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At least 235 records · Page 13Linked to original sources
PubMed1991

[Gentamycin-polymethylmethacrylate in the treatment of osteoarticular panaritium].

The authors present treatment results by Gentamicin-polymethyl methacrylate in severe forms of osteoarticular panaritium in the duration of three years when 16 patients with the age ranging form 19 to 64 Years were studied. Serial pearls 7 mm and 5 x 3 mm in diameter were used. The application of pearls was done in pale stasis, upon completing surgical treatment of the fingers and filling of the created cava. The immobilization was placed and 14 days later pearls extracted. Inflammatory process was restrained in all patients with a complete reparation of the fingers' soft tissue. In five patients who had through destruction of the phalangealarticular surfaces developed functional ankylosis in the period of rehabilitation. There were no amputations of the phalanges. Our initial experience in treating destructive inflammatory changes in phalanges by Gentamicin-polymethyl methacrylate points to the shorter treatment period and lower degree of disability when compared to the conventional treatment methods.

Adult↗
PubMed2003

A noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator-based stereotactic radiotherapy of uveal melanoma.

PURPOSE: To introduce a noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator-based stereotactic radiotherapy for uveal melanoma. METHODS AND MATERIALS: At the Department of Radiotherapy and Radiobiology, University of Vienna, stereotactic radiotherapy is offered to patients with uveal melanoma considered unsuitable for (106)Ru brachytherapy or local resection. For the present feasibility study, 8 patients were carefully selected according to their ability to fixate a small light source with the diseased eye and whether they had a rather small head to meet the limited geometric space available. A polymethyl methacrylate tube was attached to a stereotactic mask system in craniocaudal orientation supporting a 45 degrees mirror, which was placed in front of the diseased eye. At the other end of the tube, the patient was given a small fixation light, and a small camera was positioned beneath, which was shielded for use during MRI. A computer interface calculated and visualized the spatial difference of the actual and a given reference pupil position, which was defined before CT scanning, during the MRI sequences, and during treatment delivery at the linear accelerator. RESULTS: The described system can be attached to a conventional stereotactic mask system with minor modifications. Because of the large distance between the eye and the fixation light, the optical fixation system was well tolerated by all patients, and a stable position of the eye was obtained. The camera system can be used during CT and MRI without interference. Absorption of the 6-MV photon beam by the mirror and the polymethyl methacrylate tube was negligible. The computer interface designed to determine the pupil position uses an image-processing algorithm that correlates a template of the reference image with the actual image of the eye. Provided sufficient illumination of the pupil, the correlation function showed a pronounced minimum at the reference position. The precision of the algorithm was tested by phantom measurements. For a given 1 mm or 2 mm displacement, the interface reported a mean shift of 0.96 +/- 0.18 mm or 2.07 +/- 0.11 mm, respectively. CONCLUSION: The results of this study demonstrated the feasibility of a new optical fixation system for linear accelerator-based stereotaxis. The artifact-free application of the camera system during image acquisition and irradiation and the use of the computer interface, which automatically monitored eye movements with submillimeter precision, provided large improvements compared with existing techniques. Given well-defined interruption criteria and accelerated image processing, the described system has a high potential to perform automatically gated treatment beam delivery in the near future.

Humans↗
PubMed2004

Color stability of provisional prosthodontic materials.

