Proprietary Materials Research Articles

Marginal fidelity of crowns fabricated from six proprietary provisional materials

Statement of problem. The most important requirement for an interim crown is suitable marginal adaptation. Purpose. This in vitro study compared vertical discrepancies of margins for complete crowns made with six provisional materials (Provipont, Protemp Garant, Unifast LC, Triad VLC, Splintline, and Jet). Material and Methods. A direct technique was used to fabricate 60 provisional complete crowns on prepared molars with a polyvinyl siloxane impression and a vacuum-formed polypropylene sheet as matrices. A measuring microscope was used to measure vertical marginal discrepancies at ×100. Data were analyzed with Kruskal-Wallis one-way analysis of variance and Mann-Whitney U tests (α = 0.05). Results. Significant differences were found between resinous materials tested ( p = 0.0002) and multiple comparisons tests indicated no significant difference between Splintline and Protemp Garant; Provipont, Unifast LC, and Triad VLC; and Unifast LC, Triad, and Jet provisional materials. Conclusions. This study indicated that provisional crowns fabricated with Splintline and Protemp Garant interim restorative materials recorded the least marginal discrepancies. (J Prosthet Dent 1997;77:482-5.)

Performance properties of concrete repair materials

Maintenance, repair and strengthening of concrete structures has become a very important part of the activities of the concrete industry. This is reflected in the innumerable proprietary repair materials available in the market and the substantial increase in the number of firms offering specialist maintenance and repair services. Because proprietary compounds are relatively expensive and because the life cost of a repaired structure is also potentially very high, there is much need to provide engineers and specifiers with independent data with which to make appropriate decisions in this field. This paper presents information which arises from a large project on the evaluation of the performance and durability of repair materials being carried out at the Civil Engineering Materials Unit, University of Leeds. The paper includes data on the performance related properties of the following materials: 1. 1. a commercial pre-packed cementitious material; 2. 2. a commercial pre-packed cementitious material modified with polymer; 3. 3. a pozzolanic cement containing 70% ordinary Portland cement and 30% pulverised fuel ash; 4. 4. an ordinary Portland cement containing a commercial organic corrosion inhibitor. The test carried out for evaluation of the repair materials were: compressive strength, bond strength, porosity and permeability The laboratory results are discussed and the implication of potential performance of the repair materials evaluated.

Evaluation of Cold Mixes for Winter Pothole Repair

The performances of 13 proprietary cold-mix patching materials, 4 of which are currently approved under the Virginia Department of Transportation's Special Provision for High Quality Cold Patching Materials, were evaluated. Cold-mix patching materials are regularly submitted to the Materials Division for approval. The purpose of the evaluations was to determine which of the submitted materials were of the same caliber as the approved materials. The addition of materials of equal quality will promote competition in the competitive bid system. Three test sections were placed to evaluate the materials' performance. A standardized evaluation form and performance model were developed to rank the materials. The field performance results were compared with laboratory test results in an effort to develop a laboratory screening test. Design and quality control procedures were identified. These procedures were used to design a material that has performed well.

Evaluation of Cold Mixes for Winter Pothole Repair

The performances of 13 proprietary cold-mix patching materials, 4 of which are currently approved under the Virginia Department of Transportation's Special Provision for High Quality Cold Patching Materials, were evaluated. Cold-mix patching materials are regularly submitted to the Materials Division for approval. The purpose of the evaluations was to determine which of the submitted materials were of the same caliber as the approved materials. The addition of materials of equal quality will promote competition in the competitive bid system. Three test sections were placed to evaluate the materials' performance. A standardized evaluation form and performance model were developed to rank the materials. The field performance results were compared with laboratory test results in an effort to develop a laboratory screening test. Design and quality control procedures were identified. These procedures were used to design a material that has performed well.

Characterization of some proprietary soft lining materials

The physical and mechanical properties of a series of commercial denture soft lining materials have been investigated. The materials were selected to provide a representative sample of the materials widely used for this application. A total of seven products were evaluated including established and widely used acrylic and silicone materials as well as newer polyphosphazine and fluoroelastomer materials. The objective of the study was to determine minimally acceptable and desirable levels for each property which could be used as criteria or standards for the selection of proposed new materials. The results identified several areas requiring attention and future work. In particular, the importance of using fully-water-equilibrated specimens was emphasized for acrylic polymers where large property changes occurred between wet and dry conditions, and in the case of the polyphosphazine materials where the long time required for full equilibration may lead to understimates of the changes involved. Based upon the properties as measured, recommendations for appropriate standard level for each property are offered.

