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Purpose: To investigate the cumulative effects of brushing (B) or immersion (I), using different cleansing agents, on the surface roughness, hardness and color stability of a heat-polymerized denture resin, Lucitone 550 (L), and a hard chairside reline resin, Tokuyama Rebase Fast II (T)., Methods: A total of 316 specimens (10 x 2 mm) were fabricated. The specimens (n = 9) were divided into brushing or immersion groups according to the following agents: dentifrice/distilled water (D), 1% sodium hypochlorite (NaOCl), Corega Tabs (Pb), 1% chlorhexidine gluconate (Chx), and 0.2% peracetic acid (Ac). Brushing and immersion were tested independently. Assays were performed after 1, 3, 21, 45 and 90 brushing cycles or immersion of 10 seconds each. Data were evaluated statistically by repeated measures ANOVA. Tukey's honestly significant difference (HSD) post-hoc test was used to determine differences between means (α = 0.05)., Results: For L there was no statistically significant difference in roughness, except a significant decrease in roughness by brushing with D. T showed a significant effect on the roughness after 90 immersions with Ac. Hardness values decreased for L when specimens were immersed or brushed in NaOCl and Pb. The hardness of T decreased with increases in the repetitions (immersion or brushing), regardless of the cleaning method. Values of color stability for L resin showed significant color change after brushing with and immersion in Ac and Pb. Brushing with D exhibited a higher incidence of color change. For T there were no significant differences between cleaning agents and repetitions in immersion. A color change was noted after three brushings with the Ac, Chx, and D. Brushing with dentifrice decreased roughness of L. Immersion in or brushing with NaOCl and Pb decreased the hardness of L. For T, hardness decreased with increases in immersions or brushing. Color changes after the immersion in or brushing with cleaning agents were clinically acceptable according to National Bureau of Standards parameters for both resins.

Statement of Problem: Routine cleaning of a denture may increase the surface roughness of the material., Purpose: The purpose of this study was to investigate the effect of denture cleansers and time on the roughness and Candida albicans biofilm formation on a reline resin., Material and Methods: Specimens of Tokuyama Rebase Fast II (20 × 10 × 2 mm) were prepared and divided into 9 groups (n=15): Test groups were toothbrushed (30 cycles per day) in 1 of the following solutions: water, soap, or toothpaste. After toothbrushing, the specimens were immersed in solutions of water, sodium perborate, or chlorhexidine. These treatments were done once a day for 365 days. The surface roughness was evaluated at 0, 7, 15, 30, 90, 180, 270, and 365 days, and the C albicans biofilm formation was measured after 365 days. The roughness data were analyzed by 3-way repeated measures ANOVA and the Tukey test (α=.05), and the C albicans biofilm formation was analyzed by 2-way ANOVA., Results: Significant differences were found in the toothbrush and time interaction and in the toothbrush, immersion, and time interaction (P<.001). No significant differences were found between the toothbrush agent and chemical disinfection (P=.085) or between chemical disinfection and time interaction (P=.604). Brushing with dentifrice (PPb and PCh) showed a gradual decrease in surface roughness. The comparison among groups showed that PCh produced the lowest values of roughness. For C albicans biofilm formation, no significant differences were found among the experimental groups., Conclusions: The roughness values ranged from 0.31 to 0.69 μm for all evaluated groups. For all groups, no significant differences were found in the quantification of C albicans., (Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

The colour stability of acrylic resin denture teeth in beverages was investigated. A spectrophotometer measured the colour (CIE-L*a*b* system) of all specimens after storage in distilled water/for 24 h at 37 degrees C (T0). Specimens were then immersed in various beverages. After 15 days (T1) and 30 days (T2), for each material, the mean deltaE values were calculated and compared by two-way ANOVA and Tukey intervals (alpha = 0.05). In the deltaT0T1 period, specimens stored in red wine were significantly discoloured, compared to distilled water (P = 0.003). There was no difference between immersion solutions in deltaET0T2 (P = 0.772) and in deltaET1T2 (P = 0.058), and no difference between materials in all immersion periods.

