Color Stability, Surface Roughness and Flexural Strength of an Acrylic Resin Submitted to Simulated Overnight Immersion in Denture Cleansers

Impact of different chemical denture cleansers on the properties of digitally fabricated denture base resin materials

PURPOSE

To compare the impact of three different chemical denture cleansers (CDCs) (Corega, chlorhexidine, and hydrogen peroxide) on the surface roughness, microhardness, and color stability of 3D-printed, computer-aided design and computer-aided manufacturing (CAD-CAM) milled, and heat-polymerized denture base material (DBM).

MATERIALS AND METHODS

A total of 420 disc-shaped specimens (10 ± 0.1 × 2 ±0.1 mm) were fabricated using three different construction techniques: three-dimensional (3D) printing (n = 140), CAD-CAM milling (n = 140), and heat-polymerization (n = 140). Sixty specimens (20 of each DBM) were used for baseline (pre-immersion) measurements (T1) for the tested surface properties (hardness [n = 10/material] and roughness [n = 10/material]). The remaining 360 specimens (n = 120/material) were investigated for surface roughness, microhardness, and color change after immersion for 1 year (T2) in distilled water or CDCs (n = 30/solution and n = 10/test). The data were analyzed using two-way ANOVA, one-way ANOVA followed by post-hoc Tukey's test at a significance level of less than 0.05.

RESULTS

Significant differences were observed in the effects of the tested CDCs on the surface roughness, micro-hardness, and color stability of varying DBM specimens (p < 0.05). Corega showed the highest surface roughness and color change in all DBMs while H2O2 resulted in the lowest microhardness for all DBMs. The lowest changes in all tested properties were seen with distilled water followed by chlorhexidine. A significant effect of type of cleanser, denture base material, and the interaction between the two was seen on all measured properties (p < 0.05).

CONCLUSIONS

The tested CDCs significantly affected the surface properties of all DBMs but at varying degrees. Corega produced the highest negative effect on roughness and color change while H2O2 dramatically affected the microhardness. Prolonged use of CDCs should be cautiously followed.

Antifungal agents incorporated in denture base materials: a scoping review of the current evidence and technology prospecting

BACKGROUND

The aim of this study was to summarize existing data and perform technological prospecting on the effect of incorporating antifungal agents into denture base materials in inhibiting Candida spp., as well as to explore the antimicrobial properties of these materials.

METHODS

A comprehensive electronic search was carried out in six major bibliographic databases (PubMed, Scopus, Embase, Cochrane Library, Web of Science and Lilacs) until February 2024. In addition, international patent databases were also examined. The search process, study and patent selection, data extraction and risk of bias assessment were carried out independently by researchers. The collected data underwent qualitative analysis.

RESULTS

A total of 10 718 articles were identified in the searched databases, of which 40 documents were included for qualitative data analysis (articles: 31; patents: 9). The majority of the studies focused on investigating tissue conditioners (n = 14) and acrylic resins (n = 14). The primary antifungal agents studied were nystatin (n = 15) and fluconazole (n = 13). The most commonly utilized microbiological evaluation methodology was the agar diffusion test (n = 16), followed by the microdilution (n = 7) and biofilm formation assays (n = 7). All of the studies investigated the inhibitory effect of these materials against Candida species.

CONCLUSION

The incorporation of antifungal agents into denture base materials has been extensively studied and has shown a significant inhibitory response against Candida spp. across various methodological assays.

Effect of disinfectants on multispecies biofilm, the physical and mechanical properties of polymethyl methacrylate, and the corrosion of cobalt chromium alloy

STATEMENT OF PROBLEM

The optimal disinfection protocol that controls adverse effects and promotes effective antimicrobial action on removable prostheses is unclear.

PURPOSE

This in vitro study investigated the effect of disinfectant solutions on the biological, physical, mechanical, and chemical properties of removable prosthesis materials.

MATERIAL AND METHODS

Specimens of polymethyl methacrylate (PMMA) and cobalt chromium (Co-Cr) alloy were immersed in distilled water (PMMA) or artificial saliva (Co-Cr) as the control and in 0.25% sodium hypochlorite (NaOCl0.25%), 0.5% chloramine T (CT0.5%), and 0.15% Triclosan (TR0.15%). The antibiofilm activity was evaluated by microbial load and cell metabolisms of the mixed biofilm. Physical (color change, sorption, solubility, and surface roughness), mechanical (hardness, flexural, and impact strength), and chemical (corrosion) properties were analyzed before and after simulating a 5-year immersion. Laser confocal microscopy, scanning electron microscopy (SEM), and dispersive energy spectroscopy (EDS) complemented the analyses. The data were analyzed by using the Mann-Whitney U test, Kruskal-Wallis with Dunn posttests, 1-way ANOVA, and repeated measures ANOVA (α=.05).

RESULTS

All solutions were effective against bacteria, but only NaOCl0.25% eliminated Candida spp. TR0.15%, and CT0.5% increased cell metabolisms. For interaction (time and solution), there was a reduction in PMMA hardness in the control and TR0.15%. Color, sorption, solubility, and flexural strength did not change. CT0.5% and TR0.15% were similar for impact resistance. CT0.5% caused the lowest roughness. NaOCl0.25% showed the greatest corrosive potential. Dark spots were seen under SEM in Co-Cr stored with NaOCl0.25% and TR0.15%. EDS indicated different proportions of oxygen, cobalt, chromium, and molybdenum.

CONCLUSIONS

NaOCl0.25% had the best antimicrobial action. CT0.5% and TR0.15% have potential. Hardness and roughness changes were clinically acceptable, and the other properties remained unchanged. All the solutions caused color changes. NaOCl0.25% was unsatisfactory for use with Co-Cr, CT0.5% was intermediate, and TR0.15% was suitable.

Effects of simulated long-term exposure to bottled, neutral pH electrolyzed oxidizing water on the properties of denture base resins

STATEMENT OF PROBLEM

Denture stomatitis can pose serious health risks, especially to older people. Chemical denture cleaning agents must be effective, yet not adversely affect the longevity of removable dentures. Ready-to-use (RTU) neutral pH electrolyzed oxidizing water (EOW) is an effective biocide against Candida albicans biofilms on denture resins, but the effects of daily disinfection with EOW on the physical and mechanical properties of resins have not been established.

PURPOSE

The purpose of this in vitro study was to investigate the effects of simulated long-term exposure to RTU EOW on the color, surface characteristics, and flexural strength of denture base resins.

MATERIAL AND METHODS

Heat-polymerized (HP), 3D printed (3D) and computer-aided design and computer-aided manufacture (CAD-CAM)-milled (CC) denture resin specimens (square: 20×20×3.3 mm; beam: 64×10×3.3 mm) were immersed in tap water (TW), RTU EOW (Neutral Anolyte ANK; Envirolyte; EOW), or a commercial denture cleaning tablet solution (Polident 3-Minute; Glaxo SmithKline; PD), mimicking a 5-minute once daily disinfection routine performed up to 3.0 years. Color and surface roughness were recorded (n=3, squares), and changes in color (∆E00) and surface roughness (∆Ra) were calculated. Flexural strength (n=12, beams) and surface hardness (n=18, beams) were measured with a universal testing machine. The fractured surfaces of specimens were examined by scanning electron microscopy and energy dispersive spectroscopy. Data were assessed by performing the Shapiro-Wilk or D'Agostino and Pearson normality tests. Two-way ANOVA or the Kruskal-Wallis test with a post hoc Tukey HSD or Dunn multiple comparisons (α=.05) was used for statistical analyses.

RESULTS

No significant changes were found in either color or surface roughness for HP, 3D, and CC resins after 1.5-year and 3.0-year immersion in any of the agents (P>.05). The surface hardness of 3D resins reduced by 14% with TW and by 23% with EOW and PD at 3.0 years. The flexural strengths of all 3 resins were unaffected by 3.0-year immersion (P>.05).

CONCLUSIONS

Simulated long-term immersion disinfection with RTU neutral pH EOW did not adversely affect the physical and mechanical properties of HP or CC denture resins.

Efficacy of denture cleansers on Candida albicans adhesion and their effects on the properties of conventional, milled CAD/CAM, and 3D-printed denture bases

OBJECTIVES

Evaluate the efficacy of denture cleaners on the adhesion of Candida albicans and their effects on the surface, optical, and mechanical properties of resins for conventional, milled, and 3D-printed denture bases.

MATERIALS AND METHODS

A total of 240 resin samples were made, 120 for testing Candida albicans adhesion, optical stabilities (ΔE00), roughness (Ra), hydrophilicity (°), surface free energy (Owens-Wendt) and 120 samples for testing Candida albicans adhesion, surface microhardness (Knoop), flexural strength and modulus of elasticity in a three-point test, in which they were divided into 3 groups of denture resin (n = 40) and subdivided into 5 cleaners of dentures (n = 8). Data were evaluated by two-way ANOVA and Tukey's test for multiple comparisons (α = 0.05).

RESULTS

Denture cleaners with an alkaline solution and dilute acid composition were those that showed the greatest effectiveness in reducing Candida albicans (P < 0.001), however 1% NaOCl significantly affected the properties of the resins (P < 0.05). Denture 3D-printed showed that the surface microhardness was significantly lower for all cleansers (P < 0.05).

CONCLUSIONS

Listerine demonstrated superior efficacy in reducing Candida albicans with minimal effect on denture properties, whereas 1% NaOCl had a significant negative impact on the properties. The mechanical properties were significantly lower in 3D-printed resin than in other resins for all denture cleansers.

CLINICAL RELEVANCE

Denture base materials are being sold to adapt to the CAD/CAM system, increasing the number of users of dentures manufactured with this system. Despite this, there is little investigation into denture cleaners regarding the adhesion capacity of microorganisms and the optical, surface and mechanical properties of dentures, thus requiring further investigation.

