Working viscosity and non-Newtonian behavior of silicone denture liners.

PURPOSE: To evaluate flow profile and non-Newtonian behavior of 10 different silicone lining materials. METHODS: Ten commercially available silicone lining materials were selected for evaluation. The flow profile and non-Newtonian behavior of each material was measured using a shark fin testing method. Fin height and resultant base thickness were measured with a digital caliper and compared with one-way ANOVA and Student-Newman-Keuls post hoc test and fin base by Kruskal-Wallis one-way ANOVA on ranks with Dunn post hoc test with significance at P< 0.05 for both. RESULTS: Shark fin heights ranged from 9.62 ± 0.86 mm [Reline II (Soft)] to 25.54 ± 0.43 mm [Sofreliner (Medium)]. Shark fin bases ranged from 2.57 ± 0.51 mm [Sofreliner (Medium)] to 10.31 ± 0.57 mm [Reline II (Soft)]. Statistically significant differences were found between certain samples' shark fin heights as well as resultant bases (P< 0.05) indicating different rheological properties. CLINICAL SIGNIFICANCE: Silicone liner materials differ significantly with respect to flow profile and non-Newtonian behavior. While a high flow profile (low viscosity) of an elastomeric impression material improves accuracy, it may be a detriment to a denture lining material that must achieve a critical minimum thickness to provide resilience. Likewise, a low flow profile (high viscosity) material may also pose a disadvantage, requiring excessive compression and possible tissue distortion to achieve the same critical thickness. The results of this study should be considered when selecting the appropriate material for clinical application. Additional studies are indicated to further quantify rheological properties as well as correlate them to physical properties after the complete cure of the material.

Evaluation of rheological properties of soft lining materials with different composition under various temperatures.

PURPOSE: The aim of this in vitro study was to evaluate the changes the rheological properties of some soft lining materials, to compare the rheological properties and viscoelastic behaviour at different temperatures. MATERIALS AND METHODS: Five soft lining materials (acrylic and silicone based) were used. the storage modulus (G'), loss modulus (G"), tan delta (tan δ) and complex viscosity (η') were chosen and for each material, measurements were repeated at 23, 33 and 37  °C, using an oscillating rheometer. All data were statistically analyzed using the Mann Whitney U test, Kruskal Wallis test and Conover's Multiple Comparison test at the significance level of 0.05. RESULTS: Soft lining materials had different viscoelastic properties and most of the materials showed different rheological behavior at 23, 33 and 37  °C. At the end of the test (t¹5), at all the temperatures, Sofreliner Tough M had the highest storage modulus values while Visco Gel had the highest loss Tan delta values. CONCLUSIONS: There were significant changes in the rheological parameters of all the materials. Also temperature affected the initial rheological properties, and polymerization reaction of all the materials, depending on temperature increase. CLINICAL IMPLICATIONS: Temperature affected the initial rheological properties, and polymerization reaction of soft denture liner materials, and clinical inferences should be drawn from such studies conducted. It can be recommended to utilize viscoelastic acrylic-based temporary soft lining materials with lower storage modulus, higher tan delta value, and high viscosity in situations where pain complaint persists and tissue stress is extremely significant, provided that they are replaced often.

Impact of apigenin and seashell nano-additives on the antifungal and roughness behavior of a soft denture liner.

Fungal colonization of the soft denture liner is the first step in the development of denture-induced stomatitis. The study aims to assess apigenin and seashell nano-additives for their antifungal efficacy and their impact on the surface roughness of a soft denture liner. The study was accomplished in the Colleges of Dentistry in Duhok, Mosul and Hawler Medical Universities. The  Antifungal efficacy against Candida albicans was performed by the minimum inhibition concentration (MIC), for apigenin the MIC was determined by agar well diffusion and set at (0.25%, 0.5% and 1%) while for seashells, MIC was determined by broth dilution and set at (1.25%, 2.5% and 5%). Fungal adhesion was conducted on seven groups (unmodified soft liner and six groups of the modified liner with the antifungal concentrations (three for each nanoparticle). A total of forty-nine square-shaped specimens (10*10*2mm) of (GC, Super-soft, heat-cured, USA) soft liner were prepared, the adherent fungal cells were enumerated under a light microscope for each specimen in four fields and the results were expressed as fungal cells/mm2. For the surface roughness, forty-nine specimens of (20*10*3 mm) of the soft liner were prepared and the average surface roughness was obtained in µm using a profilometer (Talysurf, Taylor Hobson, UK). Apigenin and seashell-modified soft liner observed a significant decrease in both fungal adhesion and surface roughness compared to the unmodified liner and the reduction was related directly to the concentration of both additives. Apigenin and seashell nano-additives were effective as antifungal agents beside improving the surface roughness of the soft liner.

