PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Polymethyl Methacrylate”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

Intradural cement leakage: a devastatingly rare complication of vertebroplasty.

STUDY DESIGN: The aim of this case report is to examine the devastating complication that may follow vertebroplasty. OBJECTIVES: To report 1 case of intradural cement leakage caused by percutaneous vertebroplasty with polymethyl methacrylate. SUMMARY OF BACKGROUND DATA: Cement leakage is not a rare complication of vertebroplasty. But intradural cement leakage is rare. We herein report a rare but devastating complication of vertebroplasty. METHODS: A 90-year-old woman with a T12 and L1 osteoporotic compression fracture underwent percutaneous vertebroplasty using polymethyl methacrylate at local hospital. A literature search was performed to assess complications of vertebroplasty. RESULTS: She was transferred to our hospital due to abdominal pain. Physical examination revealed distended abdomen with local tenderness and weakness of both legs (muscle power: Grade 2). Plain radiograph of abdomen showed ileus and intradural cement leakage. Conservative treatment with nasogastric decompression was done, and her abdominal pain subsided 1 week later. CONCLUSIONS: Percutaneous vertebroplasty with polymethyl methacrylate is relatively safe, but it still should be proceeded under careful safeguard. The needle tip should not cross the medial border of the pedicle on the anteroposterior view before it has crossed the posterior cortex of the vertebral body on the lateral view. Good quality of image monitoring and clear visualization of cement should be helpful to prevent complications.

Aged, 80 and over↗

Bond strength of a silicone lining material to alumina-abraded and lased denture resin.

The aim of this study was to investigate the bond strength and adhesion of commercially available polydimethylsiloxane denture liner (Molloplast-B) to alumina-abraded or lased heat-cured polymethyl methacrylate denture base resin. The effect of laser irradiation on denture base resin by a surface analyzer and scanning-electron microscopy (SEM) was also determined. Laser-treated specimens demonstrated statistically significantly higher surface roughness values compared to alumina-abraded and untreated (control-group) specimens (p < 0.05). There were no statistically significant differences in surface roughness between alumina-abraded and control specimens. In the tensile debonding test, no statistically significant differences were found among the treatment modalities tested (alumina abraded, lased, and control) (p > 0.05). Molloplast-B applied to alumina-abraded polymethyl methacrylate resin surface recorded the highest mean tensile bond strength. Laser-treated specimens produced the next highest mean tensile bond strength, and untreated polymethyl methacrylate resin surface recorded the lowest tensile bond strength. Laser irradiation produced significant surface texture changes of the denture base material. However, this mechanical surface preparation of denture base before application of a resilient liner did not improve the adhesion between denture base and soft lining material.

Aluminum Oxide↗

Retention of provisional crowns fabricated from two materials with the use of four temporary cements.

STATEMENT OF PROBLEM: Practitioners often choose resin materials and temporary cements with little understanding about their effect on provisional crown retention. PURPOSE: This study evaluated the retention of provisional restorations made with 2 materials and cemented with 4 temporary cements. METHODS AND MATERIAL: Recently extracted molars were prepared with a flat occlusal surface, 4-mm axial length and 20-degree angle of convergence. Specimens were distributed into equivalent groups. Provisional crowns were constructed for each preparation with polymethyl methacrylate (Temporary Bridge Resin) or bis-acrylic composite (Protemp Garant) and later cemented with Temp-Bond, Temp-Bond NE, Temrex, and an experimental calcium hydroxide temporary cement. A second group with Temrex was evaluated using half the recommended liquid. A cementing force of 2.5 kg for 5 minutes was used. After initial bench set followed by 24 hours in room temperature water, the crowns were removed with an Instron mechanical testing machine at 0.5 mm/min. A 2-factor ANOVA was used with alpha=.05 (n = 10). Mode of debonding was analyzed with a nonparametric chi-square test of association. RESULTS: Mean dislodgment stresses ranged from 670 to 1072 kPa for polymethyl methacrylate crowns and 554 to 884 kPa for those made of composite. Differences were nearly significant for the type of provisional material (P =.061) and the cross-product interaction (P =.376) was not significant, whereas there were significant differences among the cements (P =.002) and the mode of debonding (P =.0034). CONCLUSIONS: Excluding Temp-Bond to eliminate a cross-product interaction demonstrated that the polymethyl methacrylate crowns were 19.3% more retentive than the composite crowns (P =.015). There was no statistically significant difference among the 4 temporary cements when the manufacturer's mixing instructions were followed (P =.186). However, the thicker consistency Temrex was more retentive than the recommended Temrex mix and Temp-Bond.

