Aging processes in dental thermoplastics - Thermoanalytical investigations and effects on Vickers as well as Martens hardness.

OBJECTIVE: The influence of various aging protocols, representing and accelerating influences present in the dental context, on possible changes in the microstructure and mechanical properties of thermoplastics was investigated. In order to minimize the complexity of the systems, first pure polymers and then later the equivalent dental polymeric materials were analyzed. MATERIALS AND METHODS: Pure polymers (Poly(methyl methacrylate) - PMMA, Polyoxymethylene homopolymer - POM-H, Polyether ether ketone - PEEK, Nylon 12 - PA12, Polypropylene - PP) were analyzed before as well as after applying different aging protocols relevant to the oral environment (ethanol, thermocycling, alkaline and acidic setting) by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoanalytical parameters used were glass transition temperature (Tg), melting peak and crystallization peak temperature (Tpm, Tpc) and decomposition behavior. In a second step selected commercially available dental products (Telio CAD - PMMAD, Zirlux Acetal - POMD, Juvora Natural Dental Disc - PEEKD) aged by the protocol that previously showed strong effects were examined and additionally tested for changes in their Vickers and Martens hardness by Mann-Whitney-U test. RESULTS: The combinations of pure polymers and viable aging protocols analyzed within this study were identified via TGA or DSC as PA12 & thermocycling, POM-H & denture cleanser/lactic acid/ethanol, PP & lactic acid. The dental polymeric materials PMMAD and POMD due to aging in lactic acid showed slight but significantly (p < 0.01) reduced Vickers and partly Martens hardness. PEEK showed the greatest material resistance within this study.

Anti-Microbial Effect of AgBr-NP@CTMAB on Streptococcus Mutans and Assessment of Surface Roughness Hardness and Flexural Strength of PMMA.

Purpose: To investigate the inhibition of Streptococcus mutans (S.mutans) and its biofilm by AgBr-nanoparticles (NP) @CTMAB (cetyltrimethyl-ammonium bromide) and evaluate the changes in Polymethyl methacrylate (PMMA)'s surface roughness (Ra), microhardness, and flexural strength during prolonged immersion in AgBr-NP@CTMAB for application in the denture cleaning industry. Patients and Methods: The antibacterial activity of AgBr-NP@CTMAB against S.mutans was measured colony formation assay, OD600 and laser confocal microscopy. Changes in the specimens' values for surface roughness, microhardness, and flexural strength (MPa) were measured after immersion solutions for 180 or 360 days. Results: The AgBr-NP@CTMAB solution exhibited a robust antibacterial effect on planktonic S. mutans, with a minimum bactericidal concentration of 5 µg/mL. The 10 µg/mL AgBr-NP@CTMAB solution efficiently inhibited S. mutans biofilm formation. (2) No significant difference in surface roughness after immersion in AgBr-NP@CTMAB (10 µg/mL and 20 µg/mL) comparing with distilled water (P > 0.05) and Polident had significantly higher than distilled water (P < 0.05). There was a significant decrease in the surface hardness of the PMMA specimens that were immersed in the Polident compared with those in distilled water (P < 0.05). While, no significant differences in surface hardness after immersion in the AgBr-NP@CTMAB (P > 0.05). The result of flexural strength suggested that there was no statistically significant difference (P < 0.05) between AgBr-NP@CTMAB as well as Polident and water. Conclusion: AgBrNP@CTMAB can efficiently inhibit the growth of plankton S.mutans and biofilm formation, without affecting the flexural strength, microhardness, or surface roughness of PMMA. Therefore, AgBrNP@CTMAB holds promise as a new denture cleaning agent.

Impact of effervescent denture cleaning tablets on color and surface characteristics of additively manufactured and hand-cast splint materials.

