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4-META polymethyl methacrylate shear bond strength to titanium.

Machined titanium substructures for fixed, complete arch prostheses have been used with various surface pretreatments to enhance acrylic bonding. Since traditional mechanical methods for denture base material retention cannot be used, silane and surface abrasives have been used to enhance retention. The purpose of this study was to determine if a metal bonding denture base material provided a favorable bond strength to machined titanium. Fifteen rod-shaped samples of commercially pure Grade 2 titanium were divided into two groups, five samples representing the control group and 10 samples for the experimental group. The rod samples for the control received no pretreatment, while the experimental samples were pretreated with 110 microns alumina abrasive. Meta-Dent heat-cured polymethyl methacrylate was processed around each sample in a secondary cylindrical shape approximately 0.9 x 1.0 centimeters with the titanium rods extending from each end. A Shell-Nielsen shear test was then performed at a crosshead speed of 0.5 millimeters/minute to determine the bond strength. The experimental group demonstrated a mean bond strength 3.7 times greater than the control group (significant, P = 0.0001, ANOVA). Pretreatment with 110 microns alumina air abrasive significantly enhanced the bond strength of heat-cured metal bonding polymethyl methacrylate to titanium.

Acrylic Resins↗

Contamination of polyethylene cups with polymethyl methacrylate particles: an experimental study.

The articulating surfaces of 6 ultra-high molecular weight polyethylene cups were exposed to curing polymethyl methacrylate (PMMA) bone-cement and examined with scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Three of the cups were exposed to blood and bone-cement, and the rest were exposed to bone-cement only. After removal of the bone-cement bulk, PMMA particles were found and identified in all 6 cups. The particles were verified by identifying zirconium with energy-dispersive x-ray fluorescence spectroscopy in 5 cups and with LA-ICPMS in 1 cup. The degree of surface contamination was estimated with LA-ICPMS. The number of zirconium-containing particles detected was on average 10 to 20/mm2. PMMA bone-cement left in polyethylene cups during polymerization can contaminate the articulating surface with adherent PMMA particles.

Bone Cements↗

Highly reproducible method of planar lipid bilayer reconstitution in polymethyl methacrylate microfluidic chip.

We developed a highly reproducible method for planar lipid bilayer reconstitution using a microfluidic system made of a polymethyl methacrylate (PMMA) plastic substrate. Planar lipid bilayers are formed at apertures, 100 microm in diameter, by flowing lipid solution and buffer alternately into an integrated microfluidic channel. Since the amount and distribution of the lipid solution at the aperture determines the state of the lipid bilayer, controlling them precisely is crucial. We designed the geometry of the fluidic system so that a constant amount of lipid solution is distributed at the aperture. Then, the layer of lipid solution was thinned by applying an external pressure and finally became a bilayer when a pressure of 200-400 Pa was applied. The formation process can be simultaneously monitored with optical and electrical recordings. The maximum yield for bilayer formation was 90%. Using this technique, four lipid bilayers are formed simultaneously in a single chip. Finally, a channel current through gramicidin peptide ion channels was recorded to prove the compatibility of the chip with single molecule electrophysiology.

Lipid Bilayers↗

An improved method for embedding hard tissue in polymethyl methacrylate.

An improved routine method for embedding tissue, especially hard tissue, in polymethyl methacrylate (pMMA) is described. The improvements were: the final dehydration step before MMA infiltration was performed with methanol in a Soxhlet apparatus; the stabilizer hydroquinone was not extracted from the monomer (MMA), and more important, the commonly used polymerization initiator, benzoyl peroxide (bpo), was replaced by the initiator, bis (4-tert-butylcyclohexyl)peroxydicarbonate (bbpd). Bbpd is preferred to bpo because it is not explosive, far less is needed and it has a suitable half life. Moreover, bbpd, as obtained from the manufacturer, needs no further purification, in contrast to bpo. Temperatures during bbpd initiated polymerization did not exceed 48 C. In bbpd initiated pMMA, bubbles were almost never generated.

Benzoyl Peroxide↗

Human growth hormone in polymethyl methacrylate. A controlled study of 15 hip arthroplasties.