Comparative Analysis of Properties in Chairside Silicone Denture Liners versus Heat-Cured Molloplast-B: An In-Depth In Vitro Evaluation.

BACKGROUND We investigated the bond strength, tensile strength, and water absorption properties of 4 widely used chairside silicone long-term denture soft lining materials and compared properties with those of heat-cured silicone material. MATERIAL AND METHODS Four chairside materials (GC Reline Soft, Mucopren Soft, Sofreliner Soft, and Elite Soft Relining) and a heat-cured silicone material (Molloplast B) were investigated. For tensile and shear bond strength and tensile strength, samples were prepared according to the manufacturers' instructions and the testing machine used. For water absorption, IOS 1567 was followed to prepare specimens. Bond strengths were measured using a Lloyd Instruments materials testing machine. Ten specimens for each test were prepared for each soft liner, except for water absorption and solubility tests, for which only 5 specimens were prepared. ANOVA, Bonferroni, and Kruskal-Wallis tests were used to compare values of materials and assess changes over time. RESULTS There was strong evidence of differences in the properties between materials. GC Reline Soft showed comparable tensile bond (1.4±0.6 MPa), shear bond (1.1±0.4 MPa), tensile strength (5.44±0.98), water absorption (0.92±0.2 µg/mm³), and solubility values (0.3±0.2 µg/mm3) to that of Molloplast B (1.4±0.4; 1.6±0.5; 4.53±0.9 MPa, 1.7±0.3, and 1.0±0.3 µg/mm³, respectively). The water solubility of Sofreliner Soft was significantly lower (1.5±0.8 µg/mm³) than that of Molloplast B. CONCLUSIONS There were significant differences between some properties of 4 chairside denture soft lining materials and that of Molloplast B, which had higher shear and tensile bond strength than chairside denture silicone soft lining materials but had the highest water solubility.

Denture cleanser effect on resilient liners with distinct optical characteristics.

PURPOSE: To evaluate denture cleansing solutions regarding the surface roughness and color stability of two resilient liners with distinct optical characteristics used for the maximum recommended period of use. METHODS: The specimens of each resilient liner, transparent and white, were randomly distributed into groups (n= 15) of a daily 20-minute immersion simulation of 0.25%, 0.5% and 1% sodium hypochlorite (SH) and 4% acetic acid solutions. Surface roughness (Ra) and color stability (ΔE CIELab formula and NBS systems) were measured after 7, 14, 21, 30, 60, 90, 180, and 270 days. The factors of variations analyzed were material, solutions, and time of immersion. Statistical analysis used three-way ANOVA and Tukey tests (Ra), and repeated measure ANOVA (ΔE and NBS systems), P< 0.05. RESULTS: For Ra analysis, the variations occurred regardless of time and solution, as the white liner showed the greatest changes (P< 0.001). Regarding interactions between solution and time, in the period of 21 days until 270 days, Ra was equivalent for all solutions (P= 0.001). ΔE analysis showed a difference between solutions (P= 0.000) and interaction between time and solution (P= 0.000). For the transparent liner, the greatest changes were found for 1% SH after 60 days, however, at 270 days there was a color change equivalence with 0.5% SH, while 4% acetic acid solution showed intermediate values. For the white liner, 1% SH showed the highest color changes for all evaluated times, and the other evaluated solutions were similar after 270 days. For both resilient liners, 0.25% SH showed the smallest changes for the evaluated properties. CLINICAL SIGNIFICANCE: The changes found were dependent on the concentration of the solution used, as well as the length of exposure to the solution. In addition, the white resilient liner showed to be less susceptible to color changes. For both resilient liners, 0.25% sodium hypochlorite showed the least changes for the evaluated properties.

Comparison of tensile bond strength of denture reline materials on denture bases fabricated with CAD-CAM technology.