OBJECTIVES: This study is to evaluate the color stability, surface roughness, and hardness of additively manufactured and hand-cast splint materials after a 6-month commercially available denture cleaning tablet immersion simulation. MATERIALS AND METHODS: Disc-shaped additively manufactured and hand-cast auto polymerizing acrylic resin specimens were prepared (N = 40 each). All specimens were exposed to coffee solution totally 2 days. Thereafter, all specimens were immersed into three different effervescent solutions that simulated 6 months of clinical use. The total color change (ΔE*ab), surface roughness (Ra), and Vickers hardness (Vh) were measured at baseline and after immersion protocols. A two-way ANOVA and Bonferroni's post hoc test were used for color change. The dependent t-test and ANOVA were used for roughness and hardness evaluation. RESULTS: Additively manufactured splint materials were more affected by coffee immersion. It was observed that all denture cleaning tablets induced a noticeable alteration in color of the specimens (p < 0.05). Roughness and hardness measurement changes after solution immersions were statistically significant for both splint groups (p < 0.05). On the other hand, distilled water and denture cleaning tablets created similar roughness and hardness measurements at baseline and after immersion. CONCLUSIONS: After 6 months use of tested cleaning tables, the color stability, surface roughness, and hardness of both groups were affected. The evaluation of the surface properties of splint materials could be recommended to the dentists in periodic controls during splint treatments. CLINICAL RELEVANCE: The use effervescent denture cleaning tablets altered the surface characteristics of tested splint materials over time with nonsignificant difference between each other. After 6 months, awareness should be raised about surface characteristics of splint materials.

Sargassum polycystum and Turbinaria conoides Seaweed-based Novel Denture Cleanser: An In Vitro Study.

AIM: The study ventures into evaluating the antifungal and antibacterial efficacy of commercially available denture cleanser with Sargassum polycystum, Turbinaria conoides seaweeds, and the combination of seaweeds. MATERIALS AND METHODS: Poly(methyl methacrylate) disks measuring 10 × 2 mm were fabricated. The samples are divided into four groups of 21 samples each. The denture base was coated with Candida albicans and Streptococcus mutans individually. Group I was treated with Fittydent, group II (S. polycystum and T. conoides seaweeds combination), group III (S. polycystum), and group IV (T. conoides). The colony-formation units present on the surface of the denture were evaluated before and after treatment with different denture cleansers using the serial dilution method. Statistical analysis was done using descriptive statistics, analysis of variance, and post hoc Bonferroni analysis. RESULTS: At 10-5 dilution, T. conoides (group IV) was statistically significant in reducing both C. albicans and S. mutans. At 10-10 dilution, T. conoides (group IV) and S. polycystum and T. conoides combination (group II) had high antibacterial efficacy and were statistically significant. Fittydent (group I) had higher antifungal efficacy and was statistically significant in comparison to S. polycystum (group III) alone. At 10-10 dilution, the T. conoides (group IV), S. polycystum, and T. conoides combination (group II) showed no evidence of a significant difference in comparison to Fittydent (group I). Fittydent had higher antibacterial efficacy and was statistically significant in comparison to S. polycystum (group III) alone. CONCLUSION: Sargassum polycystum and T. conoides combination and T. conoides were found to have higher antibacterial efficacy in comparison to commercially available denture cleanser and also were found to have equal antifungal efficacy in comparison to commercially available denture cleanser.

The Influence of Cleaning Solutions on the Retention of Overdenture Attachment Systems.

Dental-implant-supported reconstructions provide comfort and improvements in prosthetic function, adaptation, and stability over conventional treatment options. The objective of this study was to evaluate the effect of different denture cleansing solutions and their influence on the deterioration and loss of retention of overdenture attachments in a 12-month clinical-use simulation. In this way, ten specimens each of different brands of retentive caps made of Teflon (OT Equator® (Rhein83, Bologna, Italy), Locator® (Zest Anchors, Escondido, CA, USA), Kerator® (KJ Meditech, Gwangiu, Republic of Korea), and Locator R-Tx® (Zest Anchors, Escondido, CA, USA)) were immersed in five different cleaning solutions (Kukident® (P&G Tech, Oxford Parkway, UK), Benfix® (Laboratorios URGO S.L., Guipúzcoa, Spain), Corega® (Stafford Miller, Waterford, Ireland), and Protefix® (Neuhofer Weiche, Parchim, Germany)), and tap water was used as the control group, in a simulation that lasted 12 months. Data were analyzed using two-way ANOVA and a Tukey HSD. Furthermore, a Levene Test and Shapiro-Wilk tests were performed to assess the validation of the ANOVA assumptions. The statistical analysis was performed using R version 4.2.2 software with the significance level set to p < 0.05. There were significant statistical differences between the different manufacturers regarding the retention forces of the attachment's retentive caps (F = 322.066, p < 0.001). For the cleaning solution groups, different statistical results between Kukident® (P&G Tech, Oxford Parkway, UK) (p < 0.05) and Benfix® (Laboratorios URGO S.L., Guipúzcoa, Spain) (p < 0.05) were observed. There were no significant statistical differences between Corega® (Stafford Miller, Ireland), Protefix® (Neuhofer Weiche, Parchim, Germany), and tap water, even though the retention forces decreased in all of them.

