Effect of Tea Tree Oil Addition to Denture Liners Against Candida albicans and Bond Strength to Acrylic Denture Bases.

PURPOSE: To evaluate the effect of adding tea tree oil to denture liners on Candida albicans and bond strength to the acrylic denture base. MATERIALS AND METHODS: Disc-shaped specimens were fabricated from silicone-based resilient liner (Tokuyama, Molloplast), acrylic-based hard liner (GC Reline), and acrylic-based soft liner (Visco-gel). Tea tree oil (TTO) was incorporated into the liners at varying concentrations (0% [control], 2%, 5%, 8%). C albicans were counted by viable colony count, and optical density (OD) was measured with a spectrophotometer. The tensile strength to heat polymerized acrylic denture base was measured in a universal testing machine. The compliance of the data to the distribution of normality was evaluated using the Shapiro Wilk test. Two-way ANOVA, Bonferroni correction, and paired sample t test were performed (α = .05). RESULTS: The addition of TTO into liners provided a significant decrease in the OD values (P < .001). The control groups of the liners presented the highest colony counts, whereas increasing TTO decreased the results (P < .01). According to tensile bond strength test, 8% TTO addition resulted in a significant decrease for Tokuyama (P < .01) and Molloplast liners (P < .05), while 2% TTO resulted in significance for GC Reline (P < .001). CONCLUSIONS: Denture liners containing increasing percentages of TTO presented lower amounts of C albicans colonies and decreased bond strength to the denture bases. When using TTO for its antifungal properties, the amount added should be carefully selected because the tensile bond strength may be affected.

Soft Denture liner and microbial disinfection with contemporary and conventional agents.

AIM: The present study aimed to assess the effect of PDT, herbal and chemical disinfectants on the dental pathogen adherence to soft denture liner colonized with E. coli, C. Albicans, S.aureus, and S. mutans. MATERIAL AND METHODS: A total of 20 samples of soft-lined removable acrylic complete dentures were fabricated and subjected to the American Type Culture Collection (ATCC) for the inoculation of E.coli, C.albicans, S.mutans and S.aureus in an in-vitro setup. The samples were then randomly divided into four groups and immersed in group 1: 5 µm of Rose Bengal (RB), group 2: Neem extract, group 3: Tea tree oil (TTO), and group 4: 0.12% CHX solutions respectively. Statistical analysis was accomplished by the SPSS 10 statistical software for Windows at a significance level p< 0.05. Two-way ANOVA and Tukey's multiple comparison test were used to analyze the data and compare the means and standard deviation values of CFU/mL (log10) for exposed E. coli, C. albicans, S aureus, and S. mutans. RESULTS: Intragroup comparison indicated E.coli and C.albicans did not unveil a decrease in reduction CFU/mL (log10) when SDL irradiated with RB 5 µm. Whereas, CFU/mL (log10) values of S.aureus; 2.62±0.68 CFU/mL and S.mutans: 3.41±0.13 CFU/mL plunged significantly (p<0.05). Likewise, S. aureus and S. mutans CFU/mL (log10) strain values display reduction when treated with all four disinfectants while the count of C.albicans unveiled a significant plunge with CHX, TTO and neem extract except RB (p<0.05) CONCLUSION: 0.12% CHX and TTO have enhanced antimicrobial efficacy in reducing adhered bacterial colonies of E.coli, C.albicans, S.aureus, and S.mutans (CFU)/mL on a denture soft liner.

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.

An In Vitro Assessment of Surface Roughness, Tensile Bond Strength and Antifungal Activity of Grape Seed Extract-modified Soft Liner.