Analysis of Variance↗

Effect of different dialyzers on proteinases and proteinase inhibitors during hemodialysis.

The effect of different membrane materials on plasma levels of granulocyte elastase, 'unspecific' proteolytic (azocasein-hydrolyzing) activity, and activity and concentration of the main plasma proteinase inhibitors alpha 1-proteinase inhibitor (alpha 1PI) and alpha 2-macroglobulin during hemodialysis was investigated. Cuprophan (679.6 +/- 80.0 ng/ml) and polymethyl methacrylate (873.0 +/- 20.6 ng/ml) membranes caused a significantly higher maximal increase of plasma levels of granulocyte elastase-alpha 1-proteinase inhibitor (E-alpha 1PI) complex compared with polyacrylonitrile (395.3 +/- 56.0 ng/ml) or polysulfone (295.2 +/- 41.3 ng/ml) membranes (healthy subject 70.3 +/- 4.4 ng/ml). The activity of alpha 1PI increased significantly during hemodialysis using polyacrylonitrile (+36%) or polysulfone (+29%) membranes, whereas this increase was less using cuprophan (+6%) or polymethyl methacrylate (+8%) membranes. The reverse effect, however, was observed analyzing alpha 1PI concentrations (cuprophan +33%, polymethyl methacrylate +23%, polyacrylonitrile +12%, polysulfone +7%). 'Unspecific' proteolytic activity and non-trichloroacetic acid-precipitable small molecular weight plasma protein fraction decreased significantly during hemodialysis in the presence of all four membranes. We conclude that neutral granulocyte proteinases can be released during hemodialysis independent of the change of white blood cells during the 1st h of dialysis therapy.

Acrylic Resins↗

On the clinical deformation of maxillary complete dentures. Influence of denture-base design and shape of denture-bearing tissue.

This paper aimed to study the influence of denture base design and the shape of the denture-supporting area on the functional deformation of maxillary complete dentures. Six strain-gauged duplicate maxillary dentures were made for the study of two test subjects with different shapes of the palatal vault. Each subject was supplied with two polymethyl methacrylate dentures, one with a 1-mm-thick palatal base and the other 2 mm thick. A third denture was constructed with a cobalt-chromium base. The functional loading tests included maximum biting and the chewing of the food test samples. An analysis based on chewing time and total number of chewing cycles per test piece was also made. The results showed that surface straining is highly complex at the anterior part of the maxillary dentures constructed from polymethyl methacrylate and that increasing the denture thickness per se might not be accompanied by a reduction of strain. The results also suggest that high thrust to the supporting tissue is produced with high palatal vault dentures made in polymethyl methacrylate. The study proposes that cobalt-chromium bases may be used in maxillary dentures to reduce functional deformation and thrust to the supporting tissues at the anterior part of the maxilla.

Aged↗

[Optimized polymethyl methacrylate-embedding enables exact section examination of the femur with an uncemented femoral stem].

AIM: Embedding of larger bones, as described in this article, is not possible without marked modifications of the methods followed for small, undecalcified bone specimens. Problems such as turbidity of the PMMA, incomplete hardening of the medullary cavity due to insufficient infiltration and, especially, uncontrolled polymerization with excessive bubbling make analysis of the specimens impossible. Thus, modifications with respect to the infiltration times in the individual solutions, the benzoyl peroxide quantities added and the temperature during the polymerization phase were undertaken. METHOD: The infiltrations were performed under vacuum. A cooling circulation was created in a standard water bath with a circulator pump to facilitate extraction of the polymerization heat. The use of PMMA blocks as filling material and polymerization inductors was especially important. RESULTS: There was no turbidity or excessive bubbling of the PMMA in any of the specimens embedded with this method. Analysis of the sections showed a low-bubble medullary cavity with 01 bubble/cm(2). Up to 10 bubbles/cm(2) were observed only in the large cancellous space in the trochanteric region over a length of 56 cm. All bubbles were a maximum of 1.5 mm in size. CONCLUSION: With the described method it is possible to embed large bones in PMMA.