Growth hormone-loaded polymethyl methacrylate (PMMA) was used in 15 hip replacements. The levels of growth hormone and insulin growth factor-I from the hip and the blood were measured before, and after, implanting PMMA containing 20 mg of growth hormone. Low levels of growth hormone and insulin growth factor-I were found in the femur initially, but very high local levels were found after implanting the growth hormone-loaded PMMA. These results were compared with the low levels found in 15 patients in a control group undergoing cemented or cementless hip replacement without added growth hormone. The local levels of growth hormone and insulin growth factor-I declined rapidly during the first 72 hours and were near normal at the end of this time. Systemic levels of growth hormone and insulin growth factor-I were not affected by the implantation of growth hormone-loaded PMMA. No complications or adverse reactions were noted. However, randomized studies with long-term follow-up are mandatory before the use of growth hormone-loaded PMMA is justified.

Aged↗

Use of antibiotic-impregnated polymethyl methacrylate in horses with open or infected fractures or joints: 19 cases (1987-1995).

OBJECTIVE: To evaluate the clinical efficacy of antibiotic-impregnated polymethyl methacrylate (PMMA) in horses with open or infected fractures or joints in which internal fixation or external coaptation devices were used. DESIGN: Retrospective case series. ANIMALS: 19 horses in which antibiotic-impregnated PMMA was used as part of the treatment regimen. PROCEDURES: Medical records of each horse were reviewed, and owners and trainers were contacted to provide additional information. RESULTS: Musculoskeletal problems in these horses included 10 fractures of long bones, 2 comminuted phalangeal fractures, 5 joint injuries, and 2 chronically septic joints in which ankylosis was stimulated. Nine horses had open fractures, 8 had closed wounds and developed infection after internal fixation of fractures, and 2 had chronically septic joints. Bony union was achieved in 15 of 19 horses. Twelve horses were discharged from the hospital and survived long term. Gentamicin sulfate, tobramycin sulfate, amikacin sulfate, and cefazolin sodium were used in PMMA. CLINICAL IMPLICATIONS: Use of antibiotic-impregnated PMMA provided high local concentrations of antibiotics and should be considered in the treatment of horses with open fractures and acute and chronic bone and joint infections.

Amikacin↗

Long-term effect of sharp optic edges of a polymethyl methacrylate intraocular lens on posterior capsule opacification: a randomized trial.

PURPOSE: To compare the posterior capsule opacification (PCO) inhibiting effect of a 3-piece polymethyl methacrylate (PMMA) intraocular lens (IOL) with a sharp optic edge design with that of the round-edged version of the same IOL during a 5-year period. DESIGN: Randomized patient- and examiner-masked clinical trial with intraindividual comparison. PARTICIPANTS: Thirty-two patients with bilateral age-related cataract (64 eyes). METHODS: Each study patient had phacoemulsification cataract surgery in both eyes and received a sharp optic edge PMMA IOL in one eye and a round optic edge PMMA IOL in the fellow eye (both by Dr Schmidt in Germany). Follow-up examinations were at 1 week, 1 month, 1 year, 3 years, and 5 years. Digital retroillumination images were taken from each eye. The amount of posterior capsule opacification was assessed objectively by means of automated image analysis software (Automated Quantification of After-Cataract) at 1 year, 3 years, and 5 years after surgery. MAIN OUTCOME MEASURE: Posterior capsule opacification score: 0-10. RESULTS: The sharp optic edge IOL showed significantly less regeneratory and fibrotic PCO at 1 year, 3 years, and 5 years after surgery. The mean AQUA PCO score was 5.12 for the round-edge and 2.49 for the sharp-edge IOL (scale, 0-10; P<0.001) at 5 years. The mean difference among patients for the PCO score in the eye implanted with the sharp optic edge versus the score in the eye with the round optic edge was 2.83 at 5 years (95% confidence interval, 1.66-4.00). Due to the large number of neodymium:yttrium-aluminum-garnet laser capsulotomies that were performed (12 in the round-edge group and 4 in the sharp-edge group), there was no significant difference in visual acuity between both groups at any time point. CONCLUSIONS: Compared with the round-edge version, the sharp optic edge design of a 3-piece PMMA IOL led to significantly less PCO at 1 year, 3 years, and 5 years after surgery. However, the sharp optic edge did not lead to complete PCO prevention during this follow-up period. This finding has implications for the design of PMMA IOLs used for cataract surgery, especially in the developing world.

