Standard Polymethylmethacrylate Research Articles

Enhanced PMMA Denture Bases Using Functionalized MWCNT Fused g-C3N4 Nanocomposites

This study presents the development and analysis of a new metal-free nanocomposite that incorporates functionalized multi-walled carbon nanotubes (f-MWCNTs) with graphitic carbon nitride (g-C3N4) for reinforcing polymethyl methacrylate (PMMA) denture bases. The f-MWCNTs were integrated with g-C3N4 nanoparticles, and their structural and morphological features were examined using various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared spectroscopy (FT-IR), and Raman spectroscopy. A mechanical blending process was employed to synthesize the nanocomposite by mixing 2 wt% of the f-MWCNT/g-C3N4 with PMMA polymer powder, followed by heat curing to form the composite material. Specimens for mechanical testing were crafted to measure flexural strength, impact resistance, compressive performance, and hardness. The findings revealed that the f-MWCNT/g-C3N4-reinforced PMMA composites outperformed standard PMMA in mechanical robustness. Surface examination of the tested samples through SEM showed distinctive dimpling and roughness, indicating a toughened fracture surface in comparison to pure PMMA and g-C3N4 samples. The study concludes that this innovative f-MWCNT/g-C3N4 composite is a promising reinforcement for PMMA denture bases, enhancing both their mechanical and physical attributes.Keywords: PMMA, functionalization, MWCNTs, Graphitic Carbide Nitride, Mechanical Properties and Denture Base

Evaluating polyester resin as a viable substitute for PMMA in computed tomography dosimetry phantoms

The current study aimed to evaluate the suitability of polyester resin as an alternative material to polymethyl methacrylate (PMMA) for computed tomography (CT) dosimetry phantoms using the GEANT4/GATE Monte Carlo simulation platform. Cylindrical phantoms (32 cm diameter) constructed of polyester resin and PMMA were simulated and compared in terms of atomic composition, effective atomic number, electron density, mass density, and photon interaction mechanisms. Weighted CT dose index (CTDIw) values were calculated for each phantom at 80, 110, and 130 kVp tube voltages based on measurements of CTDI100,c and CTDI100,p. Results demonstrated that the physical properties of polyester closely matched those of PMMA, and the polyester phantom displayed equivalent dosimetric behavior to the PMMA phantom at all tube voltages tested. CTDIw values from the polyester phantom were within 1.4 % of the PMMA phantom across all tube voltages. Conversion coefficients were derived to equate polyester CTDIw values to PMMA dose equivalents. This study found that a polyester resin phantom exhibited radiation dosimetry commensurate with the standard PMMA phantom for CT dose assessment. Consequently, polyester resin represents a viable substitute material when PMMA is unavailable for construction of CT dosimetry phantoms.

Assessment of CTDI for tube voltage variations in an epoxy and polyester-resin phantoms using the platform GEANT4/GATE

The objective of this investigation was to assess the computed tomography dose index (CTDI) for various tube potentials utilizing epoxy and polyester-resin phantoms, and compare the results to those obtained from a standard polymethyl methacrylate (PMMA) phantom, employing the GEANT4/GATE simulation framework. Three cylindrical phantoms with a diameter of 32 cm were simulated from epoxy resin, polyester resin and PMMA. The phantoms were analyzed for their atomic composition, effective atomic number, electron density, and mass density. The weighted CTDI (CTDIw) was calculated for each phantom at 80, 110 and 130 kV tube potentials based on measurements of the CTDI100, c and CTDI100, p. The results demonstrated that the CTDIw values of the epoxy and polyester phantoms were dependent on the tube potential and exhibited similar trends to the PMMA phantom. The maximum discrepancy in CTDIw between the epoxy and PMMA phantoms was 3%, while the maximum difference in CTDIw between the polyester and PMMA phantoms was 2%. Therefore, the researchers concluded that the physical properties of the resin materials were comparable to PMMA, and the phantoms displayed equivalent dosimetry behavior to the PMMA phantom at all tube potentials. This study determined that epoxy and polyester resin phantoms exhibited commensurate radiation dosimetry to a standard PMMA phantom for assessing CT dose. As such, the epoxy and polyester resin phantoms may be considered as a suitable substitute for the PMMA phantom when it is not readily available.

