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PubMed2004

Evaluation of varying amounts of thermal cycling on bond strength and permanent deformation of two resilient denture liners.

STATEMENT OF PROBLEM: Two problems found in prostheses with resilient liners are bond failure to the acrylic resin base and increased permanent deformation due to material aging. PURPOSE: This in vitro study evaluated the effect of varying amounts of thermal cycling on bond strength and permanent deformation of 2 resilient denture liners bonded to an acrylic resin base. MATERIAL AND METHODS: Plasticized acrylic resin (PermaSoft) or silicone (Softliner) resilient lining materials were processed to a heat-polymerized acrylic resin (QC-20). One hundred rectangular specimens (10 x 10-mm 2 cross-sectional area) and 100 cylindrically-shaped specimens (12.7-mm diameter x 19.0-mm height) for each liner/resin combination were used for the tensile and deformation tests, respectively. Specimen shape and liner thickness were standardized. Specimens were divided into 9 test groups (n=10) and were thermal cycled for 200, 500, 1000, 1500, 2000, 2500, 3000, 3500, and 4000 cycles. Control specimens (n=10) were stored for 24 hours in water at 37 degrees C. Mean bond strength, expressed as stress at failure (MPa), was determined with a tensile test using a universal testing machine at a crosshead speed of 5 mm/min. Analysis of failure mode, expressed as a percent (%), was recorded as either cohesive, adhesive, or both, after observation. Permanent deformation, expressed as a percent (%), was determined using ADA specification no. 18. Data from both tests were examined with a 2-way analysis of variance and a Tukey test (alpha=.05). RESULTS: For the tensile test, Softliner specimens submitted to different thermal cycling regimens demonstrated no significantly different bond strength values from the control; however, there was a significant difference between the PermaSoft control group (0.47 +/- 0.09 MPa [mean +/- SD]) and the 500 cycle group (0.46 +/- 0.07 MPa) compared to the 4000 cycle group (0.70 +/- 0.20 MPa) ( P <.05). With regard to failure type, the Softliner groups presented adhesive failure (100%) regardless of specimen treatment. PermaSoft groups presented adhesive (53%), cohesive (12%), or a combined mode of failure (35%). For the deformation test, there was no significant difference among the Softliner specimens. However, a significant difference was observed between control and PermaSoft specimens after 1500 or more cycles (1.88% +/- 0.24%) ( P <.05). CONCLUSIONS: This in vitro study indicated that bond strength and permanent deformation of the 2 resilient denture liners tested varied according to their chemical composition.

Acrylic Resins↗
PubMed2002

An evaluation of the viscoelastic characteristics of soft denture liners.

PURPOSE: The purpose of this study was to evaluate the viscoelastic characteristics of a group of soft denture liners by means of a creep test. MATERIALS AND METHODS: The materials evaluated included a silicone rubber base direct liner (Sofreliner MS), a polyolefin base indirect liner (Molteno S), and a conventional tissue conditioner (Coe Soft) as a control. Cylindrical specimens of each material were fabricated using a metal mold. Half of the specimens were subjected to mechanical fatigue with a 75-N load at 1.2 Hz for 200,000 cycles. The creep test was performed on each material and condition with and without a fatigue test using low-load conditions to achieve a 10% strain on all specimens. Viscosity and elasticity were measured, and the data were statistically analyzed using 1-way analysis of variance and Fisher's Protected Least Significant Difference (PLSD) test (p < 0.05). RESULTS: The silicone rubber direct liner (1.31 +/- 2.1 MPa) exhibited a similar mean elastic property as the conventional tissue conditioner (0.90 +/- 0.22 MPa) and an intermediate viscosity between the conventional tissue conditioner (0.11 +/- 0.01 GPa. s) and polyolefin base indirect liner (9.84 +/- 1.08 GPa. s). The elasticity did not change for polyolefin and silicone rubber after the fatigue process. Significant differences in the viscosity of silicone rubber were seen with and without fatigue testing (p < or = 0.05). CONCLUSIONS: The silicone rubber was as soft as the tissue conditioner and softer than the polyolefin liner. The stiffer the material, the lower the permanent deformation observed.

Analysis of Variance↗
PubMed2002

In vitro hardness, water sorption, and resin solubility of laboratory-processed and autopolymerized long-term resilient denture liners over one year of water storage.

