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PubMed1996

The effect of plasma-treated polyethylene fiber on the fracture strength of polymethyl methacrylate.

The effect of a plasma-treated polyethylene fiber on the fracture strength of polymethyl methacrylate was evaluated in this study. Sixteen treated and 16 untreated polymethyl methacrylate bars were tested by use of a three-point compression loading apparatus. Under the conditions of this experiment the treated bars showed a mean fracture strength of 12.56 MPa compared with 9.81 MPa for the untreated samples. In addition to the increased fracture strength, the treated bars also demonstrated resistance to crack propagation. The bars remained in one piece, held together throughout the compression loading by the polyethylene fiber. The clinical implication of these findings is a reduced incidence of fixed provisional restoration failure.

Chemical Phenomena↗
PubMed1993

The shear strength of polymethyl methacrylate bonded to titanium partial denture framework material.

Premachined titanium frameworks are used in implant-supported fixed complete-arch prostheses. Traditionally, retentive mechanisms are incorporated in the wax patterns to provide retention between polymethyl methacrylate and the cast framework. Nontraditional forms of retention are needed with machined frameworks. This study determined whether three different surface characteristics of titanium improve the bond shear strength of polymethyl methacrylate. Thirty rod shaped specimens of titanium were divided into three equal groups: group 1 received no pretreatment; group 2 was pretreated with 110 microns alumina air abrasive; and group 3 was pretreated with 110 microns alumina air abrasive plus silane (clear). Denture resin was processed around each specimen. A Shell-Nielsen shear test was then performed at a crosshead speed of 0.5 mm/minute to determine the bond shear strength in kilograms per square centimeter. The bond shear strength of group 3 was 63% greater than group 1 (significant, p < 0.01; ANOVA-Scheffé interval 63 kg/cm2). The results of this study indicated that surface pretreatment of titanium with 110 microns alumina air abrasive plus silane coating significantly enhances the bond shear strength of polymethyl methacrylate.

Aluminum Oxide↗
PubMed2001

Comparison of a new bisphenol-a-glycidyl dimethacrylate-based cortical bone void filler with polymethyl methacrylate.

A newly formulated and reinforced bisphenol-a-glycidyl dimethacrylate (bis-GMA) resin (Cortoss/Orthovita, Malvern, Pa.) was compared with Simplex P polymethyl methacrylate (Stryker Howmedica Osteonics, East Rutherford, N.J.) in rabbits for up to 52 weeks and in sheep for up to 78 weeks. As seen in scanning electron microscopy and histology examinations, both implant materials were surrounded by bone at late time periods, with fibrous layers of connective tissue seen in half the Simplex P specimens. No clinically significant safety differences between implant materials were apparent. Interfacial bond strengths between the implant and bone generally increased with time, but were 4.5-fold greater with Cortoss than Simplex P at 24 weeks, and 100-fold greater at 52 weeks. Forces required to displace 316SS rods held in place with Cortoss were consistently greater than forces to displace rods held in place with Simplex P. No statistically significant differences in displacement forces were found between rods held in place with Cortoss polymerized in situ and rods held with prepolymerized Cortoss. Interfacial bond strengths were greater for Simplex P that was polymerized in situ than for prepolymerized polymethyl methacrylate specimens. Cortoss synthetic cortical bone void filler is a good candidate material to fix implants in bone. It has characteristics consistent with long-term safety and has a better ability to bond to bone than Simplex P.

Animals↗
PubMed2003

Temperature elevation after vertebroplasty with polymethyl-methacrylate in the goat spine.

Although the general complication rate for vertebroplasty is low, neural compression and thermal damage have been related to the use of polymethyl-methacrylate cement. This study focuses on the risk of thermal tissue damage after vertebroplasty. In this study, cavities were created by a transpedicular approach in the vertebral bodies (L3, L4, and L5) of four milk goats, and polymethyl-methacrylate cement was injected. In three locations (the bone-cement interface, the epidural space, and the disc space) the temperature was measured in regular intervals after injection of the cement. The mean injected volume was 0.8 ml, which accounted for a 22% volume fraction. The mean peak temperature of the bone-cement interface was 44.6 degrees C, while the maximum temperature at the epidural space and disc space was 37.0 and 37.5 degrees C, respectively. The local temperature measured after in vivo vertebroplasty did not reach values that are known to cause tissue necrosis.