STATEMENT OF PROBLEM: Studies that have analyzed the bond strength of resilient denture liners to milled denture bases are sparse, and the authors are unaware of research that has investigated the tensile bond strength of denture relining materials to 3D-printed denture bases. PURPOSE: The purpose of this in vitro study was to evaluate the tensile bond strength of both hard and soft denture reline materials on denture bases fabricated by 3D printing and computer-aided design and computer-aided manufacture (CAD-CAM) milling technology. MATERIAL AND METHODS: Injected, milled, and printed denture base specimens were fabricated (n=30) and bonded to 5 different denture reline materials: soft chairside reline (Coe Soft and PermaSoft), hard chairside reline (Tokuyama Rebase ii and Kooliner), and hard laboratory reline (ProBase Cold). Specimens of each reline material were divided into 5 groups (n=10) and were placed in distilled water for 24 hours before tensile testing. Maximum tensile stress values before failure were recorded, and the failure mode was also determined. The type of failure was analyzed by a scanning electron microscope. Statistics were analyzed with 2-way ANOVA and multiple comparison tests (α=.05). RESULTS: Overall, no statistically significant difference in tensile bond strength was found in the injected, milled, and printed denture groups. However, the printed denture base group demonstrated significantly lower values of tensile bond strength (P<.05) with PermaSoft, Tokuyama Rebase ii, and ProBase Cold groups than other denture base groups (milled and injected). The milled denture bases had the highest mean value of tensile bond strength with 4 of the 5 denture relining materials tested (Coe Soft, PermaSoft, Tokuyama Rebase ii, and Kooliner). No statistically significant difference (P>.05) was found among the injected, milled, and printed denture bases when relined with Kooliner. When comparing the denture reline type, the lowest values were seen with the soft chairside relining materials, and highest values with the hard laboratory reline material. Among the modes of failure, adhesive failures were observed predominantly with the printed denture base materials relined with soft chairside relining materials, while cohesive and mixed modes of failure were found in the milled and injected denture base groups. CONCLUSIONS: The printed denture bases had significantly lower tensile bond strength values than the injection and milled denture bases with the PermaSoft, Tokuyama Rebase ii, and ProBase Cold denture relines, while milled denture bases demonstrated the highest values of tensile bond strength for all chairside relining groups. In addition, the soft chairside relining materials showed the lowest tensile bond strength values regardless of the denture processing method with respect to the denture base type (injected, printed, and milled) compared with the hard relining materials.

Tensile bond strength of soft and hard relining materials to conventional and additively manufactured denture-base materials.

PURPOSE: Studies comparing tensile bond strength of various soft and hard denture liner materials to conventionally and additively manufactured denture base resins are lacking. The purpose of this study was to investigate the tensile bond strength between chair- and laboratory-side soft and hard relining materials and denture-base materials produced by additive manufacturing and conventional methods. MATERIALS AND METHODS: A total of 120 dimethacrylate-based additively manufactured and polymethylmethacrylate (PMMA)-based conventionally fabricated dumbbell-shaped denture-base resins were produced. Heat-cured laboratory-side soft reline material, self-cured chair-side soft reline material, and self-cured chair-side hard reline material were attached to the denture bases. The tensile force was applied to the specimens with a universal testing machine at a crosshead speed of 5 mm/min. The obtained data were analyzed with two-way ANOVA and post hoc Tukey tests. The significance level was set at α = 0.05. RESULTS: The highest tensile bond strength values were obtained in the specimens from the conventionally manufactured base and self-cured chair-side hard reline material group, and the lowest was seen in the additively fabricated base and self-cured chair-side soft reline material group (p < 0.001). Conventionally manufactured base material's tensile bond strength was higher than that of additively fabricated resin, and self-cured chair-side hard reline material's strength was higher than that of laboratory-side and chair-side soft reline materials (p < 0.001). However, no significant difference emerged between laboratory-side and chair-side soft reline materials (p = 0.405). CONCLUSIONS: All the specimens used in the present study had tensile bonding stress values for clinical use. Both denture base resins provided an increased bond to the chair-side hard relining material, although an improved bond did not emerge for the chair-side and laboratory-side soft denture reline materials.

Adherence of Candida albicans to Five Long-Term Silicone-Based Denture Lining Materials Bonded to CAD-CAM Denture Base.