Comparison of antifungal efficacy of commercially available denture cleanser and the extract of Turbinaria conoides seaweed against Candida albicans adherent to acrylic denture base resin: An in vitro study.

Aim: One of the main factors responsible for the development of Candida albicans on the surface of denture is improper maintenance of dentures. Denture hygiene can be achieved by regular cleansing of dentures using an appropriate denture cleanser. The aim of the study is to evaluate the antifungal efficacy of commercially available denture cleanser and the extract of Turbinaria conoides seaweed against C. albicans adherent to the surface of denture base resin. Settings and Design: This was an in vitro experimental study. Materials and Methods: Twenty-four Acrylic resin samples of dimension 10-mm radius and 2-mm thickness was randomly divided into two groups. The denture base resin was coated with C. albicans. The colonies present on the surface of each denture base resin were evaluated by serial dilution method. Group A was treated with commercially available denture cleanser and Group B was treated with extract of seaweed T. conoides. The colonies were then evaluated using serial dilution. Statistical Analysis Used: The colony count values obtained by serial dilution were tabulated. These values were statistically analysed using t-test. Results: Reduction of colony count is more in T. conoides than commercially available Fittydent; the difference was statistically significant with a mean difference of 65 at dilution 10-2 and 29.25 at dilution 10-3 using t-test with P < 0.001. Conclusion: Within the limitations of this in vitro study, it was proved that the extract of T. conoides seaweed and commercially available denture cleanser Fittydent was effective in reducing the colony count of C. albicans. T. conoides seaweed is statistically significant than commercially available Fittydent.

The effect of different denture cleansing solutions on the retention of polyetheretherketone locator attachments.

PURPOSE: Prosthetic cleansing solutions have been reported to cause retention loss in implant locator attachments due to the chemical alterations of these attachments. This study aimed to investigate the effects of different denture cleansing solutions on attachments with different retention values. MATERIALS AND METHODS: In this study, 160 polyetheretherketone locator attachments were divided into 4 groups according to their attachment retention values (yellow, pink, clear, and violet). Forty attachments from each group were soaked in four different cleansing solutions (n = 10). The attachments from the four groups were immersed in water, sodium hypochlorite, Corega, and Protefix solutions for a period equivalent to 6 months, according to the manufacturer's recommendations. The locator attachments were then subjected to testing using a universal testing machine. Maximum load to dislodgement according to different solutions was evaluated by one-way ANOVA test. Statistical significance was set at p < 0.05. RESULTS: The effect of denture cleansing solutions on the retentive values of attachments was statistically significant (p < 0.001). Among all cleansing solutions, the highest retention value was found in the violet attachments, and the lowest retention value was found in the yellow attachments. The lowest retention value (0.72 ± 0.05 MPa) was observed when the yellow attachments were immersed in Protefix solution, and the highest retention value (1.96 ± 0.15 MPa) was observed when the violet attachments were immersed in the Corega solution. CONCLUSION: For different colored attachments, different cleansing solutions can be suggested to patients.

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.

Effect of Denture Cleanser on the Physico-Mechanical Properties of Injection-Molded Thermoplastic Polyamides Denture Base Material: A preliminary Study.