STATEMENT OF PROBLEM: Discoloration of provisional prosthodontic materials may result in patient dissatisfaction and additional expense for replacement. PURPOSE: The purpose of this study was to determine the color stability of 5 provisional prosthodontic materials before and after immersion in distilled water or coffee for 20 days or exposure to ultraviolet (UV) light for 24 hours. MATERIAL AND METHODS: A total of 105 disc-shaped specimens (20+/-0.1 mm by 1+/-0.05 mm) were fabricated with 5 provisional prosthodontic materials: polyethyl methacrylate resins (Trim II), polymethyl methacrylate resins (Duralay; Alike), and bis-acryl methacrylate resin (Luxatemp; Integrity), according to manufacturers' instructions (n=21). Seven specimens of each material were randomly selected and immersed individually in distilled water (60 degrees C) or coffee (37 degrees C) for 20 days or exposed to UV irradiation for 24 hours, respectively. Color was measured as CIE L*a*b* with a colorimeter before and after the immersion or UV exposure. Color change (Delta E) was calculated and data were analyzed with 1-way ANOVA and the Tukey multiple comparisons test (alpha=.05). RESULTS: For specimens immersed in water, the color change of bis-acryl-methacrylate-based provisional materials (Integrity and Luxatemp) was significantly less than that of 3 methyl/ethyl methacrylate-based provisional materials (Trim II, Alike, and Duralay) (P<.002). After immersion in coffee, the 3 methyl/ethyl methacrylate-based provisional materials exhibited significantly less color change compared to the 2 bis-acryl methacrylate-based provisional materials (P<.0001). After ultraviolet irradiation, 2 bis-acryl methacrylate-based provisional materials showed significantly less color change than any of the 3 methyl/ethyl methacrylate-based provisional materials (P<.0001). CONCLUSION: Luxatemp and Integrity (bis-acryl-methacrylate-based resins) demonstrated acceptable color stability and were the most color-stable provisional prosthodontic materials tested compared to the methyl/ethyl methacrylate-based resins.

Analysis of Variance↗
PubMed2002

Effect of HEMA on bonding of Er:YAG laser-irradiated bovine dentine and 4-META/MMA-TBB resin.

The purpose of this study was to evaluate the priming effect of 2-hydroxyethylmetaclirate (HEMA) following acid treatment on resin bonding to prototype Er:YAG laser-irradiated dentine. Extracted bovine dentine following laser irradiation was acid treated by aqueous solution of 10% citric acid (10-0) or 10% citric acid/3% ferric chloride (10-3), and additionally treated with 35% HEMA. Pre-treated dentines were bonded to the polymethyl-methacrylate (PMMA) rod with 4-META/MMA-TBB resin (Super Bond C & B) and miniaturized dumbbell-shaped bonded specimens were prepared. These specimens profiled for tensile bond testing and fractured surfaces were observed by scanning electron microscopy (SEM). Cross-sections of resin-dentine interface were also examined. The HEMA treatment following acid conditioned by 10-3 or 10-0 for both laser-irradiated and non-irradiated dentines was significantly higher than that without HEMA treatment. SEM view of a fractured specimen showed some cohesive failure in cured resin, but almost all of the fractured surface shows boundary failure between the penetrated resin and underlying dentine. A cross-sectional view of the interface showed a very thick hybrid layer between the hybridized dentine and underlying dentine. It was concluded that HEMA treatment following acid conditioning provided a slightly higher bond strength for both the Er:YAG laser-irradiated and non-irradiated dentines. However, the bond strength of Er:YAG laser irradiated dentine was significantly lower than that of the non-irradiated dentine.

Animals↗
PubMed2000

Study of two cohorts of workers exposed to methyl methacrylate in acrylic sheet production.

OBJECTIVES: To study mortality among 4324 workers at two United Kingdom factories, Darwen, Lancashire and Wilton, Cleveland, producing polymethyl methacrylate (PMMA) sheet. The Darwen factory is still active, but the Wilton one was closed in 1970. Also, to investigate patterns of mortality after exposure to methyl methacrylate; in particular, mortality from colon and rectal cancer. METHODS: All male employees at the Darwen factory with a record of employment in 1949-88 and all men ever employed at the Wilton factory (1949-70) were investigated. The vital status of both cohorts was ascertained on 31 December 1995. The exposure of 1526 subjects at the Darwen plant who were engaged from 1949 onwards could be characterised. The mean duration of exposure was 7.6 years at 13.2 ppm (8 hour time weighted average), although exposures in some work groups were as high as 100 ppm. It was not possible to calculate the cumulative exposure of workers first employed at the Darwen plant before 1949 or workers at the Wilton factory. RESULTS: In the Darwen cohort, 622 deaths were identified and a further 700 deaths in the Wilton cohort. Mortalities for the cohort were compared with national and local rates and expressed as standardised mortality ratios (SMRs). In the subcohort of Darwen workers with more than minimal exposure to MMA, reduced mortalities compared with national and local rates, were found for all causes (SMR 94), and colorectal cancer (SMR 92), but mortality from all cancers was slightly increased (SMR 104). No relations were found with cumulative exposure to MMA. In the subcohort of Wilton workers, mortality from all causes of death was significantly reduced (SMR 89), but mortality from all cancers (SMR 103) and colorectal cancer (SMR 124) were increased. The excess of colorectal cancer was confined to employees with less than 1 year of employment. CONCLUSION: The study provided no clear evidence that employment at the factories or exposure to MMA had adversely affected the mortalities of workers.