STATEMENT OF PROBLEM: The clinical properties of resilient denture liners may be influenced by the method by which they are polymerized. PURPOSE: This in vitro study investigated material property changes of 2 new resilient denture lining materials that represent 2 different curing modes: autopolymerization and conventional laboratory processing. MATERIAL AND METHODS: Two silicone-based liner products were tested; one was allowed to autopolymerize (Tokuyama Soft Relining Paste), and the other was laboratory processed (Luci-Sof). Ninety-six disk-shaped specimens (31 x 10 mm) were fabricated in aluminum ring molds for hardness testing. Sixty bar-shaped specimens (44 x 8.5 x 1.2 mm) were fabricated in aluminum molds for water sorption and resin solubility testing. Shore A hardness was determined directly after specimen fabrication and after 1 day, 1 week, 1 month, 6 months, and 1 year of water storage at 37 degrees C. Water sorption and resin solubility were determined at the same time intervals. Analysis of variance and appropriate t tests were used to determine the effect of immersion duration both within and between the products tested. All statistical testing was performed at alpha=.05. RESULTS: The hardness values of the laboratory-processed material were consistently greater than those of the autopolymerized material. After 1 week of water storage, the hardness of the autopolymerized specimens stabilized, whereas the hardness of the laboratory-processed specimens increased with immersion duration. Water sorption values for the 2 test products were similar after 6 months and after 1 year of water storage. At 1 month, 6 months, and 1 year, significantly lower resin solubility (P<.05) was recorded for the autopolymerized specimens compared with their laboratory-processed counterparts. CONCLUSION: Within the limitations of this study, the laboratory-processed material was harder than the autopolymerized product and demonstrated greater resin solubility over time. The latter result was not expected.

Absorption↗
PubMed2005

Mechanical properties and bond strength of silicone-based resilient denture liners.

To evaluate the ease of manipulation and durability of 11 commercially available silicone-based resilient denture liners, extrusion force, hardness, weight change, and bond strength were determined. Extrusion force from the cartridge of each material ranged from 0.25 to 1.26 MPa at an extrusion rate of 1 cm/min. Durometer hardness, after set materials were stored in distilled water at 37 degrees C for one day, ranged from A5.9 to A47.7, and after four weeks their values increased by 4.0 to 275%. Bond strength ranged from 1.01 to 2.88 MPa after set materials were stored in distilled water at 37 degrees C for one day, but decreased to 0.59 to 1.99 MPa after 10,000 thermal cycles. These results suggested that except for one material, the rest of the evaluated materials exhibited good handling properties--for example, mixing and spreading of material can be done easily. However, some materials exhibited inadequate durability for clinical service, because hardness increased during storage and/or bond strength decreased after thermal cycling.

Absorption↗
PubMed2004

[A clinical case report of complete dentures using resilient denture liners].

PATIENTS: A man (68 years total edentulous) visited us because of masticatory soreness around the mandible. He also suffered from frequent fracture of the dentures. As the poor fitting and severe absorption of the mandible area was considered to be the main cause of the trouble, soft denture lining materials were used. After trying different types of soft denture liners over the new acrylic base dentures, the dentures were finally relined with fluoroelastomer. DISCUSSION: The condition was good and the patient was very satisfied with the lined dentures. The soft liner contributed to the improvement of the QOL of the edentulous patient. CONCLUSION: The use of soft liner was effective for this difficult edentulous case. This case concerns the guideline for the relining of soft liners.

English Abstract↗
PubMed1995

Dynamic viscoelastic properties of processed soft denture liners: Part I--Initial properties.

This research evaluated the dynamic viscoelastic properties of 12 laboratory-processed soft denture liners. Specimens, 1.4 x 3 x 40 mm, were prepared according to the manufacturer's instructions. Five specimens of each material were tested under applied strain frequencies of 1, 5, or 10 Hz and temperatures of 23 degrees C and 37 degrees C. The values at 37 degrees C and 1 Hz were judged most important because they closely approximate the service environment; therefore material comparisons were made for these conditions. Samples were tested with a custom-made dynamic viscoelastometer. The statistical significance of the results was tested by ANOVA and Scheffe's intervals test. Large differences in the storage modulus (elastic stiffness) were found. One acrylic resin, Verno-Soft, showed significantly higher storage moduli than the other materials. The viscous behavior of the materials was reflected by the loss modulus; here large differences were also found. Verno-Soft again exhibited much higher values than all of the other materials. Three other acrylic resins (Super Soft, Soft-Pak, and Justi Soft) also showed significantly higher loss moduli than the other materials. Significant differences were found in the damping factor between many of the materials. Most of the acrylic and vinyl resins had higher damping factors than the silicone and polyphosphazine rubbers. The values of the storage moduli, loss moduli, and the damping factor were affected by temperature and by applied strain frequency with some materials.