PURPOSE: Knowledge about quantifying the number as well as the retention and adhesion of Candida albicans blastoconidia to silicone denture liners is limited. Thus, the aim of this in vitro study was to explore the adherence of C. albicans to the surface of five long-term silicone-based soft denture lining materials, using artificial saliva. MATERIALS AND METHODS: A total of 50 specimens (10 × 10 × 3 mm) of five long-term resilient liners (Molloplast-B; GC Reline Soft; Elite Soft Relining; Tokuyama Sofreliner S; Ufigel SC), bonded to a computer-aided design and computer-aided manufacturing denture base, were prepared. The specimens were inoculated and incubated in artificial saliva for 1 and 24 hours with a standardized (2.8 × 106 cfu/ml) C. albicans suspension. At the end of the incubation period, the specimens were stained with acridine orange and observed using fluorescence microscopy. RESULTS: After 1 hour and in 24 hours, Molloplast B demonstrated significantly earlier adherence of C. albicans cells compared to the other chairside materials (p < 0.001 and p < 0.001, respectively), where the mean number of cells also increased in the frontal parts. Regarding the rate of C. albicans proliferation from 1 to 24 hours within the materials, there was an increase in all materials (Molloplast B: p < 0.001; GC Reline Soft: p = 0.220; Elite Soft Relining: p = 0.032; Tokuyama Sofreliner S: p = 0.001; Ufigel Sc: p = 0.001). The Ufigel Sc showed a significant 2.5-fold increase at 24 hours. CONCLUSIONS: Long-term silicone denture liners accumulate a significant amount of C. albicans blastoconidia and their coverage by them increases progressively over time.

The Impact of the Addition of Vitamins on a Silicone Lining Material to the Oral Mucosa Tissue-Evaluation of the Biocompatibility, Hydrolytic Stability and Histopathological Effect.

Background and Objectives: One's quality of life depends on overall health, and in particular, oral health, which has been and continues to become a public health issue through frequent manifestations in various forms, from simple oral stomatitis (inflammations of the oral cavity) to the complicated oral health pathologies requiring medical interventions and treatments (caries, pulp necrosis and periodontitis). The aim of this study focused on the preparation and evaluation of vitamins (vitamin A, B1 and B6) incorporated into several silicone-based lining materials as a new alternative to therapeutically loaded materials designed as oral cavity lining materials in prosthodontics. Materials and Methods: Silicone-based liners containing vitamins were prepared by mixing them in solution and becoming crosslinked, and then they were characterized using Fourier-transform infrared (FT-IR) spectroscopy to confirm the incorporation of the vitamins into the silicone network; scanning electron microscopy (SEM) to evidence the morphology of the liner materials; dynamic vapor sorption (DVS) to evaluate their internal hydrophobicity, swelling in environments similar to biological fluids and mechanical test to demonstrate tensile strength; MTT to confirm their biocompatibility on normal cell cultures (fibroblast) and mucoadhesivity; and histopathological tests on porcine oral mucosa to highlight their potential utility as soft lining materials with improved efficiency. Results: FT-IR analysis confirmed the structural peculiarities of the prepared lining materials and the successful incorporation of vitamins into the silicone matrix. The surface roughness of the materials was lower than 0.2 µm, while in cross-section, the lining materials showed a compact morphology. It was found that the presence of vitamins induced a decrease in the main mechanical parameters (strength and elongation at break, Young's modulus) and hydrophobicity, which varied from one vitamin to another. A swelling degree higher than 8% was found in PBS 6.8 (artificial saliva) and water. Hydrolytic stability studies in an artificial saliva medium showed the release of low concentrations of silicone and vitamin fragments in the first 24 h, which increased the swelling behavior of the materials, diffusion and solubility of the vitamins. The microscopic images of fibroblast cells incubated with vitamin liners revealed very good biocompatibility. Also, the silicone liners incorporating the vitamins showed good mucoadhesive properties. The appearance of some pathological disorders with autolysis processes was more pronounced in the case of vitamin A liners. Conclusions: The addition of the vitamins was shown to have a beneficial effect that was mainly manifested as increased biocompatibility, hydrolytic stability and mucoadhesiveness with the mucosa of the oral cavity and less of an effect on the mechanical strength. The obtained lining materials showed good resistance in simulated biological media but caused a pronounced autolysis phenomenon, as revealed by histopathological examination, showing that these materials may have broad implications in the treatment of oral diseases.

Effect of Professional Denture Cleaning on Surface Roughness of Silicone or Acrylic Soft Relining Materials.

The aim of this study was to investigate the effects of combining mechanical (ultrasonic) and chemical cleaning (using denture cleaners) on the surface roughness of silicone or acrylic soft relining materials. The silicone soft relining material with the lowest Shore A hardness and a acrylic soft relining material routinely used in Japan were selected. Four groups were established based on type of treatment: immersion in water (W); ultrasonic cleaning in tap water (U); ultrasonic cleaning in a hypochlorous acid denture cleanser (HU); or ultrasonic cleaning in an acidic denture cleanser (AU). Following the tests, surface roughness was determined as the arithmetic mean height of the surface (Sa) and maximum height (Sz). Data were analyzed using the Kruskal-Wallis test followed by Bonferroni correction for a multiple comparison. No significant difference was observed in the Sa or Sz of the silicone soft relining material between the 4 groups. Significant differences were observed in the Sa of the acrylic soft relining material between Groups W and HU (p=0.008) and between Groups W and AU (p=0.008), but no significant differences in the Sz among the 4 groups. Combining U with AU or U with HU yielded no increase in the surface roughness of the silicon soft relining material. The surface roughness of the acrylic soft relining material showed an increase, however, with the combination treatments used.