Purpose: The aim of this in vivo animal study was to investigate changes in the surface roughness of soft liners over time., Materials and Methods: Forty adult Wistar rats (Rattus norvergicus albinus) were fitted with acrylic custom-made palatal plates relined by dynamic impressions and tested with the following soft liners: Dentuflex (DF), Trusoft (TS), Dentusoft (DS), and Ufi Gel P (UG). Half of the animals for each tested material had the plates fitted during the material reline procedure. Their surface roughness was read immediately (IRa group, n = 5). The other half used the palatal plates for 14 days before roughness readings were performed (FRa group, n = 5). The surface roughness (Ra) of the inner surface from the relined dentures was recorded using a Surftest SJ-401 with eight readings per specimen, and mean values were obtained. Data (μm) were analyzed by two-way ANOVA and Tukey's test (α = 0.05)., Results: IRa means (2.92 ± 0.87 μm) and FRa means (3.35 ± 0.65 μm) were significantly different (p = 0.016). UG showed a lower (p = 0.01) Ra mean (2.1 ± 0.52 μm) than DF (3.94 ± 0.81 μm), TS (4.12 ± 0.64 μm), and DS (3.27 ± 0.64 μm)., Conclusions: Ufi Gel P showed the smoothest surface among the materials evaluated. The period of use resulted in changes in the surface roughness of the materials tested., (© 2013 by the American College of Prosthodontists.)

Objective: To evaluate the weight loss and the surface roughness of acrylic resins after simulated brushing tests., Material and Methods: Ten specimens of each material (Tokuyama Rebase II-TR, New Truliner-NT, Ufi Gel Hard-UH and Lucitone 550-L) were made. The wear loss (mg) by weight and the surface roughness (Ra μm) of each specimen was determined before and after brushing. The specimens were placed on the brushing machine and a total of 20,000 brushing cycles was performed. The results of weight loss and roughness values were submitted to the anova followed by the Tukey's test (p = 0.05)., Results: The mean weight loss of material L was statistically higher (p < 0.001) than that of the relines TR, UH and NT. No significant differences were found among the roughness values of resins TR, UH and L (p > 0.05). Only for L, toothbrushing increased the surface roughness. After toothbrushing, there was no significant difference between the roughness values of materials L and NT. The highest mean weight loss during the simulated toothbrushing tests was observed for L. Before the toothbrushing tests, the NT exhibited the highest mean roughness., Conclusion: Brushing resulted in increase in roughness only for resin L., (© 2011 The Gerodontology Society and John Wiley & Sons A/S.)

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., (© 2011 The Gerodontology Society and John Wiley & Sons A/S.)

Objective: To evaluate the effect of water storage time on the cytotoxicity of soft liners., Methods: Sample discs of soft liners Dentusoft, Dentuflex, Trusoft, Ufi-Gel-P and denture base acrylic resin Lucitone-550 were prepared and divided into four groups: GN: No treatment, G24: Stored in water at 37°C for 24 h; G48: Stored in water at 37°C for 48 h, GHW: Immersed in water at 55°C for 10 min. To analyse the cytotoxic effect, three samples of each group were placed in tubes with Dubelcco's Modified Eagle Mediums and incubated at 37°C for 24 h. During this period, the toxic substances were leached to the culture medium. The cytotoxicity was analysed quantitatively by the incorporation of radioactivity (3)H-thymidine checking the number of viable cells (synthesis of DNA). The data were statistically analysed using two-way anova and Tukey's honestly significant difference tests (α = 0.05)., Results: Treatments did not reduce the cytotoxicity effect of the soft liners (p > 0.05). It was found that Ufi-Gel-P had a non-cytotoxic effect, Trusoft had a slightly cytotoxic effect, Dentuflex had a moderated cytotoxic effect, Dentusoft alternated between slightly and non-cytotoxic effect, and Lucitone-550 had non-cytotoxic effect when stored in water for 48 h., Conclusion: The effect of water storage and the heat treatment did not reduce the cytotoxicity of the soft liners., (© 2011 The Gerodontology Society and John Wiley & Sons A/S.)