Acrylic Resins↗
PubMedDate not supplied

Effects of different disinfectants on physical properties of four temporary soft denture-liner materials.

OBJECTIVE: The purpose of this study was to evaluate the effects of some commonly used disinfectants on physical properties of four temporary soft denture-liner materials. METHOD AND MATERIALS: Soft-liner materials, including three plasticized acrylic resin-liners (Tempo, Immediate, Flexacryl Soft) and one silicone-based material (Ufi Gel P) were studied. Specimens prepared with the soft-liner materials were tested after the application of disinfectants (5% Deconex and 3.5% Savlex for 10 minutes; 2% sodium hypochlorite and 5.25% sodium hypochlorite for 5 minutes) and were compared with the control group (not disinfected; immersed in distilled water). Five specimens of each material were tested and data collected on days 4, 7, 11, and 15. The hardness values were determined using the Shore A hardness test. RESULTS: Water sorption test results showed that the disinfectants had statistically significant effects on water sorption values (except days 7 and 15 for Flexacryl Soft and days 4, 7, and 11 for Ufi Gel P). Water solubility and hardness test results also showed statistically significant effects on the materials by the disinfectants. CONCLUSION: Disinfectants significantly affected the physical properties of water sorption, water solubility, and hardness of the soft-liner materials.

Absorption↗
PubMedDate not supplied

Force versus time profiles of selected heat-processed denture liners.

The potential correlation of the force versus time behavior of four resilient lining materials and their acceptance by patients was investigated. Two modified acrylic resins and two silicone denture lining materials were tested. The response of the soft lining materials to a programmed indentation test was used to define a parameter for each denture liner product. A parameter defined as the "Rebound Index," using force-time data obtained from the indentation measurements, was significantly different for the modified acrylic resins compared to the silicone materials. Improved patient acceptance was correlated with higher values of this index.

Acrylic Resins↗
PubMed2001

Effects of triclosan on the cytotoxicity and fungal growth on a soft denture liner.

STATEMENT OF PROBLEM: Contamination of removable prostheses with microorganisms, particularly Candida albicans, is a common clinical problem. Microban, a broad-spectrum antimicrobial containing triclosan, recently has been proposed to inhibit microbial growth. PURPOSE: This study aimed to determine whether the addition of Microban to PermaSoft denture liner prevents the growth of C albicans and affects the cytotoxicity of the PermaSoft material. MATERIAL AND METHODS: Experimental specimen disks (5 x 1 mm each) with and without incorporated Microban were fabricated aseptically (n = 6) against polyester film to produce a smooth surface. To assess the cytotoxic effect of Microban, the MTT assay was used. To determine the effect of Microban on the growth of C albicans, disks were placed in Transwell dishes, covered with Sabouraud's broth containing an ATCC strain of C albicans, and incubated at 37 degrees C for 24 hours. Wells containing fluorocarbon resin disks or broth alone served as controls. The disks were rinsed to remove unattached C albicans and then sonicated in sterile water to remove surface organisms. Serial dilutions of the water extracts were plated on Sabouraud's agar and returned to the incubator for 24 hours. Colonies were counted with a Brunswick Colony Counter. Growth of C albicans in the internal aspects of the specimens was determined in a manner as previously described, with the exception that the specimens were sonicated to remove surface organisms, minced, and sonicated once more before making serial dilutions. The results were compared with ANOVA and Tukey intervals (alpha=.05). RESULTS: The number of colonies formed ranged from 17 to 31 x 10(5) (mean = 23 +/- 4 x 10(5)) and 14 to 69 x 10(5) (mean = 32 +/- 20 x 10(5)) for the PermaSoft with and without Microban groups, respectively. There was no statistically significant difference between PermaSoft with and without Microban. CONCLUSION: The addition of Microban did not significantly alter the cytotoxicity of the PermaSoft denture lining material or reduce the adherence of viable C albicans to the surface of PermaSoft material after 24 hours.

Analysis of Variance↗
PubMed1985

Simplified technique for placement of a medical-grade adhesive silicone denture liner.

A simplified technique for placement and care of a long-term resilient liner has been described. The procedure can be accomplished in the dental office without an investing or flasking procedure. Finishing is easily accomplished, and the retention of the liner is secure from peeling or separating. Disadvantages include the necessity of having a satisfactory denture border prior to the procedure and the tendency of RTV silicones to develop fungal growth over a period of time without proper care.

Adhesives↗