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PubMed1993

Clinical applications of a polyphosphazene-based resilient denture liner.

The use of resilient denture liners provides an invaluable modality in removable prosthodontic treatment. Treatment of atrophic mandibles, preoperative and postoperative soft tissue management, and retention of removable prosthesis are a few applications of these materials. This article describes the clinical application of a polyphosphazene-based liner (Novus, Hygenic Corp, Dayton, OH) as a denture liner and retentive material in conventional and implant overdenture rehabilitation.

Dental Implants↗
PubMed1995

Clinical application of a soft denture liner: a case report.

Patients with thin, nonresilient mucosa, poor ridge morphology, chronic xerostomia, and acquired or congenital defects are candidates for soft denture liners. Soft denture liners may be placed during fabrication of the new denture or during relining of the existing dentures. Soft mandibular denture liners are ideal for senior patients with resorbed mandibular ridges who need replacement of existing dentures to correct excessively closed vertical dimension of occlusion and for patients who have maxillary complete dentures and mandibular natural teeth, severe loss of maxillary ridge, and clenching habits. Soft denture liners should be used only when needed because of their short service life. However, for those patients who cannot tolerate hard denture bases, soft liners are an appropriate alternative treatment.

Alveolar Bone Loss↗
PubMed2000

Finite element analysis of stress relaxation in soft denture liner.

To gather knowledge related to establishing criteria for selecting soft denture liners for individual patients, the effects of certain properties of soft denture liners on stress distribution were evaluated by two-dimensional finite element analysis. A partial mandibular edentulous ridge crest was modelled. Six combinations of thickness (mucosa: 1 or 2 mm; soft denture liner: 1, 2, or 3 mm) and 18 combinations of Young's modulus (mucosa: three kinds; soft denture liner: six kinds) were analysed. The ratio of maximum to minimum stress in the mucosa (stress ratio) was calculated to estimate stress concentration. In the case of thin mucosa (1 mm thickness), the lower the Young's modulus of the soft denture liner, the lower the stress ratio. However, if the soft denture liner had a lower Young's modulus than the mucosa, stress concentrated adversely. These results suggest that the elasticity of the soft denture liner should match the elasticity of the mucosa to obtain the optimum cushioning effect.

Dental Stress Analysis↗
PubMed2002

Effect of finishing and polishing procedures on the gap width between a denture base resin and two long-term, resilient denture liners.

STATEMENT OF PROBLEM: The junction between a long-term, resilient denture liner and the denture base is difficult to finish and polish due to differences in the hardness of the materials. Gaps tend to form during finishing and polishing procedures. PURPOSE: This study measured the junctional gap between 2 long-term, resilient denture liners and a denture base material after different finishing and polishing procedures were performed. The surface smoothness of the 2 liner materials also was evaluated. MATERIAL AND METHODS: Molloplast-B and an experimental, heat-polymerized methyl siloxane-resin-based denture liner were processed (according to the manufacturer's instructions) against Lucitone 199 acrylic resin. Control specimens (n = 20) were 2 mm thick and flat. Experimental specimens (n = 64) were fabricated with a raised center section: a 3- x 5- x 15-mm half-cylindrical ridge with a junction at the top of the cylinder between the liner material and acrylic resin. The specimens were finished with 1 of 6 types of burs and polished with different combinations of rubber-impregnated acrylic polishers, pumice, and tin oxide. The finished specimens were examined and photographed with a scanning electron microscope, and the largest gap along the liner/denture base junction on each specimen was measured. Three-way analysis of variance without replication (P<.05) and post-hoc t tests were used to analyze the data and compare groups. RESULTS; Averaged across finishing and polishing techniques, a larger gap was recorded for the experimental liner material (22 microm) than for Molloplast-B (14 microm) (P<.00005). Qualitative evaluation suggested that the experimental liner material polished better than Molloplast-B. The smoothest surfaces were obtained when specimens were finished with fine-tooth cross-cut carbide burs and polished with both pumice and tin oxide. A comparison between polished and unpolished specimens, averaged over materials and finishing techniques, revealed that polishing reduced gap size (P=.015). CONCLUSION: Within the limitations of this study, the 2 denture liners tested behaved similarly. The results suggest that the size of the gap at the liner/denture base junction may be affected by finishing and polishing techniques and vary among materials.

Acrylic Resins↗
PubMed2003

Effect of thermocycling on tensile bond strength of six silicone-based, resilient denture liners.