Aged↗

Treatment of thoracolumbar burst fractures with polymethyl methacrylate vertebroplasty and short-segment pedicle screw fixation.

OBJECTIVES: We aimed to evaluate the efficacy of reinforcing short-segment pedicle screw fixation with polymethyl methacrylate (PMMA) vertebroplasty in patients with thoracolumbar burst fractures. METHODS: We enrolled 70 patients with thoracolumbar burst fractures for treatment with short-segment pedicle screw fixation. Fractures in Group A (n = 20) were reinforced with PMMA vertebroplasty during surgery. Group B patients (n = 50) were not treated with PMMA vertebroplasty. Kyphotic deformity, anterior vertebral height, instrument failure rates, and neurological function outcomes were compared between the two groups. RESULTS: Kyphosis correction was achieved in Group A (PMMA vertebroplasty) and Group B (Group A, 6.4 degrees; Group B, 5.4 degrees). At the end of the follow-up period, kyphosis correction was maintained in Group A but lost in Group B (Group A, 0.33-degree loss; Group B, 6.20-degree loss) (P = 0.0001). After surgery, greater anterior vertebral height was achieved in Group A than in Group B (Group A, 12.9%; Group B, 2.3%) (P < 0.001). During follow-up, anterior vertebral height was maintained only in Group A (Group A, 0.13 +/- 4.06%; Group B, -6.17 +/- 1.21%) (P < 0.001). Patients in both Groups A and B demonstrated good postoperative Denis Pain Scale grades (P1 and P2), but Group A had better results than Group B in terms of the control of severe and constant pain (P4 and P5) (P < 0.001). The Frankel Performance Scale scores increased by nearly 1 in both Groups A and B. Group B was subdivided into Group B1 and B2. Group B1 consisted of patients who experienced instrument failure, including screw pullout, breakage, disconnection, and dislodgement (n = 11). Group B2 comprised patients from Group B who did not experience instrument failure (n = 39). There were no instrument failures among patients in Group A. Preoperative kyphotic deformity was greater in Group B1 (23.5 +/- 7.9 degrees) than in Group B2 (16.8 +/- 8.40 degrees), P < 0.05. Severe and constant pain (P4 and P5) was noted in 36% of Group B1 patients (P < 0.001), and three of these patients required removal of their implants. CONCLUSION: Reinforcement of short-segment pedicle fixation with PMMA vertebroplasty for the treatment of patients with thoracolumbar burst fracture may achieve and maintain kyphosis correction, and it may also increase and maintain anterior vertebral height. Good Denis Pain Scale grades and improvement in Frankel Performance Scale scores were found in patients without instrument failure (Groups A and B2). Patients with greater preoperative kyphotic deformity had a higher risk of instrument failure if they did not undergo reinforcement with vertebroplasty. PMMA vertebroplasty offers immediate spinal stability in patients with thoracolumbar burst fractures, decreases the instrument failure rate, and provides better postoperative pain control than without vertebroplasty.

Adult↗

Effect of interface conditions between ultrahigh molecular weight polyethylene and polymethyl methacrylate bone cement on the mechanical behaviour of total shoulder arthroplasty.

The aim of this study was to investigate the effect of the interface condition between polymethyl methacrylate (PMMA) bone cement and the ultrahigh molecular weight (UHMWPE) glenoid component on cement stresses and glenoid component tilting in a finite element (FE) model. The background of this research is that most FE models assume bonding between the PMMA bone cement and the UHMWPE component, although it is very doubtful that this bonding is present. An FE model of a cemented glenoid component was developed and a joint compression force and subluxation force of 725 and 350 N respectively were applied. The maximal principal stresses in the cement layer ranged between 21.30 and 32.18 MPa. Glenoid component tilting ranged between 0.943 degrees and 0.513 degrees. It was found that the interface condition has a large effect on the maximal principal stresses and glenoid component tilting. Whether adhesion between the UHMWPE component and PMMA bone cement occurs is unknown beforehand and, as a result, design validation using the FE technique should be carried out both by using contact elements in combination with a coefficient of friction as well as by a full bonding at this interface.