Equipment Design↗

The effect of fiber reinforcement on the fracture toughness and flexural strength of provisional restorative resins.

STATEMENT OF PROBLEM: Fracture of provisional restorations is of concern, especially with long-span fixed partial dentures or areas of heavy occlusal stress. A number of different techniques for reinforcement of provisional restorations have been suggested; however, the effect of these techniques is largely unclear. PURPOSE: The aim of this study was to determine the fracture toughness and flexural strength of different types of provisional restoration resins reinforced with different commercially available fibers. MATERIAL AND METHODS: A total of 105 specimens were prepared in this study for each test; compact tensile specimens for the fracture toughness test and rectangular specimens for the flexural strength test. The specimens were divided into 3 groups according to the type of resin used, Jet, Trim, or Temphase (n=35), and then each group was divided into 7 subgroups (n=5) according to the type of fiber reinforcement, Construct, Fibrestick, Ribbond normal, Ribbond THM, Ribbond triaxial, or Fibrenet. Unreinforced specimens served as the control. Specimens were loaded in a universal testing machine until fracture. The mean fracture toughness (MPa.m(1/2)) and mean flexural strength (MPa) were compared by 1-way analysis of variance, followed by the Tukey standardized range test (alpha=.05). RESULTS: Fibrestick and Construct reinforcements showed a significant increase (P<.0001) in mean fracture toughness over unreinforced controls for all resins tested. Fibrestick increased the polymethyl methacrylate from 1.25+/-0.06 MPa.m(1/2) to 2.74+/-0.12 MPa.m(1/2); polyethyl methacrylate from 0.67+/-0.07 MPa.m(1/2) to 1.64+/-0.13 MPa.m(1/2); and bis-acryl from 0.87+/-0.05 MPa.m(1/2) to 1.39+/-0.11 MPa.m(1/2). Construct increased polymethyl methacrylate to 2.59+/-0.28 MPa.m(1/2); polyethyl methacrylate to 1.53+/-0.22 MPa.m(1/2); and bis-acryl to 1.30+/-0.13 MPa.m(1/2); however, there was no significant difference between Fibrestick and Construct reinforcements in the degree of reinforcement. Similarly the mean flexural strength values were significantly increased by different combinations of fiber and resin (P<.0001). CONCLUSION: The addition of fibers to provisional resin increased both fracture toughness and flexural strength.

Analysis of Variance↗

The effect of glass fiber reinforcement on the residual monomer content of two denture base resins.

OBJECTIVE: The amount of residual monomer is one of the principal factors affecting the properties of acrylic resin denture bases. In recent years, glass fibers have been used to strengthen denture base resins. The purpose of this study was to investigate the effect of glass fiber reinforcement on the amount of residual methyl methacrylate released from two different denture base resins (heat cured and autopolymerized). METHOD AND MATERIALS: Continuous unidirectional and woven preimpregnated glass fiber reinforcements (Stick and Stick Net) were used to reinforce heat-curing and autopolymerizing denture base resins. RESULTS: The release of residual methyl methacrylate from heat-cured and autopolymerized test specimens reinforced with glass fibers was significantly higher than that from unreinforced test specimens. Stick Net glass fiber reinforcement resulted in significantly higher residual monomer release than did Stick glass fiber reinforcement. Test specimens made from heat-cured denture polymethyl methacrylate released less residual methyl methacrylate than did specimens made from autopolymerized polymethyl methacrylate. CONCLUSION: Glass fiber reinforcement increases the residual monomer content of denture base resins. The level of residual monomer ranged from 0.11% to 0.37% in heat-cured resin and from 0.18% to 0.46% in autopolymerized denture base resin.

Acrylic Resins↗

Comparison of accuracy between compression- and injection-molded complete dentures.

