Resilient Denture Lining Materials Research Articles

Evaluation of the Antifungal Activity of Heat-Cured Soft Denture Liner Impregnated with Chitosan Nanoparticles

The most serious problem of the resilient denture lining materials is colonization and penetration of the soft-liner surface by Candia albicans and related Candida species. So, this research was oriented to check the antifungal effect of Chitosan nanop articles (CHs NPs) incorporated into heat-cured acrylic soft liners. 60 specimens were prepared, 30 specimens for disk diffusion test and other 30 specimens for viable count of C. albicans test. The specimens split into six groups depending on different percentages of Chitosan NPs addition: 0.5wt%, 1.5wt%, 2.5wt%, 3.5wt%, 4.5wt%, and control group withou t addition 0%). For disk diffusion test, the autoclaved soft lining samples were fitted into sterilized Petri dish containi ng Mueller Hinton agar upon which candidal suspension were swabbed then fitted the samples on the agar surface, in cubated for 24 hrs. Then the inhibition zones were measured by utilizing digital caliper ruler. For viable count test, t he autoclaved samples of soft liner were submersion in sterilized tubes containing Sabouraud dextrose broth in which a small amount of candidal suspension, incubated for 24hrs. The Results of the disk-diffusion test showed the highest mean value of the inhibition zone at 3.5wt% group follow ed by 4.5wt% group and there was no inhibition zone for control and other experimental groups. Furthermore, the vi ability test indicated the colony forming units of C. albicans were decrease as the percentage of CHs NPs increased. With limitation of this study, it was concluded the CHs NPs considered as a strong antifungal agent and the impregnation of the chitosan nanoparticles into soft liner that help to form a soft lining material with antifungal activity and minimal candida associated infection.

STUDY OF THE KNOWLEDGE AND USE OF RESILIENT DENTURE LINING MATERIALS IN CLINICAL PRACTICE

Introduction: Since the beginning of the last century until today, resilient resins have been used for the lining of partial and complete dentures with the aim to achieve more uniform distribution of masticatory pressure and to reduce the trauma of mucous membranes. The aim of this study was to investigate the knowledge and use of resilient denture lining materials (RDLMs) in clinical practice. Material and methods: The study was conducted among dental practitioners and dental technicians in 2016. A direct survey method was used, with a questionnaire containing 11 questions. Results: Over half (53.4%, n = 133) of the respondents do not use RDLMs in their practice. In the cases of retentive prosthetic field or prosthetic field with advanced atrophy, the respondents focus mainly on the surgical preparation of the prosthetic field and recommend the use of RDLMsif there are exostosis-related pain symptoms (≈41%, n = 103) or painful neurogenic points (≈ 44%, n = 105). One-third of the respondents prefer the use of long-term RDLMs, and 73% prefer to apply the indirect lining technique. Conclusion: The various types of RDLMs and their characteristics are well-known by the dental practitioners and dental technicians but rarely used, due to a number of unresolved related issues, such as ungluing of the resilient material from the denture base, appearance of an unpleasant odor, change in the color or texture of the material, etc. In our study, dental practitioners and dental technicians use RDLMsfor complete denture lining mainly in clinical cases with presented pain symptoms.

Creep and Stress Relaxation Behavior of Two Soft Denture Liners

Numerous investigators stated the indications of soft denture lining materials; but no one determined the indications of these materials according to their chemical structure. The purpose of this investigation was to evaluate the viscoelastic properties of acrylic and silicon lining materials. This study investigated and compared viscoelastic properties of two resilient denture lining materials. Tested materials were laboratory processed; one of them was silicone-based liner product (Molloplast-B), and the other was plasticized acrylic resin (Vertex™ Soft). Twenty cylindrical specimens (10-20mm in length, 11.55mm in diameter) were fabricated in an aluminum mold from each material for creep and stress relaxation testing (the study of viscoelastic properties). Tests were performed by using the universal testing machine DY-34. Collected data were analyzed with t test statistics for statistically significant differences at the 95% confidence level. There was a clear difference in creep and stress relaxation behavior between acrylic and silicone liners. Statistical study of Young's moduli illustrated that Vertex™ Soft was softer than Molloplast-B. On the other hand, the results explained that the recovery of silicone material was better than of acrylic one. The creep test revealed that the plasticized acrylic resin lining material exhibited considerable creep, whereas silicone-based liner exhibited elastic behavior. Besides, the stress relaxation test showed that relaxation of the plasticized acrylic resin material was bigger than of the silicone-based liner.