Objective: The aim of the study was to evaluate the effect of long-term disinfection procedures on the Vickers hardness (VHN) of acrylic resin denture teeth., Material and Methods: Five acrylic resin denture teeth (Vipi Dent Plus-V, Trilux-T, Biolux-B, Postaris-P and Artiplus-A) and one composite resin denture teeth (SR-Orthosit-O) were embedded in heat-polymerised acrylic resin within polyvinylchloride tubes. Specimens were stored in distilled water at 37°C for 48 h. Measurements of hardness were taken after the following disinfection procedures: immersion for 7 days in 4% chlorhexidine gluconate or in 1% sodium hypochlorite (CIm and HIm group, respectively) and seven daily cycles of microwave sterilisation at 650 W for 6 min (MwS group). In the WIm group, specimens were maintained in water during the time used to perform the disinfection procedures (7 days). Data were analysed with anova followed by the Bonferroni procedure (α = 0.01)., Results: Microwave disinfection decreased the hardness of all acrylic resin denture teeth (p < 0.001). Immersion for 7 days in 4% chlorhexidine gluconate or distilled water had significant effect on the hardness of the acrylic resin denture teeth A (p < 0.01), and 1% sodium hypochlorite on teeth T (p < 0.01). All disinfection procedures decrease the hardness of the composite resin denture teeth (p < 0.01). Teeth O exhibited the highest and teeth V the lowest hardness values in the control group (p < 0.01)., Conclusions: Disinfection procedures changed the hardness of resin denture teeth., (© 2011 The Gerodontology Society and John Wiley & Sons A/S.)

Objectives: Microleakage is a pre-stage of debonding between hard chairside relines and denture base acrylic resins. Therefore, it is important to assess them with regard to the longevity of the relined denture. This study investigated the effect of thermal cycling on the microleakage at the interface of three hard chairside reline resins and three denture base resins., Material and Methods: Rectangular bars (12 mm × 3 mm × 3 mm) of Lucitone 550, Acron MC and QC 20 were made and relined with Kooliner, Tokuyama Rebase Fast II and Ufi Gel Hard, Lucitone 550, Acron MC and QC 20 resins. Specimens were divided into one control and two test groups (n=10). In specimens of the control group, the microleakage was performed after the reline procedure. In Test Group 1, the specimens were stored for 24 h in distilled water at room temperature and in Test Group 2; the specimens were thermal cycled from 5 to 55°C for 5000 cycles with a 30-s dwell time. Subsequently, all specimens were immersed in 50% silver nitrate solutions for 24h. All specimens were sectioned longitudinally into three fractions and the lateral sections were examined (n=20). Silver nitrate stain penetration was examined under a stereoscopic lens with ×30 magnification, and the images were captured. Leica Qwin image analysis software was used to determine microleakage at the interface of the materials. Data were analysed using the Kruskal-Wallis test at a 95% level of significance., Results: For all cycles, there were no statistically significant differences between thermal cycled and non-thermal cycled groups (p>0.05)., Conclusion: It can be concluded that thermal cycling had no effect on the microleakage., (© 2010 The Gerodontology Society and John Wiley & Sons A/S.)

Objectives: To evaluate the effect of microwave postpolymerization heat treatment and water storage time on the cytotoxicity of denture base and reline acrylic resins., Method and Materials: Sample disks of 6 acrylic resins were fabricated under aseptic conditions (Kooliner, GC; Tokuyama Rebase II, Tokuyama Dental; New Truliner, Bosworth; Acron MC, GC; Lucitone 550, Dentsply; QC 20, Dentsply). The denture base acrylic resin samples were stored in water for 24 and 48 hours at 37 degrees C. The fabricated samples were further subdivided into 2 groups: (1) samples without heat treatment and (2) samples treated in a microwave. The 3H-thymidine incorporation test was used to determine the cytotoxicity of the materials. The data were statistically analyzed using the incomplete 3-way ANOVA and Tukey HSD tests (P < .05)., Results: Microwave postpolymerization heat treatment improved the biocompatibility of Tokuyama Rebase II. Tokuyama Rebase II without heat treatment and Acron MC in both experimental groups were graded as slightly cytotoxic in the group without water storage. The other resins were graded as noncytotoxic. After 24 hours of immersion in water, all materials were graded as noncytotoxic. After water storage for 48 hours, Acron MC without heat treatment and QC 20 in both experimental groups were graded as slightly cytotoxic. Lucitone 550 was graded as noncytotoxic in all experimental groups., Conclusion: Microwave irradiation may be considered an alternative to reduce the cytotoxicity of Tokuyama Rebase II. Dental practitioners should choose Lucitone 550 processed with terminal boiling stage.