Electrode-dielectric interface in thin-film DRAMs for ULSI

Abstract Mechanisms of leakage currents and d.c. breakdown are reviewed for several high-dielectric films in prototype use for ULSI DRAMs, including barium strontium titanate, lead zirconate titanate, and proprietary materials, with special emphasis upon electrode interface phenomena. The early theory of Von Hippel is reviewed, and attention is paid to the modified boundary conditions to the thermal breakdown equation given below for the finite dimensions of capacitors in real ULSI DRAMs (EB is the breakdown field):

1 kW PAFC stack: a case history

The activity on PAFC technology at the CNR Institute for Transformation and Storage of Energy started in 1983. In recent years, the research has been carried out within the framework of national programmes (ENEA-Progetto Volta). The aim was to design, build and test a 1 kW power unit, integrated with a methanol reforming unit of the same size. Development of this prototype has progressed successfully: the development of proprietary component materials (catalyst, electrodes and matrix) and engineering systems has been achieved. Scale-up of cells from laboratory size (a single cell of 72 cm 2) to a 100 W stack (six cells of 200 cm 2) and to 1 kW, (25 cells of 400 cm 2, air cooled) has been successful. The present analysis is used to emphasize the different steps which have carried us to this goal.

Water sorption and mechanical properties of light-cured proprietary composite tooth restorative materials

Seven light-cured proprietary composite restorative materials, P-50 (3M), P-10 (3M), P-30 (3M), FulFil (Caulk), Herculite (Kerr), Silux Plus (3M) and Silux (3M) were characterized in terms of water uptake at 37°C. For several of the systems, elastic modulus and glass transition temperature were evaluated with a dynamic mechanical analyser (Autovibron DDV-II-C). Model systems such as bis-GMA (75%) + triethylene glycol dimethacrylate (25%), bis-GMA (30%) + triethylene glycol dimethacrylate (10%) + lithium aluminium silicate (60%), bis-GMA + triethylene glycol dimethacrylate (14%) + barium glass (silanated) (86%) and bis-GMA + triethylene glycol dimethacrylate (14%) + zinc glass (silanated) (86%) were also studied with reference to water sorption. It was concluded that the changes in elastic modulus tend to confirm the hypothesis that the matrix-filler interface contains water. Silux and Silux Plus accommodated the greatest amount of water at the interface. Silux Plus displayed a dramatic reduction in elastic modulus c. 0°C, indicating possible melting of water clusters. It appeared that the only available hole for water clusters was at the matrix-filler interface.

Dimensional stability of condensation silicone rubbers

The linear shrinkage during 24 h after setting of a number of proprietary condensation silicone dental impression materials was studied. Weight loss and change in volume were measured over the same time period by weighing similar specimens in air and water. The weight-loss data conformed to a linear t 1 2 plot, indicating that the loss of volatile material was diffusion controlled. From the diffusion coefficient so determined, linear shrinkage values predicted from the weight loss data were compared with the experimental results. For all except the highly-filled putty materials, the correspondence between theoretical and experimental data was reasonable; in the case of the putty materials, the shrinkage was very much greater than that predicted theoretically. This is possibly due to elastic memory effects consequent on moulding the putty materials.

Methylene blue sensitized dichromated gelatin holograms: a new electron donor for their improved photosensitivity

Tetramethylguanidine (TMG) used as the electron donor in conjunction with methylene blue sensitized dichromated gelatin (MBDCG) can produce bright reflection holograms recorded at 633 nm at an exposure level of 50 mJ/cm(2). Thus DCG hologram recording and some independence from suppliers of proprietary holographic recording materials is now open to all those with low power He-Ne lasers. The high alkalinity of the system allows the unexposed coated material to have an effective lifetime at room temperature of weeks rather than days. Its low dichromate content has an environmental advantage over the usual DCG formulations. Replacement of methylene blue by eosin can produce similar photosensitivity to 514 nm. The superiority of TMG over previously reported electron donors used with MBDCG is discussed.

