Effect of Alkaline Peroxides on the Surface of Cobalt Chrome Alloy: An In Vitro Study.

PURPOSE: Removable denture hygiene care is very important for the longevity of the rehabilitation treatment; however, it is necessary to analyze the effects that denture cleansers can cause on the surfaces of prostheses. Thus, this study evaluated the effect of alkaline peroxide-effervescent tablets on the surface of cobalt-chromium alloys (Co-Cr) used in removable partial dentures. MATERIALS AND METHODS: Circular metallic specimens (12 × 3 mm) were fabricated and were immersed (n = 16) in: control, Polident 3 Minute (P3M), Steradent (S), Efferdent (E), Polident for Partials (PFP), and Corega Tabs (CT). The surface roughness (µm) (n = 10) was measured before and after periods of cleanser immersion corresponding to 0.5, 1, 2, 3, 4, and 5 years. Ion release was analyzed (n = 5) for Co, Cr, and molybdenum (Mo). Scanning electron microscopy (SEM) analysis and an Energy-dispersive X-ray spectroscopy (EDS) were conducted in one specimen. The surface roughness data were statistically analyzed (α = 0.05) with the Kruskal-Wallis test to compare the solutions, and the Friedman test compared the immersion durations. Ion release analysis was performed using 2-way ANOVA and Tukey's test. RESULTS: There was no significant surface roughness difference when comparing the solutions (p > 0.05) and the immersion durations (p = 0.137). Regarding ion release (µg/L), CT, E, and control produced a greater release of Co ions than S (p < 0.05). CT produced a greater release of Cr ions than control, S, and P3M (p < 0.05). Finally, E caused the greatest release of Mo ions (p < 0.05). SEM confirmed that the solutions did not damage the surfaces and EDS confirmed that there were no signs of oxidation. CONCLUSION: The various solutions tested did not have any deleterious effects on the Co-Cr alloy surface. Steradent, however, presented the smallest ionic release.

In Vitro Analysis of Surface Roughness of Acrylic Resin Exposed to the Combined Hygiene Method of Brushing and Immersion in Ricinus communis and Sodium Hypochlorite.

PURPOSE: To evaluate a solution based on Ricinus communis (Castor oil) for denture cleansing, comparing it to sodium hypochlorite (NaOCl) for the surface roughness of heat-polymerized acrylic resin. MATERIALS AND METHODS: Forty polished and unpolished resin specimens (90 × 30 × 4 mm) were evaluated before and after their exposure to protocol hygiene: brushing the specimens with a specific denture brush and mild soap for 3 minutes, three times a day, and immersing them in hygiene solutions (0.25% NaOCl-S1 and 0.5% NaOCl-S2; 10% R. communis-S3; saline-S4: control) for 20 minutes. Surface roughness was evaluated by rugosimeter and scanning electron microscopy (SEM) before and after the protocol. For evaluation of surface roughness, polished and unpolished surfaces were used. RESULTS: The roughness of the polished surface was not affected by time (p = 0.062), but was affected by solutions (p < 0.0001) and the interaction between factors (p = 0.005). For S1 and S4, the period did not influence the roughness. For S2, there was a change after 7 days, remaining stable after 14 days. For S3, there were changes, and stabilization occurred after 14 days. After 7 and 14 days, S2 and S3 promoted major changes, but after 21 days, there were no differences among solutions, except saline. The unpolished surface was not influenced by factors: period (p = 0.115), solution (p = 0.120), and their interaction (p = 0.382). SEM analysis showed similar results on the evaluation of surface roughness. CONCLUSIONS: The polished surface of the prosthesis was more susceptible to changes when exposed to hygiene solutions, and although the 0.5% NaOCl solution promoted an increase in the surface roughness compared with the same solution at 0.25% and R. communis at 10%, the values are clinically acceptable.

Microstructural characterization and evaluation of the properties of polymeric materials for maxillofacial prosthetics.

