New types of synthetic infusion solutions. III. Elimination and retention of poly-[N-(2-hydroxypropyl)methacrylamide] in a test organism

The elimination and retention of a new, fully synthetic plasma prosthesis of Czechoslovak origin under the working name of Duxon (poly[N-(2-hydroxypropyl)methacrylamide]) was investigated in experiments on rabbits by using a 14C-labeled polymer. Results published earlier on elimination have been confirmed and extended. Retention was examined after repeated application. The effect of molecular weight prevailed both in elimination and in retention. Polymers of lower molecular weights, which possess a good therapeutical effect, are not permanently deposited in the organism.

Soft lining materials: composition and structure

An analysis of five proprietary acrylic soft lining materials revealed that they can be classified into two groups. The first of these groups (Soft Oryl and Coe Soft) resemble the tissue conditioners in composition in that their liquid component contains no monomer. A study of their mechanical properties may reveal that these materials should, in fact, be classified as tissue conditioners. The second group (including Palasiv, Virina and Coe Super Soft) were more conventional acrylic materials which differed in the amount of plasticizer and the type of acrylic monomer used in the liquid component and in the nature of the polymer component.

Characterization of cross-linked two-phase acrylic polymers

A cross-linked network was formed in the particulate disperse phase carried over from the soluble pearls only in one material tested (L). The preparation of this material involved a slow rate of polymerization that allowed sufficient time for imbibition of the cross-linking monomer by the particles. In two of the materials (CR and S), the particulate phase was extractable and the remaining cross-linked matrix could be characterized for equilibrium swelling by volumetric measurements. Equilibrium swelling values were used to estimate densities of elastically effective chains in the network.

Elution of cadmium from dentures

Heat-cured, pink-pigmented (light veined) Stellon maxillary acrylic denture blanks were shaken in 150 ml synthetic saliva varied from 0.15 to 1.05 mug independently of elution time. With o.1N CH3COOH the amount of cadmium, varying from 1,20 to 2.55 mug, increased slowly with elution time. Another batch of Stellon gave higher values in 0.1N CH3COOH.

NMR-analysis of monomers in restorative resins

A study on the composition of the resin component of the several brands of composite resin has not been published so far. It was the purpose of the present work to fill out this gap in our knowledge of this important group of restorative materials by analyzing the monomers of the materials as delivered by the manufacturers. 24 brands of restorative resins were investigated by means of a Nuclear Magnetic Resonance spectrometer at 90 MHz. Spectra were taken of deuterated chloroform solutions of the organic part of the filling materials and compared with spectra of pure monomers that were conceivable constituents of the investigated brands. It was found that the BIS-GMA containing brands all contain at least one other monomer, most often TEDMA, in varying concentrations. The brands with MMA as main component in most cases also contain other monomers.

Shear strength of self-curing acrylic cement

The average shearing strength of surgical Simplex P bone cement has been experimentally evaluated and found to be 5,762 plus or minus 180 psi. The average shearing strength for compact bone is about 10,000 psi. Therefore surgical Simplex P does not resist shear forces as well as compact bone and should not be used as a substitute for bone whenever possible. The inclusion of 10 per cent barium sulfate U.S.P. for radiographic purposes does not adversely affect the shear strength of the cement. This amount of barium is the same percentage by weight as that found in radiopaque Simplex P in clinical usage today. Varying the loading rate between 0.005 and 0.5 in/min slightly affected the magnitude of the shear force at failure. A comparison of the effect of short term curing times on the magnitude of the shear force at failure reveals that surgical Simplex P strengthens with time. The curing periods varied from 2 to 168 hours.

Quartz fiber ultramicrobalance

Design and operation of a quartz fiber cytoanalytical balance are described. The 2-µ fiber, 3-4 mm long, is mounted in a V-shaped notch in an aluminum slide for use on an ordinary microscope. The deflection is measured with the focusing adjustment by viewing through thin glass windows, which are flush with the surfaces of the slide. Since the opening to the balance faces away from the operator, weighings can be made without closing the balance and removing time manipulator needles employed for handling the specimens. Transverse sections of single muscle cells, 0.1 µg after freeze-drying, can be weighed to within 3% under ordinary atmospheric conditions.

Use of mathematical models in the study of structure-toxicity relationships of dental compounds. I. Esters of acrylic and methacrylic acids

The toxicity of a series of esters of acrylic and methacrylic acids was determined in groups of mice, and the resultant LD50 values were analyzed with the use of the mathematical models of Free and Wilson and of Hansch to relate structure of the compounds to toxicity. Both models proved valuable in relating structures to toxicity parameters, but the more useful method for predicting toxicity was the Hansch model.

Punch-shear test for dental purposes

Average shear stress may be calculated from the force required to punch a cylinder out of a disk or plate of material. Tests on aluminum and methacrylate sheets enabled the comparison of dental restoratives with human dentin. Human dentin was found to have a greater shear strength than dental restoratives other than gold alloys.