Adult↗
PubMed1999

ESR study of MMA polymerization by a peroxide/amine system: bone cement formation.

Electron spin resonance (ESR) spectroscopy was used to gain insight at the molecular level into the curing of bone cement. Methyl methacrylate was polymerized using a N,N-dimethyl-p-toluidine (TD)/benzoyl peroxide (BPO) redox system in the presence of polymethyl methacrylate (PMMA) powder. The conventional nine-line ESR spectrum for the growing polymer radical was detected at the gel stage of polymerization. While the optimum free radical concentration was observed near the equimolar amine/BPO concentration, excess amine led to a change in the chemical structure of the trapped radical and inhibited the polymerization process. At a high amine/BPO ratio the nine-line signal disappeared and a three-line nitroxide-based radical appeared. The appearance of this nitroxide signal seems to depend on the amine/BPO molar ratio and on the presence of PMMA. An excess amount of amine with respect to BPO was found to inhibit the polymerization process. When BPO was removed, the system still polymerized but with a longer gelation time and a lower radical concentration. These results demonstrate that trapped free radicals in the bulk polymerization of MMA convert to polymeric peroxides that act as initiators in bone cement. When the accelerator 4-dimethylamino phenethyl alcohol (TDOH) was used, a higher radical concentration was observed in the polymerizing system. TDOH shows potential for being a more effective accelerator than TD for bone cement curing.

Amino Alcohols↗
PubMed2005

Systematic evaluation of FRAP experiments performed in a confocal laser scanning microscope.

The diffusion coefficient as well as the dimensionality of the diffusion process can be determined by straightforward and facile data analysis, when fluorescence recovery after photobleaching (FRAP) is measured as a function of time and space by means of confocal laser scanning microscopy. Experiments representing one-dimensional diffusion from a plane source or two-dimensional diffusion from a line source are readily realized. In the data analysis, the deviations of the actual initial conditions from ideal models are consistently taken into account, so that no calibration measurements are needed. The method is applied to FRAP experiments on solutions of Rhodamine B in glycerol and aqueous suspensions of polymethyl methacrylate microspheres.

Diffusion↗
PubMed1998

Hybrid total hip arthroplasty in patients under the age of fifty: a five- to ten-year follow-up.

In 37 patients, 45 total hip replacements were performed using contemporary cementing techniques, an uncemented Harris-Galante I acetabular component and a cemented precoated Iowa femoral component in patients under the age of 50 at the time of their surgery; 36 patients with 43 hybrid hips were living, 1 patient with 2 hybrid hips was decreased. No patients were lost to follow-up. At 5- to 10-year follow-up, eight hips were revised for aseptic loosening. No acetabular components, and eight femoral components (18%) were revised for aseptic loosening. When looking at radiographic results, including revision as well as those components that were probably or definitely loose on radiographs, 0 acetabular components and 11 femoral components (24%) were radiographically loose. These results demonstrate the excellent durability of the uncemented Harris-Galante acetabular component in the younger patient. However, the Iowa grit-blasted methyl methacrylate precoated femoral component had a magnitude increase in the prevalence of revision for aseptic femoral loosening when compared to the senior author's long-term Charnley results in this age group. The authors attribute the failure to the rough surface finish applied to the femoral component. However, the polymethyl methacrylate proximal precoating and the femoral component design may also contribute to the femoral failures.

Adult↗
PubMed2004

A selective-pressure impression technique for the edentulous maxilla.

This article describes a selective-pressure impression technique for the edentulous maxilla that is intended to compensate for the polymerization shrinkage of heat-polymerized polymethyl methacrylate resin and provides improved palatal adaptation of the definitive denture base.