This study evaluated the Shore A hardness, colour and microstructural alterations of an experimental silicone for maxillofacial prostheses. As a control, the MDX 4-4210 silicone was used. Eighty specimens of each material were randomly divided into groups of pigmentation and ageing. For microstructural analysis by Thermogravimetry, Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry, three specimens of each group were used. Anova and Tukey test (p < 0.05) was used in statistical analysis. There was significant difference in hardness depending on the materials, pigmentation and ageing and interaction between all the factors evaluated (p = 0.00). The colour change was significant due to ageing (p = 0.00) and the interaction between the factors evaluated (p = 0.00). The microstructural analyses have shown that ageing methods and pigmentations did not cause structural alterations. The results suggest that the alterations in hardness and colour do not represent important structural changes.

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.

Effect of different cleansers on the surface of removable partial denture.

Removable partial dentures (RPD) demand specific hygienic cleaning and the combination of brushing with immersion in chemical solutions has been the most recommended method for control of biofilm. However, the effect of the cleansers on metallic components has not been widely investigated. This study evaluated the effect of different cleansers on the surface of RPD. Five disc specimens (12 mm x 3 mm metallic disc centered in a 38 x 18 x 4 mm mould filled with resin) were obtained for each experimental situation: 6 solutions [Periogard (PE), Cepacol (CE), Corega Tabs (CT), Medical Interporous (MI), Polident (PO), 0.05% sodium hypochlorite (NaOCl), and distilled water (DW) control] and 2 Co-Cr alloys [DeguDent (DD) and VeraPDI (VPDI)] were used for each experimental situation. A 180-day immersion was simulated and the measurements of roughness (Ra, µm) of metal and resin were analyzed using 2-way ANOVA and Tukey's test. The surface changes and tarnishes were examined with a scanning electronic microscopy (SEM). In addition, energy dispersive x-ray spectrometry (EDS) analysis was carried out at representative areas. Visually, NaOCl and MI specimens presented surface tarnishes. The roughness of materials was not affected by the solutions (p>0.05). SEM images showed that NaOCl and MI provided surface changes. EDS analysis revealed the presence of oxygen for specimens in contact with both MI and NaOCl solutions, which might suggest that the two solutions promoted the oxidation of the surfaces, thus leading to spot corrosion. Within the limitations of this study, it may be concluded that the NaOCl and MI may not be suitable for cleaning of RPD.

Effect of different cleansers on the surface of removable partial denture

Removable partial dentures (RPD) demand specific hygienic cleaning and the combination of brushing with immersion in chemical solutions has been the most recommended method for control of biofilm. However, the effect of the cleansers on metallic components has not been widely investigated. This study evaluated the effect of different cleansers on the surface of RPD. Five disc specimens (12 mm x 3 mm metallic disc centered in a 38 x 18 x 4 mm mould filled with resin) were obtained for each experimental situation: 6 solutions [Periogard (PE), Cepacol (CE), Corega Tabs (CT), Medical Interporous (MI), Polident (PO), 0.05 percent sodium hypochlorite (NaOCl), and distilled water (DW) control] and 2 Co-Cr alloys [DeguDent (DD) and VeraPDI (VPDI)] were used for each experimental situation. A 180-day immersion was simulated and the measurements of roughness (Ra, µm) of metal and resin were analyzed using 2-way ANOVA and Tukey’s test. The surface changes and tarnishes were examined with a scanning electronic microscopy (SEM). In addition, energy dispersive x-ray spectrometry (EDS) analysis was carried out at representative areas. Visually, NaOCl and MI specimens presented surface tarnishes. The roughness of materials was not affected by the solutions (p>0.05). SEM images showed that NaOCl and MI provided surface changes. EDS analysis revealed the presence of oxygen for specimens in contact with both MI and NaOCl solutions, which might suggest that the two solutions promoted the oxidation of the surfaces, thus leading to spot corrosion. Within the limitations of this study, it may be concluded that the NaOCl and MI may not be suitable for cleaning of RPD.

