Material compatibility and antimicrobial activity of consumer products commonly used to clean dentures

Effect of sanitizing solutions on cobalt chromium alloys for dental prostheses: A systematic review of in vitro studies

STATEMENT OF PROBLEM

Given the wide use of cobalt chromium (Co-Cr) alloys, especially for removable partial dentures, and the importance of chemical solutions to complement the cleaning of dental prostheses, safe disinfection products should be identified for the regular decontamination of Co-Cr dental prostheses.

PURPOSE

The purpose of this systematic review of in vitro studies was to determine the effects on the properties of Co-Cr dental alloys of the various chemical agents used to clean dental prostheses.

MATERIAL AND METHODS

In vitro studies were included based on a literature search conducted in March 2022 in the Medline/PubMed, SCOPUS, Web of Science, Virtual Health Library, and Embase databases. Independent reviewers performed the search, selection, extraction, and analysis of the data. The review was performed based on the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. The quality of the included articles was evaluated by using parameters adapted from the Consolidated Standards of Reporting Trials (CONSORT) guidelines, and the risk of bias analysis was performed based on previous studies.

RESULTS

Among the 15 included studies, the chemical agents evaluated were alkaline peroxides and hypochlorites, mouthwashes containing cetylpyridinium chloride and chlorhexidine, diluted acids, and enzymes. Some peroxides produced increased ion release, surface roughness, and mass loss of the alloys. The hypochlorites were responsible for the greatest surface corrosion, yielding dark stains, rough regions, and depressions. Acetic and peracetic acids and mouthwashes containing chlorhexidine and cetylpyridinium did not produce significant changes in Co-Cr alloys. Most studies presented moderate risk of bias.

CONCLUSIONS

According to the included studies, mouth rinses containing cetylpyridinium chloride or chlorhexidine and solutions with acetic and peracetic acid could be safely used to chemically sanitize Co-Cr prostheses. Alkaline peroxides should be used with caution, and alkaline hypochlorite solutions should be avoided.

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.

The complex of tannic acid and cetylpyridinium chloride: An antibacterial and stain-removal cleaner for aligners

INTRODUCTION

Effective aligner hygiene is recognized as an important part of orthodontic treatments and oral hygiene. However, there is no effective cleansing method for removable aligners.

METHODS

In this study, we incorporated tannic acid (TA) with cetylpyridinium chloride (CPC) to develop the TA-CPC complex. The antibacterial properties of 15.8 mg/mL TA-CPC against Escherichia coli and Staphylococcus aureus were evaluated in vitro, which were compared with 5.1 mg/mL TA, 10.7 mg/mL CPC, a commercial denture cleansing solution (YA; 15 mg/mL), and water. As for the assessment of stain-removal ability, the aligners stained by coffee were soaked in cleansing solutions, and the color changes (ΔE∗) were calculated on the basis of the CIE L∗a∗b∗ color system, and the National Bureau of Standards system was used for the clinical interpretation of the color change. Atomic force microscope examination, tensile property assessment, and wavelength dispersive x-ray fluorescence analysis were performed to investigate the material compatibility of TA-CPC, and Cell Counting Kit-8 assay and live/dead assay were used to test the cytotoxicity of TA-CPC.

RESULTS

The results showed that TA-CPC had a positive zeta-potential, and cation-π interaction changed the chemical environments of the phenyl group in TA-CPC, resulting in greater inhibition zones of S. aureus and E. coli than other cleaners. The quantification of the biofilm biomass and the fluorescent intensities also reflected that the TA-CPC solution exhibited better antibacterial ability. As for the ability of stain removal, ΔE∗ value of group TA-CPC was 2.84 ± 0.55, whereas those of stained aligners immersed with deionized distilled water, TA, YA, and CPC were 10.26 ± 0.04, 9.54 ± 0.24, 5.93 ± 0.36, and 4.69 ± 0.35, respectively. The visual inspection and National Bureau of Standards ratings also showed that the color of stained aligners cleansed by TA-CPC was much lighter than those of the other groups. Meanwhile, TA-CPC had good compatibility with the aligner material and cells.

CONCLUSIONS

TA-CPC is a promising strategy to inhibit the formation of biofilms and remove the stains on the aligners safely, which may disinfect the aligners to improve oral health and help keep the transparent appearances of aligners without impacting the morphology and mechanical properties.