Animals↗
PubMed1996

Modified distraction-stabilization technique using an interbody polymethyl methacrylate plug in dogs with caudal cervical spondylomyelopathy.

A modified technique for distraction-stabilization that used an interbody polymethyl methacrylate plug was performed in 22 dogs with confirmed caudal cervical spondylomyelopathy. Myelographically, all compressive lesions were dynamic and predominantly located ventral to the spinal cord. Nineteen of 21 (90%) dogs for which success/failure could be determined had a successful outcome, and 11 of 22 (50%) dogs attained normal neurologic status. The 2 cases that were considered failures involved dogs that were nonambulatory tetraparetic prior to surgery and failed to improve to a functional status. Complications were self-limiting and included ventral displacement of the cement without loss of distraction in 1 dog and diskosponsylitis at an adjacent disk space in another dog. Evidence of fusion of the affected vertebrae, in the distracted position, was radiographically evident in all dogs. Use of the interbody polymethyl methacrylate plug appears to be a viable surgical treatment of caudal cervical spondylomyelopathy in dogs.

Animals↗
PubMed2001

Polymethyl-methacrylate implants in forehead and supraorbital arches reconstruction: retrospective study.

Frontobasal injuries and some other diseases of frontal sinuses sometimes require radical surgery with the obliteration of the sinus. A cosmetic correction of the forehead and supraorbital arches has to be performed after such a procedure. Nowadays, there is a wide choice of alloplastic materials on the market. We tried polymethyl methacrylate implants in correction of the exterior appearance of the forehead and supraorbital arches and followed the behaviour of the implants up to 25 years after surgery. The result was 18 (94.7%) successful implantations and one failure (5.3%) with a mild sagging of the borders of the implant. Polymethyl-methacrylate proved pliable for work and modelling, not invasive for the organism and stable. In conclusion, the cure of some frontobasal injuries and diseases with the first surgical step followed by cosmetic correction of the forehead and supraorbital arches (2nd surgical step) using this alloplastic material provides a safe, durable and aesthetically satisfactory solution for the patient.

Adult↗
PubMed1981

[Studies of dental methacrylic resin. (Part 8) Flexural and impact adhesive strength of self-curing methacrylic resin to cross-linked polymethyl methacrylate resins (author's transl)].

Heat-curing methacylic resins cross-linked with three kinds of dimethacrylates, i.e. EDMA, tri-EDMA and nona-EDMA, were prepared, and the flexural and the impact adhesive strength of the dough moulding type and the pour type self-curing methacrylic resins to them were examined. The results obtained were as follows. (1) The flexural and the impact adhesive strength of the pour type self-curing resin were higher and more stable than those of the dough moulding type one. (2) The flexural and the impact adhesive strength of self-curing resins to cross-linked adherent resins rised in order of nona-EDMA greater than tri-EDMA greater than EDMA in the range of higher concentration of cross-linking agents. This tendency was marked for the pour type resin. (3) When the dough moulding type resin was used as adhesive resin, to adherent resin cross-linked with EDMA or tri-EDMA which had relatively short chain, the respective adhesive strength of that decreased with increasing the concentration of cross-linking agent. While, to adherent resin cross-linked with nona-EDMA, which had relatively long and more flexible chain, the respective adhesive strength of the dough moulding type resin increased with increasing the concentration of cross-linking agent. (4) When the pour type resin was used as adhesive resin, to adherent resin cross-linked with EDMA or tri-EDMA, the respective adhesive strength of that showed the maximum at the concentration near 2 to 5 mole% and decreased with increasing the concentration. While, to adherent resin cross-linked with nona-EDMA, the flexural adhesive strength of the pour type resin was approximately constant without the effect of the concentration, but the impact adhesive strength of that increased with increasing the concentration. (5) The flexural adhesive strength of the dough moulding and the pour type resin under the wet condition decreased about 30 to 60% compared with under the dry condition, but the percentage of the falling for the impact adhesive strength was about 15 to 30% and relatively small. (6) The flexural adhesive strength showed a similar adhesive tendency to the tensile adhesive strength, but the impact adhesive strength showed a different adhesive tendency from those.

Adhesiveness↗
PubMed1995

Silane to enhance the bond between polymethyl methacrylate and titanium.