Objectives: This study aimed to assess the color stability, surface roughness, and flexural properties of the injection-molded thermoplastic polyamide Vertex ThermoSens denture base resin following a 3-minute immersion in Polident 3-minute denture cleanser. Methods: Sixty specimens (Vertex ThermoSens) were processed and divided into two main groups (n = 30) based on the type of test. Group 1 was further subdivided into two subgroups (n = 15): the control group immersed in distilled water (G1DW) and the test group immersed in Polident cleanser solution (G1PD). Group 2 was divided into three subgroups: a non-immersed group (G2None), a group immersed in distilled water (G2DW), and a group immersed in Polident cleanser solution (G2PD). Color change (∆E) and surface roughness measurements were conducted for group 1, and flexural modulus (E) test was performed for group 2. The CIE Lab* formula was utilized to calculate ∆E. An optical 3D surface analyzer and a three-point bending test were employed for surface roughness and E assessments, respectively. Data were subjected to statistical analysis using a paired-sample t-test for differences within each group before and after immersion. Furthermore, independent-sample t-tests and one-way ANOVA were conducted to analyze differences between groups. A significance level of P < 0.05 was considered. Results: The results revealed a slight, statistically insignificant (P > 0.05) ∆E in all color components (L*, a*, b*) after immersion in distilled water. However, after immersion in the denture cleanser, only the L* component exhibited a statistically significant ∆E (P = 0.002), which was slight in magnitude. Additionally, a significant difference was found in the ∆E between G1DW and G1PD, with G1PD showing a higher change (P = 0.007). A significant increase in surface roughness after immersion was observed in G1PD (P = 0.017), with a notable difference between G1DW and G1PD. However, the E remained unaffected (P = 0.537). Conclusion: Denture cleansers have the potential to modify the properties of thermoplastic polyamide resin. Further research is needed to explore the clinical implications of these observed changes on denture performance.

Effects of Denture Cleaning Regimens on the Quantity of Candida on Dentures: A Cross-Sectional Survey on Nursing Home Residents.

Oral care involving a denture cleaning regimen is important for reducing the incidence of systemic diseases. However, limited information is currently available on denture cleaning frequencies and regimens. Therefore, the present study investigated the relationship between the number of Candida spp. present on the complete dentures of nursing home residents and cleaning regimens. Residents were surveyed to assess their denture cleaning methods. Plaque was collected by applying a sterile swab to the mucosal surface of each examined complete denture worn by 77 residents, and the Candida spp. collected were cultured, identified, and quantified. The relationship between denture cleaning regimens and the quantity of Candida spp. was investigated. Correlation and multivariable analyses revealed that the strongest factor influencing the number of Candida spp. on dentures was the frequency of use of denture cleansers. The number of Candida spp. was the lowest on dentures cleaned daily with a denture cleanser. The present results demonstrated that the daily use of a denture cleanser effectively controlled the adherence of Candida spp. to dentures. Oral and other healthcare providers need to provide instructions on and assist nursing home residents with the daily care of dentures, using denture cleansers, including the environment where cleaning is performed.

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 resin. 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 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.

An In Vitro Evaluation of Denture Cleansing Regimens against a Polymicrobial Denture Biofilm Model.

Denture stomatitis (DS) is an inflammatory disease resulting from a polymicrobial biofilm perturbation at the denture surface-palatal mucosa interface. Recommendations made by dental health care professionals often lack clarity for appropriate denture cleaning. This study investigated the efficacy of brushing with off-the-shelf denture cleanser (DC) tablets (Poligrip®) vs. two toothpastes (Colgate® and Crest®) in alleviating the viable microorganisms (bacteria and fungi) in an in vitro denture biofilm model. Biofilms were grown on poly(methyl)methacrylate (PMMA) discs, then treated daily for 7 days with mechanical disruption (brushing), plus Poligrip® DC, Colgate® or Crest® toothpastes. Weekly treatment with Poligrip® DC on day 7 only was compared to daily modalities. All treatment parameters were processed to determine viable colony forming units for bacteria and fungi using the Miles and Misra technique, and imaged by confocal laser scanning microscopy (CLSM). Brushing with daily DC therapy was the most effective treatment in reducing the viable biofilm over 7 days of treatment. Brushing only was ineffective in controlling the viable bioburden, which was confirmed by CLSM imaging. This data indicates that regular cleansing of PMMA with DC was best for polymicrobial biofilms.

Persulfate-containing consumer products in the US market.

BACKGROUND: Persulfate compounds are reactive oxidative agents increasingly recognized as contact allergens. OBJECTIVES: The aim of this study was to identify common consumer products containing persulfate compounds in the US market. METHODS: Five publicly accessible online ingredient repositories and searches of two large online retailers were used to identify persulfate-containing consumer products. RESULTS: We identified persulfates in 23 hair colouring products, 11 denture cleansers, 8 pool/hot-tub products, 3 paints, and 3 cleaning products. CONCLUSIONS: Clinicians assessing contact dermatitis should be aware of three primary categories of consumer products that contain persulfates: denture cleansers, hair colouring products, and nonchlorine hot-tub and pool shock.