AIM: This study was conducted to evaluate the grape seed extract (GSE)-modified soft liner regarding surface roughness, tensile bond strength to the denture base material, and the antifungal activity. MATERIALS AND METHODS: The GSE powder was blended with the soft liner powder in ratios of 5 and 10% w/w, and three groups were employed: I, control; II, 5% w/w GSE-modified soft liner; III, 10% w/w GSE-modified soft liner. Evaluation parameters included surface roughness, tensile bond strength to the denture base material, and the antifungal activity. Changes in surface topography were evaluated by scanning electron microscopy. The statistical analysis was performed using the one-way ANOVA followed by the Tukey's test (α = 0.05). RESULTS: The 5% w/w GSE-modified soft liner showed a significant increase in surface roughness, while both ratios (5 and 10% w/w) of the modified-soft liner exhibited significant increase in tensile bond strength and antifungal activity (p < 0.05). CONCLUSION: The GSE of 10% w/w considerably enhanced the antifungal activity and tensile bond strength of the modified soft liner to the denture base material without compromising its surface roughness. CLINICAL SIGNIFICANCE: The 10% w/w GSE-modified soft liner may be a promising formulation with antifungal activity. It could inhibit fungal adherence and development of fungi-induced lesions or exacerbation of existing ones.

Effect of incorporating seed oils on the antifungal property, surface roughness, wettability, weight change, and glucose sorption of a soft liner.

STATEMENT OF PROBLEM: The colonization of Candida albicans on soft liners causes the deterioration of material surface properties and denture stomatitis. PURPOSE: The purpose of this in vitro study was to investigate the effect of incorporating seed oil on the antifungal properties, surface roughness, wettability, weight changes, and glucose adsorption/absorption of a soft liner. MATERIAL AND METHODS: Centratherum anthelminticum, Ocimum sanctum Linn, and Linum usitatissimum seed oils were incorporated into a soft liner, and the diameter of the inhibition zone (DIZ) was calculated relative to the growth of C albicans at 24, 48, and 72 hours and 7 days. The effect of incorporating oil on wettability was evaluated with the contact angle analyzer, and effect on surface roughness was evaluated with scanning electron microscopy. Weight changes and absorption/adsorption of glucose to the soft liner were estimated. Data were analyzed by using paired Student t tests and 2-way ANOVA (α=.01). RESULTS: Soft liner with 800 µL each of C anthelminticum and O sanctum oils showed complete inhibition at 72 hours; the DIZ on day 7 were 31.66 ±1.20 mm and 29.66 ±1.46 mm, respectively. The change in weight between time intervals differed significantly between conditions (P<.01). The addition of oils decreased the surface roughness and improved wettability significantly for O sanctum and C anthelminticum specimens (P<.01). At 72 hours, 5.5 mg of glucose was detected in the positive control, whereas no glucose was detected in the oil specimens. CONCLUSIONS: The addition of the seed oils of C anthelminticum and O sanctum to the soft liner significantly reduced the growth of C albicans, improved wettability, reduced surface roughness, and minimized the absorption and adsorption of glucose.

Evaluation of correlations between frequencies of complete denture relines and serum levels of 3 bone metabolic markers: A cross-sectional pilot study.

STATEMENT OF PROBLEM: Continuous bone resorption is the primary reason for complete denture relines. Because resorption rates vary, the frequency at which individuals require relines also varies. Currently, there are no predictors to identify individuals at risk of frequent relines or to guide clinicians in decisions related to relines. PURPOSE: The purpose of this cross-sectional pilot study was to determine the utility of measuring bone metabolic markers (C-terminal telopeptide, osteocalcin, 25-OH hydroxy vitamin D) to predict the frequency of complete denture relines. MATERIAL AND METHODS: One hundred adult participants with complete dentures (either maxillary, mandibular, or both) participated in 1 dental clinic visit involving a dental examination and brief interview to obtain relevant medical and dental history, information on medication/supplement use, and 1 laboratory blood draw for the measurement of bone metabolic markers. Data were analyzed by using the Pearson correlation, independent Student t test, or analysis of variance (α=.05). RESULTS: Significant correlations were found between the frequency of relines and C-telopeptide and osteocalcin levels but not with vitamin D or age. No significant associations with reline frequency and other factors (sex, ethnicity, presence or absence of diabetes, use of calcium and vitamin D supplements) were observed. CONCLUSIONS: Elevated levels of bone turnover markers in individuals with edentulism were associated with increased frequency of denture relines.