Different Polymers for the Base of Removable Dentures? Part II: A Narrative Review of the Dynamics of Microbial Plaque Formation on Dentures

This review focuses on the current disparities and gaps in research on the characteristics of the oral ecosystem of denture wearers, making a unique contribution to the literature on this topic. We aimed to synthesize the literature on the state of current knowledge concerning the biological behavior of the different polymers used in prosthetics. Whichever polymer is used in the composition of the prosthetic base (poly methyl methacrylate acrylic (PMMA), polyamide (PA), or polyether ether ketone (PEEK)), the simple presence of a removable prosthesis in the oral cavity can disturb the balance of the oral microbiota. This phenomenon is aggravated by poor oral hygiene, resulting in an increased microbial load coupled with the reduced salivation that is associated with older patients. In 15-70% of patients, this imbalance leads to the appearance of inflammation under the prosthesis (denture stomatitis, DS). DS is dependent on the equilibrium-as well as on the reciprocal, fragile, and constantly dynamic conditions-between the host and the microbiome in the oral cavity. Several local and general parameters contribute to this balance. Locally, the formation of microbial plaque on dentures (DMP) depends on the phenomena of adhesion, aggregation, and accumulation of microorganisms. To limit DMP, apart from oral and lifestyle hygiene, the prosthesis must be polished and regularly immersed in a disinfectant bath. It can also be covered with an insulating coating. In the long term, relining and maintenance of the prosthesis must also be established to control microbial proliferation. On the other hand, several general conditions specific to the host (aging; heredity; allergies; diseases such as diabetes mellitus or cardiovascular, respiratory, or digestive diseases; and immunodeficiencies) can make the management of DS difficult. Thus, the second part of this review addresses the complexity of the management of DMP depending on the polymer used. The methodology followed in this review comprised the formulation of a search strategy, definition of the inclusion and exclusion criteria, and selection of studies for analysis. The PubMed database was searched independently for pertinent studies. A total of 213 titles were retrieved from the electronic databases, and after applying the exclusion criteria, we selected 84 articles on the possible microbial interactions between the prosthesis and the oral environment, with a particular emphasis on Candida albicans.

Action of chitosan-based solutions against a model four-species biofilm formed on cobalt-chromium and acrylic resin surfaces

OBJECTIVE

To evaluate the anti-biofilm action of chitosan, nanoparticulate chitosan, and denture cleanser Nitradine™ against biofilms comprising Candida albicans, Candida glabrata, Staphylococcus aureus, and Streptococcus mutans.

BACKGROUND

Biofilm removal from removable partial dentures (RPD) is important for success in prosthetic rehabilitation.

MATERIALS AND METHODS

The anti-biofilm action of the experimental chitosan-based solutions and Nitradine™ was evaluated on acrylic resin and cobalt-chromium alloy through assessing cell viability, cell metabolism, residual aggregated biofilm, and extracellular polymeric substance and biofilm morphology.

RESULTS

Only chitosan reduced the viability of C. albicans on cobalt-chromium alloy surface, by 98% (a 1.7 log10 reduction in cfu). Chitosan-based solutions neither promoted substantial alteration of the metabolic activity of the four-species biofilm nor reduced the amount of the aggregated biofilm. After immersion in chitosan and nanoparticulate chitosan, viable microorganisms and extracellular polymeric substances distributed over the entire specimens' surfaces were observed. Nitradine™ reduced the viability and metabolic activity of biofilm grown on both surfaces, but it did not remove all aggregated biofilm and extracellular polymeric substances. After immersion in Nitradine™, approximately 35% of the specimens' surfaces remained covered by aggregated biofilm, mainly composed of dead cells.

CONCLUSION

Although chitosan and Nitradine™ promoted changes in the viability of microorganisms, neither solution completely removed the four-species biofilm from the Co-Cr and acrylic resin surfaces. Thus, isolated use of hygiene solutions is not indicated for biofilm control on RPDs; this requires complementary mechanical removal.

Highlights on Drug and Ion Release and Recharge Capacity of Antimicrobial Removable Prostheses

This article aimed to review the ion and drug release, recharge abilities, and antimicrobial properties of drug/ion-releasing removable prostheses, and to assess their capability in preventing and inhibiting denture stomatitis as well preventing caries and reversing carious lesions. Data was collected from published scientific papers listed in PubMed database from January 1975 to December 2021. English full-text articles, involving clinical or in vitro studies, focusing on removable prostheses and are concerned with drug/ion release and rechargeability as a way to prevent or inhibit denture stomatitis or dental caries were included. The relevant articles reported that ion- or drug-modified polymethylmethacrylate acts as a reservoir for these ions and drugs and is capable of releasing significant amounts with sustained release effect. Recharging of modified resin resulted in greater sustainability of ion and drug release, thus improving the long-term effects of protection against demineralization and reducing the adhesion of Streptococcus mutans and Candida albicans. Modifications of removable prostheses with rechargeable ions and drugs enhance remineralization, hinder demineralization, and reduce microbial adhesion in difficult-to-access areas. Selection of denture base for clinical use will consider its ability to act as an ion/drug reservoir that is capable of release and recharge.