Dental Impression Materials↗
PubMed1997

Fracture strengths of provisional restorations reinforced with plasma-treated woven polyethylene fiber.

STATEMENT OF PROBLEM: Fracture strength of interim fixed partial prosthesis is of great concern, especially in long-span restorations or areas of heavy occlusal stress. PURPOSE: Effects of a plasma-treated woven polyethylene fiber (Ribbond) on the fracture strength of polymethyl methacrylate (Coldpac) and a resin-based two-phase curing provisional restorative material (Provipont DC) were evaluated. MATERIAL AND METHODS: A polyvinyl siloxane template was used to fabricate three-unit posterior provisional prostheses on a stainless steel die with two abutments 22 mm apart. The reinforced groups were fabricated by affixing 3 mm wide pieces of fiber treated with methyl methacrylate monomer or polyisocyanate (activator part of Provipont DC) on the occlusal surfaces of abutments. The interim materials were mixed, according to the manufacturers' specifications, and placed in the template. The template was pressed on the die and held secure until complete setting of the material occurred by light curing (Provipont DC) or autopolymerization (PMMA). The specimens were divided into 4 groups of 10 each (A, reinforced Provipont DC; B, unreinforced Provipont DC; C, reinforced PMMA; and D, unreinforced PMMA). A central compressive load force was exerted on the specimen to determine the fracture load of the restorations. RESULTS: The data revealed mean fracture loads of A, 65.59 +/- 11.27 kg; B, 46.59 +/- 14.84 kg; C, 53.46 +/- 7.76 kg; and D, 49.86 +/- 14.44 kg. CONCLUSION: Plasma-treated polyethylene reinforced PMMA restorations showed no significant increase in fracture loads when compared with unreinforced restorations (p > 0.10), whereas reinforced resin-based restorations revealed significantly higher fracture loads (p < 0.01) than the unreinforced resin-based and PMMA provisional restorations.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2004

Range verification system using positron emitting beams for heavy-ion radiotherapy.

It is desirable to reduce range ambiguities in treatment planning for making full use of the major advantage of heavy-ion radiotherapy, that is, good dose localization. A range verification system using positron emitting beams has been developed to verify the ranges in patients directly. The performance of the system was evaluated in beam experiments to confirm the designed properties. It was shown that a 10C beam could be used as a probing beam for range verification when measuring beam properties. Parametric measurements indicated the beam size and the momentum acceptance and the target volume did not influence range verification significantly. It was found that the range could be measured within an analysis uncertainty of +/-0.3 mm under the condition of 2.7 x 10(5) particle irradiation, corresponding to a peak dose of 96 mGyE (gray-equivalent dose), in a 150 mm diameter spherical polymethyl methacrylate phantom which simulated a human head.

Carbon Radioisotopes↗
PubMed1998

Adhesion and tear energy of a long-term soft lining material activated by rapid microwave energy.

STATEMENT OF PROBLEM: Construction of dentures with permanent soft linings is time-consuming in the laboratory and extra costs are related to equipment and materials used. PURPOSE: The purpose of this in vitro study was to determine whether using microwave energy to activate the polymerization of a silicone rubber denture soft lining material affected its properties. MATERIAL AND METHODS: Tear energy and adhesive properties were measured in a tensile testing machine by using a pants leg tear test and peel specimens. Tear energy was measured for specimens polymerized conventionally (control) and for 3, 5, and 10 minutes in a microwave. Data were analyzed with one-way analysis of variance and a two-sample Student t test. RESULTS: The multiple comparison test failed to show a significant difference in tear energy between 3 minutes microwave activation and conventional heat curing. However, 3 minutes microwave activation revealed a significantly stronger material when compared with 5 minutes and 10 minutes (p < 0.05). Application of a two-sample Student t test failed to demonstrate a significant difference between microwave energy and conventional heat activation groups in the adhesion test. In adhesion testing, all specimens presented cohesive failure. CONCLUSIONS: This method of polymerization does not compromise the strength of a soft lining material and its adhesion to polymethyl methacrylate. This study suggests the use of 3 minutes 650 W microwave energy for processing a silicone soft lining material.