As próteses parciais removíveis (PPR) exigem higienização específica e a associação da escovação com imersão em soluções químicas tem sido o método mais recomendado para controle do biofilme. Entretanto, os efeitos destas soluções não são amplamente reportados em componentes metálicos. Este estudo avaliou o efeito de diferentes agentes de higienização na superfície dos componentes de uma PPR. Foram confeccionados 5 espécimes (disco metálico de 12 x 3 mm centralizado em uma tira de resina com 38 x 18 x 4 mm) para cada situação experimental: 6 soluções [Periogard (PE), Cepacol (CE), Corega Tabs (CT), Medical Interporous (MI), Polident (PO), hipoclorito de sódio 0,05 por cento (HS) e água destilada (AD) como controle)] e 2 ligas de cobalto-cromo [DeguDent (DD) e Vera PDI (VPDI)] foram utilizadas para cada situação experimental. Foram simuladas imersões de 180 dias. As aferições de rugosidade (Ra, μm) tanto em porção metálica quanto em resina acrílica termopolimerizável foram submetidos ao ANOVA e ao teste de Tukey. As alterações superficiais e manchas foram examinadas por meio de microscopia eletrônica de varredura (MEV). Áreas de interesse foram submetidas à espectrometria por energia dispersiva por raios X (EDS). Visualmente, puderam ser verificadas manchas nas superfícies metálicas quando utilizados HS e MI. A rugosidade dos materiais não foi afetada pelas soluções (p>0,05). As fotomicrografias evidenciaram que HS e MI ocasionaram alterações superficiais. As análises de EDS revelaram a presença de oxigênio nos grupos HS e MI, o que pode sugerir que estas duas soluções causaram oxidação das superfícies, provocando pontos de corrosão. Dentre as limitações do presente estudo, pode-se concluir que estas soluções não são apropriadas para a higienização das PPR.

Evaluation of the abrasiveness of dentifrices for complete dentures.

PURPOSE: This study analyzed the surface roughness and weight loss in Plex Glass specimens caused by dentifrices, one conventional (Sorriso) and three specific for dentures. MATERIALS AND METHODS: Specimens (n = 6) of Plex Glass were divided into 5 groups including: negative control (water); positive control 1 (Sorriso) and 2 (Corega Brite); Experimental 1 (containing Chloramine T, antimicrobial agent); and Experimental 2 (containing Zonyl, detergent). Brushing was performed in a toothbrushing machine (Pepsodent) with a soft brush and a suspension of toothpaste and distilled water for 300 minutes, representing 6 years of brushing. Weight was measured initially and after the trial period; roughness was measured after the trial period only. The results of roughness and weight loss were analyzed using ANOVA and Tukey tests at 5%. RESULTS: The negative control (2.82 +/- 4.41 mg) showed the lowest weight loss. Experimental 1 (13.62 +/- 4.29 mg) and Experimental 2 (15.4 +/- 5.80 mg) were equal statistically, and Sorriso (23.22 +/- 7.23 mg) and Corega (28.83 +/- 6.34 mg) produced the greatest weight loss. Concerning roughness, the negative control group (0.03 +/- 0.01 microm) showed the lowest value. No significant differences were found between Corega (13.43 +/- 1.65 microm), Experimental 1 (12.28 +/- 0.85 microm), and Experimental 2 (10.68 +/- 2.56 microm). The Sorriso toothpaste produced the greatest amount of surface roughness (19.15 +/- 2.36 microm). CONCLUSION: Of the tested dentifrices, the experimental preparations proved to be the least abrasive and resulted in the lowest weight loss after brushing of the acrylic. Based on these findings, the use of these experimental dentifrices is advocated. Further evaluation based on the ability of these preparations to remove biofilms is required.