Nanoparticle-Modified 3D-Printed Denture Base Resins: Influence of Denture Cleansers on the Color Stability and Surface Roughness In Vitro

This study aimed to evaluate the influence of denture cleansers on the color, stability, and surface roughness of three-dimensional (3D)-printed denture base resins modified with zirconium dioxide nanoparticles (nano-ZrO2). A total of 440 specimens were fabricated using one heat-polymerized resin, and two 3D-printed resins (NextDent and ASIGA). According to the nano-ZrO2 content, the specimens for each resin were divided into five groups (0%, 0.5%wt, 1%wt, 3%wt, and 5%wt). Each concentration was divided into four subgroups (n = 10) based on the immersion solution (distilled water, sodium hypochlorite, Corega, and Fittydent) and immersion duration (360 and 720 days). The color changes (∆E00) and surface roughness (Ra, µm) of each specimen were measured at different time intervals (base line, 360 days, 720 days) using a spectrophotometer and a non-contact profilometer, respectively. The results were statistically analyzed using ANOVA and a post hoc Tukey's test (α = 0.05). Sodium hypochlorite showed the highest significant color change of all the denture base resins (p < 0.001). The average value of ΔE00 for sodium hypochlorite was significantly higher than the values for the other solutions (Fittydent, Corega, and water) (p < 0.001). Color stability was significantly affected by immersion time for all types of solutions except Corega (p < 0.001). All of the tested immersion solutions (distilled water, sodium hypochlorite, Corega, and Fittydent) showed a significant increase in the surface roughness of all the denture base resins (p < 0.05). Surface roughness was substantially increased by immersion time for all types of solution except Fittydent (p < 0.001). Denture cleansers can result in substantial color change and affect the surface roughness of unmodified and nanoparticle-modified denture base resins. Therefore, the selection of denture cleanser and appropriate types of material is critical for denture longevity.

Effects of disinfectants on physical properties of denture base resins: A systematic review and meta-analysis

STATEMENT OF PROBLEM

The disinfection of removable dental prostheses and orthodontic appliances is essential to preventing transmission of pathogens. However, whether different disinfection solutions and durations affect the physical properties of denture base resins is unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to statistically analyze the influence of disinfectants on the physical properties of denture base resins.

MATERIAL AND METHODS

A systematic search in Medline, Embase, PubMed, and Cochrane Library databases was conducted to evaluate the effects of chemical disinfection on the physical properties of denture base resins such as surface morphology, roughness, hardness, and flexural strength. Of 1909 studies, 44 studies were included in the systematic review and 41 in the meta-analysis. Heterogeneity was analyzed by using I2 statistics. The influence of different disinfection solutions and durations on the physical properties was further analyzed, and the risk of bias evaluated. Statistical analyses were performed by using the RevMan 5.4 software program with the standardized mean differences (SMDs) and 95% confidence intervals (CIs).

RESULTS

Of the 44 included studies, 40 studies were assessed as having a low risk of bias, and 4 had an unclear risk of bias. Meta-analysis results showed that compared with the control, disinfection could not significantly affect surface roughness and hardness within 60 minutes of immersion in disinfectant solutions or flexural strength within 30 minutes (roughness: P=.79, I2=0%; flexural strength: P=.08, I2=0%; hardness: P=.05, I2=19%). In addition, the physical properties were not significantly affected when glutaraldehyde, chlorhexidine, and peracetic acid were repeatedly used for more than 30 minutes.

CONCLUSIONS

Most of the disinfectants did not reduce the physical properties of denture base resin within 30 minutes of immersion. Glutaraldehyde, chlorhexidine, and peracetic acid are recommended if longer immersion or repeated disinfection is required.

Strategies for Preventing and Treating Oral Mucosal Infections Associated with Removable Dentures: A Scoping Review

Oral infections occur due to contact between biofilm rich in Candida albicans formed on the inner surface of complete dentures and the mucosa. This study investigated historical advances in the prevention and treatment of oral mucosal infection and identified gaps in the literature. Bibliographic research was conducted, looking at PubMed, Embase, Web of Science, and Scopus, where 935 articles were found. After removing duplicates and excluding articles by reading the title and abstract, 131 articles were selected for full reading and 104 articles were included. Another 38 articles were added from the gray literature. This review followed the PRISMA-ScR guidelines. The historical period described ranges from 1969 to 2023, in which, during the 21st century, in vitro and in vivo studies became more common and, from 2010 to 2023, the number of randomized controlled trials increased. Among the various approaches tested are the incorporation of antimicrobial products into prosthetic materials, the improvement of oral and denture hygiene protocols, the development of synthetic and natural products for the chemical control of microorganisms, and intervention with local or systemic antimicrobial agents. Studies report good results with brushing combined with sodium hypochlorite, and new disinfectant solutions and products incorporated into prosthetic materials are promising.

Biofilm removal effect of diatom complex on 3D printed denture base resin

For patients who have difficulty in mechanical cleaning of dental appliances, a denture cleaner that can remove biofilm with dense extracellular polymeric substances is needed. The purpose of this study is to evaluate the efficacy of diatom complex with active micro-locomotion for removing biofilms from 3D printed dentures. The diatom complex, which is made by doping MnO2 nanosheets on diatom biosilica, is mixed with H2O2 to generate fine air bubbles continuously. Denture base resin specimens were 3D printed in a roof shape, and Pseudomonas aeruginosa (107 CFU/mL) was cultured on those for biofilm formation. Cleaning solutions of phosphate-buffered saline (negative control, NC), 3% H2O2 with peracetic acid (positive control, PC), denture cleanser tablet (DCT), 3% H2O2 with 2 mg/mL diatom complex M (Melosira, DM), 3% H2O2 with 2 mg/mL diatom complex A (Aulacoseira, DA), and DCT with 2 mg/mL DM were prepared and applied. To assess the efficacy of biofilm removal quantitatively, absorbance after cleaning was measured. To evaluate the stability of long-term use, surface roughness, ΔE, surface micro-hardness, and flexural strength of the 3D printed dentures were measured before and after cleaning. Cytotoxicity was evaluated using Cell Counting Kit-8. All statistical analyses were conducted using SPSS for Windows with one-way ANOVA, followed by Scheffe's test as a post hoc (p < 0.05). The group treated with 3% H2O2 with DA demonstrated the lowest absorbance value, followed by the groups treated with 3% H2O2 with DM, PC, DCT, DCT + DM, and finally NC. As a result of Scheffe's test to evaluate the significance of difference between the mean values of each group, statistically significant differences were shown in all groups based on the NC group. The DA and DM groups showed the largest mean difference though there was no significant difference between the two groups. Regarding the evaluation of physical and mechanical properties of the denture base resin, no statistically significant differences were observed before and after cleaning. In the cytotoxicity test, the relative cell count was over 70%, reflecting an absence of cytotoxicity. The diatom complex utilizing active micro-locomotion has effective biofilm removal ability and has a minimal effect in physical and mechanical properties of the substrate with no cytotoxicity.

Color stability, surface, and physicochemical properties of three-dimensional printed denture base resin reinforced with different nanofillers

Various materials have been introduced for the three-dimensional (3D) printing of dentures. In this study, the color stability and surface and physicochemical properties of 3D-printed denture base resins with four types of nanofiller particles were evaluated. Al2O3, ZnO, CeZr, and SiO2 nanofillers were added to a 3D printable denture base-resin matrix and subjected to digital light processing. The specimens were immersed in Coke, coffee, black tea, or distilled water for 6 days. For the assessment of color differences, 6 samples were analyzed using a spectrophotometer. In a separate investigation, surface properties of 10 samples were examined, while a different set of 6 samples was used to analyze water sorption and solubility. All experimental groups exhibited higher color stability in Coke than the control group. However, the groups containing ZnO and CeZr had lower color stability in coffee and black tea than the control group. Moreover, they had agglomerated nanofillers and lower gloss than the control group. Compared with that of the control group, the contact angle of the CeZr group and microhardness of the ZnO group were not significantly different. Water sorption was higher in the Al2O3 group, whereas the solubility of the experimental and control groups was not statistically significant. The results demonstrated the significant effect of ZnO and CeZr nanofillers on the color stability of the dentures when exposed to discoloring beverages. These results will facilitate the development of fillers that enhance the resistance of 3D printed denture base resins to discoloration in the oral environment.

Effects of disinfection with a vinegar-hydrogen peroxide mixture on the surface characteristics of denture acrylic resins

OBJECTIVE

This study aimed to investigate changes in the surface characteristics of two denture resins when disinfected with a vinegar-hydrogen peroxide (VHP) mixture.

MATERIALS AND METHODS

Microwave-polymerized or 3D printed acrylic resin disks were immersed for 900 min (simulating 90 daily uses) in the following solutions (N = 10): water; 0.5% sodium hypochlorite; hydrogen peroxide and water dilution (1:1 ratio); vinegar and water dilution (1:1 ratio); and VHP mixture. Surface roughness, Knoop microhardness, surface free energy, and scanning electron microscopic images were assessed before and after the immersions. Results were compared using the 2-way ANOVA for repeated measures and Tukey test, at 5% significance.

RESULTS

Surface roughness and microhardness did not differ (P > .05) among the solutions and times. Surface free energy and its dispersive component increased (P < .05) for all solutions. All solutions, except for water and VHP mixture, degraded microtopography.

CONCLUSIONS

The VHP mixture was not deleterious to conventional and 3D-printed resin surfaces.

CLINICAL RELEVANCE

Conventional and 3D printed resin dentures can be disinfected with a VHP mixture in a 1:1 ratio because this mixture does not substantially affect the surface characteristics after 90 daily immersions. On the contrary, sodium hypochlorite, hydrogen peroxide, and vinegar solutions, even in low concentrations, should be used with caution for denture disinfection because they may alter the resin microtopography over time.

Effect of denture cleansers on color stability and surface properties of denture base material containing titanium dioxide nanoparticles

PURPOSE

To investigate the effect of different denture cleansers on color stability, surface roughness, and hardness of polymethylmethacrylate (PMMA) infused with titanium dioxide nanoparticles (TiO2 NPs) at concentrations of 1% and 2% by weight on each.

MATERIALS AND METHODS

In this in vitro study, 90 disc-shaped specimens (10×10×2 mm) were divided into 3 main groups: the non-containing nanoparticle group (0wt% concentration), 1wt% concentration, and 2wt% concentration TiO2 NPs groups. Each group was further assorted into 3 subgroups (n = 10): immersed in distilled water, oxygenating tablet (Corega), and 0.5% sodium hypochlorite. Color change, surface roughness, and hardness values were assessed after 90 and 180 days of storage. Color changes (∆E) were measured with a spectrophotometer (VITA, Easy Shade V, Germany) and assessed using the CIE L*a*b* colorimetric system and the American National Bureau of Standards (NBS = 0.92×∆E). The surface roughness and surface hardness values were measured using a profilometer device and Vickers hardness tester, respectively. First, ANOVA-repeated measurements were performed, followed by the Tukey test. The significance level in this study was considered 0.05.