The machined surface of wrought titanium frameworks used in implant-supported, fixed prostheses does not bond well with acrylic resin. Surface pretreatment has been suggested to enhance the retention of polymethyl methacrylate to machined titanium surfaces. This study evaluated a new bonding material (Rocatec) to determine its effect on the bond strength between titanium and polymethyl methacrylate. Twenty rod-shaped specimens of grade 2 titanium (7.6 x 0.3 cm in diameter) were divided into two groups of 10 samples. Group A received no pretreatment and group B was pretreated with 110 microns alumina air abrasive and the Rocatec material. Heat-cured denture base resin was processed around each titanium sample in a cylindrical shape approximately 0.9 x 1.5 cm. A Shell-Nielsen shear test was performed with a universal testing machine at a crosshead speed of 0.5 mm/minute to determine the bond strength in megapascals (MPa). Group B specimens (23.8 +/- 1.78 MPa) had a shear strength 68% greater than group A (16.1 +/- 1.61 MPa) (p 0.0001). The results of this study indicated that surface pretreatment of grade 2 titanium with 110 microns alumina air abrasive plus Rocatec bonding material significantly enhances the shear bond strength to PMMA.

Air Pressure↗
PubMed1997

Molecular differential cross sections for x-ray coherent scattering in fat and polymethyl methacrylate.

Molecular differential cross sections for the coherent scattering of x-rays in polymethyl methacrylate (PMMA) and fat were determined from measured diffraction patterns in the interval chi = 0 to 6.4 nm-1 (chi = [sin theta/2)]/lambda; lambda being the incident wavelength having the units of nm and theta the scattering angle). All measurements were performed at a controlled temperature of 23 degrees C. The final results for PMMA show overall agreement when compared with the data existing in the literature. However, some discrepancies with the results reported by Kosanetzky et al in 1987 are found at the first three maxima. The data for filtered fat material are reported here for the first time. Finally, data sets of molecular form factors for fat and PMMA were compiled from the smoothed corrected experimental results by assuming these materials to be mono-molecular.

Adipose Tissue↗
PubMed2002

Kinetic examination of the mechanical transition of polymethyl methacrylate films prepared from aqueous dispersions.

The activation energy of the phase transition of cast polymethyl methacrylate films produced from an aqueous dispersion (Eudragit NE30D) has been estimated from Dynamic Mechanical Thermal Analysis. The value was found to lie between 170 and 350 kJ mol(-1), the variation arising from the different specimen test geometry and testing conditions. From experiments conducted at a range of frequencies and temperatures it was found possible to utilise the concept of frequency shift to produce a master curve, which could relate viscoelastic properties over the temperature range of 5-55 degrees C and a frequency range of 0.1 to 50 Hz.

Algorithms↗
PubMed1999

In vitro cytotoxicity of fibre-polymethyl methacrylate composite used in dentures.

The aim of this study was to determine the in vitro cytotoxicity of fibre-polymethyl methacrylate (PMMA) composite used in denture bases. Both heat-cured and autopolymerized PMMA were tested as the matrix of the fibre composite or as a plain denture polymer. The fibres tested included unsized E-glass and silica fibres, silica fibres which were sized with a silane coupling agent only, as well as commercially epoxy-silane or methacrylate-chrome complex sized E-glass fibres. The indirect contact cytotoxicity test by agar diffusion was carried out according to the international standard ISO 10993-5 after storing the test specimens in water for 24 h. PVC plastic was used as a positive control and polyethylene plastic was used as a negative control. Within the limitations of the agar diffusion test, it can be concluded that neither the unreinforced PMMA nor the fibre composite made from PMMA and fibres was cytotoxic.

Animals↗
PubMed1998

Comparison of decentration and tilt between one piece and three piece polymethyl methacrylate intraocular lenses.