The Effects of Er:YAG, Nd:YAG, and Ho:YAG Laser Surface Treatments to Acrylic Resin Denture Bases on the Tensile Bond Strength of Silicone-Based Resilient Liners.

OBJECTIVE: The present study was to assess the effect of surface treatments of Er:YAG, Nd:YAG, and Ho:YAG lasers on the tensile bond strength of a silicone-based resilient liner to an acrylic denture in an in vitro setting. METHODS: Experimental dumbbell-shaped specimens (75 mm) were produced by combining two acrylate pieces fabricated from heat-polymerized acrylic resin (36 mm) with 3 mm of Molloplast(®)-B filling between them. The specimens (n=200) were randomly divided in half for thermocycling, and each 100 specimen set was randomized into five groups (n=20) with different surface treatments: control (no surface treatment), sandblasting, Er:YAG laser, Nd:YAG laser, and Ho:YAG laser. A tensile bond strength test was performed. The effect of the laser surface treatments was examined with scanning electron microscopy. RESULTS: Only the Er:YAG laser increased the tensile bond strength compared with the other treatments. The other laser groups showed lower bond strengths. The Ho:YAG laser resulted in considerably reduced tensile bond strength. The scanning electron microscopy images showed that applying laser surface treatments modified the surface of the denture base resin. CONCLUSIONS: There was not an overall improvement with the use of the studied laser modalities in the adhesion quality of resilient denture liner to acrylic resin, although Er:YAG laser showed a potential to improve their adhesion. These laser modalities need to be subjected to further studies to determine optimal setup for use in prosthodontics.

Effect of surface treatments on the bond strength of soft denture lining materials to an acrylic resin denture base.

STATEMENT OF PROBLEM: Adhesive failure between acrylic resin and resilient liner material is commonly encountered in clinical practice. PURPOSE: The purpose of this study was to evaluate the effect of different surface treatments on the bond strength of 2 different resilient lining materials to an acrylic resin denture base. MATERIAL AND METHODS: Ninety-six dumbbell-shaped specimens were fabricated from heat-polymerized acrylic resin, and 3 mm of the material was cut from the thin midsection. The specimens were divided into 6 groups according to their surface treatments: no surface treatment (control group), 36% phosphoric acid etching (acid group), erbium:yttrium-aluminum-garnet (Er:YAG) laser (laser group), airborne-particle abrasion with 50-µm Al2O3 particles (abrasion group), an acid+laser group, and an abrasion+laser group. The specimens in each group were divided into 2 subgroups according to the resilient lining material used: heat-polymerized silicone based resilient liner (Molloplast B) and autopolymerized silicone-based resilient liner (Ufi Gel P). After all of the specimens had been polymerized, they were stored in distilled water at 37°C for 1 week. A tensile bond strength test was then performed. Data were analyzed with a 2-way ANOVA, and the Sidak multiple comparison test was used to identify significant differences (α=.05). The effects of the surface treatments and resilient lining materials on the surface of the denture base resin were examined with scanning electron microscopy. RESULTS: The tensile bond strength was significantly different between Molloplast B and Ufi Gel P (P<.001). The specimens of the acid group had the highest tensile bond strength, whereas those of the abrasion group had the lowest tensile bond strength. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. CONCLUSIONS: Molloplast B exhibited significantly higher bond strength than Ufi Gel P. Altering the surface of the acrylic resin denture base with 36% phosphoric acid etching increased bond strength.

Clinical trial of an experimental cleaning solution: antibiofilm effect and integrity of a silicone-based denture liner.