Implementation and evaluation of the AAPM TG 111 for radiation dosimetry in a state-of-the-art C-arm cone beam CT system

The aim of this study was to assess the dosimetric characteristics of a state-of-the-art C-arm cone beam computed tomography (CBCT) system using the methodology proposed by the American Association of Physicists in Medicine (AAPM) Task Group (TG) 111. The dose measurement methodology described in AAPM TG 111 for wide cone beam acquisitions without table translation was employed to estimate equilibrium beam length () and equilibrium dose () in various interventional task-specific protocols with different tube arc projection geometries. Dose profiles were derived from point dose measurements in the centre and peripheral locations of the ICRU/AAPM and standard polymethyl methacrylate (PMMA) body phantom. Dose measurements were performed in phantom and free-in-air using a solid-state point detector. Monte Carlo (MC) based simulation dosimetry was performed to quantify the inhomogeneous dose patterns imparted in the phantoms. Estimated and on the ICRU/AAPM phantom was up to 49.4 cm and 6.17 mGy/100 mAs, respectively. Corresponding values determined on the PMMA phantom were 139 cm and 8.8 mGy/100 mAs, respectively. Free-in-air dose measurement ranged from 1.43 mGy/100 mAs to 5.93 mGy/100 mAs. Per cent difference in and between MC simulation and solid-state point detector measurement methods in the ICRU/AAPM phantom were within 16% and 18%, respectively. Manufacturers can use the presented methodology to characterize the dosimetric properties of C-arm CBCT systems. Clinical medical physicists may follow this methodology to verify corresponding data provided by the manufacturer and check for C-arm CBCT system performance dosimetric consistency.

Identification of the computed tomography dose index for tube voltage variations in a polyester-resin phantom

The aim of this study is to measure the volumetric computed tomography dose index (CTDIvol) for different tube voltages for a polyester-resin (PESR) phantom, and to compare it to values for a standard polymethyl methacrylate (PMMA) phantom. Both phantoms are head phantoms with a diameter of 16 cm. The phantoms were scanned by a CT scanner (GE Revolution EVO 64/128 slice) with tube voltages of 80, 100, 120, and 140 kV. The other scan parameters were constant (i.e. tube current of 100 mA, rotation time of 1 s, and collimation width of 10 mm). The CTDI100,c and CTDI100,p were obtained by measuring the dose with an ionization chamber inserted into five holes within the phantoms. The CTDIvol was calculated based on the CTDI100,c and CTDI100,p values. The measurements were repeated three times for each hole. It was found that the CTDIvol values for the PESR phantom were dependent on tube voltage value, and were similar to the dependency in a PMMA phantom. The maximum CTDIvol difference between the PESR and PMMA phantoms was 7.5%. We conclude that the dose measured in the PESR phantom is similar to that in the PMMA phantom and that the PESR phantom can be used as an alternative if the PMMA phantom is not available.

Influence of the Immune Microenvironment Provided by Implanted Biomaterials on the Biological Properties of Masquelet-Induced Membranes in Rats: Metakaolin as an Alternative Spacer.