RESULTS

At all concentrations, there were significant differences in the mean color changes of samples immersed in cleansers compared to distilled water (p < 0.01). Moreover, hypochlorite caused a significant increase compared to Corega at 0wt% concentration after 90 days and at 1wt% concentration after 90 and 180 days. Evaluations also showed that the mean NBS values in all cleanser groups were in the range of appreciable change, except the water group. In addition, only hypochlorite changed the color higher than the clinically acceptable range (∆E >3.7). The mean roughness of samples immersed in hypochlorite at 0wt% concentration was significantly higher than the samples containing TiO2 NPs (p = 0.006). No significant difference was observed in surface roughness of samples containing different concentrations of TiO2 NPs immersed in different cleansers; however, hypochlorite increased the surface roughness of samples without TiO2 NPs compared to samples containing TiO2 NPs after 180 days. The immersion time in cleansers had a significant influence on the surface roughness and hardness while having no effect on the color.

CONCLUSION

In general, the cleansers had a significant effect on color change in all groups compared to distilled water. The adverse effect of hypochlorite was more than Corega. The cleansers in the samples containing TiO2 NPs did not make a significant difference in surface roughness in comparison with the distilled water groups. Surface hardness of the samples was not affected in a steady pattern by the cleansers.

Effect of denture cleansers on color stability and surface roughness of denture bases fabricated from three different techniques: Conventional heat-polymerizing, CAD/CAM additive, and CAD/CAM subtractive manufacturing

PURPOSE

Denture base materials are commonly exposed to different denture cleansers which can affect their essential properties. This study aimed to assess the effect of denture cleansers on color stability and surface roughness of poly methyl methacrylate (PMMA) denture bases fabricated from different techniques: Conventional heat-polymerizing, CAD/CAM additive and CAD/CAM subtractive.

MATERIALS AND METHODS

In this in vitro study, 24 disc-shaped specimens were fabricated by the mentioned methods for each group. The initial color and surface roughness of specimens were recorded. The specimens were randomly divided into three subgroups (n = 8): a control subgroup (distilled water), and two experimental subgroups of bioactive oxygen tablet (Corega) and 1% sodium hypochlorite solution. Then they were immersed in the solutions simulating 180 days of clinical use. Color change (∆E) was measured by a spectrophotometer according to the CIE L*a*b* color space and the American National Bureau of Standards (NBS = 0.92 × ∆E). Final surface roughness was recorded by a profilometer and its change was calculated. The Kruskal-Wallis test followed by the Wilcoxon signed rank test were used for statistical analyses (α = .05).

RESULTS

The conventional and CAD/CAM subtractive groups showed an increase in surface roughness following immersion in hypochlorite solution (p < .05). After immersion in the solutions, the highest surface roughness was noted in the conventional group, and the lowest in the CAD/CAM additive group. The CAD/CAM additive group experienced a significant color change in hypochlorite solution (p < .05) and showed the highest color change while the CAD/CAM subtractive group showed the lowest color change in all denture cleanser solutions.

CONCLUSION

Although the CAD/CAM additive denture base resins had the lowest surface roughness after exposure to denture cleanser solutions, they showed significant color change, which should be taken into account. Using hypochlorite as a denture cleanser should be cautioned due to its negative effects on the surface roughness and color stability of denture base materials.

Effect of polishing and denture cleansers on the surface roughness of new-generation denture base materials and their color change after cleansing

PURPOSE

To evaluate the effect of polishing and denture cleansers on the surface roughness (Ra ) of new-generation denture base materials that are additively, subtractively, and conventionally fabricated, while also assessing their color change after cleansing.

MATERIAL AND METHODS

One hundred and fifty disk-shaped specimens (Ø10 × 2 mm) were prepared from five denture base materials (one subtractively manufactured nanographene-reinforced prepolymerized polymethylmethacrylate (PMMA) (SM-GC), one subtractively manufactured prepolymerized PMMA (SM-PM), two additively manufactured denture base resins (AM-DT and AM-ND), and one heat-polymerized PMMA (CV) (n = 30). The Ra of the specimens was measured before and after conventional laboratory polishing, while color coordinates were measured after polishing. Specimens were then divided into three subgroups based on the denture cleanser: distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet (n = 10). The Ra and color coordinates were remeasured after nine cleansing cycles over a period of 20 days. The CIEDE2000 formula was used to calculate the color differences (ΔE00 ). Two-way analysis of variance (ANOVA) was used to analyze the Ra values before (n = 30) and after (n = 10) cleansing, while repeated measures ANOVA was used to analyze the Ra of material-time point pairs within each denture cleanser (n = 10). ΔE00 data after denture cleansing was also analyzed by using two-way ANOVA (n = 10) (α = 0.05).

RESULTS

Before polishing, Ra varied significantly among the materials. SM-GC and SM-PM had the lowest and AM-ND the highest Ra values (P < 0.001). Polishing significantly reduced Ra of all materials (P < 0.001), and after polishing, Ra differences among materials were nonsignificant (P ≥ 0.072). Regardless of the denture cleanser, the Ra of AM-DT, AM-ND, and CV was the highest before polishing when different time points were considered (P < 0.001). After cleansing, AM-ND had the highest Ra of all the materials, regardless of the cleanser (P ≤ 0.017). AM-DT had higher Ra than SM-PM when distilled water (P = 0.040) and higher Ra than SM-GC, SM-PM, and CV when NaOCl was used (P < 0.001). The type of cleanser significantly influenced the Ra of AM-DT, AM-ND, and CV. For AM-DT, NaOCl led to the highest Ra and the tablet led to the lowest Ra (P ≤ 0.042), while for AM-ND, distilled water led to the lowest Ra (P ≤ 0.024). For CV, the tablet led to lower Ra than distilled water (P = 0.009). Color change varied among the materials. When distilled water was used, SM-GC had higher ΔE00 than SM-PM and AM-DT (P ≤ 0.034). When NaOCl was used, AM-ND had higher ΔE00 than SM-GC, SM-PM, and AM-DT, while CV and SM-GC had higher ΔE00 than SM-PM and AM-DT (P ≤ 0.039). Finally, when the tablet was used, AM-ND and CV had the highest ΔE00 , while AM-DT had lower ΔE00 than SM-GC (P ≤ 0.015).

CONCLUSIONS

The tested materials had unacceptable surface roughness (>0.2 μm) before polishing. Roughness decreased significantly after polishing (<0.2 μm). Denture cleansers did not significantly affect the surface roughness of the materials, and roughness remained clinically acceptable after cleansing (<0.2 μm). Considering previously reported color thresholds, AM-ND and CV had unacceptable color change regardless of the denture cleanser, and the effervescent tablet led to perceptible, but acceptable color change for SM-GC, SM-PM, and AM-DT.

Influence of Three Different Denture Cleansers on Surface Roughness and Strength of Heat-polymerizing Resin: An In Vitro Study

AIM

The purpose of the current study was to evaluate the impact of three different denture cleansers on the strength and surface roughness of heat-polymerizing resin.

MATERIALS AND METHODS

A total of 120 resin discs (10 mm in diameter and 2 mm thick) were created using a stainless steel mold for surface roughness testing and flexural strength testing (in accordance with the American Dental Association (ADA) Specification No.12). Samples were divided into one of three groups (40 samples in each group): group I: Clanden, group II: Clinsodent, group III: Fittydent. Samples were immersed in denture-cleansing solutions for 30 minutes every day, and this process was repeated over a period of 15 days. Samples were stored in distilled water at room temperature in between the immersions. A surface analyzer was utilized to compare the surface roughness of each sample before and after immersion treatments. For recording flexural strength, each sample was subjected to three-point bending test by mounting samples on Universal testing machine. Comparing mean values between groups using one-way ANOVA and the Tukeys honest significant difference (HSD) post hoc test. A significance level of 0.05 was used for all statistical calculations Results: After 15 days, the maximum change of mean surface roughness of heat-polymerizing resin was found in Clanden denture cleanser group (2.64 ± 0.12) followed by Clinsodent group (2.26 ± 0.09) and Fittydent group (1.92 ± 0.06). After 15 days, the maximum change of mean flexural strength changes of heat-polymerizing resin was found in Clanden denture cleanser group (94.78 ± 0.14), followed by Fittydent group (98.64 ± 0.03) and Clinsodent group (99.26 ± 0.21).

CONCLUSION

Within the limitation, the current study concluded that changes were observed in surface roughness and flexural strength of all heat-polymerizing resin samples after immersion in all three denture cleansers; but least surface roughness and flexural strength changes were observed with the Fittydent cleanser group and Clinsodent group, respectively.

CLINICAL SIGNIFICANCE

Cleaning dentures is crucial for maintaining both the prosthesis and oral health; therefore, it is necessary to select a cleanser that is effective without negatively affecting the base resin's qualities over time.

Influence of Contemporary Photoactivated Disinfection on the Mechanical Properties and Antimicrobial Activity of PMMA Denture Base: A Systematic Review and Meta Analysis

PURPOSE

The present study aimed to perform a systematic review and meta-analysis to investigate the effectiveness of the contemporary photoactivated disinfection methods on the mechanical features and/or antimicrobial activity of polymethyl methacrylate (PMMA) dentures bases.

METHODS

THE FOCUSED RESEARCH QUESTION WAS: : "What is the effect of contemporary photoactivated disinfection methods as compared to conventional disinfection protocols on the mechanical features and/or antimicrobial activity of PMMA dentures bases?". An electronic literature search was carried out by the author and a senior librarian specialized in health sciences on Web of Science, PubMed, and Scopus. In vitro investigations evaluating the antimicrobial and/or mechanical effects of photoactivated disinfectants as compared to conventional chemical disinfectants on the microbes formed on PMMA denture bases were included. Meta-analysis was performed for calculating the standard mean difference (SMD) with a 95% confidence interval.