Background: Microwave energy has proved to be an effective method for disinfecting acrylic dentures. However, the effect of microwave heating on the porosity of autopolymerising denture reline resins has not been investigated., Objective: The purpose of the study was to determine the effect of microwave disinfection on the porosity of autopolymerised denture reline materials (Kooliner-K, New Truliner-NT, Tokuso Rebase Fast-TR and Ufi Gel Hard-UGH) and a conventional heat-polymerised denture base resin (Lucitone 550-L)., Material and Methods: Specimens (10 mm x 20 mm x 1 mm) were obtained from the impression surface of the palatal mucosa in a single person and divided into four groups (n = 5). The porosity was evaluated after polymerisation (C1), after two cycles of microwave disinfection (MW2), after seven cycles of microwave disinfection (MW7) and after 7 days storage in water at 37 degrees C (C2). Specimens from group MW7 were exposed to microwave disinfection daily being stored in water at 37 degrees C between exposures. All the replicas were sputter coated with gold and micrographs/digital images were taken of each replica using scanning electron microscopy at magnification x 100. The SEM micrographs were then examined using an image analyser to determine the number of pores. Comparison between materials and groups were made using Kruskal-Wallis tests., Results: MW7 resulted in a significant increase in the number from the pores of material K, but decreased in number in reline material TR and UGH reline resin. The number of pores in materials NT and L remained unaffected following microwave disinfection., Conclusion: Differences in the porosity amongst the materials and for different experimental conditions were observed following microwave disinfection.

Objective: The purpose of this study was to evaluate the effect of two post-polymerisation treatments and different cycles of polymerisation on the cytotoxicity of two denture base resins., Materials and Methods: The resins tested were Lucitone 550 and QC 20. Discs of resins were fabricated following the manufacturer's instructions. Lucitone 550 was processed by long cycle or short cycle. The resin QC 20 was processed by reverse cycle or normal cycle. The specimens were divided into groups: (i) post-polymerised in microwave for 3 min at 500 W; (ii) post-polymerised in water-bath at 55 degrees C for 60 min and (iii) without post-polymerisation. Eluates were prepared by placing three discs into a sterile glass vial with 9 ml of Eagle's medium and incubated at 37 degrees C for 24 hours. L929 cells were seeded into 96 well culture plates and DNA synthesis was assessed by (3)H-thymidine incorporation assay., Results: The results were submitted to two-way anova and Tukey HSD test. QC 20 specimens polymerised by the normal cycle and submitted to microwave post-polymerisation were graded as moderately cytotoxic. Similar results were observed for Lucitone 550 processed by long cycle without post-polymerisation. The other experimental groups were graded as not cytotoxic. After water-bath post-polymerisation, specimens of Lucitone 550 processed by long cycle produced significantly lower inhibition of DNA synthesis than the other groups., Conclusion: The long cycle increased the cytotoxicity of Lucitone 550 and water-bath post-polymerisation reduced the cytotoxicity of Lucitone 550 processed by long cycle.

Acrylic resins are widely used in the fabrication of denture bases and have been shown to be cytotoxic as a result of substances that leach from the resin. The primary eluate is residual monomer. Numerous reports suggest that residual monomer may be responsible for mucosal irritation and sensitization of tissues. This information is important, not only to assess the biologic effects of such materials, but also to enable a comparison among the different polymerization methods, thus assisting the clinician in selecting a material with minimal cytotoxicity. This article reviews the literature published from 1973 to 2000, selected by use of a Medline search, associated with cytotoxic effects usually ascribed to acrylic denture base materials.