeutic use, Calcium Fluoride metabolism, Cariostatic Agents therapeutic use, Dental Plaque metabolism, Mouthwashes therapeutic use, Sodium Fluoride therapeutic use
- Abstract
The purpose of this study is to determine whether a calcium (Ca) prerinse used before a 228 µg/g (ppm) fluoride (F) rinse would induce the formation of 'calcium fluoride-like' (CaF2-like) deposits in human dental plaque. Sixty minutes after the use of the Ca prerinse/F rinse, plaque samples were collected from 10 volunteers, homogenized, and split into 2 aliquots. The plaque mass from one aliquot was then extracted with a 'plaque-like' solution that extracted all the CaF2-like deposits. The total F in both aliquots was then determined and compared. The results demonstrated that, as in previous studies, the Ca prerinse induced large increases in plaque fluid and total plaque F. However, unlike previous results without the Ca prerinse, 30% of the plaque F deposits were CaF2 or CaF2-like. Given that maintaining an elevated F concentration in the vicinity of a developing lesion may play an important role in the cariostatic effect of this ion, and the potential advantages of CaF2-like deposits as an F source, these results suggest that a Ca prerinse may increase the cariostatic effect of topical agents.
- Published
- 2014
- Full Text
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44. Microscale surface modifications for heat transfer enhancement.
- Author
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Bostanci H, Singh V, Kizito JP, Rini DP, Seal S, and Chow LC
- Subjects
- Hot Temperature, Microscopy, Electron, Scanning, Surface Properties, Alloys chemistry, Aluminum chemistry, Energy Transfer
- Abstract
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.
- Published
- 2013
- Full Text
- View/download PDF
45. Nanofiber scaffold gradients for interfacial tissue engineering.
- Author
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Ramalingam M, Young MF, Thomas V, Sun L, Chow LC, Tison CK, Chatterjee K, Miles WC, and Simon CG Jr
- Subjects
- 3T3 Cells, Animals, Calcium Phosphates chemistry, Cell Adhesion, Cell Proliferation, Materials Testing, Mice, Microscopy, Electron, Scanning, Nanoparticles chemistry, Nanotechnology instrumentation, Osteoblasts cytology, Nanofibers chemistry, Nanofibers ultrastructure, Tissue Engineering instrumentation, Tissue Scaffolds chemistry
- Abstract
We have designed a 2-spinnerette device that can directly electrospin nanofiber scaffolds containing a gradient in composition that can be used to engineer interfacial tissues such as ligament and tendon. Two types of nanofibers are simultaneously electrospun in an overlapping pattern to create a nonwoven mat of nanofibers containing a composition gradient. The approach is an advance over previous methods due to its versatility - gradients can be formed from any materials that can be electrospun. A dye was used to characterize the 2-spinnerette approach and applicability to tissue engineering was demonstrated by fabricating nanofibers with gradients in amorphous calcium phosphate nanoparticles (nACP). Adhesion and proliferation of osteogenic cells (MC3T3-E1 murine pre-osteoblasts) on gradients was enhanced on the regions of the gradients that contained higher nACP content yielding a graded osteoblast response. Since increases in soluble calcium and phosphate ions stimulate osteoblast function, we measured their release and observed significant release from nanofibers containing nACP. The nanofiber-nACP gradients fabricated herein can be applied to generate tissues with osteoblast gradients such as ligaments or tendons. In conclusion, these results introduce a versatile approach for fabricating nanofiber gradients that can have application for engineering graded tissues.
- Published
- 2013
- Full Text
- View/download PDF
46. Long-term mechanical durability of dental nanocomposites containing amorphous calcium phosphate nanoparticles.
- Author
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Moreau JL, Weir MD, Giuseppetti AA, Chow LC, Antonucci JM, and Xu HH
- Subjects
- Time Factors, Acrylic Resins chemistry, Calcium Phosphates chemistry, Glass Ionomer Cements chemistry, Materials Testing, Nanocomposites chemistry, Nanoparticles chemistry, Silicon Dioxide chemistry
- Abstract
Half of all dental restorations fail within 10 years, with secondary caries and restoration fracture being the main reasons. Calcium phosphate (CaP) composites can release Ca and PO(4) ions and remineralize tooth lesions. However, there has been no report on their long-term mechanical durability. The objective of this study was to investigate the wear, thermal-cycling, and water-aging of composites containing amorphous calcium phosphate nanoparticles (NACP). NACP of 112-nm and glass particles were used to fabricate four composites: (1) 0% NACP+75% glass; (2) 10% NACP+65% glass; (3) 15% NACP+60% glass; and (4) 20% NACP+50% glass. Flexural strength and elastic modulus of NACP nanocomposites were not degraded by thermal-cycling. Wear depth increased with increasing NACP filler level. Wear depths of NACP nanocomposites after 4 × 10(5) cycles were within the range for commercial controls. Mechanical properties of all the tested materials decreased with water-aging time. After 2 years, the strengths of NACP nanocomposites were moderately higher than the control composite, and much higher than the resin-modified glass ionomers. The mechanism of strength loss for resin-modified glass ionomer was identified as microcracking and air-bubbles. NACP nanocomposites and control composite were generally free of microcracks and air-bubbles. In conclusion, combining NACP nanoparticles with reinforcement glass particles resulted in novel nanocomposites with long-term mechanical properties higher than those of commercial controls, and wear within the range of commercial controls. These strong long-term properties, plus the Ca-PO(4) ion release and acid-neutralization capability reported earlier, suggest that the new NACP nanocomposites may be promising for stress-bearing and caries-inhibiting restorations., (Copyright © 2012 Wiley Periodicals, Inc.)