Evaluation of the time-dependent efficacy of commercial denture or orthodontic appliance cleansers: An in vitro study.

The aim of this study was to evaluate the antimicrobial, stain and protein removal efficacy of denture or orthodontic appliance cleansers using in vitro test methods. Experimental cleansers were applied for experimental time in each evaluation method. To evaluate the microorganism removal efficacy, C. albicans and S. mutans removal rate was calculated from the specimen surface. Stain and protein removal rate was calculated using the spectrophotometer. Experimental cleansers significantly affected the microorganism removal rate for both C. albicans and S. mutans, as well as the stain and protein removal rates, at each experimental time (p<0.05). As the application time increased, the stain and protein removal rates of all experimental cleansers significantly increased (p<0.05). The present study provided in vitro evaluation methods to assess the efficacy of denture or orthodontic appliance cleansers. Also, manufacturers and researchers can predict clinical outcomes and ensure proper hygiene management of dentures or orthodontic appliances.

Effect of Food Colorants on Color of Denture Base Acrylic Resins.

BACKGROUND: Acrylic resin has been successfully used for complete denture fabrication for many years. Color stability is very crucial clinical properties for dental materials, and color change may be an indicator of aging or damaging of materials. AIM AND OBJECTIVES: This study has been designed to determine the color stability of heat cure denture base acrylic resins in commonly consumed solutions causing stains. METHODOLOGY: Four hundred disc samples of four commercially used heat cure denture base resins (Trevalon®, DPI®, Veracril®, and Pyrax®) were fabricated (100 in each group). These were checked for any change in optical density by immersing them in four different staining solutions (tea, coffee, turmeric, and betel leaf, i.e., paan) and synthetic saliva for 1-month synthetic saliva was taken as control. The denture cleansers were also evaluated for their efficacy determined by their ability to remove the stains caused by the staining solutions. RESULTS: It was observed that Trevalon® showed least change in optical density and coffee illustrated the maximum potential for staining the denture base resins and is the most difficult to be removed using a denture cleanser. CONCLUSION: It can be concluded that Trevalon® demonstrated maximum color stability. Among the staining solutions, coffee caused maximum stains.

Antifungal Effects of Herbal Extracts and Fluconazole on Heat-polymerized Acrylic Denture Base Resin as Denture Cleanser: An In Vitro Study.

AIM: The study aimed to investigate the antifungal effects of herbal extracts and fluconazole on heat-polymerized acrylic denture base resin as a denture cleanser. MATERIALS AND METHODS: Several essential oils, such as origanum oil and grape seed oil and commercially available antifungal agent fluconazole were used as denture cleansers and their antifungal efficacy was evaluated using a spectrophotometer. Overall, 68 samples were obtained and were divided into four groups, each containing 17 samples. These samples were immersed in Sabouraud dextrose broth consisting of Candida albicans for 16 hours and later in these antifungal solutions for 8 hours and their antifungal efficacy was measured. Data were subjected to an ANOVA test. RESULTS: Among the study groups origanum oil showed the maximum antifungal activity with a mean optical density at 0.072 ± 0.014 followed by fluconazole (0.094 ± 0.155), and least by grape seed oil (0.190 ± 0.071). CONCLUSION: Results of this in vitro study showed that origanum oil was more effective than commercially available antifungal agents, and among the tested groups oregano oil was a potential agent in lowering the C. albicans colony. CLINICAL SIGNIFICANCE: Origanum oil, being a herbal product, can be considered as a denture cleanser and also be used as an effective alternative to commercially available antifungal agents without any side effects.

Evaluation of antibacterial activity against Candida albicans according to the dosage of various denture cleansers.