Satisfaction with resilient denture liner versus acrylic resin telescopic prostheses for patients with ectodermal dysplasia: A nonrandomized crossover clinical trial.

STATEMENT OF PROBLEM: Patients with ectodermal dysplasia are characterized by anodontia or oligodontia. How their challenging prosthodontic rehabilitation might be optimized is unclear. PURPOSE: The purpose of this crossover study was to evaluate the effect of resilient denture liner versus acrylic resin copings in complete overdentures for patients with ectodermal dysplasia. Outcome measures included patient satisfaction, retention, and periodontal health of the abutment tooth. MATERIAL AND METHODS: Ten partially edentulous participants diagnosed with ectodermal dysplasia were recruited from the Faculty of Dentistry, Cairo University, Egypt, and enrolled in this crossover clinical trial. All participants received acrylic resin coping-retained maxillary complete overdentures (group N, stage 1). The acrylic resin copings were then replaced by a resilient denture liner (group S, stage 2). Patient satisfaction, retention, and periodontal health parameters were evaluated 1 week and 3 months after the completion of each stage. Patient satisfaction was assessed with a validated, reliable questionnaire. The results of the periodontal probing depths were tested with repeated measures ANOVA followed by the Bonferroni correction for pairwise comparisons. Tooth mobility, patient satisfaction, retention, and gingival index were tested by using the Wilcoxon signed ranked test. Ordinal data as the sixth and seventh domains of patient satisfaction were tested by using the McNemar test for paired comparisons (α=.05). RESULTS: Three months after overdenture delivery, a statistically significant difference was found between the groups regarding retention (P=.025), probing depth (P<.001), and gingival index (P=.011) favoring the acrylic resin coping-retained overdentures. Results of tooth mobility (P=.035), overall attitude (P=.041), ease of eating (P=.023), denture comfort (P=.024), and degree of teasing (P=.038) on wearing the denture showed a statistically significant difference between the groups, favoring the resilient denture liner. CONCLUSIONS: In children with oligodontia and ectodermal dysplasia, the resilient denture liner-retained maxillary complete overdenture enhanced patient satisfaction and tooth mobility of anterior teeth, while minimally jeopardizing the periodontal condition of the abutment teeth.

Assessment of Tensile Bond Strength of a Soft Liner to the Denture Base Resin with Different Surface Treatments: An In Vitro Study.

AIM: The aim of the current research was to evaluate the tensile bond strength of a soft liner to the denture base resin with different surface management techniques. MATERIALS AND METHODS: Dies made up of stainless steel and having dimensions of 40 × 10 × 10 were used to fabricate polymethyl-methacrylate resinous blocks. To make sure of the regularity of the soft liner in the test, dies made up of stainless steel and having dimensions of 10 × 10 × 3 were fabricated to serve as spacers. These acrylic resinous blocks were allocated to three groups depending upon the particular surface management technique as: group I-Absence of surface treatment (Control), group II-Surface management with methyl methacrylate (MMA) monomer, and group III-Surface management with Phosphoric acid. All the samples underwent thermocycling at 5° centigrade and 55° centigrade in two water baths for 500 cycles at a dwell tenure of 30 seconds in every bath to reproduce the oral circumstances. The samples were then subjected to testing in the universal testing machine for evaluation of the tensile strength. RESULTS: The highest tensile strength was noted in the soft liner with denture base resin that was subjected to treatment with a monomer having a mean score of 1.88 ± 0.11 in pursuit by surface management using phosphoric acid at 1.16 ± 0.90 as well as the control group at 0.94 ± 0.02 in that order. There was a statistically noteworthy disparity amid the three dissimilar surface management techniques with a p-value <0.001. There was a statistically noteworthy differentiation amid group I vs group II as well as group II vs group III with a p-value <0.001. However, there was no statistically significant disparity amid group I vs group III with p-value >0.001. CONCLUSION: The current research arrived at the conclusion that the samples subjected to treatment with MMA monomer exhibited higher and noteworthy bond strength than those attained by additional surface management techniques for soft lining of the denture base resins. CLINICAL SIGNIFICANCE: Soft denture lining materials play a pivotal position in contemporary prosthodontic practice as they possess the ability to restore the health of swollen as well as deformed mucosal tissues. They are comfortable in those individuals who are unable to endure pressure from occlusal forces, like in a situation of residual ridge resorption, sore tissues, and ridges that attain a knife-edge shape. Failing bond causes delamination of the reliner and therefore lack of adaptability of the denture to the oral mucosal tissues. For this reason, superior bonding to the denture base beneath is critical for the clinical triumph of relining agents.