RESULTS

Four out of eight studies concluded that photoactivated disinfectants, including riboflavin-mediated photodynamic therapy (PDT), hematoporphyrin-mediated PDT, poly-L-glycolic acid loaded with methylene blue, Erbium, chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser, erbium-doped yttrium-aluminum-garnet (Er:YAG) laser, and chitosan-mediated PDT, demonstrated a significant reduction in colony-forming unit per milliliter (CFU/mL) of exposed viable colonies of Escherichia coli (E. coli), Streptococcus mutans (S. mutans), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans) comparable to the conventionally used chemical disinfectants of PMMA denture bases. Contrarily, two studies concluded that the PMMA denture base colonized with C. albicans and disinfected with conventional chemical disinfectants showed the greatest anti-fungal efficaciousness. All the included studies concluded that the application of photoactivated disinfectants does not negatively impact the mechanical features of the PMMA denture bases colonized with microbes including E. coli, S. mutans, S. aureus, and C. albicans. The meta-analysis revealed statistically significant reduction in C. albicans counts (CFU/mL [Log10]) (p < 0.00001) and improvement in the flexural strength (p = 0.0002) of PMMA-based denture base after the application of conventional disinfectants, while a statistically significant improvement in the fracture strength of PMMA-based denture base was observed after the application of photoactivated disinfectants (p = 0.03).

CONCLUSION

According to the systematic review (qualitative synthesis), photoactivated disinfectants demonstrated comparable mechanical features and antimicrobial activity of PMMA dentures bases to conventional chemical disinfectants suggesting their potential to be utilized as an alternative to conventional chemical disinfectants. However, the meta-analysis (quantitative synthesis) revealed that the application of conventional disinfectants demonstrated better outcomes related to antimicrobial activity and flexural strength of PMMA-based denture based.

Effect of Effervescent Denture Cleansers on 3D Surface Roughness of Conventional Heat Polymerized, Subtractively, and Additively Manufactured Denture Base Resins: An In Vitro Study

PURPOSE

To compare the change in surface roughness of denture bases fabricated using three different techniques (additive manufacturing, subtractive manufacturing, and conventional heat-polymerizing) when immersed in two commonly available denture cleansers.

MATERIALS AND METHODS

One hundred and seventeen disc-shaped denture base specimens (39/group), were fabricated by subtractive manufacturing (Wieland), additive manufacturing (NextDent Denture 3D+), and conventional heat-polymerizing (Meliodent) techniques, following the manufacturers' instructions. Specimens were randomly divided into 3 groups and immersed in two effervescent denture cleansing solutions and distilled water to simulate 180 days of denture cleansing. A 3D optical noncontact surface profilometer was used to record the surface roughness of the tested denture base materials before and after immersion. Two-way ANOVA, followed by Bonferroni post hoc test, was used to assess the effects of denture cleansers on surface roughness of tested denture base resins.

RESULTS

When immersed in Fixodent and Fittydent effervescent denture cleansing solutions, the highest change in absolute surface roughness (∆Sa, in μm) was observed in additively manufactured denture base material (0.181 ±0.018 and 0.079 ±0.008), followed by heat-polymerized denture base material (0.149 ±0.012 and 0.059 ± 0.011), while subtractively manufactured denture base material showed the least change (0.110 ±0.026 and 0.038 ±0.007), respectively. There was a difference in the extent of change in surface roughness between the denture cleansers. The change in surface roughness was much higher with the Fixodent denture cleanser as compared to the Fittydent denture cleanser.

CONCLUSION

Subtractively manufactured denture base resin displayed the lowest change while additively manufactured denture base resin displayed the highest change in surface roughness in both denture cleansers, but the extent of change in surface roughness was variable.

Efficacy of Denture Cleansers on Microbial Adherence and Surface Topography of Conventional and CAD/CAM-Processed Denture Base Resins

This study assessed the efficacy of five denture cleansers on the microbial adherence and surface topography of conventional and CAD/CAM denture base resins. Acrylic resin discs were fabricated using conventional, milling, and 3D printing methods (N = 180). The discs were contaminated with dual species of Candida albicans and Streptococcus mutans biofilm for 72 h and then disinfected with either of the denture cleansers (Fittydent cleansing tablets, 2% Chlorhexidine gluconate, 0.2% Chlorhexidine gluconate, 0.5% sodium hypochlorite, and 1% sodium hypochlorite (n = 10). Distilled water served as the control group. The colony-forming units of the microorganisms were calculated, followed by post-treatment surface roughness. Data were statistically analyzed using one-way ANOVA, paired t-test, and post hoc Tukey HSD test (α = 0.05). Among the denture cleansers, 2% Chlorhexidine gluconate, 0.5% sodium hypochlorite, and 1% sodium hypochlorite had the best cleansing effect on the resin discs and demonstrated zero growth of colonies for both the species. Comparing the material groups, the 3D-processed discs showed higher colony-forming units followed by the conventional and CAD/CAM milled group. The highest surface roughness was demonstrated by the 3D-printed discs (0.690 ± 0.08 μm), followed by the conventional (0.493 ± 0.11 μm) and the milled groups (0.301 ± 0.08 μm). The tested chemical denture cleansers affected the Candida albicans and Streptococcus mutans adhesion compared to control discs immersed in distilled water. The clinician may recommend to their patient to use 2% chlorhexidine gluconate for the disinfection of CAD/CAM PMMA denture base materials.

Effect of cigarette smoke and denture cleansers on the surface properties and color stability of CAD-CAM and conventional denture base resins

This study aimed to evaluate the hardness, roughness, and color stability of heat- and microwave-polymerized polymethyl methacrylate (PMMA), polyamide, and CAD-CAM PMMA resins when exposed to cigarette smoke (CS) and immersed in a denture cleanser (DC). Specimens of each resins were divided into four subgroups (n=10). The DC and CS+DC specimens were immersed in a DC; the CS and CS+DC specimens were exposed to CS; and the control (C) specimens were kept in distilled water. Hardness, roughness, and color measurements were performed. DC and CS significantly affected the roughness and color of all resins (p<0.05). However, these did not affect the hardness of the CAD-CAM PMMA resin (p>0.05). The CAD-CAM PMMA resin presented the lowest roughness, highest hardness, and lowest ΔE₀₀ values. While the roughness of all resins exposed to CS when immersed in DC decreased, the ΔE₀₀ values of the conventional PMMAs also decreased. Although this decreases were not significant, it may be advisable to use DC for smokers to decrease discoloration and roughness especially for conventional PMMAs resins.

Effects of long-term cinnamaldehyde immersion on the surface roughness and color of heat-polymerized denture base resin

STATEMENT OF PROBLEM

Cinnamaldehyde has been successfully used for the short-term disinfection of dentures; however, its long-term effects on the surface and color properties of denture base materials remain unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of simulated immersion in cinnamaldehyde for up to 5 years on the surface roughness and color parameters of a heat-polymerized denture resin.

MATERIAL AND METHODS

Eighty Ø10×5-mm disk-shaped specimens were prepared from microwave heat-polymerized polymethylmethacrylate (PMMA) and immersed in 4 solutions (n=20): TW-tap water (control), SH - 0.5% sodium hypochlorite, PX-alkaline peroxide, and CA-cinnamaldehyde (27 μg/mL). The immersion protocol simulated 104 cycles (3.5 months), 913 cycles (2.5 years), and 1825 immersion cycles (5 years) of a daily immersion cleaning protocol, with immersion times ranging from 10 to 20-minutes. Surface roughness (Sa) and the color parameters of CIELab (L∗ a∗ b∗, ΔEab), CIEDE2000 (ΔE00), and the National Bureau of Standards (NBS) were analyzed at baseline (t=0) and after the immersion cycles. The data were analyzed by 2-way analysis of variance (ANOVA) for repeated measures and the Tukey post hoc test (α=.01).

RESULTS

Sa was significantly increased in all groups after 1825 cycles compared with baseline (P<.01), regardless of the solution. Only the time factor significantly affected ΔEab, ΔE00, and NBS parameters, which were below the perceptibility and acceptability thresholds. After a simulated 5-year immersion, the surface roughness and color values of CA-treated specimens were not statistically different from those of the other groups (P>.01).

CONCLUSIONS

Cinnamaldehyde solution (27 μg/mL) produced minor effects on the surface roughness and color parameters of a heat-polymerized denture base resin similar to those of 0.5% sodium hypochlorite and alkaline peroxide after a 5-year simulated immersion.

Do denture cleansers influence the surface roughness and adhesion and biofilm formation of Candida albicans on acrylic resin? Systematic review and meta-analysis

PURPOSE

To evaluate the influence of denture cleansers on the surface roughness, Candida albicans adhesion, and biofilm formation on denture base acrylic resins.

STUDY SELECTION

Electronic databases and gray literature were searched using an individual search strategy. In vitro studies that evaluated the effects of immersion in denture cleansers on the surface roughness (µm) and antimicrobial activity (CFU/mL) on samples of heat-polymerized denture base acrylic resins were included.

RESULTS

After screening, 17 studies were included, and a qualitative synthesis was performed. After assessing the risk of bias, only nine studies were included in the meta-analysis. The meta-analysis results showed that the evaluated solutions (0.5% sodium hypochlorite, 1% sodium hypochlorite, alkaline peroxide, and natural substances) did not influence the roughness of the acrylic resin. However, in the qualitative analysis, it was not possible to confirm an association between roughness and C. albicans adhesion and biofilm formation on the acrylic resin samples.

CONCLUSION

Denture cleansers did not affect the surface roughness of denture base acrylic resins.

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.

Effect of Candida albicans Suspension on the Mechanical Properties of Denture Base Acrylic Resin

Yeast-like fungi such as Candida albicans (C. albicans) are the primary pathogenic microorganism in the oral cavity of denture wearers. The research available so far, conducted according to a protocol based on the exposure of specimens to a C. albicans suspension and their cutting with water cooling, shows that hard polymethyl methacrylate (PMMA) prosthetic materials are not only surface colonized, but also penetrated by microorganisms in a short time. This justifies the hypothesis that exposure to a suspension of the C. albicans strain causes the changes in mechanical properties due to surface colonization and/or penetration of the samples. In the current study, the chosen mechanical properties (flexural strength, flexural modulus, tensile strength, impact strength, ball indentation hardness, and surface Vickers hardness at 300 g load) of the PMMA denture base material Vertex RS (Vertex-Dental, The Netherlands) exposed for 30, 60, and 90 days to a suspension of C. albicans were investigated. The potential penetration of yeast was examined on the fractured surfaces (interior of specimens) to eliminate the risk of the contamination of samples during cutting. There was no influence on the flexural strength, flexural modulus, tensile strength, impact strength, or ball indentation hardness, but a significant decrease in surface hardness was registered. Microscopic observations did not confirm the penetration of C. albicans. On the surface, blastospores and pseudohyphae were observed in crystallized structures and in traces after grinding, which indicates that in clinical conditions, it is not penetration but the deterioration of surface quality, which may lead to the formation of microareas that are difficult to disinfect, causing rapid recolonization.

