PURPOSE: The aim of this study was to evaluate the effect of delayed time, surface treatment, and repair materials on repair of bisacryl composite resin through comparison of shear bond strength and to evaluate the utility of bis-acryl composite resin repair using polymethyl methacrylate resin. MATERIALS AND METHODS: A total of 90 bis-acryl composite resin specimens were fabricated and classified into 9 test groups, each of 10 pieces according to delayed time, surface treatment and repair material. The shear bond strength of each specimen was measured using a universal testing machine immediately after fabrication and analyzed using a statistical analysis program (IBM SPSS statistics 20). After the shear bond strength measurement, the fracture surface of the specimen was observed. RESULTS: The highest shear bond strength (17.54 ± 3.14 MPa) was observed in the experimental group bonded immediately with a light-curing flowable composite resin using a bonding agent. CONCLUSION: When repairing bis-acryl composite resin, it is necessary to consider whether to remake according to the delayed time. For effective repair, it is desirable to consider appropriate materials and surface treatment methods according to the site or purpose of use.
Polymethyl Methacrylate

The author performed an experiment to measure the bonding strength of acrylic bone cement when the bonding surfaces of bones were under various conditions; namely different axial compression forces and different means of preservation of bones, in the air and in Hartman's solution. Mechanical tests for compression forces revealed that the bonding strength was greatest when the bonding surfaces were dry, being weaker when soaked with alcohol and whole blood, in that order. When different strengths of axial compression forces were applied, the bonding strength was greatest at 5 kg of compression force, being weaker at 3 kg and 1 kg, in that order. The bonding strength was greater when the bones were preserved in the air than in Hartman's solution.
Polymethyl Methacrylate

There have been many investigations on non-biodegradable materials acting as an antibiotic carrier for local drug delivery systems based on polymethyl methacrylate (PMMA) beads. However, the material is non-degradable and non-porous so that less than 5% of the encapsulated drug is released. In order to obtain better release of the antibiotics, greater porosity of the beads would be required. Adding fillers could increase the bead’s porosity, thus improving the antibiotic release from the beads. The purpose of the study is to optimize release kinetics of gentamicin from handmade beads by adding fillers such as glycine and sodium chloride in different concentrations. Terms of percolation theory will qualitatively be applied in interpreting the final results. Model beads were made by blending the antibiotics (gentamicin) with powdered PMMA, prepared with the inclusion of glycine and different concentration of sodium chloride in 100% monomer. To determine the gentamicin release, beads were placed in phosphate buffered saline (PBS) and aliquots were taken at designated times to measure the gentamicin concentration. Addition of glycine yielded 16 % release of the total amount of gentamicin incorporated in 24 hours. Subsequent addition of sodium chloride resulted in an increased gentamicin release, with little or no difference in gentamicin release once 16 g or more sodium chloride was added (gentamicin release 100% of the amount incorporated). In conclusion, addition of glycine and sodium chloride resulted in an increased release of gentamicin; however, the combination without sodium chloride seemed to have an inhibitory effect on the gentamicin release.
Polymethyl Methacrylate

No abstract available.
Polymethyl Methacrylate*

PURPOSE: To design and test the CT simulator phantom for geometrical test. MATERIAL AND METHODS: The PMMA phantom was designed as a cylinder which is 20 cm in diameter and 24 cm in length, along with a 25x25x31 cm3 rectangular parallelepiped. Radio-opaque wires of which diameter is 0.8 mm are attached on the other surface of the phantom as a spiral. The rectangular phantom was made of four 24x24x0.5 cm3 square plates and each plate had a 24x24 cm2, 12x12 cm2, 6x6 cm2 square line. The squares were placed to face the cylinder at angles 0degrees, 15degrees, 30degrees, respectively. The rectangular phantom made it possible to measure the field size, couch angle, the collimator angle, the isocenter shift and the SSD, the measurements of the gantry angle from the cylindrical part. A virtual simulation software, AcQSimTM, offered various conditions to perform virtual simulations and these results were used to perform the geometrical quality assurance of CT simulator. RESULTS: A 0.3~0.5 mm difference was found on the 24 cm field size which was created with the DRR measurements obtained by scanning of the rectangular phantom. The isocenter shift, the collimator rotation, the couch rotation, and the gantry rotation test showed 0.5~1 mm, 0.5~1degrees0.5~1degrees, and 0.5~ 1degreesdifferences, respectively. We could not find any significant differences between the results from the two scanning methods. CONCLUSION: The geometrical test phantom developed in the study showed less than 1 mm (or 1degrees) differences. The phantom could be used as a routine geometrical QC/QA tools, since the differences are within clinically acceptable ranges.
Polymethyl Methacrylate ; Silver Sulfadiazine