AIM: This study evaluated the antibiofilm effect of an experimental solution of 2% Ricinus communis (R. communis) on a silicone-based denture liner by means of a randomized clinical trial, as well as the integrity of such liner following a cleansing regimen with such solution. MATERIALS AND METHODS: About 30 complete denture wearers had their lower dentures relined with a silicone-based denture liner and randomly allocated to cleanse their dentures by means of: (A) a specific toothbrush for complete dentures and dentifrice; (B) soaking in an experimental 2% R. communis solution; and (C) association of A and B. Considered outcomes were biofilm coverage area (%), microbial counts by means of the deoxy-ribonucleic acid (DNA) checkerboard hybridization technique and physical integrity of the soft liner, assessed during a time interval of 60 days. Mean group values were compared by analysis of variance (ANOVA) and Tukey tests or generalized linear method (α = 0.05). RESULTS: The mechanical method presented the lowest biofilm percentage (1.45 ± 1.03) if compared to the chemical method (2.96 ± 1.98) and the associated one (2.71 ± 1.76). After 60 days (3.37 ± 2.04), biofilm accumulation was higher than at 15 days (1.28 ± 0.77) and 30 days (2.46 ± 1.54). The denture liner was less deteriorated and kept its physical integrity when the mechanical method was applied. The chemical method presented higher effectiveness against microorganisms, including some Candida species. CONCLUSION: The 2% R. communis solution presented stronger antimicrobial capacity than brushing on a silicone-based denture liner after immersion. However, it was not superior to the mechanical method in preserving the physical integrity of the material and in biofilm removal. CLINICAL SIGNIFICANCE: Soft denture liners hygiene is a very important issue and not conclusive in the literature. The experimental solution of 2% R. communis evaluated presented promising antimicrobial potential and should be more explored to be recommended as cleanser.

Evaluation of the properties of a tissue conditioner containing origanum oil as an antifungal additive.

STATEMENT OF PROBLEM: Adherence and colonization of Candida albicans on tissue conditioners is common and results in irritation of the denture-bearing mucosa. PURPOSE: The purpose of this study was to investigate the antifungal activity and properties of a tissue conditioner by incorporating origanum oil. MATERIAL AND METHODS: Origanum oil at varying concentrations was incorporated into a poly(methyl methacrylate) based tissue conditioner (Visco-gel), and its antifungal activity against Candida albicans was evaluated at 1 day and 1 week by using the agar punch well method. The adherence of Candida albicans, surface roughness, tensile strength, and bond strength of the tissue conditioner with an optimized origanum oil concentration were evaluated. The data were subjected to 2-way ANOVA (α=.05). RESULTS: Sixty vol% origanum oil in tissue conditioner (Visco-gel) showed a mean inhibitory zone of 21.00 ± 1.58 mm at 1 day and 13.44 ± 0.88 mm at 1 week. The control group showed 90 ± 6.80 yeast cells/mm(2) at 1 day and 165 ± 7.63 yeast cells/mm(2) at 1 week, whereas the group with origanum oil showed 16 ± 1.15 yeast cells/mm(2) at 1 day and 32 ± 4.00 yeast cells/mm(2) at 1 week. Surface roughness was less with the incorporation of origanum oil. Tensile strength at 1 day was 0.91 ± 0.52 N for the control group, whereas the group with origanum oil showed 0.16 ± 0.05 N. At 1 day, the bond strength of 3.97 ± 0.75 MPa was observed with control specimens, whereas tissue conditioner with origanum oil showed a bond strength of 3.73 ± 0.65 MPa. CONCLUSIONS: Within the limitations of this in vitro study, origanum oil can be used as an additive to tissue conditioner to reduce the adherence of Candida albicans without significantly affecting its bond strength to heat-polymerized acrylic resin.

Surface roughness of denture base and reline materials after disinfection by immersion in chlorhexidine or microwave irradiation.