Efficacy of chemical and Photoactivated disinfectants against Candida Albicans and assessment of hardness, roughness, and mass loss of acrylic denture base resin

AIM

The present study aimed to assess the antimicrobial efficacy of hematoporphyrin derivative, sodium hypochlorite (NaOCl), glutaraldehyde (GaH), and a chlorhexidine (CHX) on mass loss (ML), microhardness, and surface roughness (Ra) of acrylic denture base colonized with C. Albicans.

MATERIAL AND METHODS

A total of 40 heat cure acrylic resin dentures were fabricated and inoculated by the American Type Culture Collection (ATCC) of C. Albicans in an in-vitro situation. Specimens were divided into four groups (n=10) based on the method of disinfection. Hematoporphyrin derivatives, 1% NaOCl, 2% GaH, and 4% CHX.The pre and post candida (CFU/ml) counts were recorded before and after immersion. ML, microhardness, and Ra of acrylic denture were also assessed. Statistical analysis was executed for CFU/mL (log10) for exposed C. Albicans by two-way ANOVA and Tukey's multiple tests (p>0.05). For normality of the data, Dunnet's Simultaneous test was performed.

RESULTS

In terms of candida strain analysis, pretreatment to posttreatment comparisons revealed a reduction in mean Candida count in all groups (p<0.05). The highest ML value after post candida disinfection of acrylic denture was observed in 2% GaH (1.587 ± 0.25) treated specimens. The least microhardness value was found in group 1 when treated with hematoporphyrin (0.97 ± 0.22 VHN) which was significantly different from other groups (p<0.05). Group 1 surface treated with hematoporphyrin derivate (1.84 ± 0.22 μm) showed the highest Ra values (p<0.05).

CONCLUSION

Acrylic denture base resin colonized with C. Albicans when treated with a chemical disinfectant of 4% chlorhexidine displayed the highest antimicrobial efficacy with reduced mass loss, less surface roughness, and maximum denture hardness.

Effect of denture cleansers on the surface properties and color stability of 3D Printed denture base materials

OBJECTIVES

To evaluate the effect of denture cleansers on surface roughness, hardness and color stability of 3D-printed resins compared to heat-polymerized resins.

METHODS

Acrylic specimens (N=160) were prepared using one heat-polymerized (HP) and three 3D-printed denture base resins. Specimens per material were randomly divided into four groups (n = 10) according to immersion solutions as follows: distilled water (DW), sodium hypochlorite (NaOCl), effervescent tablet 1 or effervescent tablet 2. Color changes (∆E) were measured using a spectrophotometer. Surface roughness (Ra, µm) and microhardness were evaluated. The results were analyzed using one- and three-way ANOVA with Tukey's post hoc test (α = 0.05).

RESULTS

After 360 days of cleaning protocols, we observed a significant increase in the surface roughness of tested materials (P<0.001). Hardness values significantly decreased in all groups (P<0.001), except HP and ND specimens, cleaned with effervescent tablet 1 (P>0.05) and AS specimens with effervescent tablet 2 (P=0.051). According to the National Bureau of Standards (NBS) score, all denture base specimens had 'perceivable' to 'extremely marked' color change after immersion in NaOCl, while immersion in effervescent tablets 1 and 2 resulted in a 'slight' to 'marked' color change.

CONCLUSION

3D-printed denture bases exhibited changes in surface roughness, hardness and color of 3D-printed dentures similar to HP denture base material. The use of denture cleansers resulted in a time-dependent increase in surface roughness and a decrease in hardness. The color change was significant with NaOCl, while effervescent denture cleansers produced a minimal color difference.

CLINICAL SIGNIFICANCE

Denture cleansers seem to influence surface properties over time. The degree of impact is mainly dependent on the type of cleanser selected, regardless of the type of denture base material.

Disinfection efficacy and fracture strength of PMMA denture-based polymer with chlorhexidine, PDT utilizing Rose Bengal and hematoporphyrin, and Er, Cr: YSGG laser

OBJECTIVE

The study aimed to assess and compare disinfection efficacy and fracture strength of PMMA based DBPs using chlorhexidine (CHX), PDT utilizing Rose Bengal (RB) and hematoporphyrin HPD, and Er,Cr:YSGG laser (ECL) induced antimicrobial action against in-vitro biofilms colonized with C.albicans, S.aureus, S. mutans, and E. coli.

MATERIAL AND METHODS

American Type Culture Collection (ATCC) of C.albicans, S.aureus, S. mutans and E. coli were cultured. Forty-eight PMMA-based denture base plates (DBPs) were prepared by heat-cure acrylic resin and contaminated by in-vitro biofilm under-stimulated in-vitro conditions. DBPs were treated with group1; ECL group 2; RB 5µm, group 3; HPD 500 mg/L and group 4; 0.12% CHX (controls) respectively, for the disinfection of biofilms. All photosensitizers (PS) were activated by LED at a different wavelength. Each contaminated DBP was sprayed on all its surfaces with the aforementioned photosensitizers and CHX. One-way analysis of variance (ANOVA) was used to test the efficacy of disinfection and fracture load testing. Tukey multiple comparison tests were performed to compare means of CFU/mL (log10) for exposed E. coli, C. albicans, S aureus, and S. mutans.

RESULTS

Specimens in group 1 disinfected with erbium laser, group 3 disinfected with HPD, and group 4 sterilized with chemical disinfection were effective in decreasing bacterial load CFU/mL (log10) against C.albicans, S. aureus, S.mutans, and E. Coli (p>0.05). Intergroup comparison demonstrated ECL, CHX and HPD demonstrated a comparable reduction against C.albicans and S.aureus (p>0.05). Similarly, S.mutans and E.coli were sensitive against all experimental groups (p>0.05). no significant difference in fractural load analysis among the different investigated groups was noted (p>0.05).

CONCLUSION

ECL and HPD photosensitizer revealed a significant reduction in CFU/ml of exposed viable colonies of C.albicans, S.aureus, S. mutans, and E. coli comparable to 0.12% CHX mediated disinfection of PMMA-based DBPs. Irrespective of the type of disinfection no influence of disinfection was noted on the fracture load of PMMA DBPs.

Evaluation of microhardness in two types of denture bases after using sodium hypochlorite and NatureDent disinfecting agents

Background. Chemical agents, in combination with mechanical methods, play an important role in reducing microbial plaque on denture surfaces. However, these methods might change the mechanical behavior of acrylic resins, including microhardness and surface roughness. This in vitro study investigated the effect of two disinfectants, i.e., water and sodium hypochlorite, on the microhardness of conventional heat-cured and TiO₂ nanoparticle-reinforced acrylic resins. Methods. Sixty acrylic resin specimens were divided into two groups, and the samples in each group were randomly assigned to three subgroups (n=10). Heat-cured specimens and 1 wt% TiO₂ acrylic resin were prepared and immersed in three solutions: water, a solution prepared with NatureDent pills, and 1% sodium hypochlorite for 30, 60, and 90 days. Microhardness tests were performed on each sample at each immersion stage. The data were analyzed using descriptive statistical methods, three-way and one-way ANOVA, repeated-measures t test, and Tukey HSD tests using SPSS 17. P values<0.05 were considered significant. Results. All three independent parameters, including resin, solution, and time, significantly affected microhardness (P<0.05). The microhardness of both specimen types, i.e., conventional heat-cured and TiO₂ nanoparticle-reinforced acrylic resins, immersed for 30, 60, and 90 days, was the highest and lowest in water and hypochlorite solutions, respectively. Regarding 90 days, the microhardness values of conventional heat-cured and TiO₂ nanoparticle-reinforced acrylic resins were 17.050±0.094 and 19.953±0.053 in water, 15.675±0.069 and 18.965±0.037 in hypochlorite, and 16.713±0.122 and 19.39±20.113 in NatureDent solutions, respectively. Conclusion. Disinfecting two types of acrylic resin specimens decreased their microhardness as a function of immersion time for up to 90 days in the three solutions. However, the magnitude of hardness lost was less for TiO₂ nanoparticles-reinforced acrylic resin.

Complete denture hygiene solutions: antibiofilm activity and effects on physical and mechanical properties of acrylic resin

BACKGROUND

Appropriated denture hygiene is a predictive factor for longevity of rehabilitation treatment and maintenance of the oral mucosal health. Although, disinfectant solutions are commonly used as denture cleansers, the impact of these solutions on acrylic resin-based dentures remain unclear.

OBJECTIVE

To evaluate, in vitro, the antibiofilm activity of complete denture hygiene solutions and their effects on physical and mechanical properties of acrylic resin.

METHODOLOGY

For antibiofilm activity measurement acrylic resin specimens were contaminated with Candida albicans, Candida glabrata and Streptococcus mutans. After biofilm growth, the specimens were assigned to the hygiene solutions: Distilled water (Control); 0.2% Sodium hypochlorite (SH); Efferdent Power Clean Crystals (EPC) and 6.25% Ricinus communis (RC). The viability of microorganisms was evaluated by agar plate counts. In parallel, physical, and mechanical properties of the acrylic resin were evaluated after simulating a 5-year period of daily immersion in the previously mentioned solutions. The changes in surface roughness, color, microhardness, flexural strength, impact strength, sorption and solubility were evaluated. Data were compared by ANOVA followed by the Tukey test or Kruskal-Wallis followed by the Dunn test depending on the distribution (α=0.05).

RESULTS

Regarding antibiofilm action, SH eliminated all microorganisms while EPC and RC exhibited moderate action against S. mutans (p=0.001) and C. glabrata (p<0.001), respectively. Relative to effects on the physical and mechanical properties of the acrylic resin, RC led to higher values of color change (p=0.030), hardness (p<0.001), surface roughness (p=0.006) and flexural strength (p<0.001). Moreover, RC induced the highest values of changes in solubility (p<0.001). EPC promoted greater changes in surface morphology, whereas immersion in SH retained the initial appearance of the acrylic resin surface. All hygiene solutions reduced the impact strength (p<0.05).