Antimicrobial activity of cleansers on the cobalt-chromium surface of removable partial denture: a systematic review

This study aimed to review systematically the literature about the antimicrobial action of evaluated cleansers on the Co-Cr alloy of RPD. The search was conducted in MEDLINE/PubMed, Scopus, Lilacs, Embase and Science Direct May, 2022. The review was performed based on PRISMA guidelines and recorded in Open Science Framework. Independent reviewers performed the search, selection, extraction, and analysis of the data. The risk of bias of the in vitro and clinical trials studies was analyzed by the Joanna Briggs Institute tool. A total of 187 articles were found and 9 were included. The cleansers that showed antimicrobial action were 2% and 5.25% sodium hypochlorite, 0.12% chlorhexidine and NitrAdine effervescent tablet. Polident, Corega Tabs effervescent tablets and 5 mg/mL chitosan solution showed intermediate effects. Propolis and green tea toothpaste were not effective. Three articles presented a high risk of bias and 6, low risk. The cleansers that showed the highest antimicrobial efficacy on Co-Cr alloy were 0.12% chlorhexidine digluconate and NitrAdine and can be safely used on RPD framework.

Revisiting Oral Antiseptics, Microorganism Targets and Effectiveness

A good oral health status is mostly dependent on good oral hygiene habits, which knowingly impacts systemic health. Although controversial, chemical oral antiseptics can be useful in adjunct use to mechanical dental plaque control techniques in the prevention and management of local and overall health and well-being. This review aims to revisit, gather and update evidence-based clinical indications for the use of the most popular oral antiseptics, considering different types, microorganism targets and effectiveness in order to establish updated clinical recommendations.

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.

Efficacy of Antimicrobial Agents in Dentifrices: A Systematic Review

The aim of this systematic review was to verify if the presence of different antimicrobial agents in dentifrices is effective in reducing the number of microorganisms for disease prevention. This review followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and was registered with the Open Science Framework (OSF). A search was conducted in the PubMed, Embase, Scopus, and Web of Science databases. Two independent authors reviewed the titles and abstracts according to the inclusion criteria, which comprised in vitro studies published in English that evaluated the efficacy of antimicrobial agents in dentifrices and their antimicrobial activity. A total of 527 articles were found. Of these, 334 were included for reading of the title and abstract, and 69 were selected for reading in full. In the end, 39 articles remained in this review. Triclosan, sodium fluoride, and sodium monofluorophosphate were the most commonly used chemical antimicrobial agents. Among the herbal agents, miswak extract and neem extract were the most commonly used. The presence of antimicrobial agents in dentifrice formulations can promote the reduction of the number of microorganisms involved in oral diseases, but with variations in their effectiveness, depending on the agent used and the microorganism evaluated.

Evaluation and comparison of flexural strength, surface roughness and porosity percentage of denture base resins incorporated with Thymoquinone and silver nano-antimicrobial agents-an in vitro study

Aim

To evaluate and compare the flexural strength, surface roughness and porosity percentage of acrylic denture base material modified with two antimicrobial agents, Thymoquinone (TQ) and Silver nanoparticles (AgNP).

Materials and methods

A total of 90 specimens were fabricated and divided into groups A, B and C with 30 specimens each. Of the 30 specimens, 10 specimens measuring 65mmx 10mmx 2.5 mm were used to study the flexural strength, 10 specimens measuring 10 mm × 20 mm × 3 mm to study surface roughness and 10 specimens measuring 10 mm × 20 mm × 3 mm to study porosity percentage. Group A specimens were made of unmodified denture base resin, group B and C were modified with 2.5% AgNP and 1% TQ respectively. The specimens were processed in the conventional manner. A universal testing machine was used to measure flexural strength and a profilometer was used to measure surface roughness. Porosity percentage was evaluated with help of a desiccator. The data obtained was subjected to statistical analyses using One-way ANOVA and the Tukey-post hoc test, with statistical significance at p ≤ 0.05.

Results

Addition of 2.5% AgNP and 1% TQ to acrylic denture base resin significantly reduced flexural strength and increased the porosity percentage (p < 0.01) but within clinically acceptable limits. No significant difference was found in the surface roughness between the various groups tested.

Conclusions

Heat cured acrylic denture base resins modified with 2.5% AgNPs,1% TQ exhibited clinically acceptable flexural strength and surface properties and could be incorporated into the denture base material as an antimicrobial agent.

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.

Antimicrobial Properties of Silver-Modified Denture Base Resins

The surface quality of denture base resins allows for easy colonization by microorganisms including Candida albicans and Staphylococcus aureus, which cause major diseases of the oral cavity such as denture stomatitis. The widespread use of silver nanoparticles (AgNPs) in various fields of medicine has led to research of their possible application in dentistry, mostly in the prevention of bacterial adhesion, proliferation, and biofilm formation. The aim of the study was to synthesize cold and heat-curing denture base resins modified with AgNPs and AgCl, and evaluate the potential of the modified resins to reduce the growth of C. albicans and S.aureus. The produced material was characterized by Fourier transform infrared spectroscopy (FTIR). The antimicrobial potential of the modified material was demonstrated by the disc-diffusion method, microdilution method, and a modified microdilution method (i.e., disk-diffusion method in broth with viable counting). Spectroscopy confirmed the incorporation of biocidal materials into the structure of the denture base resins. The AgCl and AgNPs modified resins showed an antimicrobial effect. The significance of the study is in the potential therapeutic effects of the modified materials for prevention and threating staphylococci and candida in elderly patients, who are in most cases denture wearers and have a greater susceptibility to develop opportunistic infections. Modified denture base resins can significantly reduce the presence of infection at the point of contact between the denture and the mucous membrane of the prosthetic restoration. Biological tests of modified denture base resins will follow.