BACKGROUND: This study evaluated the effect of disinfection by immersion and microwave irradiation on the roughness of one denture base resin (Lucitone-L) and five relining materials, three hard (Tokuyama Rebase II-TR, New Truliner-NT, Ufigel Hard-UH) and two resilient (Trusoft-T, Sofreliner-S). METHODS: Fifty specimens were made and divided into groups: CL2 specimens were brushed with 4% chlorhexidine (1 min), immersed in the same solution (10 min) and immersed in water (3 min); MW2 specimens were immersed in water and microwave irradiated (650W; 6 min); CL2 and MW2 specimens were disinfected twice; CL7 and MW7 specimens were submitted to seven cycles using chlorhexidine or microwave irradiation, respectively; W specimens were not disinfected and remained in water (37°C; 7 days). RESULTS: Results were statistically analysed (p = 0.05) and revealed that, at baseline, the highest mean value was observed for T (p < 0.001). Material NT showed increase in roughness after the first (p = 0.003), second (p = 0.001), seventh (p = 0.000) cycles of microwave disinfection and after 7 days of immersion in water (p = 0.033). CONCLUSIONS: Resilient liner S presented significant increase in roughness after the second cycle of disinfection with chlorhexidine (p = 0.003). Material T exhibited significantly decreased roughness in group W (p = 0.010), while microwaving produced severe alterations on its surface.

Evaluation of experimental cleanser solution of Ricinus communis: effect on soft denture liner properties.

OBJECTIVE: This study evaluated colour stability, hardness and roughness of soft denture liners after immersion in various cleansers. MATERIALS AND METHODS: Thirty specimens (14 mm × 4 mm) of Elite Soft Relining (ES) and Mucopren Soft (MS) were randomly immersed in distilled water at 37°C, sodium hypochlorite 1%, and an experimental Ricinus communis solution (RC) for 7, 15 and 183 continuous days. RESULTS: anova (p < 0.05) and Tukey's test indicated that after T7 (µ =8.79 ± 7.36); T15 (µ = 4.23 ± 2.62) and T183 (µ = 8.78 ± 3.16), MS presented a higher increase in hardness than ES. After T7, MS underwent an increase in roughness (µ = 0.09 ± 0.80); ES underwent a decrease (µ = -0.08 ± 0.16). RC caused the smallest variation in roughness. After T15, both materials presented an increase in roughness. After T183, ES (µ = -0.30 ± 0.48) presented a higher roughness variation than MS (µ = -0.07 ± 0.32). Hypochlorite caused an increase in roughness (µ = 0.02 ± 0.19). CONCLUSION: After all periods ES presented higher colour alteration than MS; highest colour alteration was caused by hypochlorite. Both materials were more stable after immersion in RC.

Color stability of chemically activated reline resin after microwave disinfection: a 1-year clinical trial.

PURPOSE: To evaluate the effect of microwave disinfection on the color stability of a hard chairside reline resin after a 1-year service period. METHODS: 40 adult patients aged between 30-75 years, who required denture reline treatment, participated in this study. Tokuyama Rebase II was used to reline complete maxillary dentures. The edentulous subjects were randomly divided into two groups (n=20) and dentures were cleansed according to two methods: CG (control group) - brushing with coconut soap and soft toothbrush; DG (disinfection group) - brushing according to previous methods and microwave disinfection once a week for 3 minutes at 650W. Color parameters in L*a*b* were recorded by spectrophotometer immediately after the reline, at 7 and 15 days, 1, 3, 6 and 9 months and 1 year post-placement. Data were analyzed by two-way repeated-measures ANOVA and Tukey tests (alpha = 0.05). RESULTS: Color alteration values of DG were significantly lower than those of CG (P<0.05). Color changes observed after 15 days were greater than values obtained at 7 days recall (P<0.05). All color changes observed for the CG were considered noticeable (between 1.5 and 3.0 NBS). In DG, color change was slight (between 0.5 and 1.5 NBS). There were statistically significant differences between L* values obtained initially and after 3 months, between 15 days and 3 months and between 15 days and 1 year (P<0.05). No significant differences were observed between group and time for the parameters a* and b*.