Minimally important differences for the EORTC QLQ-C30 in prostate cancer clinical trials.

BACKGROUND: The aim of the study was to estimate the minimally important difference (MID) for interpreting group-level change over time, both within a group and between groups, for the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) scores in patients with prostate cancer. METHODS: We used data from two published EORTC trials. Clinical anchors were selected by strength of correlations with QLQ-C30 scales. In addition, clinicians' input was obtained with regard to plausibility of the selected anchors. The mean change method was applied for interpreting change over time within a group of patients and linear regression models were fitted to estimate MIDs for between-group differences in change over time. Distribution-based estimates were also evaluated. RESULTS: Two clinical anchors were eligible for MID estimation; performance status and the CTCAE diarrhoea domain. MIDs were developed for 7 scales (physical functioning, role functioning, social functioning, pain, fatigue, global quality of life, diarrhoea) and varied by scale and direction (improvement vs deterioration). Within-group MIDs ranged from 4 to 14 points for improvement and - 13 to - 5 points for deterioration and MIDs for between-group differences in change scores ranged from 3 to 13 for improvement and - 10 to - 5 for deterioration. CONCLUSIONS: Our findings aid the meaningful interpretation of changes on a set of EORTC QLQ-C30 scale scores over time, both within and between groups, and for performing more accurate sample size calculations for clinical trials in prostate cancer.

Effect of cigarette smoke on color stability and surface roughness of different soft denture lining materials. An in vitro study.

PURPOSE: To evaluate the effect of cigarette smoke on the surface roughness and color stability of three different soft denture liners. METHODS: Three commonly used commercially available, chair-side, long-term vinyl polysiloxane soft denture liners were used for this study [Sofreliner Tough (S) Soft, Silagum Comfort Soft Relining, and GC Reline Soft\. Thirty disk-shaped specimens of each material, with a diameter of 25 mm and thickness of 2 mm, were fabricated. Initial color and surface roughness readings were recorded. The specimens of each group were randomly divided into two groups (n= 15): the control group (C) and the study group (S). The control group specimens were stored in distilled water and the study group samples were exposed to cigarette smoke in a custom-made smoking chamber. Final color and surface roughness readings were recorded. A single operator performed all the measurements. The differences in color and surface roughness were calculated. Statistical analysis was performed using two-way ANOVA, post-hoc Tukey test, and paired t-test. For all the analyses, a P< 0.05 was regarded as statistically significant. RESULTS: After exposure to smoke, all groups showed a significantly perceptible color change (ΔE > 3.7). The greatest color change was seen in the Silagum group (ΔE= 8.94 ± 0.42), followed by the Sofreliner group (ΔE= 7.85 ± 0.47), with the least change in the GC reline group (ΔE= 3.87 ± 0.46). The mean color change after smoke exposure showed a statistically significant difference among all three study groups. The highest change in surface roughness was observed in the Silagum group (ΔR= 0.687 ± 0.14) followed by the GC reline group (ΔR= 0.265 ± 0.12), with the least change in the Sofreliner group (ΔR= 0.238 ± 0.06). There was a statistically significant difference between each group before and after exposure to smoke. Exposure to cigarette smoke caused significant changes in the color and surface roughness of all three soft denture liners tested in this study. The extent of these changes varied for each material. CLINICAL SIGNIFICANCE: Proper selection of soft denture liners is essential to avoid premature replacement, due to esthetic and hygiene reasons in cigarette smokers.

Surface Characterization, Biocompatibility and Antifungal Efficacy of a Denture-Lining Material Containing Cnidium officinale Extracts.

Herein, we investigated the surface characterization and biocompatibility of a denture-lining material containing Cnidium officinale extracts and its antifungal efficacy against Candida albicans. To achieve this, a denture-lining material containing various concentrations of C. officinale extract and a control group without C. officinale extract were prepared. The surface characterization and biocompatibility of the samples were investigated. In addition, the antifungal efficacy of the samples on C. albicans was investigated using spectrophotometric growth and a LIVE/DEAD assay. The results revealed that there was no significant difference between the biocompatibility of the experimental and control groups (p > 0.05). However, there was a significant difference between the antifungal efficiency of the denture material on C. albicans and that of the control group (p < 0.05), which was confirmed by the LIVE/DEAD assay. These results indicate the promising potential of the C. officinale extract-containing denture-lining material as an antifungal dental material.