Antimicrobial Activity of Various Disinfectants to Clean Thermoplastic Polymeric Appliances in Orthodontics

There is a lack of research evidence on the risk–benefits of the various disinfectants in cleaning products and cleansing regimens. This systematic review compared the antimicrobial activity of various chemical disinfectants to disinfect the thermoplastic polymeric appliances in orthodontics. The study was carried out using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Cochrane Handbook of Systematic Reviews of Interventions. An electronic search was conducted on Pubmed, Google Scholar, Scopus, ScienceDirect, and Springer. Two authors independently investigated the risk of bias in duplication. A total of 225 articles were collected. After removing duplicates, 221 articles remained, and after filtering their titles and abstracts, 11 articles met eligibility qualifications remained. Finally, nine articles that met the criteria were selected. It showed that both over-the-counter orthodontic appliance cleaners and applied-chemical disinfectants were effective against bacteria. The duration and frequency of usage guidelines cannot be concluded.

The Effect of Denture Cleansing Solutions on the Retention of Precision Attachments: An In Vitro Study

This study aimed to investigate the effect of different cleansing solutions on the retention of precision attachments. A precision attachment patrix was embedded into acrylic resin and the matrix was placed onto the patrix. The red (high retention, 8 N), yellow (regular retention, 6 N), and green (reduced retention, 4 N) plastic matrixes of the attachments (n = 32) were soaked in three different denture cleansing solutions (sodium laureth sulfate, sodium bicarbonate-sodium perborate, sodium bicarbonate) for a duration simulating 6 months of clinical use. The control group was soaked in tap water. A universal testing machine was used to measure the retention values of attachments after they were soaked in denture cleansers. The retention values were compared among the groups with repeated-measures analysis of variance followed by the Tukey HSD test (p = 0.05). Yellow attachments were affected by sodium laureth sulfate, sodium bicarbonate-sodium perborate, and water (p = 0.012). Green attachments’ retention increased after immersion in sodium laureth sulfate (p = 0.04) and water (p = 0.02). Red attachments’ retention increased after immersion in sodium laureth sulfate or sodium bicarbonate-sodium perborate (p = 0.045). Water did not affect the retention of red attachments. Because sodium bicarbonate tablets did not affect the retention of attachments, clinicians may recommend their use as a cleanser. Clinicians also may inform patients using fixed and removable partial prostheses with precision attachments of a possible increase in retention after the use of sodium laureth sulfate or when using sodium bicarbonate-sodium perborate with yellow and red attachments.

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.

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.

Evaluation of YouTube as an information source for denture care

STATEMENT OF PROBLEM

Denture cleaning is indispensable to the maintenance of good oral and systemic health for denture users. Nowadays people often consult YouTube about health-related topics, including denture care. However, the quality of the information about denture care presented on YouTube is unknown.

PURPOSE

The purpose of this study was to evaluate the usefulness and quality of popular videos about denture care shared by different uploaders on YouTube and to evaluate the demographic characteristics of the videos.

MATERIAL AND METHODS

Google Trends showed that "denture cleaning" was the most searched keyword on the topic. This keyword was used to search YouTube videos. Of the 200 most-watched videos, 109 videos were selected for analysis. Included videos were analyzed for their demographic data, including number of views; number of likes, dislikes, and comments; days since upload; duration and number of subscribers; an 8-point usefulness score system, a global quality scale (GQS); video sources; target groups; and primary purposes of the videos. Statistical analyses were conducted by using the Kruskal-Wallis test, post hoc Mann-Whitney U test, Pearson chi-squared test, and Spearman correlation analysis, which was used to investigate the relationship among total content score, GQS score, and video demographics. Cohen kappa statistics was used to measure the reliability of the investigator's evaluations of the videos (α=.05).

RESULTS

Based on the usefulness score, 59.6% of the videos were classified as poor, 32.1% as moderate, and 8.2% as good. No statistically significant differences were found among usefulness scores according to the video demographics, except lower GQS score of poor content videos (P<.001). The overall mean ±standard deviation GQS score was 1.92 ±1.0 out of 5. Videos were primarily uploaded (38.5%) from commercial companies. No statistically significant difference was found between video sources and usefulness scores (P>.05). The number of videos with poor content was significantly higher than the number with moderate and good content among the videos primarily intended for the education of health professionals (P<.001).

CONCLUSIONS

The majority (59.6%) of YouTube videos on denture care received poor content quality ratings, independent of video demographics. Therefore, YouTube is not suitable as the only source of information on denture care. Dentists and prosthodontists should take more responsibility for enriching the content of video-sharing platforms because this content can affect the behavior of patients and their attitudes about denture care.

Effect of Ozone on Corrosion Behavior of a Cobalt–Chromium Alloy Used in Removable Partial Denture Framework: An In Vitro Study

Aim:

The aim of this study was to evaluate the effect of the ozonated water on corrosion of a cobalt–chromium (Co-Cr)-based alloy, which is applied for the fabrication of metal frameworks of removable partial dentures.