Adhesiveness↗
PubMed2000

Additional factors for the estimation of mean glandular breast dose using the UK mammography dosimetry protocol.

The UK and European protocols for mammographic dosimetry use conversion factors that relate incident air kerma to the mean glandular dose (MGD) within the breast. The conversion factors currently used were obtained by computer simulation of a model breast with a composition of 50% adipose and 50% glandular tissues by weight (50% glandularity). Relative conversion factors have been calculated which allow the extension of the protocols to breasts of varying glandularity and for a wider range of mammographic x-ray spectra. The data have also been extended to breasts of a compressed thickness of 11 cm. To facilitate the calculation of MGD in patient surveys, typical breast glandularities are tabulated for women in the age ranges 40-49 and 50-64 years, and for breasts in the thickness range 2-11 cm. In addition, tables of equivalent thickness of polymethyl methacrylate have been provided to allow the simulation for dosimetric purposes of typical breasts of various thicknesses.

Adipose Tissue↗
PubMed2002

Acrylic cranioplasty and axial pattern flap following calvarial and cerebral mass excision in a dog.

A 4 kg Chihuahua was presented with seizures and a large mass on his dorsal cranium. The mass had regrown after two previous attempts to remove it. Histological examination had shown the mass to be a multilobular osteochondroma (osteochondrosarcoma). A CT scan revealed destruction of the dorsal cranial bones by the mass and compression of cerebral cortex. A craniotomy was performed to excise the mass and attached skin, leaving a large deficit of calvarial bone and skin. A cranioplasty was performed in situ, using polypropylene mesh and polymethyl methacrylate. A caudal auricular axial pattern flap was placed directly over the cranioplasty to fill the skin defect. This unusual reconstruction resulted in good recovery, function and cosmetic effect, although tumour regrowth was seen within the cerebral cortex.

Animals↗
PubMed2002

Preoperative identification of a bone-cement allergy in a patient undergoing total knee arthroplasty.

Allergy to polymethyl methacrylate bone-cement or its components is unusual. Because of the potential for an inflammatory response in an allergic patient and the possibility of pain and loosening if a cemented implant is used, it is imperative to identify patients with this allergy to modify their treatment. We report the case of an otherwise healthy 60-year-old woman who needed a total knee arthroplasty and who had an allergy to methyl methacrylate bone-cement identified preoperatively. The appropriate evaluation for a patient who is suspected to have an allergy to bone-cement or its components is reviewed.

Arthroplasty, Replacement, Knee↗
PubMed2000

Percutaneous transpedicular vertebroplasty with PMMA: operative technique and early results. A prospective study for the treatment of osteoporotic compression fractures.

Vertebroplasty-percutaneous cement augmentation of osteoporotic vertebrae is an efficient procedure for the treatment of painful vertebral fractures. From a prospectively monitored series of 70 patients with 193 augmented vertebrae for osteoporotic and metastatic lesions, we analysed a group of 17 patients suffering from back pain due to osteoporotic fractures. The reinforcement of 45 vertebral bodies in these patients led to a significant and lasting pain reduction (P < 0.01 ). The presented technique is useful, as, in one session, at least four injections can be performed when required, allowing the prophylactic reinforcement of adjacent vertebrae as well. The use of a low-viscosity polymethyl methacrylate (PMMA) in combination with a non-ionic liquid contrast dye provides a reliable and safe procedure. Extraosseous cement leakage was seen in 20% of the interventions; however, none of them had clinical sequelae.

Aged↗
PubMed2000

[Results of implantation of endocapsular distance rings].

Endocapsular distance ring increases possibilities of extraction subluxated cataract. Its importance consists of stabilisation of capsular bag and with the possibility of implantation posterior intraocular lens. In the group there are 20 patients with implanted 21 distance rings. The period of follow up was 4-24 months. We used of a polymethyl methacrylate distance ring from firms Erilens, Morcher and IOLTechnology. Indication for the implantation of a distance ring was dialysis less than 2 quadrants, it depends on size and type of distance ring. The authors evaluate complications during the operation and early and later results after operation.

Cataract Extraction↗