STATEMENT OF PROBLEM: A clinically significant incisal pin opening may occur after processing complete dentures if a compression molding technique is used. To recover the proper vertical dimension of occlusion, a time-consuming occlusal adjustment is necessary that often destroys the anatomy of the artificial teeth. A new injection molding process claims to produce dentures that require few, if any, occlusal adjustments in the laboratory after processing. PURPOSE: This laboratory study compared incisal pin opening, dimensional accuracy, and laboratory working time for dentures fabricated by this new injection system with dentures constructed by the conventional compression molding technique. MATERIAL AND METHODS: Two groups of 6 maxillary and 6 mandibular dentures were evaluated as follows: group 1 (control), Lucitone 199, compression molded with a long cure cycle; and group 2, Lucitone 199, injection molded with a long cure. Incisal pin opening was measured with a micrometer immediately after deflasking. A computerized coordinate measuring machine was used to measure dimensional accuracy of 3-dimensional variations in selected positions of artificial teeth in 4 stages of denture fabrication. Analysis of variance (ANOVA) and t tests were performed to compare the groups. RESULTS: A significant difference was found in pin opening between groups (t test). Horizontal dimensional changes evaluated with repeated measures ANOVA revealed no significant differences between groups. However, analysis of vertical dimensional changes disclosed significant differences between the groups. There was no appreciable difference in laboratory working time for flasking and molding denture bases between the injection and compression molding techniques when polymethyl methacrylate resin was used. CONCLUSION: The injection molding method produced a significantly smaller incisal pin opening over the standard compression molding technique. The injection molding technique, using polymethyl methacrylate, was a more accurate method for processing dentures. There were no appreciable differences in laboratory working time between the injection and compression molding techniques.

Analysis of Variance↗

Disc extrusion in a Rottweiler dog with caudal cervical spondylomyelopathy after failure of intervertebral distraction/stabilisation.

A Rottweiler dog was presented with an 8 week history of hindlimb ataxia. Neurological examination localised the lesion to the cervical spinal cord. Myelography demonstrated dynamic compressive lesions at C5-6 and C6-7 consistent with a diagnosis of caudal cervical spondylomyelopathy. Distraction/stabilisation of both discs was performed using interbody polymethyl methacrylate. Both implants subsequently failed leading to extrusion of the remaining dorsal annulus fibrosus of the C5-6 intervertebral disc and nonambulatory tetraparesis. A ventral slot combined with distraction/stabilisation using screws and polymethyl methacrylate was performed and resulted in nearly full neurological recovery.

Animals↗

Endotoxin affinity for provisional restorative resins.

PURPOSE: This study compared the relative affinity of Porphyromonas gingivalis and Escherichia coli endotoxin, bacterial cell envelope lipopolysaccharide (LPS), for three provisional resins. MATERIALS AND METHODS: As-polymerized and pumiced polymethyl methacrylate and polyethyl methacrylate resin discs were exposed to 1,000 endotoxin U/mL P. gingivalis or E. coli LPS in water for 24 hours at 37 degrees C, whereas control discs were placed in LPS-free water. LPS-treated discs were transferred at 24-hour intervals to fresh, LPS-free water for up to 96 hours, and the incubated eluates were tested for the presence of LPS. RESULTS: Initial adherence of P. gingivalis LPS to as-polymerized and pumiced-finish resin was a function of resin type, but surface characteristics modified adherence levels. When steady rates of elution were reached at 72 to 96 hours, as-polymerized specimens released significantly greater LPS levels than pumiced samples. Comparison of initial adherence of P. gingivalis and E. coli LPS with pumiced resins showed that adherence was based on a combination of LPS and resin type. P. gingivalis LPS had a greater relative affinity for polyethyl methacrylate, and E. coli LPS has a greater relative affinity for polymethyl methacrylate. Regardless of resin type, P. gingivalis LPS eluted at levels greater than E. coli LPS. CONCLUSIONS: The affinity of LPS for provisional resins seems to be a function of selective interactions based on the chemical nature of the resin, the surface finish of the resin, and the molecular structure of the LPS.

Analysis of Variance↗

Intrapelvic granuloma formation six years after total hip arthroplasty in a dog.