Materials and Methods:

In this in vitro study, a total of 30 disk-shaped samples of a Co-Cr alloy were papered and randomly divided into two groups of 15 specimens. In group 1 (control), the specimens were stored in distilled water (DW), and in group 2, the specimens were stored in ozonated water. Around 90 immersions were performed, and the weight change of each specimen was determined. The ion release was analyzed using an inductively coupled plasma-optical emission spectrophotometer. The potentiodynamic polarization test was performed for each group to assess the corrosion resistance of the Co-Cr alloy. The statistical analysis was performed using SPSS version 22. Data were analyzed by independent samples’ t-test.

Results:

The results showed no significant difference between the weight changes of the two groups. The test using an inductively coupled plasma-optical emission spectrophotometer demonstrated no significant difference between the groups in Co and Cr ions release. In the potentiodynamic polarization test, both groups present similar corrosion behavior, and ozonated water has no deleterious effect on the corrosion resistance and passive range of the Co-Cr alloy compared to DW.

Conclusion:

As compared to DW, ozonated water has no significant deleterious effect on the corrosion resistance of the Co-Cr frameworks and can be used for cleaning the removable partial dentures.

Does microwave and hydrogen peroxide disinfection reduce Candida albicans biofilm on polymethyl methacrylate denture surfaces?

STATEMENT OF PROBLEM

Whether the disinfection of polymethyl methacrylate (PMMA) dentures eliminates Candida albicans biofilm is unclear.

PURPOSE

The purpose of this in vitro study was to determine the antimicrobial effect of immersion in hydrogen peroxide (H₂O₂) and subsequent application of microwaves on the formation of C albicans biofilm on the surface of polished and unpolished PMMA disks.

MATERIAL AND METHODS

Polished and unpolished PMMA disks (n=40) were mounted in a Center for Disease Control (CDC) biofilm reactor by adding yeast-dextrose-peptone (YPD) broth inoculated with C albicans in a cell suspension for 24 hours. After this period, the PMMA disks (n=8) were disinfected with 5 different solutions: saline solution, 1% sodium hypochlorite (NaOCl), H₂O₂, H₂O₂ microwaved at 650 W for 3 minutes (H₂O₂/μw), and distilled water microwaved at 650 W for 3 minutes (H₂O/μw). On the polished and unpolished surface of each disk, arbitrary fluorescence units (AFU) were quantified with the live/dead bacterial viability kit (Invitrogen) by using confocal laser scanning microscopy (CLSM) to evaluate 10 different areas of each surface; these were counted as the colony-forming units (CFUs). The mean values were compared by using the Mann-Whitney U test (α=.05).

RESULTS

Polished surfaces disinfected with H₂O₂/μw obtained the lowest viable cells (9.76 AFU) and nonviable cells (12.46 AFU) compared with H₂O/μw and H₂O_2. In the unpolished surface the lowest mean values of viable cells (14.64 AFU) and nonviable cells (12.46 AFU) were obtained for the PMMA disks disinfected with H₂O/μw compared with H₂O₂/μw and H₂O₂. Both polished and unpolished disks showed significant difference (P<.05) compared with the group of PMMA disks immersed in saline solution. No CFUs were detected in the polished or unpolished PMMA disks immersed in H₂O₂/μw or in NaOCl.

CONCLUSIONS

H₂O₂ alone did not eliminate the formation of the biofilm of C albicans; however, in combination with the use of the microwave at 650 W for 3 minutes, the biofilm formation of C albicans on polished surfaces was reduced. The number of AFUs of viable-nonviable cells and CFUs depended on whether the surfaces are polished or unpolished.

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.

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.

Biological and Mechanical Properties of Denture Base Material as a Vehicle for Novel Hydroxyapatite Nanoparticles Loaded with Drug

Purpose: This study aimed to evaluate the biological and mechanical properties of the poly(methyl methacrylate) (PMMA) denture base material as a vehicle incorporating novel hydroxyapatite nanoparticles (HA-NP) loaded with metronidazole (MZ) drug.

Methods: HA-NP was prepared via wet-chemical-method, characterized by XRD, SEM/EDX, TEM, Fourier-transform infrared spectroscopy (FTIR), as well as the measurement of surface area and pore-size distribution. Four drug delivery formulas were prepared in the form of discs (10 x 2 mm) as follows: F1 (MZ/ HA-NP/PMMA), F2 (HA-NP/ PMMA), F3 (control-PMMA) and F4 (MZ/PMMA). Characterization of all formulas was performed using differential scanning calorimetry (DSC) and FTIR. MZ release rate, antimicrobial properties against three oral pathogens, cytotoxicity (MTT assay) and surface micro-hardness were also assessed. Statistical analysis of data was performed using one-way ANOVA test (P < 0.05).