Colour change of soft denture liners after storage in coffee and coke.

This study was to evaluate the colour change of soft denture liners after thermocycling and storage in coffee and coke. Four liners, two silicone-based (Sofreliner S and Reline GS) and two acrylic resin-based (Soft Confort and Dentuflex), were evaluated in this study. Ten samples were obtained for each group. After 2000 cycles of thermocycling with baths of 5°C and 55°C, five samples were stored in coffee and the remaining samples in coke. The colour alteration was evaluated in a reflection spectrophotometer before and after thermocycling, and after 1, 3, 24, 48 and 96h of storage in coffee and coke. Data were submitted to anova and Tukey's HSD test (α=0.05). Thermocycling and storage period represented a higher statistically significant influence for the resin liners than for the silicone materials. Coke did not influence the colour stability of the materials during storage. However, the coffee solution generated statistically significant colour alteration in the material Soft Confort. In the comparison between the coffee and coke solutions, there was no statistically significant difference for colour alteration only for the material Dentuflex. The silicone liners presented better colour stability following thermocycling and storage independent of the solution. The coffee solution was a statistically significant factor for colour alteration of the material Soft Confort.

Effect of ageing and immersion in different beverages on properties of denture lining materials.

OBJECTIVES: To evaluate the color stability and hardness of two denture liners obtained by direct and indirect techniques, after thermal cycling and immersion in beverages that can cause staining of teeth. MATERIAL AND METHODS: Seventy disc-shaped specimens (18 x 3 mm) processed by direct (DT) and indirect techniques (IT) were made from Elite soft (n=35) and Kooliner (n=35) denture liners. For each material and technique, 10 specimens were subjected to thermal cycling (3,000 cycles) and 25 specimens were stored in water, coffee, tea, soda and red wine for 36 days. The values of color change, Shore A hardness (Elite soft) and Knoop hardness (Kooliner) were obtained. The data were subjected to ANOVA, Tukey's multiple-comparison test, and Kruskal-Wallis test (P<0.05). RESULTS: The thermal cycling promoted a decrease on hardness of Kooliner regardless of the technique used (Initial: 9.09± 1.61; Thermal cycling: 7.77± 1.47) and promoted an increase in the hardness in the DT for Elite Soft (Initial: 40.63± 1.07; Thermal cycling: 43.53± 1.03); hardness of Kooliner (DT: 8.76± 0.95; IT: 7.70± 1.62) and Elite Soft (DT: 42.75± 1.54; IT=39.30± 2.31) from the DT suffered an increase after the immersion in the beverages. The thermal cycling promoted color change only for Kooliner in the IT. Immersion in the beverages did not promote color change for Elite in both techniques. The control group of the DT of Kooliner showed a significant color change. Wine and coffee produced the greatest color change in the DT only for Elite Soft when compared to the other beverages. CONCLUSION: The three variation factors promoted alteration on hardness and color of the tested denture lining materials.

Effect of ageing and immersion in different beverages on properties of denture lining materials