Shear bond strength of three silicone lining materials bonded to heat-cured denture resin

This research compared the adhesive strength of three resilient denture lining materials cured with two different curing modes: autopolymerized (Mollosil plus, GC Reline Soft), and conventional laboratory processing (Molloplast-B); bonded to heat-cured acrylic resin. The findings showed that all the lining materials were acceptable for clinical use; there were no statistically significant differences among the bond strengths of the studied silicone materials. However, the bond strength became higher when Molloplast-B was applied to unpolymerized polymethyl methacrylate PMMA and processed together than it was applied to polymerized PMMA.

Influence of methyl mercaptan at early setting stages on the properties of self curing addition silicone resilient denture lining materials

The aim of the present study was to clarify the influence of early setting conditions on the properties of self curing addition silicone resilient denture lining materials. Four auto-mix types of commercial self curing addition silicone resilient denture lining materials were used. Agar plates containing various concentrations of methyl mercaptan (MMP) were prepared and cylindrical specimens (10mm in height and 10mm in diameter) of silicone liners were set on the agar plate. The Shore A hardness of the agar-contacted surface of the specimen was measured at 0, 1, 7 and 28 days after stored in 37 degrees C water. The viscoelastic properties (instantaneous elastic modulus, coefficient of viscosity and permanent deformation) of two silicone liners, which showed a great decrease in the Shore A hardness by agar contact, were determined by a creep meter. The Shore A hardness, coefficient of viscosity, and instantaneous elastic modulus deceased when the specimen was set on the MMP containing agar plate, but the permanent deformation of these specimens increased. The exposure to MMP at the early setting stage influenced the properties of self curing addition silicone resilient denture lining materials.

Research projects related to complete dentures published in 2008 by members of the Japan Prosthodontic Society

This article reviews the findings of the original papers related to complete dentures published in the Journal of the Japan Prosthodontic Society (Nippon Hotetsu Shika Gakkai Zasshi), Vol. 52, 2008. A total of six articles focused on complete dentures or materials related to complete dentures were selected and summarized. A variety of subjects in relation to removable prosthodontics were discussed in the articles, including denture plaque control, resilient denture lining materials or denture adhesives, and assessment and/or anatomical analysis of prognosis of complete dentures.

Evaluation of adhesive properties of three resilient denture liners by the modified peel test method

The characteristics of adhesive properties between a denture base and resilient denture liner were investigated by a modified peel test with an L-shaped metal attachment. Three commercially resilient denture lining materials, namely GC Reline Soft (S), GC Reline Extra Soft (ES), and GC Reline Ultra Soft (US), were evaluated. Acrylic resin (GC Acron) was used as denture base material. Peel specimens consisting of the denture base acrylic resin and resilient denture liner were tested after storage for 1 and 30 days in distilled water at 37°C. The modified peel test method gave load–displacement curves and work of adhesion (WA) values of the denture base material and resilient denture liner. The WA of specimens after 1 day of storage ranged from 1.71 to 2.55Nmm−1 and increased in the order from US to S to ES. On the other hand, the WA of specimens after 30 day of storage ranged from 1.44 to 2.47Nmm−1 and increased in the order from US to ES to S. US had significantly lower WA after 1 and 30 days of storage than did S and ES (P<0.05). Comparison of the WA between 1 and 30 days, reveals large differences for ES and US, but not for S. This could be explained by the difference in failure modes. Within the limitations of this investigation, it was concluded the modified peel test is effective for evaluating the adhesion between denture base material and a resilient denture liner.

Water sorption, solubility, and tensile bond strength of resilient denture lining materials polymerized by different methods after thermal cycling