BACKGROUND: The extent of the decentration and tilt was prospectively compared between one piece polymethyl methacrylate (PMMA) and three piece PMMA intraocular lenses (IOLs) which were implanted in the capsular bag after performing continuous curvilinear capsulorhexis. METHODS: 91 patients underwent a one piece PMMA IOL implantation in one eye as well as the implantation of the three piece PMMA IOL with polyvinylidene fluoride loops in the opposite eye. The length of the lens decentration and the angle of the tilt were quantitated using the anterior eye segment analysis system (EAS-1000) at 1 week as well as 1, 3, and 6 months postoperatively. RESULTS: The mean length of the decentration in the one piece IOL was smaller than that in the three piece IOL at 1 week (p = 0.0092), 1 month (p = 0.0044), 3 months (p = 0.0069), and 6 months (p = 0.0010) postoperatively. However, no significant difference was found in the degree of the tilt between the two types of IOLs throughout the observation periods. CONCLUSION: These results clarified that the one piece PMMA IOL with rigid PMMA haptics implanted in the capsular bag provides a better centration than the three piece PMMA IOL with flexible haptics, whereas the tilt was the same between the two types of IOLs.

Aged↗
PubMed1999

Unpolymerized surface layer of autopolymerizing polymethyl methacrylate resin.

The aim of this study was to determine the thickness of the unpolymerized surface layer of autopolymerizing polymethyl methacrylate (PMMA) resin. Powder: liquid (P/L) ratios of 10:4-10 by weight of the PMMA were tested, and the PMMA resin was polymerized at 55 degrees C either in water or in air under an air pressure of 100 kPa or 300 kPa. Five samples were polymerized for each of the test groups. The thickness of the unpolymerized surface layer, i.e. inhibition depth of PMMA, was measured by a light microscopic technique with polarized light. The inhibition depth of the samples polymerized in air under 100 kPa pressure varied from 39 to 174 microns, and the samples polymerized under 300 kPa pressure had an inhibition depth of 91-391 microns. The P/L ratio and the polymerization pressure had a significant effect on the inhibition depth (P < 0.001). No inhibition layer was observed in the samples polymerized in water. The results suggest that in order to obtain an adequate degree of polymerization on the surface of autopolymerizing PMMA resin, the polymerization process should be carried out in water.

Air↗
PubMed1982

Flexure and residual astigmatism with Polycon and polymethyl methacrylate lenses on toric corneas.

Previous investigators have shown that thin polymethyl methacrylate (PMMA) contact lenses (less than or equal to 0.12 mm) flex on toric corneas, thereby altering the residual astigmatism. The present study was designed to evaluate the flexure and residual astigmatism of gas permeable Polycon contact lenses on toric corneas and compare the results with those obtained with PMMA lenses on the same corneas. Eight subjects (16 eyes) with corneal toricities ranging from 1.25 to 4.25 D wore four pairs of identical Polycon and PMMA lenses. The only lens parameter that varied was center thickness, which ranged from 0.07 to 0.16 mm. Flexure and residual astigmatism were measured on all corneas with all lenses in a double-masked fashion. Our results indicate that Polycon lenses undergo significantly more flexure and alter residual astigmatism more on toric corneas than PMMA lenses at all center thicknesses evaluated. For both materials, flexure and residual astigmatism increased as center thickness decreased. The clinical implications of these findings are discussed.

Adult↗
PubMedDate not supplied

Use of ceftazidime-impregnated polymethyl methacrylate beads in the treatment of Pseudomonas osteomyelitis.

Antibiotic-impregnated polymethyl methacrylate beads have been used in other countries to treat osteomyelitis. The drug of choice for this has historically been gentamicin. The authors have chosen ceftazidime to treat iatrogenic Pseudomonas aeruginosa osteomyelitis in rabbit femurs. After implanting the beads, the rabbits were killed at various times in the treatment period. Rabbits were killed at 15 days and later showed no signs of current osteomyelitis, including cultures and histologic examination. Blood antibiotic levels were measured at euthanasia and were minimal for all animals. It appears that ceftazidime may be an effective alternative to gentamicin, especially in treating gentamicin-resistant P. aeruginosa.

Animals↗
PubMed2003

Use of antibiotic-loaded polymethyl methacrylate beads in the management of musculoskeletal sepsis--a retrospective study.