Effects of ethanol on the surface and bulk properties of a microwave-processed PMMA denture base resin.

PURPOSE: This study evaluated the effect of different concentrations of ethanol on hardness, roughness, flexural strength, and color stability of a denture base material using a microwave-processed acrylic resin as a model system. MATERIALS AND METHODS: Sixty circular (14 x 4 mm) and 60 rectangular microwave-polymerized acrylic resin specimens (65 x 10 x 3 mm(3)) were employed in this study. The sample was divided into six groups according to the ethanol concentrations used in the immersion solution, as follows: 0% (water), 4.5%, 10%, 19%, 42%, and 100%. The specimens remained immersed for 30 days at 37 degrees C. The hardness test was performed by a hardness tester equipped with a Vickers diamond penetrator, and a surface roughness tester was used to measure the surface roughness of the specimens. Flexural strength testing was carried out on a universal testing machine. Color alterations (DeltaE) were measured by a portable spectrophotometer after 12 and 30 days. Variables were analyzed by ANOVA/Tukey's test (alpha= 0.05). RESULTS: For the range of ethanol-water solutions for immersion (water only, 4.5%, 10%, 19.5%, 42%, and 100%), the following results were obtained for hardness (13.9 +/- 2.0, 12.1 +/- 0.7, 12.9 +/- 0.9, 11.2 +/- 1.5, 5.7 +/- 0.3, 2.7 +/- 0.5 VHN), roughness (0.13 +/- 0.01, 0.15 +/- 0.07, 0.13 +/- 0.05, 0.13 +/- 0.02, 0.23 +/- 0.05, 0.41 +/- 0.19 mum), flexural strength (90 +/- 12, 103 +/- 18, 107 +/- 16, 90 +/- 25, 86 +/- 22, 8 +/- 2 MPa), and color (0.8 +/- 0.6, 0.8 +/- 0.3, 0.7 +/- 0.4, 0.9 +/- 0.3, 1.3 +/- 0.3, 3.9 +/- 1.5 DeltaE) after 30 days. CONCLUSIONS: The findings of this study showed that the ethanol concentrations of tested drinks affect the physical properties of the investigated acrylic resin. An obvious plasticizing effect was found, which could lead to a lower in vivo durability associated with alcohol consumption.

The effect of polymerization cycles on color stability of microwave-processed denture base resin.

PURPOSE: This study evaluated the effect of different microwave polymerization cycles on the color changes of a microwave-processed denture base resin after accelerated aging and immersion in beverages. MATERIALS AND METHODS: Specimens of light pink acrylic resin were divided into three groups according to polymerization cycle: (A) 500 W for 3 minutes, (B) 90 W for 13 minutes + 500 W for 90 seconds, and (C) 320 W for 3 minutes + 0 W for 4 minutes + 720 W for 3 minutes. Control groups were a heat-processed acrylic resin (T) and a chemically activated denture repair resin (Q). Eight specimens per group were aged in an artificial aging chamber and evaluated at 20, 192, and 384 hours. Another series of 40 specimens per group were immersed in water, coffee, tea, cola, or red wine and evaluated at 1, 12, and 36 days. Color was measured by a spectrophotometer before and after aging or immersion. Color changes (DeltaE) were analyzed by ANOVA/Bonferroni t-test (alpha = 0.05). RESULTS: Mean DeltaE (+/- SD) after 384 hours of accelerated aging were (A) 2.51 +/- 0.50; (B) 3.16 +/- 1.09; (C) 2.89 +/- 1.06; (T) 2.64 +/- 0.34; and (Q) 9.03 +/- 0.40. Group Q had a significantly higher DeltaE than the other groups. Color changes of immersed specimens were significantly influenced by solutions and time, but the five groups showed similar values. Mean DeltaE at 36 days were (water) 1.4 +/- 0.8; (coffee) 1.3 +/- 0.6; (tea) 1.7 +/- 0.5; (cola) 1.4 +/- 0.7; and (red wine) 10.2 +/- 2.7. Results were similar among the five test groups. CONCLUSIONS: Color changes of the microwave-polymerized denture base resin tested were not affected by different polymerization cycles after accelerated aging or immersion in beverages. These changes were similar to the conventional heat-polymerized acrylic resin test, but lower than the repair resin after accelerated aging.