The clinical properties of resilient denture lining materials may be influenced by the methods used to polymerize them. This study evaluated and compared water sorption, solubility, and tensile bond strength of 2 resilient liner materials polymerized by different methods after being thermal cycled. Two acrylic resin-based resilient liner materials were evaluated: 1 (Light Liner) polymerized by visible light, and 1 (Ever-Soft) processed by 2 different methods: hot water bath and microwave energy. To evaluate water sorption and solubility, 10 disc-shaped specimens (50 x 0.5 mm) were fabricated for each polymerization method, using acetate matrices. The specimens were dried and thermal cycled (2000 cycles) between baths of 5 degrees C and 55 degrees C. After thermal cycling, the specimens were weighed, dried, and weighed again to calculate the water sorption values and solubility. For tensile bond strength assessment, 12 rectangular specimens measuring 83 mm in total length and with a cross-sectional area of 10 x 10 mm were fabricated using each polymerization method. The specimens were also thermal cycled (2000 cycles) and, afterwards, tested in a universal testing machine at a crosshead speed of 6 mm/min with 100 Kg load cell. The type of failure was determined by use of stereoscopic microscopy. The data (for water sorption and solubility, n = 30, and for tensile bond strength, n = 36) were submitted to 1-way analysis of variance. The means were compared using the Bonferroni test (alpha=.05). For water sorption the results showed no significant differences among the polymerization methods. Light Liner showed the lowest solubility values (5.3% +/- 0.3%) when compared to Ever-Soft (hot water bath: 7.3% +/- 1.1% and microwave energy: 7.8 +/- 0.9%). For tensile bond strength, Ever-Soft polymerized by microwave energy (0.7 +/- 0.0 MPa) showed the greatest and most significant ( P <.05) value when compared to Ever-Soft polymerized by hot water bath (0.5 +/- 0.1 MPa) and Light Liner polymerized by visible light (0.5 +/- 0.0 MPa). Most Ever-Soft specimens polymerized by microwave energy and Light Liner specimens showed adhesive/cohesive failures. However, Ever-Soft polymerized by hot water bath showed 50% adhesive/cohesive and 50% adhesive failures. The results at the reline material-resin bond interface showed the absence of cohesive failures. Within the limitations of this study, Light Liner showed the lowest solubility values. Ever-Soft should be polymerized by microwave energy to obtain the greatest tensile bond strength values. Materials polymerized by microwave energy and visible light showed predominantly adhesive/cohesive failures.

Effect of a denture cleanser on weight, surface roughness, and tensile bond strength of two resilient denture liners

Statement of problem Denture cleansers used in clinical practice can damage resilient denture lining materials. Purpose This study evaluated the effects of a denture cleanser on weight change, roughness, and tensile bond strength on 2 denture resilient lining materials. Material and methods Forty specimens of microwave acrylic resin (Onda-Cryl), 30 mm in diameter and 4 mm thick, were prepared to verify weight change and surface roughness. The specimens were divided into 4 groups consisting of 10 specimens each, relined with a resilient liner (Coe Soft or Dentusoft), and treated (Polident or tap water). To evaluate tensile bond strength, 12 specimens were used for each group. All specimens were stored in artificial saliva for 15 days, immersed once a day in Polident or tap water, and evaluated at 0 hours and after 24 hours and 7 and 15 days. Roughness was evaluated by use of a profilometer. Weight changes were recorded in milligrams and expressed as the percentage of weight difference between the periods of evaluation. Tensile bond strength was determined with a universal testing machine. The specimens were placed under tension until failure by a cross-speed of 5 mm/min with a 500 Kg load cell. The type of failure was determined by use of stereoscopic microscopy at original magnification ×8. The data were submitted to analysis of variance and compared by Tukey’s test (α=.05). Results Specimens immersed in Polident showed higher and significant ( P<.05) weight changes (%) than those immersed in water between 24 hours and 7 days (Coe Soft-Polident: 0.48 ± 0.09; Coe Soft-water: 0.28 ± 0.09; Dentusoft-Polident: 0.44 ± 0.16; Dentusoft-water: 0.22 ± 0.15) and between 7 and 15 days (Coe Soft-Polident: 0.08 ± 0.04; Coe Soft-water: −0.17 ± 0.05; Dentusoft-Polident: 0.01 ± 0.04; Dentusoft-water: − 0.24 ± 0.03). There was significant difference ( P<.05) in roughness (in micrometers), between treatments after 7 days (Coe Soft-water: 4.07 ± 0.22; Coe Soft-Polident: 3.36 ± 0.52; Dentusoft-water: 3.68 ± 0.72; Dentusoft-Polident: 3.26 ± 0.41) and 15 days (Coe Soft-water: 4.88 ± 0.29; Coe Soft-Polident:3.53 ± 0.61; Dentusoft-water: 4.42 ± 1.12; Dentusoft-Polident: 3.68 ± 0.37). Tensile bond strength was highest ( P<.05) after 15 days (Coe Soft-water: 5.19 ± 0.93; Coe Soft-Polident: 4.40 ± 0.38; Dentusoft-water: 4.42 ± 1.15; Dentusoft-Polident: 4.84 ± 1.14). Most failures were cohesive (Coe Soft: 76.04% and Dentusoft: 82.29%). Conclusion Within the limitations of this in vitro study, specimens immersed in Polident demonstrated increased weight changes of resilient liners when compared with tap water, but surface roughness and tensile bond strength were unaffected.

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 × 10 × 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° and 55°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/cm2. 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/cm2, all of the materials were acceptable for clinical use. (J Prosthet Dent 2003;89:303-10.)