Macrophages play a key role in the inflammatory phase of wound repair and foreign body reactions-two important processes in the Masquelet-induced membrane technique for extremity reconstruction. The macrophage response depends largely on the nature of the biomaterials implanted. However, little is known about the influence of the macrophage microenvironment on the osteogenic properties of the induced membrane or subsequent bone regeneration. We used metakaolin, an immunogenic material, as an alternative spacer to standard polymethylmethacrylate (PMMA) in a Masquelet model in rats. Four weeks after implantation, the PMMA- and metakaolin-induced membranes were harvested, and their osteogenic properties and macrophage microenvironments were investigated by histology, immunohistochemistry, mass spectroscopy and gene expression analysis. The metakaolin spacer induced membranes with higher levels of two potent pro-osteogenic factors, transforming growth factor-β (TGF-β) and bone morphogenic protein-2 (BMP-2). These alternative membranes thus had greater osteogenic activity, which was accompanied by a significant expansion of the total macrophage population, including both the M1-like and M2-like subtypes. Microcomputed tomographic analysis showed that metakaolin-induced membranes supported bone regeneration more effectively than PMMA-induced membranes through better callus properties (+58%), although this difference was not significant. This study provides the first evidence of the influence of the immune microenvironment on the osteogenic properties of the induced membranes.

Effect of MOSFET dosimeters’ calibration method on calibration factors and radiation doses measured with the dosimeters in radiology

MOSFET dosimeters have widely been used to measure radiation doses caused by x-rays. When using the MOSFET dosimeters, calibration factors (CFs) have a direct effect on reliability of dose measurements. The aim of this paper was to study the effect of various calibration methods on the CFs of the MOSFET dosimeters. The CFs were measured on clinical digital x-ray angiography (XA) and computed tomography (CT) devices using a calibrated CT ionization chamber and a standard polymethyl methacrylate (PMMA) phantom. The measurements were conducted by having the dosimeters (1) in air, (2) on the surface of the PMMA phantom and (3) inside the phantom. A statistically significant difference was seen between the CFs measured on the XA and CT devices. The CFs measured on the CT device were 20%–165% higher than those measured with the XA device (p < 0.001) in every calibration geometry. Furthermore, the calibration geometry had a notable effect on the CFs on CT. The CFs on the surface of the phantom were 18%–25% higher than in air (p < 0.05), and the CFs inside the phantom were 32%–39% smaller than in air (p < 0.05). These results suggest that the calibration of the MOSFET dosimeters should be conducted with the same device that is used in actual dose measurements. Also, the scattering conditions and the calibration geometry should be similar in the calibration and subsequent dose measurements.

Maxillary resection prosthesis fabricated from urethane dimethacrylate for a patient with polymethyl methacrylate allergy: A clinical report

The surgical resection of malignant tumors often leads to severe bone and soft-tissue deficits that can result in difficulty swallowing, impaired speech, and facial disfigurement. Prosthetic rehabilitation of these patients becomes an integral part of the patient’s recovery and allows for improvement in quality of life. This clinical report describes a patient who underwent an anterior maxillectomy secondary to squamous cell carcinoma. After the insertion of a polymethyl methacrylate (PMMA) interim resection prosthesis, the patient developed a severe allergic stomatitis reaction in the oral cavity and oropharynx. By using the patch test approach, true PMMA allergy was diagnosed along with a suitable PMMA replacement for the prosthesis. A subsequent prosthesis was fabricated from urethane dimethacrylate in place of the standard PMMA.

The Masquelet Technique: Can Disposable Polypropylene Syringes be an Alternative to Standard PMMA Spacers? A Rat Bone Defect Model.