Adhesiveness↗

Some aspects of the tensile strength of undirectional glass fibre-polymethyl methacrylate composite used in dentures.

The aim of this study was to determine the tensile strength and E-modulus of unidirectional denture glass fibre-polymethyl methacrylate (GF-PMMA) composite with various fibre contents. The experimental values of tensile strength and E-modulus were compared with values obtained by a theoretical calculation. Autopolymerized PMMA test specimens (n = 6, per group) were reinforced with unidirectional E-glass fibres which had been wetted in a mixture of PMMA powder and monomer liquid. After storing the test specimens for 40 days in water at 37 degrees C, the tensile strength and E-modulus of the test specimens were measured. The increased amount of fibres in the PMMA matrix (up to 14.8% by weight) increased the mean tensile strength of the test specimens from 40.5 MPa to 91.2 MPa (P < 0.001) and the E-modulus from 2057 MPa to 3751 MPa (P < 0.001). The experimental tensile strength and Emodulus values were considerably lower than those based on the theoretical calculations. This was assumed to be due to the percentage of glass fibres unimpregnated with the PMMA resin. The presence of unimpregnated glass fibres was determined using light microscopy. The results of this study suggest that a new method of incorporating the glass fibres into the PMMA resin matrix should be developed in order to obtain a well-impregnated fibre composite reinforcement with high durability.

Analysis of Variance↗

Posterior foraminotomy or anterior discectomy with polymethyl methacrylate interbody stabilization for cervical soft disc disease: results in 292 patients with monoradiculopathy.

STUDY DESIGN: Retrospective study of patients who underwent either ventral microdiscectomy and polymethyl methacrylate (PMMA) interbody stabilization or posterior foraminotomy for the treatment of cervical monoradiculopathy caused by soft disc disease. OBJECTIVES: To evaluate the long-term outcome after 2 different surgical procedures in the treatment of cervical radiculopathy, compare them with each other and with previous data from other surgical techniques, and outline the indications, advantages, and disadvantages of each procedure. SUMMARY OF BACKGROUND DATA: Cervical disc disease can lead to morphologic different disc lesions, which again may differ in clinical presentation, operative treatment, and outcome. This study provides a clinical long-term follow-up of ventral and dorsal approaches. METHODS: Follow-up evaluation (mean 72.1 +/- 25.9 months) after surgery of monoradicular symptoms was performed in 292 patients. Patients with hard disc disease, myelopathy, neoplasms, or traumatic or recurrent cervical disc disease were excluded. A total of 124 patients (42.5%) underwent ventral microdiscectomy and PMMA stabilization (group A), and in 168 patients (57.5%), a posterior foraminotomy was performed (group B). The outcome was determined according to Odom criteria based on a questionnaire or a telephone interview and was related to the following variables: morphologic findings, neurologic findings, duration of symptoms, operation technique applied, age, sex, and cervical level involved. RESULTS: The success rate (Odom I + II) without consideration of morphologic findings was higher after anterior microdiscectomy with PMMA stabilization (93.6%) than after posterior foraminotomy (85.1%) (P < 0.05). The success rate was higher in cases with pure soft discs in both groups (A: 96.6%; B: 85.8%) than in cases with a mixture of soft and hard discs (A: 90.6%; B: 80%), without gaining statistical significance. Complications related to surgery occurred in 6.5% (group A) and 1.8% (group B) of patients (P < 0.05). CONCLUSION: The findings show that apparently a higher success rate results after anterior microdiscectomy with PMMA interbody stabilization for treatment of degenerative cervical monoradiculopathy than after posterior foraminotomy. Considering the type of morphology of the pathology that causes the radiculopathy, pure soft discs have a better outcome than mixtures of soft and hard discs, independent of the chosen approach. Although statistically significant differences in clinical data were found in both groups, both approaches seem to have equivalent value in individual indications.

Adult↗

The effect of the antimicrobial peptide, Dhvar-5, on gentamicin release from a polymethyl methacrylate bone cement.