The purpose of this paper is to describe a new apparatus which utilizes the principle of Van Tieghems hanging drop culture method. After using various methods of culturing fungi authors have found van Tieghems method to yield the most satifsymg result. Until now, this method has been slightly more tedious due to durability, storage, and quantity of culture necessary for each species. The new apparatus consists of 20mm plexiglass tubing cut in 16mm lengths and attache to a 16cm x12cm x2mm plexiglass plate with paraffin or manicure. These tubes a.re ranged in rows approximately 6cm apart with at least 8mm between tubes. Plates of varying sizes can be made to accornodate specific experimente. The authors developed thse inexpensive unbreakable plexiglass plates to allow for aimultaneous growth of various fungi and therefore more accurate comparison. Since these plates can be stored and handled easily, most af the disadvantages of using van Tieghems hanging drop culture rnethod have been eliminated.
Fungi ; Paraffin ; Polymethyl Methacrylate*

STATEMETN OF PROBLEM: The viscoelastic property is the most important and peculiar charac-teristics of soft liners. But the authorized standard is not certainly established than other den-tal materials. PURPOSE OF STUDY: This study is aimed to compare the initial flow of gelation of the modified soft liner with 4-META with that of PMMA soft liners using dynamic method and evaluate the clinical acceptance of the trial materials. MATERIAL AND METHOD: This study consists of 3 groups with the given % of 4-META powder in the Coe soft liquid; 0%, 5%, 10% Each group was tested for 10 times to record the change of G'values during 3 hours. the gelation time was recorded by the oscillating rheometer with parallel plate with 1 rad/sec. RESULTS: As the results of this study, the gelation time of modified soft liner was elongated by 5 to 6 minutes. CONCLUSION: The mean gelation time of modified soft liner could be within the range of clin-ically acceptable.
Polymethyl Methacrylate ; Rheology*

The purpose of this study was to measure and evaluate radiation dose for MDCT parameters. Patient dose for various combination of MDCT parameters were experimentally measured, using MDCT (GE light speed plus 4 slice, USA), model 2026C electrometer (RADICAL 2026C, USA), standard Polymethylmethacrylate (PMMA) head and body CT dosimetry phantoms. In clinical situations, for a typical abdominal scan performed with MDCT at 120 kVp, 180 mAs, 20 mm collimation, and a pitch of 0.75, CTDIw, CTDIvol were measured as 20.2 mGy, 26.9 mGy, respectively. When scan length is assumed as 271.3 mm, DLP and measured effective dose of the abdominal would be calculated as 729.1 mGy cm, 10.9 mSv, respectively.
Head ; Humans ; Polymethyl Methacrylate

OBJECTIVE: The authors evaluate the differences in the pedicle screw pull-out strength between an unaugmented screw and a screw augmented by high pressurized PMMA in an embalmed human lumbar cadaveric spine. METHODS: Pedicle screws were inserted in the 50 pedicles of cadaver lumbar spine after measuring the bone mineral density(BMD) of the specimens. The pedicle screw was inserted without augmentation on the left pedicle and with augmentation by a vertebral reconstruction with high pressurized PMMA on the right side. The pedicle screw was inserted before the hardening of bone cement on the right side. A computed tomographic scan was done to evaluate the location of the PMMA and PMMA/ screw interface. After that, a screw pullout strength test was performed. RESULTS: There were positive correlations between the pull-out strength and BMD in the control group (r=0.7339). The average pull-out strength of the augmented group was 168% greater than that of the control group(p<0.05). The pull-out strength of the augmented group was correlated with in the volume of the PMMA. CONCLUSION: A pedicle screw that is augmented with PMMA will provide a more rigid fixation than that of an unaugmented screw, especially in the low BMD group of the specimens.
Cadaver* ; Humans ; Polymethyl Methacrylate ; Spine

The purpose of this study was to evaluate the bond strength of reline resin to pressure injection type thermoplastic denture base resin.The denture base resins used in this study were Hipolycarbonate(High Dental Co.,Japan),Acetal dental(Pressingdental s.r.l.,Repubblica di San Marino)of thermoplastic resin and Acron MC(GC Dental Industrial Co.,Japan)of heatcured resin.The reline resins used were Lucitone 199(Dentsply international Inc.,USA),Tokuso rebase(Tokuyama Corp.,Japan),and Lightdon-U(Dreve-Dentamid-Gmbh,Germany).The reline resins are representative of heat-cured,self-cured,and light-cured resin respectively.Bond strength was examined by use of a three-point transverse flexural strength test. The results were as follows: 1.The bond strength of Lucitone 199 to Acron MC was the highest. 2.The bond strengths of Lucitone 199 and Tokuso rebase to Hi-polycarbonate resulted in a value of approximately one half that of Lucitone 199 to Acron MC,and there were no significant differences between these and the bond strength of Tokuso rebase to Acron MC(p<0.05). 3.The bond strengths of reline resins to Acetal dental were lower than those of reline resins to Hi-polycarbonate. 4.For all base resins Lightdon-U showed lower bond strength than the other reline resins.
Denture Bases* ; Dentures* ; Polymethyl Methacrylate