Usually, the two-stage Masquelet induced-membrane technique for extremity reconstruction begins with a polymethylmethacrylate (PMMA) cement spacer-driven membrane, followed by an autologous cancellous bone graft implanted into the membrane cavity to promote healing of large bone defects. In exceptional cases, spacers made of polypropylene disposable syringes were successfully used instead of the usual PMMA spacers because of a PMMA cement shortage caused by a lack of resources. However, this approach lacks clinical evidence and requires experimental validation before being recommended as an alternative to the conventional technique. To (1) develop and (2) validate a critical-sized femoral defect model in rats for two stages of the Masquelet technique and to (3) compare the biological and bone healing properties of polypropylene-induced membranes and PMMA-induced membranes in this model. Fifty male Sprague Dawley rats aged 8 weeks old received a 6-mm femur defect, which was stabilized with an external fixator that was converted into an internal device. In the development phase, the defect was filled with PMMA in 16 rats to determine the most favorable timing for bone grafting. Two rats were excluded since they died of anesthetic complications. The other 14 were successively euthanized after 2 weeks (n = 3), 4 weeks (n = 4), 6 weeks (n = 4), and 8 weeks (n = 3) for induced membrane analyses. In the validation phase, 12 rats underwent both stages of the procedure using a PMMA spacer and were randomly assigned to two groups, whether the induced membrane was preserved or removed before grafting. To address our final objective, we implanted either polypropylene or PMMA spacers into the defect (Masquelet technique Stage 1; n = 11 rats per group) for the period established by the development phase. In each group, 6 of 11 rats were euthanized to compare the biological properties of polypropylene-induced membranes and PMMA-induced membranes using histological qualitative analysis, semiquantitative assessment of the bone morphogenic protein-2 content by immunostaining, and qualitative assessment of the mesenchymal stromal cell (MSC; CD31-, CD45-, CD90+, and CD73+ phenotypes) content by flow cytometry. Quantitative measurements from serum bone turnover markers were also performed. The five remaining rats of each group were used for Masquelet technique Stage 2, in which rat bone allografts were implanted in the induced membrane cavity after the polypropylene or PMMA spacers were removed. These rats recovered for 10 weeks before being euthanized for microCT quantitative measurements and bone histology qualitative assessment to evaluate and compare the extent of bone regeneration between groups. Induced membrane analyses together with serum bone turnover measurements indicated that a 4-week interval time between stages was the most favorable. Removal of the induced membrane before grafting led to almost constant early implant failures with poor bone formation. Four-week-old rats with polypropylene-triggered induced membranes displayed similar histologic organization as rats with PMMA-driven induced membranes, without any difference in the cell density of the extracellular matrix (4933 ± 916 cells per mm2 for polypropylene versus 4923 ± 1284 cells per mm2 for PMMA; p = 0.98). Induced membrane-derived MSCs were found in both groups with no difference (4 of 5 with polypropylene versus 3 of 3 with PMMA; p > 0.99). Induced membrane bone morphogenic protein-2 immunolabeling and serum bone turnover marker levels were comparable between the polypropylene and PMMA groups. MicroCT analysis found that bone regeneration in the polypropylene group seemed comparable with that in the PMMA group (29 ± 26 mm3 for polypropylene versus 24 ± 18 mm3 for PMMA; p > 0.99). Finally, qualitative histological assessment revealed a satisfactory endochondral ossification maturation in both groups. Using a critical-sized femoral defect model in rats, we demonstrated that polypropylene spacers could induce membrane encapsulation with histologic characteristics and bone regenerative capacities that seem like those of PMMA spacers. In a same bone site, polymers with close physical properties seem to lead to similar foreign body reactions and induce encapsulating membranes with comparable bone healing properties. Polypropylene spacers made from disposable syringes could be a valuable alternative to PMMA. These results support the possibility of a cementless Masquelet technique in cases of PMMA shortage caused by a lack of resources.

Development of In-House Head Computed Tomography Dose Index Phantoms Based on Polyester-Resin Materials

Introduction: Computed tomography dose index (CTDI) phantoms are used to optimize CT examinations in terms of image quality and the received dose. In this study, we aimed to develop cost-effective head CTDI phantoms from polyester-resin (PESR) materials as alternative phantoms. Material and Methods: The PESR was mixed with methyl ethyl ketone peroxide (MEKP) as a catalyst. The ratios of MEKP to PESR were 1:150, 1:200, 1:250, and 1:300, respectively. The phantom dimensions were designed similar to the standard CTDI phantom, i.e., length of 15 cm and diameter of 16 cm with five holes (diameter, 1.31 cm). The CTDI measurements using the PESR-MEKP phantoms were compared with the CTDI measurements using the standard polymethyl methacrylate (PMMA) phantom. Results: The results showed that the CTDI valuesof the PESR-MEKP phantoms were slightly higher (up to 6%) than the standard PMMA phantom. It was found that the CTDI measured by the PESR-MEKP phantom with a ratio of 1:300 had the least significant difference from the standard PMMA phantom; also, at this ratio, the phantom was the most homogeneous. Conclusion: The head CTDI phantoms based on PESR-MEKP materials were developed and evaluated in this study. It was found that the PR-MEKP phantom with a MEKP-to-PESR ratio of 1:300 was insignificantly different from the standard PMMA phantom. Also, the phantom was constructed easily at a more reasonable cost, compared to the standard phantom.