- Published
- 2012
- Full Text
- View/download PDF
47. Nanocomposite containing CaF(2) nanoparticles: thermal cycling, wear and long-term water-aging.
- Author
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Weir MD, Moreau JL, Levine ED, Strassler HE, Chow LC, and Xu HH
- Subjects
- Dental Stress Analysis, Materials Testing, Surface Properties, Acrylic Resins chemistry, Calcium Fluoride chemistry, Composite Resins chemistry, Nanocomposites chemistry, Nanoparticles, Silicon Dioxide chemistry
- Abstract
Objectives: Fluoride (F) releasing dental restoratives are promising to promote remineralization and combat caries. The objectives of this study were to develop nanocomposite containing calcium fluoride nanoparticles (nCaF(2)), and to investigate the long-term mechanical durability including wear, thermal-cycling and long-term water-aging behavior., Methods: Two types of fillers were used: nCaF(2) with a diameter of 53 nm, and glass particles of 1.4 μm. Four composites were fabricated with fillers of: (1) 0% nCaF(2)+65% glass; (2) 10% nCaF(2)+55% glass; (3) 20% nCaF(2)+45% glass; (4) 30% nCaF(2)+35% glass. Three commercial materials were also tested. Specimens were subjected to thermal-cycling between 5°C and 60°C for 10(5) cycles, three-body wear for 4×10(5) cycles, and water-aging for 2 years., Results: After thermal-cycling, the nCaF(2) nanocomposites had flexural strengths in the range of 100-150 MPa, five times higher than the 20-30 MPa for resin-modified glass ionomer (RMGI). The wear scar depth showed an increasing trend with increasing nCaF(2) filler level. Wear of nCaF(2) nanocomposites was within the range of wear for commercial controls. Water-aging decreased the strength of all materials. At 2 years, flexural strength was 94 MPa for nanocomposite with 10% nCaF(2), 60 MPa with 20% nCaF(2), and 48 MPa with 30% nCaF(2). They are 3-6 fold higher than the 15 MPa for RMGI (p<0.05). SEM revealed air bubbles and cracks in a RMGI, while composite control and nCaF(2) nanocomposites appeared dense and solid., Significance: Combining nCaF(2) with glass particles yielded nanocomposites with long-term mechanical properties that were comparable to those of a commercial composite with little F release, and much better than those of RMGI controls. These strong long-term properties, together with their F release being comparable to RMGI as previously reported, indicate that the nCaF(2) nanocomposites are promising for load-bearing and caries-inhibiting restorations., (Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
48. MRI of pregnancy-related issues: müllerian duct anomalies.
- Author
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Robbins JB, Parry JP, Guite KM, Hanson ME, Chow LC, Kliewer MA, and Sadowski EA
- Subjects
- Female, Humans, Pregnancy, Pregnancy Complications surgery, Pregnancy Outcome, Sensitivity and Specificity, Urogenital Abnormalities surgery, Magnetic Resonance Imaging methods, Mullerian Ducts abnormalities, Pregnancy Complications diagnosis, Urogenital Abnormalities diagnosis
- Abstract
Objective: Müllerian duct anomalies can adversely affect pregnancy outcomes and can result in clinical symptoms. This article will review the appropriate management of patients with müllerian duct abnormalities., Conclusion: Whereas uterine and vaginal septa, vaginal agenesis, and unicornuate uterus can be managed surgically, other uterine anomalies tend to be managed clinically. Hence, appropriate management depends on a reliable assessment of pelvic anatomy. MRI can accurately display female pelvic anatomy and is, therefore, useful in guiding therapy.
- Published
- 2012
- Full Text
- View/download PDF
49. Improve the Strength of PLA/HA Composite Through the Use of Surface Initiated Polymerization and Phosphonic Acid Coupling Agent.
- Author
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Wang T, Chow LC, Frukhtbeyn SA, Ting AH, Dong Q, Yang M, and Mitchell JW
- Abstract
Bioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent ζ-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas.
- Published
- 2011
- Full Text
- View/download PDF
50. An image-based comprehensive approach for automatic segmentation of left ventricle from cardiac short axis cine MR images.
- Author
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Huang S, Liu J, Lee LC, Venkatesh SK, Teo LL, Au C, and Nowinski WL
- Subjects
- Algorithms, Humans, Image Enhancement methods, Ventricular Dysfunction, Left physiopathology, Image Interpretation, Computer-Assisted methods, Magnetic Resonance Imaging, Cine methods, Pattern Recognition, Automated methods, Ventricular Dysfunction, Left diagnosis
- Abstract
Segmentation of the left ventricle is important in the assessment of cardiac functional parameters. Manual segmentation of cardiac cine MR images for acquiring these parameters is time-consuming. Accuracy and automation are the two important criteria in improving cardiac image segmentation methods. In this paper, we present a comprehensive approach to segment the left ventricle from short axis cine cardiac MR images automatically. Our method incorporates a number of image processing and analysis techniques including thresholding, edge detection, mathematical morphology, and image filtering to build an efficient process flow. This process flow makes use of various features in cardiac MR images to achieve high accurate segmentation results. Our method was tested on 45 clinical short axis cine cardiac images and the results are compared with manual delineated ground truth (average perpendicular distance of contours near 2 mm and mean myocardium mass overlapping over 90%). This approach provides cardiac radiologists a practical method for an accurate segmentation of the left ventricle.
- Published
- 2011
- Full Text
- View/download PDF
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