STATEMENT OF PROBLEM: Adhesion failure between silicone resilient denture lining materials and denture base resin is commonly encountered in clinical practice. Adhesion failure results in localized unhygienic conditions at the debonded regions and often causes functional failure of the prosthesis. PURPOSE: The purpose of this study was to investigate the effect of thermocycling on the tensile bond strength of 6 soft lining materials. MATERIAL AND METHODS: Six commonly used silicone-based resilient denture liners (Ufigel C, Ufigel P, Mollosil, Molloplast B, Permafix, and Permaflex) were chosen for the investigation. The bond strength was determined, in tension, after processing to PMMA. The resilient denture liners for each group (n = 24) were 10 x 10 x 3 mm and were processed between 2 polymethyl methacrylate specimens according to manufacturer's instructions. Two PMMA specimens were prepared by investing brass dies with a 3-mm-thick spacer in a denture flask. Specimens were made by processing the resilient denture liners against the polymerized PMMA block. After polymerization, the brass spacer was removed from the mold, the 2 PMMA resin specimens were trimmed, and the surfaces to be bonded were smoothed. The PMMA block was placed back into the molds and the resilient denture liners were packed into the space made by brass spacer, trial packed, and polymerized according to the manufacturer's instructions. Half of the specimens for each group were stored in water for 24 hours, and the other half were thermocycled (5000 cycles) between baths of 5 degrees and 55 degrees C. All specimens were placed under tension until failure in a universal testing machine at a crosshead speed of 5 mm/min. The maximum tensile stress before failure and mode of failure were recorded. The mode of failure was characterized as cohesive, adhesive, or mixed mode, depending on whether the fracture surface was in the soft liner only, at the denture base-soft liner interface only, or in both. Failure strength was recorded in kg/cm(2). Results were tested by multiple analysis of variance (ANOVA) for mode of failure (adhesive, cohesive, and mix), 2-way ANOVA (storage-products), and 1-way ANOVA (storage-products interaction, before and after thermocycling). Duncan's test was used to determine whether significant changes in the tensile bond properties of the materials occurred during thermocycling. RESULTS: Varying degrees of bond strengths were found for soft lining materials and were significantly different (P<.05). Results of this study also indicated that the bond strengths of soft lining materials had significantly decreased after thermocycling except Ufigel C and Mollosil. CONCLUSIONS: Because the adequate adhesive value for soft lining materials is given 4.5 kg/cm(2), all of the materials were acceptable for clinical use.

Adhesiveness↗
PubMed1994

Shock-absorbing behavior of four processed soft denture liners.

The cushioning effect of soft denture liners was evaluated with the use of a free drop test with an accelerometer. The materials tested included SuperSoft, Kurepeet-Dough, Molteno Soft, and Molloplast-B brands. All materials were found to reduce the impact force when compared with denture base resin. A 2.4 mm layer of soft denture material demonstrated good shock absorption. The Molloplast-B and Molteno Soft materials showed excellent shock absorption. When the soft denture liner was stored in distilled water for 180 days, the damping effect recorded for all materials tested was increased. The aging of all materials also affected the cushioning effect.

Absorption↗
PubMed1990

Clinical compliance of two resilient denture liners.

Although intra-oral-setting resilient denture liners have been used for 30 years to treat the severely resorbed residual ridges of elderly patients, their clinical physical properties are not well understood. The effect of clinical usage on the compliance (compressibility, flexibility) of two intra-oral-setting resilient denture liners was measured in 10 patients, for up to 30 days. The clinical compliance of Material B (Coe-Comfort) was found to be significantly greater than Material A (Veltec) for up to 14 days. At 24 h both materials had significant compliance reductions from the original 1 h measurement. These compliance reductions continued throughout the testing period. For up to 14 days of clinical usage there were no significant differences between the compliance reductions of the two materials. The study suggests that (i) Material B would provide more effective tissue conditioning of abused residual ridge mucosa than Material A; and (ii) a functional impression made with these materials should be left in the mouth for at least 24 h before the cast is poured.

Acrylic Resins↗
PubMed1989

Clinical evaluation of a new resilient denture liner in long-term use.

The new resilient denture liner "M" was evaluated for adhesion, color stability, surface texture, tissue response, deterioration and denture base stability, at periods of 1 month, 3 months and about 30 months after denture liner application. At the observation of approximately 30 months, the usage of 17 dentures had been discontinued within 2 years, and 6 dentures continued to be used. It could be considered that the main reasons why 17 dentures were discontinued were poor fitting caused by deterioration, and a decrease in the strength of the denture base caused by the denture liner lining. It was suggested that "M" was appropriate for long-term use (about 2 to 3 years), if patients faithfully practice denture cleaning, and if the strength of denture base is considered.

