A. Koran

Physical property comparison of 11 soft denture lining materials as a function of accelerated aging

Soft denture-lining materials are an important treatment option for patients who have chronic soreness associated with dental prostheses. Three distinctly different types of materials are generally used. These are plasticized polymers or copolymers, silicones, or polyphosphazene fluoroelastomer. The acceptance of these materials by patients and dentists is variable. The objective of this study is to compare the tensile strength, percent elongation, hardness, tear strength, and tear energy of eight plasticized polymers or copolymers, two silicones, and one polyphosphazene fluoroelastomer. Tests were run at 24 hours after specimen preparation and repeated after 900 hours of accelerated aging in a Weather-Ometer device. The data indicated a wide range of physical properties for soft denture-lining materials and showed that accelerated aging dramatically affected the physical and mechanical properties of many of the elastomers. No soft denture liner proved to be superior to all others. The data obtained should provide clinicians with useful information for selecting soft denture lining materials for patients.

Color Stability of Restorative Resins Under Accelerated Aging

The color stability of seven commercial composite resins, an unfilled resin, and three glazes was studied under conditions of accelerated aging by reflection spectrophotometry and visually with Munsell color tabs. After aging for 900 hours, most of the resins had lower values of luminous reflectance and excitation purity and higher values of dominant wavelength and contrast ratio compared to values at baseline.

Color stability of long-term soft denture liners.

The use of resilient denture liners in complete denture construction has become increasingly popular for providing comfort for denture wearers. The primary disadvantage of these materials is that the physical and mechanical properties change rapidly with time in a service environment. The purpose of this study is to evaluate the color stability of five commercially available soft denture liners as a function of accelerated aging. Color measurements were made before aging with a colorimeter and data processor. The samples were then weathered for 100 hours in an accelerated aging chamber in the presence of a xenon ultraviolet visible-light source, an intermittent water spray at 110 degrees F, and 90% humidity. After aging, color measurements were made again and color differences (delta E) were calculated. Results were statistically tested with analysis of variance and Scheffé intervals were calculated at 0.96. It was concluded that accelerated aging can be used to evaluate color stability of soft denture liners.

Sorption and solubility of 12 soft denture liners

The long-term stability of a soft denture liner depends to a large extent on the sorption and solubility of the liner. Because sorption and solubility are accompanied by a volumetric change, bacterial infestation, hardening, and color change, it is a physical property of importance. The purpose of this investigation was to determine the sorption and solubility of 12 soft denture liners (Verno-Soft, Super Soft, ProTech, Soft-Pak, Flexor, Novus, Molloplast-B, Durosoft, Justi Soft, Velvesoft, VinaSoft and Prolastic). They include nine copolymers, two silicones and one polyphosphazene fluoroelastomer. The sorption and solubility test was performed as outlined in American Dental Association (ADA) specification 12 for denture base polymers. Five specimens of each material were tested and data were collected at 1 week, 1 month, 3 months, 6 months, and 1 year. Sorption data varied from 0.2 to 5.6 mg/cm2 at 1 week; 0.3 to 12.5 mg/cm2 at 1 month; 0.1 to 22.0 mg/cm2 at 3 months; 0.1 to 13.6 mg/cm2 at 6 months; and 0.1 to 35.7 mg/cm2 at 12 months. Solubility data varied from 0.0 to 0.4 mg/cm2 at 1 week; 0.1 to 0.8 mg/cm2 at 1 month; +0.1 to 1.2 mg/cm2 at 3 months; 0.0 to 1.9 mg/cm2 at 6 months; and +0.2 to 2.3 mg/cm2 at 1 year. A statistical analysis of the data by two-way ANOVA and calculated Tukey intervals showed significant differences between materials at all time intervals. The results of this study have clinical implications because the sorption and solubility may affect the long-term life expectancy of the soft denture liner.

Color Stability of Elastomers for Maxillofacial Appliances

The color stability of polyvinyl chloride, polyurethane, and silicone polymers for maxillofacial applications was determined after accelerated aging using reflectance spectrophotometry. On the basis of color stability after accelerated aging, and ease of processing, several silicone materials were the most promising.

The Color Accuracy of the Kubelka-Munk Theory for Various Colorants in Maxillofacial Prosthetic Material

The reflectance model developed by Kubelka and Munk was evaluated for agreement in color prediction of thick pigmented samples and for linearity of optical absorption and scattering coefficients with concentration of colorant in maxillofacial elastomer. The colorants tested were generic opacifiers, dry mineral earth pigments, and fibrous colorants. Significant linear relationships were commonly found between the optical coefficients and the concentration of the colorants. These relationships indicated occasional optical interaction between the colorants and the elastomer. Color differences between theoretical and observed colors of the thick samples averaged 2.96, 3.47, and 1.60 for the opacifiers, mineral earth pigments, and fibrous colorants, respectively, when measured using the CIELAB uniform-color space. The agreement between theoretical and observed colors was significantly closer for the fibrous colorants than for the dry mineral earth pigments of the same labeled color.