A 9-year-old Golden Retriever that had undergone left total hip arthroplasty 6 years previously was evaluated because of constipation and tenesmus. Abdominal radiography and ultrasonography revealed a large intrapelvic mass that was contiguous with a mass of polymethyl methacrylate that had been extruded through a defect in the medial wall of the acetabulum at the time of total hip arthroplasty. Clinical signs resolved following resection of the mass and associated polymethyl methacrylate from the pelvic canal. Results of histologic examination of the mass were consistent with a diagnosis of foreign body granuloma, most likely secondary to particulate debris. There was no clinical or radiographic evidence of aseptic loosening of the acetabular or femoral components, and the mass may have represented a response to wear debris.

Animals↗

Percutaneous vertebroplasty: a new technique for treatment of painful compression fractures.

Vertebroplasty is an effective technique in which polymethyl methacrylate, a surgical cement, is injected into a vertebral body. This technique provides increased strength and pain relief in vertebrae weakened by osseous lesions as metastases, multiple myeloma, and aggressive hemangiomas, and from osteoporotic fractures. Infrequent serious complications are mainly related to polymethyl methacrylate leakage into the spinal canal and around vital soft tissue structures. Complications are decreased by careful fluoroscopic guidance and meticulous radiological technique. Indications should be dictated by a multidisciplinary team approach.

Back Pain↗

Enhancement of stability following anterior cervical corpectomy: a biomechanical study.

STUDY DESIGN: An in vitro biomechanical study of various reconstructive techniques following decompression of the spondylotic cervical spine. OBJECTIVE.: To evaluate the biomechanical stability of anterior cervical plate fixation following three strategies of decompression for multilevel cervical spondylosis (three levels) of the cervical spine: three level discectomy, single corpectomy and discectomy, and a two-level corpectomy. SUMMARY OF BACKGROUND DATA: The main goals of surgical treatment for cervical myelopathy include adequate decompression and stabilization while maintaining or restoring cervical lordosis. Cervical decompression is often performed through a corpectomy followed by strut-graft reconstruction. An anterior cervical plate with end-fixation (two points of fixation) is then used to span the construct. The authors propose an alternative to multilevel corpectomy and long-segment end construct plate fixation. Often times, the cervical stenosis is confined to the area of the degenerative discs. As a result, the authors feel that either multilevel discectomy or a corpectomy combined with discectomy followed by segmental plate fixation may provide adequate decompression with increased biomechanical rigidity as compared to cervical plate-constructs with end-fixation only. METHODS: Seven human cadaveric fresh-frozen cervical spines from C1-T1 were utilized. Three-dimensional motion analysis with an optical tracking device was used to determine motion following various reconstruction methods. All seven cervical spines underwent testing in a randomized order. The end construct model consisted of a corpectomy at C4 and C5 with a polymethyl methacrylate strut graft and an anterior cervical PEAK (DePuy-AcroMed) plate. The two segmental constructs also utilized the PEAK plate with one construct undergoing discectomies at C3-C4, C4-C5, and C5-C6 with polymethyl methacrylate interbody grafts and the other segmental construct undergoing a discectomy at C3-C4 and a corpectomy of C5. All specimens underwent a pure moment application of 2 Nm with regards to flexion-extension, lateral bending, and axial rotation. RESULTS.: The three-level discectomy and combined one-level discectomy and corpectomy with segmental fixation was significantly more rigid in flexion-extension and lateral bending than the two-level corpectomy with end-construct plate fixation (P < 0.05). There was no increase in stability during extension between the end construct (two-level corpectomy) reconstruction model and the un-instrumented corpectomy and grafted specimen. No difference was noted between the segmental constructs and the end-construct with regards to axial rotation. CONCLUSIONS: Cervical myelopathy is traditionally treated with a multilevel corpectomy and an end-construct plate fixation spanning the strut graft. A large moment arm is generated at the ends of the construct, potentially leading to plate migration or dislodgment. Often times, adequate decompression can be achieved with either a multilevel discectomy or a combined discectomy and corpectomy with segmental plate fixation. This study clearly demonstrates that segmental plate fixation affords a more biomechanically rigid method of reconstruction with regards to flexion-extension and lateral bending than end-construct plate fixation. The increased rigidity afforded by segmental fixation may significantly decrease the likelihood of plate dislodgement in the setting of anterior instrumentation alone following anterior alone, long segment reconstruction procedures.