Evaluation of interface pressure and temperature management in five wheelchair seat cushions and their effects on user satisfaction.

BACKGROUND: Factors such as the manufacturing materials, shape or even the mechanical and thermal response of sitting Pressure Redistribution Support Surfaces (PRSS) can be potential contributors to pressure ulcers. However, few studies have compared a number of characteristics of the most frequently used devices. OBJECTIVE: To compare three potential contributors to pressure ulcers in five commercial PRSS: pressure redistribution, temperature and perceived comfort. METHOD: Study with a cross-over randomized design in healthy volunteer participants. Data was collected in a temperature and relative humidity controlled environment. To assess thermal response, the temperature (Flir-E60) of the region of interest was captured before and after use of each PRSS for further analysis. The region of interest was the gluteal zone. To assess the pressure redistribution a pressure mat (XSensor®) was used between the 5 cushion and each study participant using a standardized method. Finally, a subjective perception questionnaire recorded comfort, adaptability and thermal sensation parameters. Data analysis levels of significance were set at 0.05. RESULTS: A total of 22 participants completed the assessments. There were no statistically significant differences in baseline temperatures between PRSS (>0.05). Pressure redistribution analysis showed significant differences between all PRSS in all variables evaluated except in the maximum and peak pressure index al sacrum. The subjective assessment suggested no major user-perceived differences between PRSS. CONCLUSION: Seat cushions made of open cell polyurethane foam blocks of variable hardness and the horseshoe cushion (also open cell polyurethane foam) seem to provide a more effective pressure relief characteristic than those injected with polyurethane foam and gel in most of the studied pressure variables. However, the cushions provide similar thermal response and perceived comfort.

Evaluation of viscoelastic properties, hardness, and glass transition temperature of soft denture liners and tissue conditioner.

Soft denture liners and tissue conditioners are widely used for the denture patients to cushion masticatory force and condition abused tissues, respectively. This study assessed methods for the evaluation of the viscoelasticity and glass transition temperature (Tg) of the silicone permanent soft liner, acrylic permanent soft liner, and tissue conditioner. Three rheological parameters of storage modulus (E'), loss modulus (E''), and loss tangent ([Formula: see text]), Tg, and hardness were determined using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and the Shore A0 hardness test. Five specimens were measured for each material. The time-temperature superposition principle was applied to produce master curves of E', E'', and [Formula: see text] for the tested materials at a reference temperature of 37 °C. The acrylic permanent soft liner and tissue conditioner exhibited viscoelastic behavior and sensitivity to frequency, especially at lower frequencies. The silicone permanent soft liner showed elastic behavior and was frequency-independent. Tg for the acrylic permanent soft liner was higher than that for the tissue conditioner, which in turn was higher than that for the silicone permanent soft liner for both DMA and DSC. In DMA, a higher frequency led to higher Tg values. A positive linear relationship was found between Shore A0 hardness and E' values, but not E'' and [Formula: see text] values. Shore hardness reflects elasticity, but not viscosity. The results of the present study can be used to improve methods for evaluating the viscoelasticity and Tg of soft denture liners and tissue conditioners.

Retention force and allowable range of the angle of an implant-supported overdenture attachment system using healing screws and a silicone resilient denture liner.