Explorative study on the antibacterial effects of 3D-printed PMMA/nitrides composites

Following the rising interested on 3D-printing technologies, this research explores the possibility to apply nitride-polymethylmethacrylate composite coatings on 3D printed parts in order to increase their resistance to bacteria colonization. Four different nitrides were tested: silicon, zirconium, hafnium and aluminum. Trans-micrometric particles of hafnium nitride (average size 1 µm) could be dispersed better than the other three nitrides (average size between 8 and 10 µm), but the chemical analysis confirmed that the former, due to the higher surface area, are more prone to spontaneous oxidation in air. After deposition, the surface of the various coatings contained between 40% (silicon nitride) and 90% (hafnium nitride) of exposed ceramic particles. All composite materials showed antibacterial effects when compared to standard polymethylmethacrylate, with hafnium nitride being the most effective against E. coli and aluminum nitride against S. epidermidis. It has been postulated that while Si3N4 long-term antibacterial effects are granted by the constant dissolution of the SiO2 surface layer, zirconium and hafnium composites are effective because they possess antibacterial properties both in their nitride and oxide forms.

S53P4 bioactive glass scaffolds induce BMP expression and integrative bone formation in a critical-sized diaphysis defect treated with a single-staged induced membrane technique

Critical-sized diaphysis defects are complicated by inherent sub-optimal healing conditions. The two-staged induced membrane technique has been used to treat these challenging defects since the 1980’s. It involves temporary implantation of a membrane-inducing spacer and subsequent bone graft defect filling. A single-staged, graft-independent technique would reduce both socio-economic costs and patient morbidity. Our aim was to enable such single-staged approach through development of a strong bioactive glass scaffold that could replace both the spacer and the graft filling. We constructed amorphous porous scaffolds of the clinically used bioactive glass S53P4 and evaluated them in vivo using a critical-sized defect model in the weight-bearing femur diaphysis of New Zealand White rabbits. S53P4 scaffolds and standard polymethylmethacrylate spacers were implanted for 2, 4, and 8 weeks. Induced membranes were confirmed histologically, and their osteostimulative activity was evaluated through RT-qPCR of bone morphogenic protein 2, 4, and 7 (BMPs). Bone formation and osseointegration were examined using histology, scanning electron microscopy, energy-dispersive X-ray analysis, and micro-computed tomography imaging. Scaffold integration, defect union and osteosynthesis were assessed manually and with X-ray projections. We demonstrated that S53P4 scaffolds induce osteostimulative membranes and produce osseointegrative new bone formation throughout the scaffolds. We also demonstrated successful stable scaffold integration with early defect union at 8 weeks postoperative in critical-sized segmental diaphyseal defects with implanted sintered amorphous S53P4 scaffolds. This study presents important considerations for future research and the potential of the S53P4 bioactive glass as a bone substitute in large diaphyseal defects. Statement of significanceSurgical management of critical-sized diaphyseal defects involves multiple challenges, and up to 10% result in delayed or non-union. The two-staged induced membrane technique is successfully used to treat these defects, but it is limited by the need of several procedures and bone graft. Repeated procedures increase costs and morbidity, while grafts are subject to donor-site complications and scarce availability. To transform this two-staged technique into one graft-independent procedure, we developed amorphous porous scaffolds sintered from the clinically used bioactive glass S53P4. This work constitutes the first evaluation of such scaffolds in vivo in a critical-sized diaphyseal defect in the weight-bearing rabbit femur. We provide important knowledge and prospects for future development of sintered S53P4 scaffolds as a bone substitute.