CONCLUSION

SH presented the most effective antibiofilm activity. In addition, changes on properties were observed after immersion in RC, which were considered within acceptable limits.

Disinfection of acrylic denture resin polymer with Rose Bengal, Methylene blue and Porphyrin derivative in photodynamic therapy

AIM

The study aimed to assess the effect of in-vitro chlorhexidine and antimicrobial photodynamic therapy (aPDT) disinfection protocols against acrylic resin specimens colonized with S. mutans, S. aureus, E. coli, and C. albicans.

MATERIAL AND METHODS

Reference strains of S. mutans, S. aureus, E. coli, and C. albicans were tested. Sixteen blocks of acrylic specimens were prepared by heat-cure acrylic resin and contaminated by in-vitro biofilm growth. Specimens in group 1, group 2 and group 3 were treated with Rose Bengal (RB), methylene blue (MB) 500 mg/L and porphyrin derivative (PD) 5 ml respectively, for the sensitization of biofilms. All photosensitizers (PS) were activated by LED at different wavelength. CHX was prepared in sterile distilled water and applied for 60 s. Each contaminated specimen was sprayed on all its surfaces with the aforementioned photosensitizers and control CHX. One-way analysis of variance (ANOVA) model was used to test the effect of the treatments and Tukey multiple comparison tests to compare means OF CFU/mL (log10) for exposed E. coli, C. albicans, S aureus, and S. mutans RESULTS: Specimens treated with 0.12% CHX (control) demonstrated a significant reduction in CFU/mL (log10) for exposed E. coli; 2.04±0.07 CFU/mL, C. albicans; 2.09±0.85 CFU/mL, S aureus; 3.04±0.11 CFU/mL, and S. mutans; 2.54±0.91 CFU/mL. The intragroup comparison revealed E.coli did not exhibit a decrease in reduction CFU/mL (log10) when acrylic resin irradiated with RB 5 µm. Whereas, CFU/mL (log10) values of S.aureus; 3.62±0.68 and S.mutans; 3.41±0.13 plummeted (p<0.05). Intergroup comparison showed E.coli values to display comparable reduction when disinfected with MB 500 mg/L and 0.12% CHX; 3.16±0.34 and 2.04±0.07 CFU/mL (log10) (p<0.05).

CONCLUSION

Photosensitizers (RB, MB, PD) are selective in reducing bacterial count on acrylic resin blocks. CHX was found to be effective against all bacteria E.coli, C.albicans, S.aureus, and S.mutans at a concentration of 0.12%.

Color Stability and Surface Properties of PMMA/ZrO2 Nanocomposite Denture Base Material after Using Denture Cleanser

Objectives

This study aimed to evaluate denture cleanser effects on color stability, surface roughness, and hardness of PMMA denture base resin reinforced with nano-ZrO₂.

Materials and Methods

A total of 420 specimens were fabricated of unreinforced and nano-ZrO₂ reinforced acrylic resin at 2.5% and 5%, resulting in 3 main groups. These groups were further subdivided (n = 10) according to immersion solution (distilled water, Corega, sodium hypochlorite, and Renew) and immersion duration. Surface roughness, hardness, and color were measured at baseline (2 days-T₀) in distilled water and then after 180 and 365 days of immersion (T₁ & T₂) in water or denture cleansing solutions. Data was collected and analyzed using two-way ANOVA followed by Bonferroni post hoc test (α = 0.05).

Results

Surface roughness increased significantly after denture cleanser immersion of unmodified and nano-ZrO₂-modified PMMA materials while hardness decreased (P < 0.001). The denture cleansers significantly affected the color of both PMMA denture bases (P < 0.001). The immersion time in denture cleansers significantly affected all tested properties (P < 0.001). Within denture cleansers, NaOCl showed the highest adverse effects (P < 0.05) while Renew showed the least adverse effects.

Conclusion

Denture cleansers can significantly result in color change and alter the surface roughness and hardness of denture base resin even with ZrO₂ nanoparticles addition. Therefore, they should be carefully used.

Phytotherapy in the management of denture stomatitis: A systematic review and meta-analysis of randomized controlled trials

Medicinal plant extracts are commonly applied for infectious diseases and are perceived as alternatives to conventional antimicrobial agents. We aimed to confirm the efficacy of phytotherapy for denture stomatitis compared with conventional therapies and placebo. A comprehensive literature search was conducted in Pubmed, Embase, Cochrane Library (CENTRAL), Scopus, and Web of Science, in addition to manual searching. Randomized controlled trials (RCTs) published in English, and studying the treatment of denture stomatitis with herbal medicines, were included. The outcome measures included the relief of clinical signs, reduced Candida colony counts, adverse effects, and patient satisfaction. Nineteen RCTs were included for a systematic review based on selection criteria. Two of them were analyzed using a random-effects model. There was no difference in the relief of clinical signs (odds ratio (OR) = 0.96; 95% confidence interval (CI): 0.43-2.15) and microbiological improvement (OR = 1.74; 95% CI: 0.55-5.45) between propolis and miconazole. Most of the included studies showed that phytomedicines had fewer side effects and more patient satisfaction than antifungals or disinfectants. However, further RCTs with more standardly prepared herbal formulations are required to verify the clinical efficacy of phytotherapy as an alternative or adjunctive therapy for denture stomatitis.

Influence of Removable Denture Cleaning Agents on Adhesion of Oral Pathogenic Microflora In Vitro: A Randomized Controlled Trial

Introduction:

Removable dentures are used by 20% of the population. These may be accompanied by denture stomatitis in 15-70% of patients. The choice of the optimal cleansing agent for removable dental prostheses is of high significance.

Aim:

The aim of our research was to study the influence of removable denture cleansing products on the adhesion of microorganisms and yeast.

Materials and Methods:

We manufactured 144 specimens of standardized round shape with a diameter of 10 mm from 4 types of modern polymeric materials used by prosthetic dentistry to produce removable dentures, 12 specimens of each material were placed into suspensions of bacterial cultures of Staphylococcus aureus, Escherichia coli, Candida albicans, then into “ClearaSept” (Test group 1), “Рrotefix active cleanser” (Test group 2), saline solution (Control group), followed by nutrient media. The adhesion index was calculated and analyzed.

Results:

There was no reliable lowering of adhesion index of Staphylococcus Aureus to all materials detected in Test group 1 (U=6, p>0.05 for Bio XS; U=8, p>0.05 for Dental D, Denotokeep Peek, Vertex Rapid Simplified). In Test group 2, the adhesion index of Staphylococcus Aureus reliably decreased to all materials compared to the Control group (U=0, p≤0.01). The adhesion index of Candida albicans and Escherichia coli to all materials in Test group 1 had a minor to moderate reliable reduction compared to the Control group (U=0, p≤0.01). Test group 2 showed a significant reliable decrease in Candida albicans and Escherichia coli adhesion index to all materials in comparison with the Control group (U=0, p≤0.01).

Conclusion:

The research showed an unreliable or minor and moderate reliable decrease in microorganisms adhesion index depending on the microorganism species after treatment of denture material specimens by antibacterial soap “ClearaSept” and a reliable significant decrease in microbial and yeast adhesion after application of Protefix active cleaner solution, which demonstrates a more significant antimicrobial effect in comparison to “ClearaSept” against Staphylococcus aureus, Escherichia coli, and Candida albicans.

Surface roughness of acrylic resins used for denture base after chemical disinfection: A systematic review and meta-analysis

OBJECTIVE

This study aimed to systematically review the literature regarding the surface roughness of polymethylmethacrylate (PMMA) for denture bases, disinfected with different chemical agents and analyse the outcomes of the included studies.

BACKGROUND

Various chemical disinfection protocols to clean the removable dental prosthesis are reported in the literature, however systematic reviews analysing the outcomes in the surface roughness of the PMMA are lacking.

METHODS

The Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) checklist was used to structure this systematic review. The inclusion criteria were as follows: clinical trials, in vitro studies, studies in English and studies comparing the effects of chemical disinfection products on the surface roughness of PMMA. An electronic search was performed in the following databases: PubMed/MEDLINE, Scopus and Web of Science.; we also conducted a manual search for articles published in specific journals of dental prostheses and dental materials.

RESULTS

Thirteen in vitro studies in this systematic review and meta-analysis. According to the meta-analysis, the effects of 0.5% (P = .32; MD: 0.06; CI: -0.05 to 0.17; heterogeneity: P < .00001; I²  = 92%) and 1% NaOCl solutions (P = .27; MD: 0.01; CI: -0.01. to 0.03; heterogeneity: P = .03; I²  = 55%) did not statistically differ between the groups studied. Effects of alkaline peroxide were statistically significant (P = .0009; MD: 0.01; CI: 0.01-0.02; heterogeneity: P = .004; I²  = 65%), suggesting that it promotes deterioration of the PMMA surface.

CONCLUSION

The alkaline peroxide, when used as a disinfectant, generated changes on the surface roughness of PMMA and should be used with caution; however, NaOCl, even at different concentrations, caused fewer changes on the surface of the denture base.

Effect of Cleanser Solutions on the Retention Force of O'ring Attachment: An in Vitro Study

The aim of this study was to evaluate the effect of cleaning solutions on the retention force of o-ring-type overdenture attachments. The effect of four solutions on nitrile rings were evaluated: Cepacol (C), Cepacol with fluoride (CF), Listerine (L) and 0.05% sodium hypochlorite (SH); deionized water (DW) was used as a control. Matrices containing two implants and abutments and acrylic specimens with the metal capsules were obtained and divided into the groups. A simulation of 90 overnight immersions (8 h) was performed, and the tensile strength value was obtained at the beginning (T0) and in every 30 days (T1, T2 and T3) (n=6). In order to analyze o-ring surface damage after the immersions, a scanning electron microscopy (SEM) was used (n=1). For statistical analysis of the results, analysis of variance (ANOVA) and multiple comparisons with Bonferroni adjustment (test power=1.000; a=0.05) were used. There was a significant difference for the factors time (p<0.001), solution (p<0.001) and for the interaction time × solution (p<0.001). Considering the times of each solution, only for DW there was no significant loss of retention over time. Comparing the solutions in each moment, there was no difference among the solutions in T0. From T1, CF and SH provided less retention than DW (p<0.005). Through SEM it was possible to observe changes in the surface of the CF and SH nitrile o-rings. CF and SH should be avoided due to deleterious action in o-rings.