Adult↗
PubMedDate not supplied

Finishing and polishing of a poly (fluoroalkoxyphosphazene) resilient denture liner.

A raised ridge of Novus resilient denture liner was removed from samples using one of three burs, three stones, or a coarse sandpaper disc. Samples were polished using pumice alone, tin oxide alone, or both agents. A flat, unfinished sample served as a control. Average surface roughness of control samples was 0.96 microns. Average surface roughness measurements for reduced samples ranged from 7.21 microns (sandpaper disc) to 3.34 microns (Prolastic wheel). Without polishing, sandpaper discs and serrated burs produced rougher surfaces than stones or the nonserrated bur. The sandpaper disc reduced the liner the quickest. There were no significant differences between treatments or controls after the use of pumice alone or after the use of a combination of pumice and tin oxide. An acceptable finishing protocol for this poly(fluoroalkoxyphosphazene) resilient liner appears to differ from that previously established for a silicone resilient denture liner.

Analysis of Variance↗
PubMed1995

Dynamic viscoelastic properties of processed soft denture liners: Part II--Effect of aging.

The proper functioning of soft denture liners depends to a great extent on their mechanical properties. As with many polymers these materials are affected by aging. Twelve soft denture liners were processed by a laboratory according to the manufacturers' directions. Five specimens of each material were tested without aging. Five additional specimens of each material were subjected to 900 hours of accelerated aging in a Weather-Ometer instrument. These were tested with a dynamic viscoelastometer at three frequencies and two temperatures, and data for 37 degrees C and 1 Hz was obtained. Two of the ethyl methacrylate resins demonstrated the largest increases in storage (E') and loss moduli (E") after aging. These materials also showed the greatest overall E' and E". One denture liner material exhibited 673% and 488% increases in E' and E", and other materials showed smaller increases. The effects of aging on the damping factor (tan delta) were varied and five materials showed increased tan delta. Only two ethyl methacrylate resins developed lower tan delta. All the silicone and polyphosphazine rubbers showed small changes after aging and had the lowest tan delta values. Significance of differences between materials and treatments was tested with ANOVA, Scheffé intervals, and t-tests at a = 0.05. The ethyl methacrylate soft denture liners were affected the most by accelerated aging, and the silicones and polyphosphazine were least affected. The ethyl methacrylate resins also had the greatest values of E', E", and tan delta after aging.

Acrylic Resins↗
PubMed1994

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.

Absorption↗
PubMed2005

In vitro evaluation of the bonding of auto-polymerizing soft denture liner to cobalt-chromium alloy.

This study evaluated the effects of surface pre-treatments on the bonding of auto-polymerizing silicone soft denture liner to a Co-Cr alloy denture base after cyclic thermal stressing. The bonding surfaces of Co-Cr alloy cylinders (8 mm diameter and 4 mm high) were polished with a 600-grit silicon carbide paper. The bonding surfaces received one of three pre-treatments, which included either the application of a metal primer, a metal primer after air abrasion, or a resin primer after adhesive resin coating. Tensile specimens were fabricated by polymerizing a 2-mm thickness of soft denture liner between a pair of pre-treated denture base cylinders. Failure loads were measured by tensile testing after subjecting the specimen to 0, 5, 10, 20, and 30 thousand thermal cycles. Seven specimens were fabricated for 15 groups, including three pre-treatments and five thermal cycle groups. Failure loads of resin-bonded specimens, which were formerly reported, were used as references. All data were statistically analysed by two-way anova and Bonferroni test at the 95% confidence level. Adhesive resin coating of the metal surface was effective in enhancing the failure loads up to 5000 thermal cycles. However, failure loads of all metal-bonded groups were significantly lower than those of resin-bonded groups at all thermal cycling intervals. The results of this in vitro study implied that polymerizing adhesive resin on the Co-Cr alloy might be a promising method, when the clinicians need to acquire improved bonding of an auto-polymerizing soft denture liner to Co-Cr alloy denture bases.

Air Abrasion, Dental↗
PubMed1999

Influence of lining design of three processed soft denture liners on cushioning effect.