Results: DSC thermograms showed compatibility among MZ, HA-NP and PMMA along with physical stability over 6 months storage period at room temperature. FTIR spectroscopy proved the absence of any possible chemical interaction with MZ. MZ-HA-NP/PMMA formula showed relatively better drug release compared to MZ-PMMA. Both formulas showed statistically significant antimicrobial potentials against two microbial strains. MTT demonstrated reduction in cell cytotoxicity after 96 hours with the least value for HA-NP. Surface micro-hardness revealed non-significant reduction compared with the control PMMA.

Conclusion: A novel biocompatible drug nanocarrier (HA-NP) was developed and incorporated in PMMA denture base material as a vehicle to allow prolonged sustained drug release to manage oral infections.

Impact of household vinegar on calculus removal and mechanical properties of orthodontic resin

PURPOSE

This study evaluated calculus removal efficacy of household vinegar and its effect on autopolymerizing orthodontic resin following repeated immersion.

METHODS

A total of 72 sectioned specimens of orthodontic retainers with calculus deposits following cleaning with the help of immersion in vinegar of different dilutions between 12.5% and 100%, tap water, effervescent tablets, and mechanical debridement were digitally analyzed. Changes in Ca and Fe ions in vinegar were assessed by atomic emission spectroscopy (AES). For mechanical testing, autopolymerizing polymethyl methacrylate (PMMA) samples were similarly grouped and immersed for 78 cycles and their flexural strength and hardness measured. Fourier-transform infrared spectroscopy (FTIR) was performed to evaluate changes in their chemical composition. One-way analysis of variance (ANOVA) and Tukey's test were used to analyze the differences in the mean flexural strength and hardness between the groups (p ≤ 0.05).

RESULTS

A minimum immersion of 2 h in 25% vinegar solution combined with brushing attained efficiency of 74.13 ± 22% calculus removal. Whereas, tap water and effervescent tablets had 15% and 49% efficiency, respectively. AES results showed diffusion of Ca ions from calculus into the vinegar solution as a plausible mechanism for its structural weakening and removal. Results of mechanical testing showed that undiluted vinegar solution affected the flexural strength of PMMA and this effect was significantly different from that of the effervescent tablets and the remaining vinegar concentrations. There was no significant difference in hardness between the groups. The FTIR showed no changes in the chemical composition of PMMA samples following repeated immersions.

CONCLUSION

Vinegar can be useful in the removal of calculus from dental appliances but should be used in diluted forms to minimize side effects.

Effectiveness of denture microwave disinfection for treatment of denture stomatitis: A systematic review and meta-analysis

OBJECTIVE

The aim of this systematic review was to evaluate the effectiveness of removable complete denture disinfection using microwaves for the treatment of denture stomatitis.

METHODS

This review identified studies comparing the efficacy of microwave prosthesis disinfection (I) to topical antifungal therapy (C) in the treatment of denture stomatitis (O), which included only individuals who used complete dentures and presented with denture stomatitis (P). The search was performed in six databases and identified 1524 records; after the removal of duplicates, 816 articles remained. Three articles were selected for qualitative synthesis and two for meta-analysis. Random-effects meta-analysis estimated the polled effects of microwave disinfection and antifungal therapy on the Candida counts and clinical manifestation of denture stomatitis. The GRADE approach was used to estimate the certainty of evidence.

RESULTS

All included studies reported significant reductions in Candida counts and the frequency of denture stomatitis of groups subjected to microwave disinfection of dentures and topical antifungal therapy with nystatin. Significative differences between treatments were only detected for Candida quantification in the palate, within 90 days follow-up period (SMD = 0.47, 95% CI = 0.02-0.91). Meta-analyses did not show any further differences between treatments (p > .05), considering the Candida quantification in dentures and the frequency of clinical signs of denture stomatitis. The certainty of the evidence was considered as low, according to GRADE approach.

CONCLUSION

Microwave disinfection of complete dentures can be considered as efficient as antifungal therapy for the treatment of denture stomatitis. However, further well-designed studies are necessary to confirm such evidence.

Antimicrobial activity of effervescent denture tablets on multispecies biofilms

PURPOSE

To investigate the impact of peroxide-based solutions in reducing viability and metabolic activity of multispecies biofilms on denture base acrylic resin surfaces and for removing them from these surfaces.

BACKGROUND

Denture cleansers are effective in reducing monospecies biofilm; however, studies evaluating their action on multispecies biofilms are scarce.

MATERIALS AND METHODS

Sixty-nine denture base acrylic resin specimens (Ø 15 × 3 mm) were sterilised then contaminated with Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa to form multispecies biofilms. Biofilms were grown for 24 hours; subsequently, specimens were immersed in three different cleansing solutions (n = 9): nitradine (NI), fixodent (FX) and phosphate-buffered saline (Control), according to the respective manufacturer's instructions. After applying the hygiene protocols, viability of microorganisms was evaluated by counting colony-forming units and assessing metabolic activity. Moreover, biofilm removal capacity was estimated based on extension of cell-covered areas visualised in fluorescent microscopy micrographics.