Evaluation of a computerized method for denture biofilm quantification: inter-examiner reproducibility.

PURPOSE: The objective of this work was to evaluate the accuracy and inter-examiner reproducibility of the computerized method Image Tool 2.02 (Windows, version 2.02, University of Texas Health Science Center, San Antonio, TX) in the quantification of complete denture biofilm. MATERIALS AND METHODS: Two hundred digital photographs of the internal surface of complete upper dentures with biofilm dyed in 1% neutral red were used. The photographs were burned to a CD and sent to two researchers who received practical training and written instructions on how to use the method; then, in a 20-day period, the stained biofilm on the internal surface was measured, and ten photographs were analyzed daily. Each examiner independently quantified the percentage of stained area on each photograph. The inter-examiner reproducibility (i.e., agreement) was estimated by calculating an intra-class correlation coefficient (ICC) based on an ANOVA mixed model (SPSS software, Chicago, IL). RESULTS: The ICC showed excellent agreement (ICC = 0.993, p < 0.001). The difference in the percentage of the stained area recorded by the two examiners was < or =1 point for 187 (93.5%) of the 200 photographs. CONCLUSIONS: The obtained results suggest that the computerized method aided by the Image Tool software (2.0) can be employed to quantify complete denture biofilm, seeing that it demonstrated inter-examiner reproducibility of the results.

Bond strength and degree of infiltration between acrylic resin denture liner after immersion in effervescent denture cleanser.

PURPOSE: The purpose of this study was to investigate the effect of sodium perborate on the bond strength and degree of infiltration between acrylic resin/resilient denture liners. MATERIALS AND METHODS: Three denture liners (Elite Soft, Mucopren Soft, Kooliner) were investigated. Twenty specimens (83 x 10 x 10 mm(3)) of each material were made by processing the denture liners against two polymerized PMMA blocks. Ten specimens for each material were stored in artificial saliva at 37 degrees C (control group: TBS1), and the other ten specimens were stored in artificial saliva at 37 degrees C combined with sodium perborate (experimental group: TBS2). All specimens were placed under tension until failure in a Universal Testing Machine at a crosshead speed of 5 mm/min after 7 (T7) and 60 (T60) days (n = 5). Failure strength (MPa) was recorded, and mode of failure was characterized as cohesive, adhesive, or cohesive/adhesive. For the infiltration tests, ten circular specimens (14-mm diameter x 2-mm thick) of each material were stored in artificial saliva and 0.5% methylene blue at 37 degrees C (control group: I1), and ten specimens were stored in artificial saliva and 0.5% methylene blue at 37 degrees C combined with daily immersions for 5 minutes in an effervescent solution of sodium perborate (experimental group: I2). The degree of infiltration was obtained through photographs and using Software Image Tool after 120 days. RESULTS: For Kooliner, the statistical test did not show a significant difference in the bond strength due to the influence of the immersion period or to the use of sodium perborate. Elite Soft presented a significant increase in the average tension in T7 and in T60 in both TBS1 and TBS2. Inversely, the Mucopren suffered a significant decrease in the tension value in the same period as the TBS1 group as well as in the TBS2. The infiltration percentage was analyzed with the Kruskal-Wallis test (26.18; p < 0.05), which indicated significant differences between the compared averages for the groups. Comparing the averages of materials, the statistical test did not show significant differences between the control (I1) and experimental (I2) groups after 120 days. CONCLUSIONS: The use of sodium perborate did not promote significant alterations in the evaluated properties. Kooliner presented the best results.