The objective of this study was to investigate the release mechanism and kinetics of the antimicrobial peptide, Dhvar-5, both alone and in combination with gentamicin, from a standard commercial polymethyl methacrylate (PMMA) bone cement. Different amounts of Dhvar-5 were mixed with the bone cement powders of Osteopal and the gentamicin-containing Osteopal G bone cement and their release kinetics from the polymerized cement were investigated. Additionally, the internal structure of the bone cements were analysed by scanning electron microscopy (SEM) of the fracture surfaces. Secondly, porosity was investigated with the mercury intrusion method and related to the observed release profiles. In order to obtain an insight into the mechanical characteristics of the bone cement mixtures, the compressive strength of Osteopal and Osteopal G with Dhvar-5 was also investigated. The total Dhvar-5 release reached 96% in the 100 mg Dhvar-5/g Osteopal cement, whereas total gentamicin release from Osteopal G reached only 18%. Total gentamicin release increased significantly to 67% with the addition of 50mg Dhvar-5/g, but the Dhvar-5 release was not influenced. SEM showed an increase of dissolved gentamicin crystals with the addition of Dhvar-5. The mercury intrusion results suggested an increase of small pores (< 0.1 microm) with the addition of Dhvar-5. Compressive strength of Osteopal was reduced by the addition of Dhvar-5 and gentamicin, but still remained above the limit prescribed by the ISO standard for clinical bone cements. We therefore conclude that the antimicrobial peptide, Dhvar-5, was released in high amounts from PMMA bone cement. When used together with gentamicin sulphate, Dhvar-5 made the gentamicin crystals accessible for the release medium presumably through increased micro-porosity (< 0.1 microm) resulting in a fourfold increase of gentamicin release.

Antimicrobial Cationic Peptides↗

Influence of polymerization conditions on monomer elution and microhardness of autopolymerized polymethyl methacrylate resin.

Residual monomer contents and surface hardness are important factors in determining the serviceability of provisional restorations. The intent of this study was to systemically evaluate the effects of curing conditions on provisional polymethyl methacrylate (PMMA) resins which utilize a free-radical polymerization reaction. Combinations of the three curing factors of temperature, pressure, curing environment (water/air) were adjusted during the fabrication of autopolymerized specimen disks. The initial hardness of tested materials was measured with a microhardness tester 1 h after disc fabrication, and the amounts of residual methyl methacrylate (MMA) released into water were analyzed by reverse-phase HPLC after 7 d of water immersion. Results from multiple regressions showed that curing temperature was the dominant factor in improving resin surface hardness, whereas curing in water was the key factor for reducing the quantity of residual monomer. The pressure factor, which was thought to be critical for managing autopolymerized resins, showed no significant influences on the properties tested. ANOVA results showed that provisional PMMA resins cured in hot water, with or without pressure, significantly reduced the amount of residual MMA elution (up to 80%) and increased the microhardness values (up to 50%).

Acrylic Resins↗

Polymethyl methacrylate microspheres in collagen.

Artecoll was developed about 20 years ago and underwent a number of production changes until it recently became FDA approved under the new name of Artefill. This product contains 20% polymethyl methacrylate (PMMA) microspheres with a diameter of 30 to 40 microm, which are suspended in a 3.5% atelo-collagen solution. The PMMA microspheres are now purified and no longer have an electrostatic charge, which in part was the cause for the early granulomatous reactions. Further, PMMA has long been known as bone cement and has been used in cosmetic surgery with a very good safety record. PMMA microspheres are biologically inert and nondegradable. The treatment results are therefore permanent and technical errors as well as incorrect injections will last. Due to the early record of granuloma formation, there is still a debate as to whether this product-as well as all other permanent fillers-should be injected for cosmetic reasons or not. With proper indications, excellent injection techniques, and realistic expectations as to what can be expected, this product has now proved to be one of the superior permanent filler substances.

Biocompatible Materials↗

Comparison of acrylic and polymethyl methacrylate lenses in a pediatric population.