PURPOSE: The purpose of this study is to compare the antibacterial activity of currently purchasable denture cleansers against Candida albicans. MATERIALS AND METHODS: This study used tablet-type denture cleansers, Polident®, Coolingdent® and Fittydent®, along with liquid denture cleansers, Hexamedine®, Listerine® and Apple vinegar®. The antibacterial activities of denture cleansers were evaluated based on the number of C. albicans and concentrations of the denture cleansers. RESULTS: In the 0.5 × 106 cfu/ml culture medium, the C. albicans' death rate of Polident® was significantly lower than those of Fittydent®, Hexamedine®, Listerine®, and Apple vinegar®(P<.05). In the 0.5 × 107 cfu/, the C. albicans' death rates of Polident® and Coolingdent® were significantly lower than those of Fittydent®, Hexamedine®, Listerine® and Apple vinegar®(P<.05). The C. albicans' death rates of Polident® and Coolingdent® were significantly decreased at 0.02 g and 0.01 g. The C. albicans' death rate of Fittydent® was significantly decreased at 0.005 g (P<.05). The C. albicans ' death rate of Hexamedine® was significantly decreased at 1/16 dilution. The C. albicans' death rate of Listerine® was decreased at 1/8 dilution, and the antibacterial activity of Apple vinegar® was decreased at 1/4 dilution (P<.05). CONCLUSION: As the number of C. albicans increased, the antibacterial activities of the denture cleansers decrease. In the tablet-type denture cleanser, all denture cleansers showed 100% C. albicans' death rate when used at a dose of 1 tablet. One denture cleanser showed the same antibacterial effect with only 1/3 of a tablet. In the liquid type denture cleanser, the level of dilution required was different for each denture cleanser.

Efficacy of low-molecular weight chitosan against Candida albicans biofilm on polymethyl methacrylate resin.

BACKGROUND: Candida biofilm is a major cause of denture stomatitis. We aimed to compare the efficacy of low-molecular-weight chitosan solutions against Candida albicans biofilm on polymethyl methacrylate (PMMA) resin. METHODS: Various types of chitosan were tested for anti-Candida activity by broth dilution. Two types were selected for further testing on 24-hour C.albicans biofilm formed on PMMA specimens. Specimens were randomly distributed among experimental groups, including 0.1% and 0.2% acetic acid, 3 and 6 mg/mL of oligomer chitosan and 30 kDa chitosan solutions, effervescent tablet (Polident), and 0.2% chlorhexidine, and immersed for 5 min to 12 h. The viability of C. albicans after cleansing were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Remaining viability was calculated into percentage relative to respective controls and analyzed using ANOVA with Tukey post-hoc tests. Live/dead fluorescence microscopy was also performed. RESULTS: Chitosan solutions had high efficacy against C. albicans biofilm on PMMA. The mean relative viability compared to control after 12-h immersion was 6.60 ± 4.75% and 12.72 ± 6.96% for 3 and 6 mg/mL oligomer, respectively, and 11.68 ± 4.81% and 18.08 ± 6.20% for 3 and 6 mg/mL 30 kDa chitosan, respectively. CONCLUSIONS: Low-molecular-weight chitosan solution is an effective antifungal denture cleanser that can significantly reduce C. albicans viability in biofilm on PMMA.

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.

Evaluation of various denture cleansers on color stability and surface topography of polyetherketoneketone, polyamide, and polymethylmethacrylate.

The aim of this study was to evaluate the effect of sodium perborate effervescent tablets and citric acid solution on the color stability and surface topography of a new generation of high-performance polymer polyetherketoneketone (PEKK), thermoinjection-molded polyamide, and polymethylmethacrylate (PMMA). Fifty disc-shaped specimens were fabricated (10 mm × 2 mm) from PEKK (P group), polyamide (D group), and PMMA (M group). These groups were divided into five subgroups (n = 10) according to the storage media. The test groups were immersed in the following solutions: distilled water (Control), Corega, Protefix, Perlodent, and Curaprox. The color stability values (ΔE) were measured using a spectrophotometer before and after immersion in distilled water and four different denture cleansers for 8 hr/day for 140 days. Topography alterations after treatments were assessed with scanning electron microscopy (SEM). Data were analyzed by one-way analysis of variance (ANOVA) followed by Tukey's Honest Significant Difference test. The p < .05 was considered significant. All denture cleansers increased the ΔE values relative to the baseline values in the M, D, and P groups (p < .05). The Perlodent denture cleanser demonstrated the highest ΔE value in all groups, which was unacceptable. Curaprox denture cleanser showed the lowest ΔE value in the M and D groups (p < .05). Curaprox in all groups showed a ∆E value less than 3.7. For patients who have PEKK- and polyamide-based prosthesis, the use of citric acid-based cleansers may be more recommended than sodium perborate-containing cleansers because of its clinically acceptable color changes on polymers in terms of color stability.