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 × 10 mm) were fabricated in aluminum ring molds for hardness testing. Sixty bar-shaped specimens (44 × 8.5 × 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°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 α=.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. (J Prosthet Dent 2002;88:139-44.)

Interactions between thermal cycled resilient denture lining materials, salivary and serum pellicles and Candida albicansin vitro. Part II. Effects on fungal colonization

In the present study, the growth of a single isolate of Candida albicans on saliva-, serum-coated or protein free (uncoated), thermocycled (4-70 degrees C for 1 min, respectively; 0, 1000 and 10 000 times) seven commercial soft lining materials were investigated, by adenosine triphosphate (ATP) analysis. In the case of control resilient liners (not thermocycled and uncoated), the fungal colonization appeared to depend upon the type of commercial resilient liner used. Thus, the lowest colonization was observed with fluoric and heat-cured silicone materials, cold-cured silicone materials, except for one product, and heat-cured acrylic resin exhibited the highest colonization capacity, and cold-cured acrylic resilient liners exhibited the intermediate. However, the fungal colonization on the materials was significantly promoted both by thermal cycling (ANOVA, P<0.01) and a layer of protein coating (saliva, P<0.01; serum, P<0.01). These results, taken together, suggest that the ageing of the materials and the biological fluids of the host promote yeast colonization on resilient lining materials.

Overdenture retention of four resilient liners over an implant bar

Statement of problem. Resilient denture liners offer an alternative method of designing implant-retained overdentures. Space is provided in the overdenture to envelop the implant bar with a resilient liner to be applied chairside or processed in the laboratory. The degree of retention may vary and these materials change over time. Purpose. This study evaluated the retention on an implant/bar prosthesis with overdentures lined with 4 resilient denture lining materials, after cyclic insertion and removal over a simulated 1.5-year period. Material and methods. Four implants were placed in a mandibular edentulous cast and a gold bar superstructure was made. Overdentures were processed in Lucitone-199 and Tokuyama, Luci-Sof, Molloplast-B, and PermaSoft (with and without sealer) lining materials, cured according to manufacturers’ instructions. Each of 5 overdentures contained each liner and were cycled 2740 times (simulating 1.5 years of service at 5 insertions daily) in 37°C water in an Instron at 20 cm/min. Insertion and retention force were measured. Results. The 3 silicone rubber liners were 3 to 5 times more retentive than the plasticized acrylic liner initially. After cycling, Tokuyama soft liner (autopolymerized silicone) gained 14% retention, Luci-Sof (heat-cured silicone) gained 8%, Molloplast-B (heat-cured silicone) lost 12%, whereas PermaSoft (autopolymerized plasticized acrylic) with sealer lost 43%, and without sealer lost 60%. PermaSoft lining material also chafed and crumbled after cycling and was significantly less retentive in most statistical comparisons. Conclusions. All the silicone-based resilient liners retained the overdentures well. The plasticized acrylic was less retentive initially, and lost significant retention after 2740 cycles, compared with silicone-based resilient liners. (J Prosthet Dent 1999;81:568-73.)

A new temporary soft lining material

The viscoelastic properties of a new light-activated temporary denture soft lining material have been monitored in vitro using a force/distance probe. Its baseline behaviour was characteristic of an elastic material and its compliance considerably less than that of both a short-term and a long-term soft lining material which were used as controls. Sample thickness had no appreciable effect on this compliance. These results suggest that the new product is likely to be perceived as being significantly harder by a patient. Twenty-four weeks' immersion in distilled water had no significant effect on either the compliance or elasticity of the test material and would suggest an improved durability when compared to other conventional short-term resilient denture lining materials, albeit at the expense of compliance.

Effects of denture cleansers on direct soft denture lining materials

The deterioration of six commercial resilient denture lining materials immersed in seven groups of denture cleansers was investigated. Although the grades of deterioration of these soft liners were not related to the amount of peroxide content or the pH of denture cleansers, the effects of peroxide cleansers were, with few exceptions, more severe than those of the other types. For example, an enzyme cleanser caused severe changes of one soft liner. The grades of surface porosity were correlated well with the log of the gelation time of the tissue conditioners (except for one soft liner), in four kinds of peroxide cleansers. These results suggest that various components of denture cleansers and soft lining materials, particularly peroxides, in cleansers and gel formation components of soft liners play important roles in the deterioration of soft liners caused by cleansers.