PURPOSE: To compare the intra-patient incidence of posterior capsular opacification (PCO) and their post operative course, in children with bilateral cataract, following implantation of acrylic (Group 1) and polymethyl methacrylate (PMMA) (Group 2) intraocular lenses (IOLs). MATERIALS AND METHODS: This was a prospective, interventional intra-patient case series. Twenty-five children with bilateral cataract, 5 years and older, underwent cataract surgery and implantation of an acrylic (AcrySof MA30BA, Alcon, Fortworth, TX) in one eye and PMMA (Indo Am IAB 203, Ocular Vision, Inc.) IOL in the other eye of each patient. They were followed up for an average of 11.1 +/- 9.5 months to assess the incidence of clinically significant PCO and occurrence of postoperative complications. RESULTS: Twenty-three children (46 eyes), were included in this study. Post-operatively, 22(95.6%) patients with acrylic IOLs and 20 (86.9%) patients with PMMA IOLs, either maintained or improved their vision. In the acrylic and PMMA IOL groups respectively, the incidence of clinically significant PCO was 21% (4) and 75% (12) ( P =0.002), with a median onset at 2.9 months and 0.7 months. Other complications included pupillary capture in 2 (8.7%) eyes and uveal prolapse in 1 (4.3%) eye in the acrylic group and increased uveal inflammation in 6 (26.1%) eyes and presumed noninfectious endophthalmitis in 2 (8.7%) eyes in the PMMA group. CONCLUSION: Incidence of PCO and post operative uveal inflammation is significantly less with acrylic lenses and were safe to use in pediatric eyes.

Acrylic Resins↗

Corneal endothelial response to refitting polymethyl methacrylate wearers with rigid gas-permeable lenses.

Thirteen persons who had been wearing only polymethyl methacrylate (PMMA) contact lenses for 3 years or more were switched to a contact lens material providing greater oxygen transmissibility (Itafocon A) while keeping other contact lens parameters the same. Monitoring of corneal endothelial cells during the first 4 months of the rigid gas-permeable (RGP) lens daily wear showed no significant change in the coefficient of variation of cell area (polymegethism) or percentage of hexagonal endothelial cells at the end of 4 months. However, paired data did show a small, but significant, decrease in cell density at the end of 4 months (3174 to 2908 cells/mm2). The results suggest that a sudden shift in the general corneal environment toward more available oxygen may have some early effect on endothelial cell density, but changes in endothelial cell size variation and form are not determined.

Adult↗

The effect of polymethyl methacrylate on latex-free surgical gloves.

In the current medical environment of increased awareness about latex sensitivity, more patients are presenting with known latex allergy. One such patient presented to us for total knee arthroplasty. During this procedure, we noticed holes in our latex-free surgical gloves when polymethyl methacrylate (PMMA) was being handled. Through subsequent testing of different brands of latex-free surgical gloves with various brands of bone-cement, we found that Allergard latex-free surgical gloves are destroyed by contact with PMMA. Biogel Neotech and Duraprene latex-free gloves show no such destruction. These results indicate that Allergard gloves should not be used in procedures in which bone-cement is employed. Biogel Neotech and Duraprene latex-free gloves are an acceptable alternative.

Arthroplasty, Replacement, Knee↗

Acrylic resin-fiber composite--Part II: The effect of polymerization shrinkage of polymethyl methacrylate applied to fiber roving on transverse strength.

This study determined the effect of polymerization shrinkage of polymethyl methacrylate (PMMA) coating of fiber roving on the transverse strength of an acrylic resin-glass fiber composite. The test specimens were heat-cured acrylic resin reinforced with glass fibers. The glass fiber rovings were treated with four PMMA-MMA mixtures (30 specimens per group) of various ratios assumed to have different amounts of polymerization shrinkage. A transverse strength test was used to determine the fracture resistance of the test specimens and the polymerization shrinkage of the PMMA-MMA mixtures was measured. After the specimens were fractured, single glass fibers used to reinforce the test specimens were studied by SEM. The fracture resistance of the specimens was statistically different (p < 0.001) among treatments, and the polymerization shrinkage of the PMMA-MMA mixture also varied as the calculations predicted. The SEM micrographs showed differences in thickness of the acrylic resin layer on the surface of the fibers with PMMA-MMA mixtures of various ratios. According to the results, the ratio that caused only minor polymerization shrinkage of PMMA in the glass fiber roving improved the fracture resistance of the test specimens and seemed to increase the amount of PMMA inside the fiber roving.

Analysis of Variance↗