X-ray dose reduction using additional copper filtration for dental cone beam CT.

This study aims to quantitatively evaluate the effect of additional copper-filters (Cu-filters) on the radiation dose and contrast-to-noise ratio (CNR) in a dental cone beam computed tomography (CBCT). The Cu-filter thickness and tube voltage of the CBCT unit were varied in the range of 0.00-0.20mm and 70-90kV, respectively. The CBCT images of a phantom with homogeneous materials of aluminum, air, and bone equivalent material (BEM) were acquired. The CNRs were calculated from the voxel values of each homogeneous material. The CTDIvol was measured using standard polymethyl methacrylate CTDI test objects. We evaluated and analyzed the effects of tube current and various radiation qualities on the CNRs and CTDIvol. We observed a tendency for higher CNR at increasing tube voltage and tube current in all the homogeneous materials. On the other hand, the CNR reduced at increasing Cu-filter thickness. The tube voltage of 90kV showed a clear advantage in the tube current-CNR curves in all the homogeneous materials. The CTDIvol increased as the tube voltage and tube current increased and decreased with the increase in the Cu-filter thickness. When the CNR was fixed at 9.23 of BEM at an exposure setting of 90kV/5mA without a Cu-filter, the CTDIvol at 90kV with Cu-filters was 8.7% lower compared with that at 90kV without a Cu-filter. The results from this study demonstrate the potential of adding a Cu-filter for patient dose reduction while ensuring the image quality.

Sample Preparation of Posaconazole Oral Suspensions for Identification of the Crystal Form of the Active Pharmaceutical Ingredient.

Determination of the polymorphic form of an active pharmaceutical ingredient (API) in a suspension could be really challenging because of the water phase and the low concentration of the API in this formulation. Posaconazole is an antifungal drug available also as an oral suspension. The aim of this study was to develop a sample-preparation method for polymorphic identification of the dispersed API by increasing the concentration of the API but with no compromise of polymorph stability. For this purpose, filtration, drying and centrifugation were tested for separating the API from the suspending medium. Centrifugation was selected because it succeeded in separating Posaconazole API with no polymorph transformation during the process. During this study, it was found that Posaconazole in oral suspensions is Form-S. However, when slower scanning rates were used for acquiring an XRPD pattern with better signal/noise ratio, Posaconazole was converted to Form I due to water loss. In order to protect the sample from conversion, different approaches were tested to secure an airtight sample including a commercially available XRPD sample holder with a dome-like transparent cap, standard polymethylmethacrylate (PMMA) sample holders covered with Mylar film, transparent pressure-sensitive tape and a transparent food membrane. Only usage of the transparent food membrane was found to protect the API from conversion for a period of at least two weeks and resulted in a Posaconazole Form-S XRPD pattern with no artificial peaks.

Monte Carlo Simulation of the Computed Tomography Dose Index (CTDI) Using GATE

This work relates to the study and characterization of the CTDI (Computed Tomography Dose Index) for the 16 slices CT scanner. The CTDI has been simulated with the Monte Carlo code GATE for PMMA (polymethylmethacrylate) digital phantoms of various diameters (1–50 cm) at various kVp (80, 110, 130) and mAs (100, 200, 300, 400 mAs) levels. After using a High-Performance Computing (HPC) station, a good agreement was observed (less than 1.18% for head phantom and 1.85% for body phantom for all applied voltages) between simulations and experimental measurements with standard PMMA phantoms. Results of simulations demonstrated the following. Firstly, GATE is an adapted tool to estimate CTDI values and can be used to optimize CT parameters in clinical applications. Secondly, Monte Carlo simulation may be able to estimate the absorbed dose when the CTDI method has limitations (use of homogeneous standards cylindrical phantom, the dose measurement in air not in tissue).