Water sorption of plasticized denture acrylic lining materials

The objective was to characterize water sorption of plasticized denture acrylic lining materials, with determination both of uptake and diffusion coefficient (D). Feasibility was investigated first for simple binary mixtures of poly(methyl methacrylate), PMMA, and various phthalate plasticizers prepared by radiation polymerization of methyl methacrylate/plasticizer solutions. These were shown to be tractable when samples were saturated with water and then characterized in desorption measurements. Plasticizers were found to decrease the uptake of water. This decrease was attributed to the hydrophobic nature of the plasticizers and also to their ability to fill microvoids in PMMA which, in their absence, would be available to water. Values of D increased monotonically with increasing volume fractions of plasticizer. It appeared that values of D increased more rapidly in cases where large proportions of plasticizer resulted in samples which were above their glass transition temperature, Tg, at the temperature of testing water sorption. Desorption measurements were extended satisfactorily to a model system made from poly(ethyl methacrylate) powder, methyl methacrylate, and dibutyl phthalate, which was polymerized with a conventional redox initiator. Water desorption results were compared with various proprietary materials which were also characterized with respect to Tg and, cursorily, to composition.

Characterization and development of transducer elastomers

The failure of underwater transducers is often related to problems with the materials used, such as elastomers, ceramics, adhesives, coatings, and fill fluids. The general practice has been to select proprietary materials from different commercial sources, and use them as they are available for the fabrication of a transducer. Such practices allow the designer very little control of the quality of the materials. The result is the production of devices that are doomed to fail because they are nonreproducible, or contain materials incompatible to each other. In recent years, improper choices of elastomer have been typical in causing large numbers of failure in sonar transducers. Research efforts at NRL-USRD have therefore been focused on the development of composition—property relationships for elastomers by using well-characterized samples. Instrumentational techniques were developed for the analysis of chemical and acoustical properties. These techniques were subsequently used for materials evaluation and quality control. Based on these research results, specialty elastomers were also successfully developed for specific transducer applications. [Work supported by ONT and NAYSEA.]

Effect of Two Polymeric Coatings on Fruit Quality of ‘Bartlett’ and ‘d’Anjou’ Pears

Abstract ‘Bartlett’ and ‘d’Anjou’ pears (Pyrus communis L.) coated with either Pro-long or Nutri-Save, two proprietary fruit-coating materials, were firmer, higher in titratable acidity, and greener in skin color than noncoated fruit stored in air at 0°C. Coated fruit were, in most instances, comparable to noncoated fruit stored in controlled atmospheres (CA). The incidence of core breakdown in ‘Bartlett’ pears and superficial scald in ‘d’Anjou’ pears were lower in coated fruit than in noncoated fruit kept in air storage. The incidence of scald in CA-stored noncoated fruit was usually comparable to and sometimes lower than in the air-stored coated fruit. Normal fruit ripening, however, was adversely affected by the coating compounds, particularly in ‘Bartlett’ pears. Coated ‘Bartlett’ pears tended to develop a blotchy appearance of green interspersed with yellow when held at ripening temperatures.

Slow crack propagation in a heavily‐filled particle reinforced epoxide resin

AbstractThe fracture properties of two proprietary composite dental restorative materials and a model composite system were studied to determine the effects of filler concentration, exposure to water, and particle/polymer adhesion on subcritical crack propagation. Particle content ranged from 36 to 60 volume percent. The double torsion (DT) test was used to measure relationships between the stress intensity factor (K1) and the speed of decelerating cracks or the rate of loading in dry and wet materials in air at laboratory conditions. Materials with weak particle/polymer interfaces fractured by continuous crack growth in both dry and wet conditions. In dry and wet materials with strong interfaces, continuous cracking also occurred at the low end of the range of speeds observed (10−7 to 10−3 m/s), but under test conditions of high crack speeds unstable (stick‐slip) crack propagation was found in dry specimens and in wet model composites with 41 percent vol, filler. Water had a corrosive effect lowering K1c for continuous crack propagation. The exponential dependence of K1c on crack velocity, representing the viscoelastic response of the materials, was positively correlated to the filler concentration and the plasticizing effect of water. Observations on fracture surfaces indicate that low velocity cracks (<10−5 m/s) propagate through regions of high stress concentrations (interfaces, corners, pores) while at higher crack velocities failure occurs by a combination of interparticle and transparticle fracture.