Effects of denture cleaning solutions on the retention of Hader bar clips

STATEMENT OF PROBLEM

The clinical performance of implant-retained overdentures (IODs) with plastic bar clips made of different materials in the same design and dimensions may vary according to the patient's daily home care procedures. However, information about the effects of denture cleaning solutions on the retention of Hader bar clips is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the retention of Hader bar clips made of different polymers after being soaked in denture cleaning solutions.

MATERIAL AND METHODS

Ninety Hader bar clips made of polyamide (PA, n=30), polytetrafluoroethylene (PTFE, n=30), and polyetherketoneketone (PEKK, n=30) materials were tested. Two multiunit abutments were screwed onto the implant analogs and embedded into an acrylic resin block in a standardized position. The digital scanning of the abutments was acquired, and the bar patrix of each material system milled from a cobalt-chromium (Co-Cr) alloy disk by using computer-aided design and computer-aided manufacturing (CAD-CAM). After the milled bar patrices were screwed onto abutments and the metal housings of the bar clips were embedded into acrylic resin blocks, they were connected passively at the same angulation to a universal testing machine. The initial retention values of all Hader bar clips were measured, and each material system was divided into 3 subgroups (n=10) before soaking in the cleaning solutions: distilled water (DW), 5% sodium hypochlorite (NaOCl), or sodium bicarbonate-sodium perborate (SBSP). Each material was soaked for the equivalent of 3 months of clinical use. The final retention values of each Hader bar clip were measured. The data were statistically analyzed by using a 2-way analysis of variance (ANOVA), the Tukey honestly significant difference (HSD) test, and the paired sample t test (α=.05).

RESULTS

The 2-way ANOVA showed that the denture cleaning solution, the clip material, and their interactions led to significantly different retention values (P<.001). A decrease was observed for the retention values of all test groups after soaking in the cleaning solutions (P<.05). No retention was observed for the PTFE clips after soaking in the 5% NaOCI solution.

CONCLUSIONS

The denture cleaning solutions negatively affected the retention of Hader bar clips, regardless of the type of solution and clip material. The 5% NaOCI solution not only decreased the retention of PTFE clips but also completely degraded it. It is recommended that 5% NaOCI solution be avoided for the daily care of IODs with PTFE clips.

Cinnamaldehyde is a biologically active compound for the disinfection of removable denture: blinded randomized crossover clinical study

BACKGROUND

Fungal infections associated with the use of dentures, like denture stomatitis, are difficult to prevent and treat. This in situ study aimed to investigate the efficacy of cinnamaldehyde for the disinfection of complete removable dentures, and the effect on the physical and mechanical properties (Vickers microhardness, color, and surface roughness) of the acrylic resin.

METHODS

Acrylic resin disks were inserted into the dentures of a probabilistic sample of 33 complete denture users, that used cinnamaldehyde (27 μg/mL) and 0.5% sodium hypochlorite solutions in a 20 min/7-days protocol of dentures immersion in each solution, with a wash-out period of 7 days, to constitute a crossover-study. The disks were analyzed before and after the immersion, for the presence of microorganisms (CFU/mL) and by scanning electron microscope (SEM). Also, the surface roughness (Ra) and Vickers microhardness were measured, and color parameters were analyzed using the National Bureau of Standards (NBS) method. Data was analyzed by Wilcoxon and Friedman (microbiological evaluation), paired t-test (color and roughness) and independent t-test (Vickers hardness) (α = 0.05).

RESULTS

A significant reduction (P < 0.05) in the number of microorganisms was observed for each species (total microorganisms, Streptococcus mutans, and Candida spp.), with no significant differences (P > 0.05) between hypochlorite and cinnamaldehyde. There was an increase in the roughness and a decrease in the hardness of the test specimens, with no difference between the two disinfectant substances (P > 0.05). Both hypochlorite and cinnamaldehyde also caused changes in color, considered as "perceptible" by the NBS classification, but with no significant difference between disinfectant substances (P < 0.05), and under the clinically acceptable limit (ΔE ≤ 3.7).

CONCLUSION

The 27 μg/mL cinnamaldehyde solution was effective against all evaluated microorganisms and caused minor alterations in hardness, surface roughness, and color parameters, with no clinical relevance.

Effects of Denture Cleansers on the Flexural Strength of PMMA Denture Base Resin Modified with ZrO2 Nanoparticles

PURPOSE

The additions of zirconium oxide nanoparticles (nano-ZrO₂ ) to denture base materials have produced nanocomposites with satisfactory properties, although there is a lack of research investigating the effects of denture cleansers on these materials. This study aimed to evaluate the effect of denture cleansers on the flexural strength of denture base materials modified with nano-ZrO₂ .

MATERIALS AND METHODS

A total of 270 specimens were fabricated from pure and nano-ZrO₂ reinforced acrylic resins at 2.5% and 5%, resulting in 3 main groups. The groups were further divided into subgroups (n = 10) according to immersion solution (distilled water, Corega, sodium hypochlorite, and Renew) and immersion duration. Flexural strength was measured at baseline (T₀ ) in distilled water and after 180 and 365 days of immersion (T₁ and T₂ ) in denture cleansers. Data were collected and analyzed using repeated measure ANOVA and Bonferroni post hoc tests (α = 0.05).

RESULTS

The flexural strength of the nano-ZrO₂ modified denture base material decreased significantly after immersion in different denture cleansers at different immersion durations in comparison to baseline (T₀ ) (p < 0.001). Sodium hypochlorite showed the highest reduction in flexural strength followed by Corega, while Renew cleansing solution resulted in the least change.

CONCLUSION

Denture cleansers can significantly affect the flexural strength of nano-ZrO₂ modified denture base materials and thus should be used cautiously.

Assessment of surface roughness changes on orthodontic acrylic resins by all-in-one spray disinfectant solutions

Background. The disinfection of orthodontic acrylic resins might change the physical and mechanical properties of these materials. We aimed to investigate the impact of four different commercially available disinfectants on the surface roughness of acrylic resins used for orthodontic appliances.

Methods. Four disinfectant solutions (BirexSE, Opti-Cide3, COEfect MinuteSpray, and CaviCide Spray) were used to disinfect orthodontic acrylic resins using the spraying method. The resins were subjected to repeated disinfection protocols. Distilled water, also applied via spraying method, was used as a control. Surface roughness was scrutinized to examine the extent of surface topography changes by stylus profilometry. Data normality was evaluated via the Shapiro–Wilk test, followed by the Wilcoxon Signed-Rank test for non-parametric data or paired Student’s t-test for parametric data to compare intra-group differences in roughness before and after the use of the disinfectant solutions.

Results. Some of the disinfectants (BirexSE and CaviCide) resulted in significant changes in surface roughness values before and after the disinfection compared to the controls (P<0.05). The groups that were in contact with distilled water, Opti-Cide, and Coeffect did not exhibit significant differences in surface roughness before and after the intervention (P>0.05). However, from a clinical perspective, the resulting variations in surface roughness (<%0.15) induced by these solutions might not reflect clinically significant differences.

Conclusion. The use of disinfectant solutions is unlikely to harm the surface of orthodontic acrylic resins. Oral care providers need to be attentive to the interpretation and implementation of clinically significant changes in their evidence-based approach regarding potential material damages by disinfection sprays.

Effect of Antibacterial Silver-Releasing Filler on the Physicochemical Properties of Poly(Methyl Methacrylate) Denture Base Material

Colonization of polymeric dental prosthetic materials by yeast-like fungi and the association of these microorganisms with complications occurring during prosthetic treatment are important clinical problems. In previously presented research, submicron inorganic particles of silver sodium hydrogen zirconium phosphate (S-P) were introduced into poly(methyl methacrylate) (PMMA) denture base material which allowed for obtaining the antimicrobial effect during a 90 day experiment. The aim of the present study was to investigate the flexural strength, impact strength, hardness, wear resistance, sorption, and solubility during three months of storage in distilled water. With increasing S-P concentration after 2 days of conditioning in distilled water, reduced values of flexural strength (107-72 MPa), impact strength (18.4-5.5 MPa) as well as enhanced solubility (0.95-1.49 µg/mm3) were registered, but they were at acceptable levels, and the sorption was stable. Favorable changes included increased hardness (198-238 MPa), flexural modulus (2.9-3.3 GPa), and decreased volume loss during wear test (2.9-0.2 mm3). The percentage changes of the analyzed properties during the 90 days of storage in distilled water were similar for all materials.

Effect of mechanical and chemical cleaning on surface roughness of silicone soft relining material

PURPOSE

This study aims to investigate the effect of mechanical and chemical cleaning on the surface roughness of silicone soft relining materials.

METHODS

We selected silicone soft relining materials with the highest (Soft) and lowest (Supersoft) Shore A hardness. In the abrasion test, specimens were cleaned 50,000 times using a kitchen sponge (Sponge), a soft (Soft brush) or hard (Hard brush) denture brush, or stored in water (No cleaning). In the immersion test, specimens were immersed in either water (Water), neutral peroxide denture cleanser (Neutral), alkaline peroxide denture cleanser (Alkaline), or hypochlorite denture cleanser (Hypochlorite) for 1440 h. Surface roughness of the arithmetic mean height of the surface (Sa) and maximum height (Sz) were measured before and after the tests. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

In the abrasion test, significant differences were observed for Sa and Sz with Soft relining materials, but not for No cleaning and Sponge. In the immersion test, significant differences were observed for Sa and Sz with Soft relining materials, but not between Water and Neutral or Water and Alkaline. Significant differences were observed with Supersoft, except between Water and Neutral or Water and Alkaline for Sa and between Water and Neutral for Sz.

CONCLUSIONS

Mechanical cleaning using a sponge did not increase the surface roughness of the material with a high Shore A hardness. Furthermore, neutral peroxide denture cleanser did not increase the roughness of materials with high and low Shore A hardness.

