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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.

Biocompatible Materials↗

Physical-property comparison of a chairside- or laboratory-polymerized permanent soft-liner during 1 year.

PURPOSE: This investigation examined the influence of polymerization mode and water storage duration on the Shore A hardness, water sorption, resin solubility, and glass transition temperature of Permasoft, a commercial soft denture liner that is polymerized either chairside or in the laboratory. MATERIALS AND METHODS: Specimen disks (31-mm diameter x 10 mm thick) and bars (44 x 8.5 x 1.2 mm) were polymerized following manufacturer's recommendations. The chairside polymerization process was simulated by pouring the mixed components into a mold and processing at 70 degrees C for 15 minutes under 2-psi pressure. Laboratory-polymerized specimens of the same dimensions were fabricated by processing under 500-psi pressure at 100 degrees C for 45 minutes. Specimens were stored in distilled water at 37 degrees C for 1, 7, and 30 days, and 6 and 12 months. Specimens were tested for Shore A hardness, water sorption, resin solubility, and glass transition temperature after the prescribed interval. To determine the effects of polymerization mode and storage time on material properties, a repeated-measures ANOVA (hardness data) and a two-way ANOVA (sorption and solubility data) with appropriate post-hoc tests were used. RESULTS: Shore A hardness values increased from a low of 9.4 (+/- 0.5) units immediately after fabrication to a maximum of 15.9 (+/- 1.1) units after 1 year. Mode of polymerization did not influence hardness (p = .9851). Water-sorption values ranged from 4.2 (+/- 0.2%) of dry weight to 14.7 (+/- 2.5%) after 1 year. Resin solubility varied from 10.3 (+/- 0.6%) of preimmersion weight to 15.4 (+/- 1.1%), and immersion duration had no effect on solubility. In addition, after 1 year of storage, no difference in resin solubility or water sorption was found with respect to cure mode. The glass transition temperature for chairside-polymerized samples approximated -10 degrees C, while that for labpolymerized samples approximated -15 degrees C. CONCLUSIONS: With regard to the material properties evaluated in this study, clinically processed Permasoft liner was equivalent to the laboratory-processed material.

Absorption↗

Curing efficiency of visible light- and dual-cured denture reliners.

PURPOSE: The purpose of this study was to evaluate the curing efficiency of 8 light- and dual-cured denture reliners. MATERIALS AND METHODS: The curing efficiency was measured with Fourier infrared micromultiple internal reflectance spectroscopy, calculating the percentage of remaining carbon double bonds on the top and bottom surfaces of each specimen immediately after exposure to the extraoral light-curing unit according to the manufacturer's instructions and after 1 week of storage in dark and dry conditions. Another group of specimens was photopolymerized initially through a denture base resin prior to the extraoral light-curing polymerization. Five specimens of each reliner were tested. RESULTS: The dual-cured reliners showed no statistically significant differences (P > 0.05) between top and bottom surfaces after immediate exposure to the light-curing unit. On the contrary, light-cured reliners revealed significant differences. The majority of the reliners showed reduction of the percentage of remaining carbon double bonds at both surfaces after 1 week of storage in dark and dry conditions. Photopolymerization of light-cured reliners through a denture base resin induced an increased amount of remaining carbon double bonds, whereas no effect was observed in dual-cured materials. CONCLUSION: Dual-cured denture liners exhibited distinct advantages over light-cured ones concerning the curing efficiency.

Acrylic Resins↗

Intraoral-appliance modification to retract the premaxilla in patients with bilateral cleft lip.

Management of the protrusive premaxilla in patients with bilateral cleft lip is challenging for the reconstructive team. Several intra- and extraoral orthopedic techniques to reposition the protrusive premaxilla prior to bilateral cleft lip repair have been presented in the literature. A modification to a previously described tissue-borne palatal plate with a latex strap is presented. In the modified plate, the latex strap is replaced by an orthodontic elastomeric chain, and the chain over the prolabium is covered with soft denture liner. This appliance is effective in retracting the premaxilla, noninvasive, easy to construct and adjust, economic, well tolerated by the patient, and accepted by the parents.

Cleft Lip↗

Denture soft linings: materials available.

Denture soft lining materials are products which are applied to the fitting surfaces of dentures for the purpose of achieving a more equal distribution of load and reduction of local point pressures. These materials have provided a focus for research and controversy for over 100 years. In that time large numbers of products have been advanced as the ideal soft denture liner. This paper discusses the five main groups of materials that have been available to dentists: the natural rubbers, vinyl co-polymers, hydrophilic polymers and the silicone and acrylic based soft lining materials.

Acrylic Resins↗

Clinical implications of resilient denture lining material research. Part II: Gelation and flow properties of tissue conditioners.