Adhesion properties of resilient lining materials bonded to light-cured denture resins

This study compared the adhesive strength of three resilient denture lining materials with different chemical compositions when bonded to visible light-cured (VLC) denture base resin. Shear adhesive strength was evaluated using a simple overlap-joint model. Three different bonding agents were used and the effect of water on the bonding strength was evaluated by a series of samples tested after storage for 4 months. The findings showed that all of the lining materials were acceptable for clinical use but that water storage reduced their bond strength to VLC resin.

弾性裏装材の摩耗に関する研究

Abrasion of denture liners was studied using three kinds of resilient lining materials. The weight was markedly decreased with the frequency of brushing in polyolefin and silicone materials. Decreases in weight were hardly recognized in polyfluoroethylene material.The mean roughness and maximum height were markedly increased with the frequency of brushing in polyolefin and silicone materials. On the other hand, these were hardly increased in polyfluoroethylene material.Scanning electron microscopy after 100, 000 times of brushing revealed the appearance of distinct line-like marks in polyolefin and silicone materials, while such marks were not observed in polyfluoroethylene material.In scanning electron micrcscopy, the surface texture of the three resilient denture lining materials were not changed after dipping in a denture cleaning-solution for one month.These results suggest that mechanical brushing and chemical soke-cleaning are suitable for Cleaning of polyfluoroethylene material, while chemical soak-cleaning is suitable for polyolefin and silicone materials.

Influence of thickness, boxing, and storage on the softness of resilient denture lining materials

T he clinical usefulness of soft denture lining material is well establishecl.‘-4 They may be used where the oral mucosa covering the denture-bearing area is of inadequate thickness or exhibits a reduced tolerance to the load applied to it and for patients with bruxism. Previous investigations into the softness of resilient lining materials have used different test methods.‘-’ The resilience of a soft material depends on its thickness and its inherent physical properties; therefore, the thickness of soft lining material is critical in the eventual success or failure in clinical use. The optimum thickness of the liner to be applied to the denture is controversial. It is impossible to recommend a standard thickness that can be used with all materials because a 1 mm thickness would be satisfactory with softer materials whereas a 3 mm thickness might be necessary with the harder materials.3 Other reports have stated that the liner should be at least 3 mm thick,” that the liner must be as thick as possible to be effective,” that the optimum benefit in softness is obtained with a lining of 2 to 3 mm thickness,8 and that using liner thickness of more than 2 mm does not materially increase the resilience.’ Previous studies have shown that water can be absorbed into the lining material and that the plasticizer or other constituent of the soft lining can be leached out, thus changing its physical properties.6s ** “3 l3 Fig. 1. Mold assembly for preparing samples.

The nature of the interface between polymethyl methacrylate denture base materials and soft lining materials

Four of the commonly used resilient denture lining materials were investigated. They were of different chemical composition, physical forms and processing cycles. Scanning electron microscope examinations of the interface between the liners and the regular acrylic resin base material were carried out in an attempt to assess the bonding of these materials to the denture base, and to evaluate the reliability of their use. The physical and mechanical bonding properties of the resilient lining materials to acrylics were studied, which included tensile, shear, peel and compression tests to measure the efficacy of the joint between the acrylic and the lining materials and its resistance to various external damaging loads. The effect of water on the liner/denture base interface and on the liner's bonding properties to acrylics was also investigated, and the validity of roughening the tissue surface of the denture base prior to processing the liner was assessed. The findings point to the advisability of using the acrylic type of soft liners whenever resilient liners are indicated. Roughening the fitting surface of the denture base to which the resilient lining materials are to be applied has a weakening effect on the bond between the lining and the denture base. Long-term exposure of the liners to water has a destructive effect. The infusion of the water into the material leads to swelling and stresses build up at the denture base interface and these tend to promote distortion and reduction in bonding.

A Study of the Interface between Resilient Denture Liners and Polymethylmethacrylate

Four of the commonly used resilient denture lining materials were investigated, they were of different chemical composition, physical forms and processing cycles.Scanning electron microscope examinations of the interface between the liners and the regular acrylic resin base material were carried out in an attempt to assess the bonding of these materials to the denture base, and to evaluate the reliability of their use.The effect of water on the liner/denture base interface was also investigated, and the validity of roughening the tissue surface of the denture base prior to processing the liner was assessed.The findings point to the advisability of using the acrylic type of soft liners whenever resilient liners are indicated. Roughening the fitting surface of the denture base to which the resilient lining materials is to be applied has a weakening effect on the bond between the lining and the denture base.Long term exposure of the liners to water has a destructive effect. The infused water into the material leads to swelling and stresses build up at the denture base interface and these tend to promote distortion and reduction in bonding.