The purpose of this study was to evaluate the influence of the lining design of a soft denture liner on its cushioning effect, using a free drop test and an accelerometer. The peak instantaneous acceleration value was computed. The materials tested were SuperSoft(R) (SS), Kurepeet-Dough(R) (KD), and Molloplast-B(R) (MB). Soft denture liners 2 mm in thickness were placed in test denture bases using three different configurations. Specimens were tested at 24 h and at 180 days after storage in distilled water at 37 degrees C. A three-way ANOVA was used to analyse the data (P=0.05) and Tukey intervals were computed. It was found that all three materials were effective in reducing the impact force. The lining design that had the soft denture liner extended to the periphery of the denture base demonstrated the greatest shock absorbability of all the tested designs. A silicone denture liner using lining design 1 was the most effective in reducing the shock transmitted to the denture bases.

Acceleration↗
PubMed1991

Microwave processing of permanent soft denture liners.

This article describes a technique of processing a resilient soft denture liner using microwave irradiation. The technique employs a specially designed flask that can be heated in a microwave oven. The flask can be either fabricated using commonly available dental laboratory materials or purchased commercially. The microwave polymerization of the resilient soft denture liner reduces the potential warpage of the denture base that can occur during the conventional process of boiling in water for 2 hours. Additionally, microwave irradiation reduces processing time to less than 1 hour, allowing the dentist the opportunity to reline a patient's denture in a single visit. The technique is simple and requires no extensive or elaborate dental laboratory equipment.

Denture Liners↗
PubMed1997

Resiliency of surface-sealed temporary soft denture liners.

STATEMENT OF PROBLEM: Studies have suggested that coating a temporary soft denture liner with a semiset methyl methacrylate resin extends the period of resiliency of the liner. PURPOSE: This study determined whether coating three temporary soft denture liners with two different denture surface sealants, followed by thermocycling, affected the resiliency of the liners. MATERIAL AND METHODS: thirty 20 x 12.5 mm cylindrical samples each of Lynal, Coe Soft, and Visco-Gel soft lining materials were prepared and divided into three groups of 10 uncoated samples, 10 Palaseal-coated samples, and 10 mono-poly coated samples. Samples were thermocycled from 5 degrees C to 45 degrees C for 500 cycles and then compressed 10 mm on an Instron universal testing machine. Resiliency was determined by measuring the energy absorbed by the soft liners when stressed to a specific yield point. RESULTS: Two-way ANOVA indicated a significant difference among materials (p = 0.0001) and among treatments (p = 0.0001). One-way ANOVA of each material group revealed a significant difference among Lynal groups (p = 0.0001) and a significant difference among Visco-Gel groups (p = 0.030). CONCLUSIONS: Surface-coating Lynal samples with Palaseal or mono-poly and Visco-Gel samples with Palaseal significantly increased the resiliency of these samples in the laboratory when compared with uncoated samples.

Absorption↗
PubMedDate not supplied

Bond strength of six soft denture liners processed against polymerized and unpolymerized poly(methyl methacrylate).

The bond strength of six commercial soft denture liners was evaluated by a two-phase tensile test. The soft denture liners investigated were VinaSoft, Prolastic, Flexor, Molloplast-B, Novus, and SuperSoft. The samples were fabricated by processing them (1) against polymerized poly(methyl methacrylate), and (2) against unpolymerized poly(methyl methacrylate). The soft denture liners were processed according to the manufacturers recommendations. The samples were tested using an Instron Universal Testing Machine. The mode of failure, adhesive or cohesive, was also recorded. The bond strength when processed against unpolymerized poly(methyl methacrylate) ranged from 0.48 to 2.60 MPa, and when processed against polymerized poly(methyl methacrylate) the bond strength ranged from 0.94 to 2.56 MPa. A two-way analysis of variance (P = .05) revealed a significant increase in bond strength when the liners were processed against polymerized poly(methyl methacrylate), except for Novus, which had no change, and VinaSoft, which decreased. The Tukey interval between materials was .22 and between methods of polymerization was .08. Four of the six liners investigated demonstrated increased bond strength when processed against polymerized poly(methyl methacrylate). It was concluded that bonding can be influenced by the processing method.

Acrylic Resins↗
PubMed1991

[Study of cell supportability of clinically used soft denture liners].

The application of six soft denture liners showed different effects on the growth of gingival fibroblasts. The morphological and autoradiographical analyses revealed a graduated cellular biocompatibility. The results provide information for further examinations in more detail concerning the clinical biocompatibility of these materials.

Biocompatible Materials↗