The clinical effectiveness of tissue conditioners and functional impression materials is influenced by their gelation and flow properties. Laboratory tests were previously conducted that simulated the conditions of clinical use to the extent possible on six commercial intraoral-gelling resilient denture liners. The liners were found to vary significantly in their gelation times and to flow throughout the 7-day study. Their initial flow after mixing was influenced most by the time of loading. While extrapolations to the clinical environment require caution, the results of this study imply that the dentist should (1) adapt clinical techniques to the gelation times of particular materials, (2) reduce the initial flow of some materials by delaying denture placement on the supporting mucosa, and (3) expect the materials to be effective tissue conditioners for at least 7 days.

Acrylic Resins↗

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↗

Polyurethane elastomer as a possible resilient material for denture protheses: a microbiological evaluation.

A polyurethane elastomer was microbiologically evaluated in vitro for its potential use in resilient denture liners. Specimens were immersed in suspensions of ten selected oral microorganisms; this was followed by viable cell counts at intervals during a 16-week period. Results indicated that the polyurethane neither supported the growth of the organisms nor was it degraded.

Candida↗

[Study on visible-light curing soft resins consisting of fluoropolymers. 1. Effect of fluoroalkyl methacrylate monomers].

New experimental visible-light cured soft resins were prepared by combining 4 kinds of fluoroalkyl methacrylate monomers with a vinylidene fluoride/hexafluoropropylene copolymer, or a vinylidene fluoride/tettrafluroethylene/hexafluoropropylene copolymer. Some properties of the resins prepared were examined to determine their value as a soft denture liner material. Water contact angles were more than 90 degrees in all cases and increased with the increase in the number of fluorine atoms in the fluoroalkyl groups. Hardness (JIS A) was less than 50 for the softes resin. Water sorption after 10 weeks was 3-4.5 wt %. Solubility 0.1-0.3 wt% and amount of residual monomer 0.2 wt% were very low. The properties of these new experimental resins were comparable or superior to the commercial soft materials available.

Acrylic Resins↗

The effect of accelerated ageing on the mechanical properties of soft denture lining materials.

The purpose of this study was to determine the effect of simulated ageing on the physical properties of some soft denture liners. The hardness, tensile strength and percentage elongation values were determined before and after ageing treatment. At the end of the experimental ageing process softening was observed only in Simpa and Ufigel L materials. It was established that ageing had insignificant effect on the hardness of other materials. It can be presumed that there will not be significant time-related changes in the hardness of these materials. Molloplast B preserved its highest value after the ageing process, whilst that of Simpa decreased to become comparable with Ufigel P.

Biocompatible Materials↗

The creep behavior of denture-supporting tissues and soft lining materials.

This study examined the desirable properties of a soft denture liner. The physical behavior of palatal mucosa of young adults was quantified by analyzing creep behavior using Voigt's four-element model. Instantaneous elastic recovery was significantly smaller than instantaneous elastic displacement, and delayed elastic recovery was significantly larger than delayed elastic displacement (P < .05). Viscous recovery was small but detectable. To ascertain whether the characteristics of the mucosa can be replaced with a soft material, a new soft lining material was developed and both behaviors, especially after load release, were compared with each other. It was indicated that by properly controlling the amounts of the crosslinking agent and inorganic filler of the soft material, its properties may be made to approximate those of the mucosa.

Acrylic Resins↗

[Study on visible-light curing soft resins consisting of fluoropolymers. 2. Effect of fluoroalkyl alpha-fluoroacrylate monomers].

New experimental visible-light cured soft resins were prepared by combining a vinylidene fluoride/hexafluoropropylene copolymer (2-6 F), or a vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer (2-4-6 F) with 2,2,3,3-tetrafluoropropyl alpha-fluoroacrylate (4 FFA), 2,2,3,3,3-pentafluoropropyl alpha-fluoroacrylate (5 FFA), 2,2,3,3,4,4,5,5-octafluoropentyl alpha-fluoroacrylate (8 FFA), or 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl alpha-fluoracrylate (12 FFA). Some properties of the resins prepared were measured to determine whether they would be candidate materials for the soft denture liner. Water contact angles increased with the increase in the number of fluorine atoms contained in the monomers: 85-90 degrees in 4 FFA, 90-93 degrees in 8 FFA, and 92-93 degrees in 12 FFA. Softer resins were obtained with 2-4-6 F, especially by the combination with 8 FFA giving the softest resin with a hardness of 43-46 (JIS A). Water sorption after 10 weeks was considerably low: 0.4-2%: 0.4-0.9% in 4 FFA/2-6 F and about 2% in 8 FFA/2-4-6 F. Solubility was 0.2-0.4% in the resins with 4 FFA and 1.0-1.4% with 8 FFA or 12 FFA. Amount of residual monomer was low, and the maximum was 0.4% in the resin with 12 FFA. Thus hardness and water sorption of the resins prepared were superior to those of the commercial soft materials.

Denture Liners↗