Weight loss of four calcium hydroxide-based materials following a phosphoric acid etching and washing cycle

Four proprietary calcium hydroxide lining materials were subjected to a phosphoric acid etching and washing cycle similar to that which occurs during clinical procedures. It was found that one material suffered greater weight loss than the remaining three materials.

The development of high impact strength denture-base materials

In the present work novel reinforcing systems for poly(methylmethacrylate) have been developed based on low-molecular-weight (15–35 000) polybutadiene-based polymers with suitable reactive end-groups for grafting. A range of copolymers was prepared with varying amounts of the polybutadiene-based polymer as the bead component of a denture-base resin system. The actual polybutadiene content of the bead phase was also varied by blending the copolymer with ordinary poly(methylmethacrylate). Multifactorial experiments were carried out on a number of such systems, and evaluated with respect to impact strength, Young's modulus and viscoelastic properties. Denture-base materials have now been developed which have properties comparable to the best of existing proprietary materials. The advantage of using low-molecular-weight polybutadiene-based materials is that they can be added to methylmethacrylate monomer, without greatly affecting viscosity, and hence do not require modified techniques for polymerization.

Water absorption characteristics of dental microfine composite filling materials: I. Proprietary materials

Long-term water absorption characteristics have been studied for four microfine composite filling materials over a period of some three years. By measuring gravimetrically the kinetics of successive absorption/desorption cycles, equilibrium uptake, diffusion coefficients, and solubility data have been obtained. Equilibrium uptake and solubility data are best rationalized if expressed as volume/volume rather than weight/weight. Diffusion coefficients were similar to those obtained previously for conventional composites.

Effects of surface characteristics and water on the bonding of soft lining materials to PMMA

Abstract An analysis was made of the effect of surface characteristics and water on the physical and mechanical bonding properties of five proprietary resilient lining materials to polymethylmethacrylate. After storage in water at 37°C for four months, the prepared specimens were examined using tensile, shear, and T-peel tests to measure the possible changes in the efficiency of the liner/acrylic joint and the resistance of bonding to various external damaging loads. It was found that the water absorbed by the liners resulted in marked reduction in their bonding to acrylics.

Conversion in different depths of ultraviolet and visible light activated composite materials.

Studies by means of infrared multiple internal reflection spectroscopy of ultraviolet and visible light polymerized composite resin materials indicated that the degree of conversion below the surface is nearly constant for most of the materials investigated until a depth is reached where the degree of conversion rapidly decreases. The maximum depth of cure has also been measured for some proprietary dental composite resin materials. This investigation has demonstrated that the conversion at different depths and the maximum curing depth are dependent on the composition of the composite filling material, light source, and exposure time. With respect to the activating system it was found that with visible light activated materials larger curing depths were obtained than with ultraviolet light activated materials. Better results with respect to curing depth were also obtained with materials containing conventional inorganic fillers than with those containing so-called microfillers.The limiting factor for tota...

Development of blood-compatible elastomers. V. Surface structure and blood compatibility of avcothane elastomers.

The Avcothane 51 elastomer, a member of a series of proprietary materials best characterized as polyurethane/poly(dialkylsiloxane) block copolymers, displays considerable hemocompatibility without any incorporated anticoagulants. In the form of intra-aortic balloons, the elastomer was implanted in several thousands of cardiac patients without intolerable hematologic effects. Hemocompatibility has been assumed to result from a predominantly dispersion-type surface force field whose intensity fluctuates within small domains, maintaning adsorbed blood proteins in an unstable state. The relative hemocompatibility of films, which were obtained from a prepolymer solution cast on substrates impenetrable to the solvent, is a function of the effective surface molecular structure. This can vary as a function of preparative conditions (temperature and rate of evaporation), and has been correlated with an anisotropic distribution of the silicone component in cured films. The concentration of this component in surface layers was quantified independently by IRATR spectroscopy and electron-microprobe analysis, giving consistent results. An IRATR index, which is computed from the ratio of absorptivities measured at 13.00 and 12.62 mu and is inversely proportional to the relative silicone content of surface layers, was found to correlate with the apparent hemocompatibility determined by different in vitro methods. Optimized reproducible hemocompatibility is attained by strict process controls.