STATEMENT OF PROBLEM: Changes in the intraoral condition immediately after implant placement and in patients using fixed prosthetic appliances with implant abutments cause problems that require the use of an easily adjustable implant-supported overdenture system. PURPOSE: The purpose of this in vitro study was to develop a simulated implant-supported overdenture attachment system by using healing screws for the patrix and a silicone resilient denture liner for the matrix and to investigate the initial retention force, time-course changes, and allowable range of the angle between attachments. MATERIAL AND METHODS: Tests on the retention force and allowable range of the angle were performed. Attachments using tissue-level healing screws (height: 2.0 and 3.0 mm) for the patrix and a silicone resilient denture liner for the matrix were prepared. In the retention force measurement test, the frequency of insertion and removal was set at 3 per day to simulate a 4-month relief period. The joined attachment model was pulled apart, and the maximum traction (N) required to remove it was defined as the retention force. The retention force was measured every 90 times (representing the number of insertions and removals per month). To test the allowable angle range, 2 patrices were used. The angle between the 2 patrices was set at 0, 10, 20, and 30 degrees, and the angular limit for joining with the matrix was measured. The initial retention force of the healing screw attachments was compared with that of a polymeric O-ring by using 1-way layout ANOVA followed by the Bonferroni test (α=.05). To analyze time-course changes in the 2 types of healing screw attachments, the retention force before insertion and removal was compared with that after repeated insertions and removals for each simulated period using 1-way layout ANOVA followed by the Dunnett test (α=.05). RESULTS: The initial retention force of the 2.0- and 3.0-mm healing screws was 2.4 ±0.1 and 2.6 ±0.2 N. After repeating insertions and removals to simulate use for 4 months, the retention force of the 2.0- and 3.0-mm healing screws was 1.8 ±0.2 and 2.2 ±0.1 N, respectively, both showing significant differences from the initial retention force (P<.05). The allowable angle range test revealed that insertion and removal of the healing screws was possible up to 30 degrees. CONCLUSIONS: Under the conditions of this in vitro study, repeated insertion and removal attenuated the retention force but was still equivalent to the retention force of the O-ring. The allowable range of the angle between patrices for insertion and removal was up to 30 degrees.

Bond strength of soft liners to denture base resins and the influence of different surface treatments and thermocycling: A systematic review.

STATEMENT OF PROBLEM: Occasional debonding between soft liners and denture base resin is common and limits the longevity of a relined prosthesis. PURPOSE: The purpose of this systematic review was to compare the bond strength of commercially available soft liners with that of polymethyl methacrylate (PMMA) and urethane dimethacrylate (UDMA) denture base resins after different surface treatments and thermocycling. MATERIAL AND METHODS: Searches were performed by 2 independent reviewers in the MEDLINE/PubMed and Cochrane Library databases from January 1990 to December 2018 to identify published journal articles related to this subject. Subsequently, a hand search was also carried out for all the articles mentioned in the references of the identified full articles. RESULTS: A total of 61 articles were initially identified through database searches by the 2 reviewers. Twenty-four of the 61 articles met the inclusion criteria for qualitative analysis. Four of 6 articles showed that laser pretreatment of denture base resins increased their bonding to soft liners. Seven of 8 articles concluded that airborne-particle abrasion caused deterioration of the bonding between the liner and denture base resin. Four of 6 studies showed that acid etching, silica coating, primer or monomer application, and immersion in acetone or isobutyl methacrylate (iBMA) resulted in improved bond strengths between the liner and resin. One study reported that oxygen plasma treatment also resulted in improved bond strengths. Seven of 8 articles concluded that thermocycling resulted in decreased bond strengths. CONCLUSIONS: Laser treatment, oxygen plasma pretreatment, primer or monomer application, and immersion in acetone or iBMA resulted in improved bonding of the denture base resin to soft liners. However, airborne-particle abrasion and thermocycling resulted in deterioration of the bond.

Effect of argon plasma and Er:YAG laser on tensile bond strength between denture liner and acrylic resin.

STATEMENT OF PROBLEM: The separation of a denture liner from the denture base can be a clinical problem. Different surface treatments to increase the bond have been evaluated, but studies comparing the effect of argon plasma and erbium-doped yttrium aluminum garnet (Er:YAG) laser on the bond between acrylic resin and a denture liner are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of argon plasma and Er:YAG laser treatments on the bond strengths of acrylic resin to 2 denture liners. MATERIALS AND METHODS: Heat-polymerized acrylic resin (Acron Duo) was bonded to silicone soft-liner materials (Molloplast B, n=30; Mollosil, n=30) to create control specimens (n=10), argon plasma treatment (n=10), and Er:YAG laser treatment (n=10). Silicone liners were polymerized on resin specimens. The tensile bond strength test was performed with a crosshead speed of 10 mm/min with a 10-N load until failure. Data were analyzed by using the Kruskal-Wallis test and unpaired t test (α=.05). RESULTS: The laser group showed significantly higher bond strength than the argon plasma group for both Molloplast-B (P=.001) and Mollosil (P<.001). The highest tensile bond strength values were determined in the laser-treated Molloplast-B group (1.325 ±0.119 MPa) while the lowest bond strength values were determined in the Mollosil control group (0.384 ±0.018 MPa). CONCLUSIONS: Argon plasma and Er:YAG laser applications increases the tensile bond strength between soft-liner material and resin. Er:YAG laser treatment results in higher bond strength values than treatment with argon plasma for 1 minute.