Comparison of the physical properties of 11 soft denture liners

Soft denture liners are an important treatment option for patients who have chronic soreness associated with their prostheses. The objective of this study is to determine the tensile strength, elongation, hardness, tear strength, and tear energy of eight plasticized polymers or copolymers, two silicones, and one polyphosphazene fluoroelastomer. Tests were made on samples that were stored in a humidor for 24 hours before testing. The range of data is as follows: tensile strength, 8 to 85 kg/cm2; percent elongation, 150% to 542%; hardness, 25 to 95 Shore-A units; tear energy, 1.43 x 10(6) to 40.4 x 10(6) ergs/cm2; tear resistance, 2.6 to 26.3 kg/cm. It can be concluded that (1) the data obtained can be useful in characterizing the performance of soft denture liners, (2) there is considerable variability in the physical/mechanical properties of soft denture liners, and (3) the required essential properties for soft denture liners are as yet not known.

Physical properties of three maxillofacial materials as a function of accelerated aging

This study compares the tensile strength, elongation, Shore-A hardness, and tear resistance of three silicone maxillofacial materials before and after aging to provide comparative data for evaluation of new or experimental elastomers. The materials evaluated were MDX-4-4210, Factor II (A-2186), and Cosmesil. Tests were conducted 24 hours after specimen preparation and were repeated after aging for 900 hours in a Weather-Ometer device. Five samples were made for each material under all test conditions. After testing, mean values were calculated for all materials under all test conditions and were compared by two-way analysis of variance and Tukey intervals at p < or = 0.05.

Elastomers for maxillofacial applications

Systematic evaluations of the properties of prosthetic facial materials began to appear in 1969 with a report by Cantor et a/. ’ They reported that plasticized poly(methyl methacrylate) was the best material with respect to resistance to tearing and degree of elongation. A year later, Walter2 reported the specific gravity, water sorption, thermal conductivity, strain in compression, and permanent deformation on an acrylic ester resin, two silicone rubbers and a pourable latex rubber. The laboratory results and clinical trials indicated that the ‘high compressibility and good tissue compatibility of the acrylic polymer made it the choice over the other elastomers. In 1971, Roberts3 published the physical properties of a heat-cured silicone material and two room-temperature cured silicone elastomers and found tensile strengths from 300-1000 Ibs/in*, ultimate elongations from lOO-350%. tear strengths from 20-100 Ibs/in and hardnesses from 45-50 Shore A numbers. The following year, Sweeney et aL4 determined the properties of a poly(vinyl chloride) maxillofacial material and proposed a set of requirements for such materials including an accelerated aging test for evaluating changes in colour but not mechanical properties. In 1973 a symposium was held to discuss priorities in dental biomaterials research5. At that symposium Castleberry discussed the choices and challenges of materials for external maxillofacial prostheses. Materials reviewed at that time were poly(vinyl chloride), heatand room-temperature cured silicones, silphenylene[poly(siIphenylenedimethylsiloxane)] , and polyurethanes. The next year, Lontz et aL7 reported how the properties of polysiloxanes could be modified by oils and crosslinking agents to approximate the stress-strain profiles of human tissues such as aorta and tendon. Since 1974 there has been a significant increase in research on maxillofacial materials by Koran and Craig8, Goldberg et a/.g-1 l, Yu et al. ‘*, May et al. 13, Gonzalez14, and Koran and co-workers15-20. It is the purpose of this paper to review the developments of maxillofacial materials in the 1970’s.

Materials Science Physical Properties of Maxillofacial Elastomers Under Conditions of Accelerated Aging

The stability of the physical properties of various commercially available maxillofacial prosthetic materials was evaluated with the use of an accelerated aging chamber. The tensile strength, maximum percent elongation, shear strength, tear energy, and Shore A hardness were determined before and after accelerated aging. Results indicate that silicone 44210, a RTV rubber, is a promising elastomer for maxillofacial application.The stability of the physical properties of various commercially available maxillofacial prosthetic materials was evaluated with the use of an accelerated aging chamber. The tensile strength, maximum percent elongation, shear strength, tear energy, and Shore A hardness were determined before and after accelerated aging. Results indicate that silicone 44210, a RTV rubber, is a promising elastomer for maxillofacial application.