RESULTS

Microbial counts were solution-dependent; NI was effective against all microorganisms (P < .05). FX exhibited moderate antimicrobial action, reducing P aeruginosa (P < .05) and S aureus (P < .05) viability by approximately 2 logs. Both peroxide-based solutions reduced metabolic activity (P < .001) and biofilm-covered areas on specimen surfaces (P < .001).

CONCLUSION

Under the experimental conditions tested, these results demonstrated that peroxide-based solutions had favourable antimicrobial activity but promoted no broad elimination of aggregated multispecies biofilm. NI might be more suitable as complementary chemical agent for controlling multispecies denture biofilm.

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.

Evaluation of the Efficacy of Different Cleaning Methods for Orthodontic Thermoplastic Retainers in terms of Bacterial Colonization

Objective

This study investigated the antimicrobial efficacy of three different cleaning methods on Streptococcus mutans (SM) and Lactobacillus (LB) bacteria colonization in vivo. The three different cleaning methods were applied by volunteers on clear vacuum formed retainers (VFRs).

Methods

In this prospective, cross-over study, a total of 21 volunteers were included. All VFRs used by the volunteers were cleaned using three different cleaning methods in a sequence. These methods were peroxide-based cleanser tablets (PBCTs) plus brushing, control (only brushing), and vinegar plus brushing, respectively. The obtained salivary, VFR material, and periodontal data were statistically compared by factorial design repeated measures analysis of variance.

Results

The SM and LB bacteria counts on VFRs after using both PBCTs and vinegar were statistically similar (p>0.05), but bacteria counts were statistically lower than the control method (p<0.01). There were no statistically significant differences between the SM and LB bacteria counts in saliva samples taken before and after the application of the cleaning methods (p>0.05). Similarly, there were no significant differences between periodontal data obtained from plaque and bleeding indices at all study times. The periodontal pocket depth gradually decreased in the successively performed cleaning applications (p<0.05).

Conclusion

The application of PBCTs and vinegar to VFRs at sequential time intervals resulted in similar bacteria counts. The higher LB counts and similarly higher SM counts on the VFR samples indicate that mechanical cleaning only (control method) is not adequate to obtain hygiene. Salivary flora was not correlated with bacteria counts of VFRs.

Impact of frequency of denture cleaning on microbial and clinical parameters - a bench to chairside approach

Objective: Robust scientific and clinical evidence of how to appropriately manage denture plaque is lacking. This two-part study (i) developed an in vitro model of denture plaque removal, and (ii) assessed effectiveness of these approaches in a randomised clinical trial.

Method: (i) a complex denture plaque model was developed using the dominant microbial genera from a recent microbiome analyses. Biofilms formed on polymethylmethacrylate were brushed daily with a wet toothbrush, then either treated daily for 5 days or only on Days 1 and 5 with Polident® denture cleanser tablets (3 min soaking). Quantitative and qualitative microbiological assessments were performed. (ii), an examiner-blind, randomised, crossover study of complete maxillary denture wearers was performed (n = 19). Either once-daily for 7 days or on Day 7 only, participants soaked dentures for 15 min using Corega® denture cleansing tables, then brushed. Denture plaque microbiological assessment used sterilized filter paper discs.

Results: The in vitro model showed daily cleaning with denture cleanser plus brushing significantly reduced microbial numbers compared to intermittent denture cleaning with daily brushing (p < 0.001). The clinical component of the study showed a statistically significant reduction in denture plaque microbial numbers in favour of daily versus weekly treatment (aerobic bacteria p = 0.0144). Both in vitro and in vivo studies showed that denture plaque biofilm composition were affected by different treatment arms.

Conclusions: This study demonstrated that daily denture cleansing regimens are superior to intermittent denture cleansing, and that cleansing regimens can induce denture plaque compositional changes. Clinicaltrials.gov registration: NCT02780661.

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

PURPOSE

Removable denture hygiene care is very important for the longevity of the rehabilitation treatment; however, it is necessary to analyze the effects that denture cleansers can cause on the surfaces of prostheses. Thus, this study evaluated the effect of alkaline peroxide-effervescent tablets on the surface of cobalt-chromium alloys (Co-Cr) used in removable partial dentures.

MATERIALS AND METHODS

Circular metallic specimens (12 × 3 mm) were fabricated and were immersed (n = 16) in: control, Polident 3 Minute (P3M), Steradent (S), Efferdent (E), Polident for Partials (PFP), and Corega Tabs (CT). The surface roughness (μm) (n = 10) was measured before and after periods of cleanser immersion corresponding to 0.5, 1, 2, 3, 4, and 5 years. Ion release was analyzed (n = 5) for Co, Cr, and molybdenum (Mo). Scanning electron microscopy (SEM) analysis and an Energy-dispersive X-ray spectroscopy (EDS) were conducted in one specimen. The surface roughness data were statistically analyzed (α = 0.05) with the Kruskal-Wallis test to compare the solutions, and the Friedman test compared the immersion durations. Ion release analysis was performed using 2-way ANOVA and Tukey's test.