OBJECTIVE: To assess the use of antibiotic-loaded polymethyl methacrylate beads in the management of chronic osteomyelitis of different aetiologies: infected osteosynthesis, infected open fractures, and haematogenous osteomyelitis. METHODS: Records of 49 patients with chronic osteomyelitis who were treated at Department of Orthopaedics, Kasturba Medical College, from 1995 to 1999 were studied retrospectively. The diagnosis of chronic osteomyelitis was made on the basis of clinical and radiographic features. Of the 49 patients, 4 had haematogenous osteomyelitis, which later proved to be tuberculosis, and were thus excluded. Antibiotic-loaded acrylic beads were implanted in the remaining patients after thorough debridement. The implant was removed primarily in 16 patients with infected osteosynthesis, who then underwent decompression and sequestrectomy. All wounds were closed primarily. Peri-operative antibiotics were given for 7 days. Beads were removed at the end of 3 weeks followed by bone grafting in 26 patients. Patients were followed up for an average period of 3.7 years. RESULTS: The infective organisms were sensitive to gentamycin in 26 cases and resistant in 19 cases; 14 cases were sensitive to cefuroxime, 11 to cloxacillin, 8 to ampicillin, and 5 to cotrimoxazole. Seven cases were resistant to all antibiotics tested. Of the 19 patients with gentamycin-resistant infection, only one had a poor result. No adverse systemic side-effects such as ototoxicity or nephrotoxicity were seen. Infection did not recur in 39 patients, but 6 patients had low-grade persistent infection at the last follow-up visit. CONCLUSION: In chronic infections, especially those following osteosynthesis, antibiotic beads are a valuable adjuvant. The most valuable advantage is that the wound can be closed primarily, thereby reducing the incidence of nosocomial infections and requirement of nursing care.

Adolescent↗
PubMed2000

In vitro adherence of Staphylococcus epidermidis to polymethyl methacrylate and acrysof intraocular lenses.

PURPOSE: To investigate the adherence of one clinically relevant ocular isolate of Staphylococcus epidermidis to polymethyl methacrylate (PMMA) and Acrysof (Alcon Surgical, Fort Worth, TX) intraocular lenses (IOLs). DESIGN: Experimental study. PARTICIPANTS: The authors examined the in vitro adherence of one clinically relevant ocular isolate of S. epidermidis. Adherence was tested on 12 PMMA IOLs and 12 Acrysof IOLs. METHODS: Six IOLs (three of each type) were placed in different test tubes containing bacterial suspension (10(8) cfu/ml) and incubated at 37 degrees C. At different times (3 minutes, 30 minutes, and 90 minutes), each IOL type was removed from the test tube, rinsed in sterile phosphate-buffered saline, and transferred into sterile brain-heart infusion broth. The broth with the IOL was sonicated on low power for 3 minutes to remove adhered bacteria. Two serial 10-fold dilutions of the broth containing the dislodged bacteria were plated on mannitol agar plates. The plates were incubated overnight at 37 degrees C and then bacterial colonies were counted. All assays were performed in triplicate. Additional lenses (three of each type) were incubated with S. epidermidis for different times (3 minutes, 30 minutes, and 90 minutes) and then examined with scanning electron microscopy. MAIN OUTCOME MEASURES: The number of adhered bacteria per area (mm ) of IOL optic was calculated. Statistical analysis included calculation of arithmetic means and 95% confidence intervals (t test). RESULTS: Direct counting of viable adherent bacteria released by sonication showed that the amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes' incubation in S. epidermidis suspension was 0.1 x 10(2)/mm2, 3.6 x 10(2)/mm2, and 11 x 10(2)/mm2 (PMMA IOLs), and 4.4 x 10(2)/mm2, 3.1 x 10(2)/mm2, and 2.3 x 10(2)/mm2 (Acrysof IOLs). Direct counting of adherent bacteria in scanning electron microscopy photographs revealed that the total amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes' incubation in S. epidermidis suspension was 1.1 x 10(2)/mm2, 4.4 x 10(2)/mm2, and 5.5 x 10(2)/mm2 (PMMA IOLs) and 13 x 10(2)/mm2, 33.9 x 10(2)/mm2, and 72 x 10(2)/mm2 (Acrysof IOLs). CONCLUSIONS: Results suggest that in vitro adherence of S. epidermidis to IOLs is influenced by IOL materials. After 3 minutes' incubation, Acrysof IOLs appeared to be more permissive to S. epidermidis adherence than PMMA IOLs. The difference was statistically significant (P < 0.05). However, at 90 minutes, Acrysof IOLs had a lower viable bacterial count than did the PMMA IOLs. Bacterial adherence appeared to be greater in areas with surface irregularities. Adherence of S. epidermidis to IOLs may play a role in the pathogenesis of some forms of endophthalmitis after cataract surgery.

Acrylic Resins↗