OBJECTIVES: To evaluate the color stability and hardness of two denture liners obtained by direct and indirect techniques, after thermal cycling and immersion in beverages that can cause staining of teeth. MATERIAL AND METHODS: Seventy disc-shaped specimens (18 x 3 mm) processed by direct (DT) and indirect techniques (IT) were made from Elite soft (n=35) and Kooliner (n=35) denture liners. For each material and technique, 10 specimens were subjected to thermal cycling (3,000 cycles) and 25 specimens were stored in water, coffee, tea, soda and red wine for 36 days. The values of color change, Shore A hardness (Elite soft) and Knoop hardness (Kooliner) were obtained. The data were subjected to ANOVA, Tukey's multiple-comparison test, and Kruskal-Wallis test (P<0.05). RESULTS: The thermal cycling promoted a decrease on hardness of Kooliner regardless of the technique used (Initial: 9.09± 1.61; Thermal cycling: 7.77± 1.47) and promoted an increase in the hardness in the DT for Elite Soft (Initial: 40.63± 1.07; Thermal cycling: 43.53± 1.03); hardness of Kooliner (DT: 8.76± 0.95; IT: 7.70± 1.62) and Elite Soft (DT: 42.75± 1.54; IT=39.30± 2.31) from the DT suffered an increase after the immersion in the beverages. The thermal cycling promoted color change only for Kooliner in the IT. Immersion in the beverages did not promote color change for Elite in both techniques. The control group of the DT of Kooliner showed a significant color change. Wine and coffee produced the greatest color change in the DT only for Elite Soft when compared to the other beverages. CONCLUSION: The three variation factors promoted alteration on hardness and color of the tested denture lining materials.

Color stability of denture acrylic resins and a soft lining material against tea, coffee, and nicotine.

PURPOSE: The purpose of this study was to investigate the effect of four solutions [saliva (control group), saliva+tea, saliva+coffee, saliva+nicotine] on the color of different denture base acrylic resins (heat-polymerized, injection-molded, autopolymerized) and a soft denture liner. MATERIALS AND METHODS: Twenty specimens from each type of test material were prepared (2.5 mm diameter, 2 mm thickness). Five specimens from each test material (heat-polymerized, chemically polymerized, injection-molded acrylic resin, soft denture reliner) were stored in each solution in 37 degrees C in a dark environment. Colorimetric measurements were done on the 1st, 7th, and 30th days. Color differences among specimens immersed in saliva (control group), and staining solutions were evaluated over time. Data were statistically analyzed with one-way analysis of variance (ANOVA) (alpha= 0.05). ANOVA was followed by Tukey test to find which groups differed from each other. RESULTS: Significant color shifts occurred in heat-polymerized and injection-molded acrylic resins in coffee and in soft liner in nicotine over time (p < 0.05) (DeltaE > 1). The color shift of soft liner in nicotine was significantly different than that of the remainder of the test materials in nicotine (p < 0.05). The color shift magnitudes of each test material in coffee and tea were not significantly different when compared among the test material groups (p > 0.05). CONCLUSIONS: The effect of staining solutions on the color of each test material in each session was perceivable by the human eye (DeltaE > 1); however, the color shifts of all test materials were clinically acceptable (DeltaE < 3.7) except for soft liner in nicotine, which was not clinically acceptable over time. Therefore, minimizing drinking of such beverages and use of tobacco, particularly when soft liner is applied, may be advantageous for denture wearers for long-term color stability.

Effect of repeated cycles of chemical disinfection on the roughness and hardness of hard reline acrylic resins.

OBJECTIVE: The aim of this study was to assess the effect of repeated cycles of five chemical disinfectant solutions on the roughness and hardness of three hard chairside reliners. METHODS: A total of 180 circular specimens (30 mm x 6 mm) were fabricated using three hard chairside reliners (Jet; n = 60, Kooliner; n = 60, Tokuyama Rebase II Fast; n = 60), which were immersed in deionised water (control), and five disinfectant solutions (1%, 2%, 5.25% sodium hypochlorite; 2% glutaraldehyde; 4% chlorhexidine gluconate). They were tested for Knoop hardness (KHN) and surface roughness (microm), before and after 30 simulated disinfecting cycles. Data was analysed by the factorial scheme (6 x 2), two-way analysis of variance (anova), followed by Tukey's test. RESULTS: For Jet (from 18.74 to 13.86 KHN), Kooliner (from 14.09 to 8.72 KHN), Tokuyama (from 12.57 to 8.28 KHN) a significant decrease in hardness was observed irrespective of the solution used on all materials. For Jet (from 0.09 to 0.11 microm) there was a statistically significant increase in roughness. Kooliner (from 0.36 to 0.26 microm) presented a statistically significant decrease in roughness and Tokuyama (from 0.15 to 0.11 microm) presented no statistically significant difference after 30 days. CONCLUSIONS: This study showed that all disinfectant solutions promoted a statistically significant decrease in hardness, whereas with roughness, the materials tested showed a statistically significant increase, except for Tokuyama. Although statistically significant values were registered, these results could not be considered clinically significant.