RESULTS

There was no significant surface roughness difference when comparing the solutions (p > 0.05) and the immersion durations (p = 0.137). Regarding ion release (μg/L), CT, E, and control produced a greater release of Co ions than S (p < 0.05). CT produced a greater release of Cr ions than control, S, and P3M (p < 0.05). Finally, E caused the greatest release of Mo ions (p < 0.05). SEM confirmed that the solutions did not damage the surfaces and EDS confirmed that there were no signs of oxidation.

CONCLUSION

The various solutions tested did not have any deleterious effects on the Co-Cr alloy surface. Steradent, however, presented the smallest ionic release.

In Vitro Evaluation of the Inhibitory Activity of Thymoquinone in Combatting Candida albicans in Denture Stomatitis Prevention

Candida albicans adhesion and proliferation on denture bases may lead to denture stomatitis, which is a common and recurrent problem in denture wearers. The goal of this study was to assess the inhibitory effect of thymoquinone incorporated in the polymethyl methacrylate denture base material against Candida albicans. Eighty acrylic resin specimens were fabricated and divided into eight groups (n = 10) according to thymoquinone concentrations of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, and 5% of acrylic powder. Two methods were used to evaluate the effect of thymoquinone on Candida albicans: the slide count and the serial dilution test. A multivariate analysis of variance (MANOVA) and the post-hoc Tukey’s Honestly Significant Difference (HSD) test were performed to compare the difference of means between the observations taken at various intervals with baseline. The p value was statistically significant at ≤0.05. According to the slide count and the serial dilution test, the mean number of adhered Candida albicans in the control group was 5436.9 ± 266 and 4691.4 ± 176.8; however, this number dramatically decreased to 0 ± 0 and 32.4 ± 1.7 in group 8 (concentration 5%). These results suggest that the incorporation of thymoquinone into the acrylic resin denture base material might be effective in preventing Candida albicans adhesion.

Impact of Denture Cleansing Solution Immersion on Some Properties of Different Denture Base Materials: An In Vitro Study

PURPOSE

To evaluate the effect of several denture cleansing solutions on the color stability, surface roughness, and flexural strength of three denture base materials.

MATERIALS AND METHODS

Twenty-seven specimens were prepared using heat-polymerized (HP) denture base material, 27 using autopolymerized (AP) denture base material, and 27 using visible-light-polymerized (VLP) denture base, creating a total of 81 specimens. The specimens were randomly divided into three groups (n = 27): the distilled water group (DWG), Corega group (CG), and Renew group (RG). Color changes (ΔE), surface roughness (Ra, nm), and flexural strength (MPa) of each specimen were measured using a spectrophotometer, an optical profilometer, and a universal testing machine, respectively. The results were statistically analyzed using a one-way ANOVA and a post hoc Tukey's test (α = 0.05).

RESULTS

The only statistically significant color change detected was in the VLP resin treated with Corega and Renew. There was a significant increase in the surface roughness of all denture resin groups after immersion in Corega. Immersion in Renew significantly increased surface roughness only in the HP and AP specimens. The only significant reduction in flexural strength was detected in the HP resin after immersion in Corega (p < 0.05).

CONCLUSIONS

Within the limitations of this study, it can be concluded that Corega has a significantly greater negative impact than distilled water on the flexural strength of HP resin base materials. Renew significantly increased the surface roughness of AP and HP, while Corega increased the surface roughness of all resin materials.

Fabrication of denture base materials with antimicrobial properties

STATEMENT OF PROBLEM

Acrylic resin denture base resins are colonized by oral and nonoral bacteria and Candida species. This reservoir of microorganism causes denture stomatitis, which can be implicated in some life-threating infections in older denture wearers.

PURPOSE

The purpose of this in vitro study was to incorporate quaternized N,N-dimethylaminoethyl methacrylate (DMAEMA) monomer into a denture base resin and investigate its antimicrobial and mechanical properties.

MATERIAL AND METHODS

Quaternized ammonium monomer (QAM) was synthesized through the reaction of octyl bromide and DMAEMA. The synthesized QAM was incorporated into a denture base resin system (8 to 12 wt%). The resulting material was characterized by Fourier transform infrared spectroscopy. The in vitro antimicrobial property was determined by direct contact test against Escherichia coli, Staphylococcus aureus, and Candida albicans. Release of the QAM was also tested by means of an agar diffusion test. Mechanical properties were measured with a 3-point bend test, and results were analyzed and compared using ANOVA and the Tukey post hoc test (α=.05).

RESULTS

Spectroscopy confirmed the formation of quaternized ammonium modified denture base (QAMDB). The decrease in number of viable cells of E coli, S aureus, and C albicans was more than 99% for 12%-QAMDB in comparison with that of the control groups. An overall decline was observed in the flexural strength and flexural modulus of the fabricated resins (P<.05), but no differences were observed for strain at break or fracture work of the specimens (P>.05).

CONCLUSIONS

Denture base resins containing immobilized QAM provided high antibacterial activity, but the flexural strength and flexural modulus of the denture base resins decreased.