Translucent Customized Cranial Implants Made of Clear Polymethylmethacrylate: An Early Outcome Analysis of 55 Consecutive Cranioplasty Cases.

Large skull reconstruction, with the use of customized cranial implants, restores cerebral protection, physiologic homeostasis, and one's preoperative appearance. Cranial implants may be composed of either bone or a myriad of alloplastic biomaterials. Recently, patient-specific cranial implants have been fabricated using clear polymethylmethacrylate (PMMA), a visually transparent and sonolucent variant of standard opaque PMMA. Given the new enhanced diagnostic and therapeutic applications of clear PMMA, we present here a study evaluating all outcomes and complications in a consecutive patient series. A single-surgeon, retrospective, 3-year study was conducted on all consecutive patients undergoing large cranioplasty with clear PMMA implants (2016-2019). Patients who received clear PMMA implants with embedded neurotechnologies were excluded due to confounding variables. All outcomes were analyzed in detail and compared with previous studies utilizing similar alloplastic implant materials. Fifty-five patients underwent cranioplasty with customized clear PMMA implants. Twenty-one (38%) were performed using a single-stage cranioplasty method (ie, craniectomy and cranioplasty performed during the same operation utilizing a prefabricated, oversized design and labor-intense, manual modification), whereas the remaining 34 (62%) underwent a standard, 2-stage reconstruction (craniectomy with a delayed surgery for cranioplasty and minimal-to-no implant modification necessary). The mean cranial defect size was 101.8 cm. The mean follow-up time was 9 months (range, 1.5-39). Major complications requiring additional surgery occurred in 7 patients (13%) consisting of 2 (4%) cerebrospinal fluid leaks, 2 (4%) epidural hematomas, and 3 (4%) infections. In addition, 3 patients developed self-limiting or nonoperative complications including 2 (4%) with new onset seizures and 1 (2%) with delayed scalp healing. This is the first reported consecutive case series of cranioplasty reconstruction using customized clear PMMA implants, demonstrating excellent results with regard to ease of use, safety, and complication rates well below published rates when compared with other alloplastic materials. Clear PMMA also provides additional benefits, such as visual transparency and sonolucency, which is material specific and unavailable with autologous bone. Although these early results are promising, further studies with multicenter investigations are well justified to evaluate long-term outcomes.

Development of a head CT dose index (CTDI) phantom based on polyester resin and methyl ethyl ketone peroxide (MEKP): a preliminary study

This paper aims to develop phantoms for measurement of computed tomography dose index (CTDI) based on a polyester resin mixed with methyl ethyl ketone peroxide (MEKP) as catalyst. CT number and CTDI values of the polyester resin phantoms were compared with a standard polymethyl methacrylate (PMMA) phantom as reference. The percentage of MEKP was varied from 0.3 to 0.6 wt%. The polyester resin phantoms had diameter of 160 mm, length of 150 mm and five cylindrical holes with diameter of 13.5 mm. One hole was positioned at the centre of the phantom and the other four near its periphery, 10 mm from the edge. The results show that the CT number of the polyester resin phantom was about 1%–9% higher than that of the standard PMMA phantom. Among the polyester resin phantoms, the one with 0.3 wt% MEKP is closest to the standard PMMA phantom in terms of CT number. In addition, the difference in weighted CTDI value between the 0.3 wt% polyester resin phantom and the PMMA is less than 5%. Thus, the 0.3 wt% polyester resin is potentially used as an alternative to the standard PMMA, with the advantage of a lower cost.