Color change evaluation of denture soft lining materials in coffee and tea.

This study evaluated the color stability of soft denture liners after being exposed to coffee and tea solutions for different time periods. Four soft denture liners and a denture base polymer were tested. Five specimens of each material were immersed in either coffee or tea solution at 50 +/- 1 degrees C for one, three, nine, 24, 48, and 96 hours. Color measurements were made using a reflectance spectrophotometer before and after the specimens were exposed to the solutions. After 96 hours' immersion in coffee and tea solutions, coffee produced more marked color changes than did tea for all the materials tested. Surface roughness (Ra) of the materials after being cured against a stainless steel surface was also measured with a contact-type surface roughness measuring instrument. Due to the different surface structures, which thus accounted for the different Ra values, the materials behaved differently when immersed in different solutions.

Effect of denture base surface pretreatment on microleakage of a silicone-based resilient liner.

STATEMENT OF PROBLEM: Microleakage between resilient liner and denture base resins is a significant clinical problem, often responsible for debonding of the resilient liner from the denture base resin. PURPOSE: This study investigated the effect of 2 surface treatments, airborne-particle abrasion (APA) and wetting with methyl methacrylate monomer (MMA), on microleakage between a silicone-based resilient liner and denture base resin using a gamma camera imaging technique. MATERIAL AND METHODS: Thirty-three specimens, each having 2 plates measuring 40 x 40 x 2 mm, were prepared by packing and processing an acrylic denture base resin (QC-20) into square plates following manufacturer's instructions. Specimens were divided into 3 groups (n=11) as APA-, MMA-, and control-treatment groups. For the APA group, the inner surfaces of both plates were airborne-particle abraded with 250-microm Al 2 O 3 particles and, for the MMA group, surfaces were treated with monomer (QC-20). Control specimens were not surface treated. Following application of an adhesive (Ufi Gel P-specific), a silicone lining material (Ufi Gel P) was prepared and applied to the inner surfaces of all 33 specimens. Eleven size-matched polymethyl methacrylate (PMMA) specimen blocks (40 x 40 x 6 mm) were prepared to calculate the level of residual radioactivity for the denture base itself, the entire outer surface count (OSC). All specimens and PMMA blocks were immersed in a radioactive solution (thallium-201 chloride) for 24 hours. Specimen activities (gamma-ray cts/sec, representing thallium-201 concentration) were then measured using a high-resolution gamma camera. The amount of OSC-subtracted total specimen counts was a direct indicator of the quantity of inward diffusing tracer. The subtracted values were analyzed using a 1-way analysis of variance (ANOVA) and Bonferroni multiple comparison tests (alpha=.05). RESULTS: OSC levels averaged 754 +/- 110 gamma-ray cts/sec. OSC-subtracted APA, control, and MMA values were 5,546 +/- 1,534, 3,392 +/- 738, and 1,405 +/- 392 gamma-ray cts/sec, respectively. All 3 groups were significantly different ( P <.05) from each other. Surface wetting with MMA showed the lowest microleakage values among all specimen groups. CONCLUSION: In terms of microleakage, surface treatment with MMA monomer preceding the adhesive application demonstrated lower values than adhesive application alone. APA pretreatment resulted in 4 times the microleakage found in MMA-treated specimens, and 1.5 times the microleakage of the untreated control. None of the surface pretreatments completely prevented microleakage. Microleakage between the silicone-based resilient liner and denture base resin can be quantitatively determined using the gamma camera imaging technique.