Anti-biofilm Action of Chenopodium ambrosioides Extract, Cytotoxic Potential and Effects on Acrylic Denture Surface

Considering the challenge to control Candida-associated denture stomatitis, the search for antifungal substances derived from natural sources has become a trend in the literature. In this study the following effects of Chenopodium ambrosioides extract (CAE) were investigated: action against biofilms of Candida albicans, its cytotoxic potential, and changes caused in acrylic resin. The CAE was characterized by High Performance Liquid Chromatography (HPLC). The susceptibility of C. albicans to CAE was investigated by Minimum Inhibitory Concentration and Minimum Fungicidal Concentration (MIC and MFC) tests. Acrylic resin disks were fabricated, and C. albicans biofilms were developed on these for 48 h. Afterward the disks were immersed for 10 min in: PBS (Negative Control); 1% Sodium Hypochlorite (1% SH, Positive Control) or CAE at MIC or 5xMIC. The biofilms were investigated relative to counts and metabolic activity. The cytotoxic potential in keratinocytes and fibroblasts was verified by MTT test. Change in color and roughness of the acrylic resin was analyzed after 28 days of immersion in CAE. The data were analyzed by the ANOVA considering a 5% level of significance. The main compounds detected by HPLC were kaempferol and quercetin. Both MIC and MFC obtained the value of 0.25 mg/mL. The MIC was sufficient to significantly reduce the counts and activity of the biofilm cells (p < 0.0001), while 5xMIC resulted in almost complete eradication, similar to 1% SH. Keratinocytes and fibroblasts exposed to the MIC and 5xMIC presented cell viability similar to that of the Control Group (p > 0.05). No important changes in acrylic resin color and roughness were detected, even after 28 days. It could be concluded that the immersion of acrylic resin in C. ambrosioides extract in its minimum inhibitory concentration was effective for the reduction of C. albicans biofilms without any evidence of cytotoxic effects or changes in roughness and color of this substrate.

Effect of cleansers on denture base resins’ structural properties

Introduction:

We assessed the effect of different available denture cleansers on the roughness and hardness of polyetherketoneketone, thermoinjection-molded polyamide, and polymethylmethacrylate.

Materials and Methods:

A total of 150 disc-shaped specimens were fabricated (10 mm × 2 mm) from these three denture base resins, and divided into five subgroups ( n = 10) according to immersion procedures. One of these groups subjected to distilled water served as control, whereas other groups were subjected to daily cleansing with four denture cleansers (Corega, Protefix, Curaprox, and Perlodent) for 8 h a day for 140 days. The surface roughness and hardness values of specimens were recorded by measuring twice at baseline, and again after application of chemical solutions. Topography alterations after treatments were assessed with scanning electron microscopy. The data were subjected to statistical analysis and comparison among groups was done using Kruskal Wallis and Wilcoxon Signed Ranks tests. P-value <0.05 was considered significant.

Results:

The surface roughness of polyetherketoneketone, polymethylmethacrylate, and polyamide dentures was increased significantly by chemical solutions of denture cleansers. While the hardness value of polyetherketoneketone was not affected significantly after immersion in denture cleansers, those of polymethylmethacrylate and polyamide decreased significantly. Compared with Curaprox, the effervescent tablets significantly altered the surface hardness and roughness of polyamide.

Conclusion:

Denture cleansers can considerably alter the surface roughness and hardness of denture base resins and should be used carefully depending on the material.

Comparative evaluation of the effect of plant extract, Thymus vulgaris and commercially available denture cleanser on the flexural strength and surface roughness of denture base resin

Aim

This study aims to evaluate and compare the effect of plant extract (thyme essential oil solution) and commercially available denture cleanser on the flexural strength and surface roughness of denture base resin.

Settings and Design

Comparative In-vitro study. Chemical denture cleansers play a vital role in maintaining the hygiene and serviceability of the dentures. Bacterial resistance to these chemical agents paved way to plant-extracts as novel denture cleansing agents. However, the effect of these plant-extract denture cleansers on the physical and surface characteristics of denture base resins has not been evaluated.

Material and Methods

A total of 90 heat polymerizing denture base material (Trevalon, Dentsply) samples were fabricated and divided into 3 groups with 30 samples each. Samples from each group were immersed in their respective denture cleanser solution (Group A- Distilled water(control); Group B- Fittydent denture cleanser; Group C- Thyme essential oil solution denture cleanser) for a simulated overnight 8hr immersion for 180 days. The samples were evaluated for increase in surface roughness and flexural strength using Tally-surf Surface Profiler and Instron Universal Testing Machine respectively. Results obtained were statistically analyzed using one-way ANOVA.

Statistical Analysis Used

Oneway ANOVA , Post hoc Tukey's test.

Results

Thyme essential oil solution group showed minimal increase in surface roughness (ΔRa) with values comparable to that of the control group which had the least increase in surface roughness and Fittydent group showed significant increase (P < 0.05) in surface roughness. For flexural strength, statistically significant difference (P < 0.05) was observed among the three groups with Fittydent group showing the highest flexural strength followed by control group and Thyme essential oil solution group. However, the decrease in the flexural strength was not of clinical significance.

Conclusion

Plant extract - thyme essential oil denture cleanser was superior in preserving the surface roughness of denture base resins compared to commercially available denture cleanser. Clinically significant difference in flexural strength was not observed between the denture cleanser groups.

An in vitro study to evaluate and compare the surface roughness in heat-cured denture-based resin and injection-molded resin system as affected by two commercially available denture cleansers

Background:

Denture hygiene is of utmost importance to maintain the dentures as well as the underlying tissues in appropriate health. Various denture cleansers as well as denture-based materials have evolved in the market; however, the effect of denture cleansers on different types of denture-based materials has not been very well documented.

Aim:

The purpose of this in vitro study was to evaluate and compare the surface roughness in heat-cured denture-based resin and injection-molded resin system as affected by two commercially available denture cleansers for a period of 15, 30, and 45 days.

Methodology:

A standardized metal die was fabricated to make 120 denture-based resin discs of uniform dimensions. The samples of heat-cured denture-based resin and injection-molded thermoplastic denture-based resin were immersed in the two denture cleansing solutions for a period of 15, 30, and 45 days, respectively. The surface roughness was evaluated by surface profilometer TR200. The data were subjected to statistical analysis and the comparison of quantitative data was done using unpaired t-test and repeated-measures ANOVA test.

Results:

The surface roughness values (Ra) of heat cured denture base resin samples when immersed in two denture cleansers were 0.22 μm at 0 days, 0.27 and 0.29 μm at 15 days, 0.29 and 0.31 μm at 30 days, 0.30 and 0.31 μm at 45 days whereas for injection moulded samples surface roughness values were 1.31 & 1.27 μm at 0 days, 1.46 & 1.66 μm at 15 days, 1.50 & 1.69 μm at 30 days, and 1.50 & 1.69 μm at 45 days.

Conclusion:

The surface roughness (Ra) increased significantly in injection-molded polyamide denture-based resin samples when immersed in both the denture cleansers. Whereas, heat-cured denture-based resin samples did not reveal any significant surface changes at the various time intervals. Hence, the use of denture cleansers is questionable in thermoplastic resins.

Antimicrobial and cytotoxic effects of denture base acrylic resin impregnated with cleaning agents after long-term immersion

The coadjutant method for denture cleansing most used by denture wearers is immersion in chemical agents, which are toxic when in direct contact with cells. However, clinically, the contact between these chemical agents and prosthetic tissues does not occur directly, but rather with what remained impregnated into acrylic bases, even after rinsing the disinfected dentures. This study evaluated the antimicrobial and cytotoxic effects of a denture acrylic resin after successive cycles of daily overnight immersion in 1% sodium hypochlorite (1%NaClO) and 2% chlorhexidine digluconate (2%CHX), simulating the periods of 9 months or 1.5 year. Microbiological and cytotoxic assays were performed, respectively, by broth microdilution method (Candida albicans or Staphylococcus aureus) and MTT assay. Chemical residues of 2%CHX impregnated into the denture acrylic resin had an antimicrobial effect on both immersion periods, which was not observed with those of 1%NaClO. However, residues of 2%CHX were severely cytotoxic to human gingival fibroblasts compared to those of 1%NaClO and acrylic resin (not submitted to the denture cleansers), which were slightly cytotoxic. Even at low concentrations recommended for overnight soaking of removable dentures, the chemical residues of CHX may result in some degree of toxicity to the denture-bearing mucosa after long-term daily immersion.

Evaluation of biofilm removal and adverse effects on acrylic resin by diluted concentrations of sodium hypochlorite and Ricinus communis solutions

PURPOSE

To verify whether 0.1% and 0.2% sodium hypochlorite (NaOCl), and 8% Ricinus communis (RC) were able to remove denture biofilm without causing deleterious effects to acrylic resin.

BACKGROUND

Previous data show that denture cleansers are effective in reducing biofilm; however, they can change acrylic resin properties.

METHODS

In a crossover trial, 47 denture wearers brushed and soaked their dentures (20 min/14 d): control, 0.85% saline; SH1, 0.1% NaOCl; SH2, 0.2% NaOCl and RC. Denture biofilm on the intaglio surface was stained, photographed and quantified (Image Tool® ). Furthermore, 80 rectangular and 80 disc-shaped specimens (Lucitone 550) were assigned into tested solutions (n = 20), simulating 5 years of daily short immersions (20 minutes). A colorimeter and the National Bureau of Standards units (NBS) determined colour data (ΔE). Surface roughness and flexural strength were measured using rugosimeter and universal testing machine, respectively. Data were compared by the Friedman test (α = .05) followed by Wilcoxon, corrected by Bonferroni (α = .005) (clinical) and Kruskal-Wallis followed by the Dunn test (α = .05) (laboratorial).

RESULTS

SH2 (MR=1.77) showed lower biofilm coverage; SH1 (MR = 2.37) and RC (MR = 2.74) presented intermediated values. RC (1.10 [0.96:1.75]) revealed higher colour alteration than SH1 (0.71 [0.62:0.80]) and SH2 (0.74 [0.58:0.85]); however, NBS classified all solutions as "trace" (0.0-0.5). There was no statistical significance for surface roughness (P = .760) and flexural strength (P = .547).

CONCLUSIONS

The 0.2% NaOCl showed the best clinical performance and did not cause adverse effects on acrylic resin on laboratory analyses.

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.