The ‘apple core’ cement spacer for the management of massive bone loss in two-stage revision knee arthroplasty for infection

Antibiotic-loaded cement spacers are used in two-stage revision knee arthroplasty for infection, but commercially available spacers may not always be suitable for significant bone loss or soft tissue failure in multiply revised cases. We describe a technique for producing an on-table, static, reinforced cement spacer – the ‘apple core’ spacer – with the intended outcome of providing joint stability in such patients, prior to undertaking a second-stage procedure. Following a radical debridement, the spacer is made of three components: (1) a ‘central bar’ of external fixator connecting rods, combined using cerclage wires as needed; (2) a standard polymethylmethacrylate cement ‘apple core’; and (3) a covering ‘skin’ of high dose antibiotic-loaded cement, which is stippled as it sets, to increase the surface area and facilitate antibiotic elution. This technique was performed in nine patients who underwent two-stage salvage revision for complex, recurrent infected total knee arthroplasty at a single institution. All patients successfully went on to definitive second-stage reimplantation and have retained their limbs. The ‘apple core’ cement spacer allows massive bone defects to be effectively managed between staged revision procedures.

Improved Wear Rate Resistance, Compression Strength and Hardness of Polymethylmethacrylate Resin with Orange Peel Powder for Artificial Denture Base

The material utilized for manufacturing artificial dentures should have high-grade mechanical properties in order to resist heavy forces inside the mouth. This study includes investigation of some of the mechanical properties (wear rate resistance, compression strength, and hardness) of the specimens prepared by (hand lay-up) method. The wear behavior experiments were performed on (a pin-on-disk tester) under various factors 5%, 8%, 11%, 14%, 17% weight fraction of orange peel, (10, 15, 20 N) load applied and (5, 10, 15 minutes) sliding time, and analysis these experimentally by using the Taguchi’s experimental design (L9) (MINITAB 16). Tests explicated that the specimens (polymethylmethacrylate - 17% orange peel) composites have the best wear rate resistance, compression strength and hardness shore D (0.040×10-5 cm3/N.mm, 142 MPa, 86 shore D) respectively than other specimens (polymethylmethacrylate - 5%, 8%, 11%, 14% wt. orange peel) and these specimens better than the specimens standard polymethylmethacrylate, which could be attributed to the homogeneous dispersion of orange peel particles in the polymethylmethacrylate resin matrix. The results (signal to noise ratio) showed the factors (17% weight fraction) orange peels, (20 N) load applied, and (5 min) sliding time gives the best wear rate resistance. The results of the analysis of variance showed the sliding time (C) is the essential factor effect on the wear rate resistance followed by (A) weight fraction of orange peels and (B) load applied were less affected on wear behavior rate.

Surface Structures of Cosmetic Standard Poly Methyl Methacrylate UV Evaluation Plates and their Influence on the in vitro Evaluation of UV Protection Abilities of Cosmetic Sunscreens.

Cosmetic standard poly methyl methacrylate (PMMA) UV evaluation plates, i.e., roughened PMMA plates, are used in the EU and the US for the in vitro evaluation of UV protection abilities of sunscreen, such as in vitro UVA-PF and critical wavelength for the Broad-spectrum approval. In our previous studies, inhomogeneity in the thickness of a pseudo-sunscreen layer applied on a flat quartz plate was observed to alter UV transmission. Thus, the surface roughness of the standard plates should have a significant influence on the in vitro evaluation. In the present study, we have analyzed the surface structures of three cosmetic standard PMMA UV evaluation plates: Helioplates HD6 (Sa = 6 µm) and ISO plates (Ra = 2 and 5 µm). A decamethylcyclopentasiloxane and 2-propanol-mixed solvent solution of acrylsilicone resin was prepared, and the solution was added dropwise onto the plates. After the evaporation of the solvents, the plates were cut and the cross section was analyzed using SEM-EDS. The distribution of silicon atoms at the cross-section suggested that the maximum depth of penetrating of acrylsilicone resin was larger than Ra for all the standard plates, and the surface structure was significantly different for each standard plate. In addition, cracks into which the acrylsilicone resin deeply penetrated were observed on the surface of some plates. Clear-solution-type pseudo-sunscreen samples in which UV absorbers and acrylsilicone resin were dissolved were deposited on the standard roughened PMMA plates. It was observed that the addition of acrylsilicone resin drastically changed the net UV transmission. The degree to which the hollows of the roughened surface were filled with the pseudo-sunscreen samples determined the variation of UV transmittance.