Biomechanical Phenomena↗

Strength determination of periodontal splints fabricated from acid-etched retained materials.

Six systems (one polycarboxylate, one polymethyl methacrylate, one unfilled BIS-GMA resin, two combinations of methyl cyanoacrylate and polymethyl methacrylate, and one combination of unfilled BIS-GMA and filled composite resin) were evaluated for in vitro retention to acid-etched human enamel. Also tested were one unfilled-filled resin combination backed by perforated orthodontic band metal and another unfilled resin backed by stainless steel wire mesh. Significant differences in retention were found. Results show that retention depends pril surface and to resist subsequent chemical degradation.

Acid Etching, Dental↗

Staged exchange arthroplasty for shoulder sepsis.

Eight patients with shoulder sepsis were treated with staged exchange arthroplasty using antibiotic-impregnated polymethyl methacrylate spacers shaped and fitted to the patient's anatomy after extensive joint débridement. Intravenous antibiotic therapy followed for a minimum of 3 months. At the end of 6 months, the patients were evaluated for any clinical or laboratory signs of infection; none were encountered. Exchange prosthetic reconstructions were performed using standard implants fixed with antibiotic-impregnated polymethyl methacrylate cement. Three patients underwent a revision to total shoulder arthroplasty, whereas 5 underwent hemiarthroplasty of the humerus with local capsular flap covering of the glenoid. All patients experienced substantial pain relief and improvement in function despite limited total overhead motion, showing this technique to be a satisfactory salvage procedure for managing sepsis of the glenohumeral joint primarily and after total shoulder arthroplasty.

Adult↗

Effects of relining on long-term marginal stability of provisional crowns.

Provisional resins crowns are commonly placed to protect prepared teeth, but the marginal adaptation of interim crowns has always been a problem. These experiments examined the effects of thermocycling and occlusal loading on relined and unrelined polymethyl methacrylate resin transitional crowns. Three groups of interim crowns were made on a cast metal die tooth preparation; unrelined, relined correction, and paint-on correction. After thermocycling and occlusal loading of the specimens, the change in mean marginal gap was significantly greater for the unrelined group. Axial changes were greatest for relined group and least for the unrelined group. These results suggested that relining of polymethyl methacrylate interim crowns can be useful to prevent increases in marginal gap width during extended intraoral periods.

Analysis of Variance↗

Biological response to a supraDescemetic synthetic cornea in rabbits.

OBJECTIVE: To evaluate the biocompatibility of a novel nonpenetrating keratoprosthesis (supraDescemetic synthetic cornea) in a rabbit model. METHODS: Seven rabbits received a supraDescemetic synthetic cornea (7-mm diameter, 350-microm-thick optical zone, 100-microm-thick peripheral flange) in their healthy right eyes. A surgical technique was developed that allowed implantation of the device on top of the bare Descemet membrane. Three rabbits received a supraDescemetic synthetic cornea made of hydroxyethyl methacrylate-methyl methacrylate(26), 1 received a hydroxyethyl methacrylate-N-vinyl pyrrolidone(75) mesoplant, and 3 were implanted with devices made of polymethyl methacrylate. All rabbits were euthanized after 8 weeks; the eyes were enucleated and examined by conventional histological and immunohistochemical evaluations. RESULTS: All eyes became quiet within several days. The Descemet membrane remained transparent during the observation period. Indirect ophthalmoscopy performed through the prosthesis allowed accurate examination of the posterior pole. Histological evaluation of the implanted corneas displayed no signs of an acute or chronic inflammatory reaction to the supraDescemetic synthetic cornea in 5 eyes; a few inflammatory cells were detected in the corneas of 2 rabbits. The interface between the Descemet membrane and the mesoplant displayed ingrowth of very thin (<10-microm) tissues colonized by keratocytes in 3 of the 7 corneas. CONCLUSIONS: This study validates the biocompatibility of this new type of nonpenetrating keratoprosthesis. Because opening of the anterior chamber is not required with the supraDescemetic synthetic cornea, the risk for intraocular infection is minimal, and the implantation procedure is less traumatic compared with a penetrating device.

Animals↗