Effect of antifungal gels incorporated into a tissue conditioning material on the growth of Candida albicans

Enhanced antimicrobial efficacy of chlorhexidine-encapsulated halloysite nanotubes incorporated in presurgical orthopedic appliances: an in vitro, controlled study

AIMS AND OBJECTIVE

Presurgical infant's orthopedic appliances (PSIOs) play an increasingly crucial role in the interdisciplinary management of neonatal CLP, aiming to improve and maintain adequate nasolabial aesthetics, followed by primary lip/nasal surgery in both unilateral and bilateral CLP cases. The use of PSIOs in cleft lip and palate patients can lead to contamination with oral microflora, acting as a potential reservoir for infectious microorganisms. Acrylic surfaces might provide retention niches for microorganisms to adhere, and inhabit, which is difficult to control in immunocompromised patients, thus predisposing them to increased infection risks. The objective of this multi-assay in vitro study was to investigate the effects of incorporating chlorhexidine-loaded halloysite nanotubes (CHX-HNTs) fillers on the morphological, cytotoxic, release, and antimicrobial characteristics of self-cured acrylic polymethyl methacrylate (PMMA) material used in pre-surgical orthopedic appliances.

METHODS

Disk-shaped PMMA specimens were prepared with varying proportions of CHX-HNTs. A control group without any addition served as a reference, and four experimental samples contained a range of different concentrations of CHX-HNTs (1.0, 1.5, 3, and 4.5 wt%). The antimicrobial efficacy was assessed using an agar diffusion test against common reference microorganisms: Candida albicans, Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus agalactiae. Cytotoxicity was examined using the L929 cell line (mouse fibroblasts) through a (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide, MTT) cell viability assay. The release kinetics of CHX were monitored using UV-spectral measurements. The statistical analysis used a one-way ANOVA followed by Tukey's post hoc test.

RESULTS

The integration of CHX-HNTs in PMMA exhibited a substantial dose-dependent antifungal and antibacterial effect against microorganisms at tested mass fractions (1.0 to 4.5 wt%). CHX release was sustained for up to 60 days, supporting prolonged antimicrobial activity. Furthermore, no significant cytotoxicity was determined in the L929 fibroblast cell line (control), indicating the biocompatibility of the CHX-HNTs-enhanced PMMA.

CONCLUSION

Incorporating CHX-HNTs in PMMA successfully enhanced its antimicrobial properties, providing sustained CHX release and superior antimicrobial efficacy. These findings demonstrate the potential of antimicrobial nanoparticles in dental therapies to improve therapeutic outcomes. However, rigorous further clinical trials and observational studies are warranted to validate the practical application, safety, and efficacy.

CLINICAL RELEVANCE

This study has the potential to make a major impact on the health of infants born with cleft lip and palate by helping to reduce the prevalence of infectious illnesses. The incorporation of CHX-HNTs into PMMA-based appliances is a novel promising preventive approach to reduce microbial infections.

Development of a chlorhexidine delivery system based on dental reline acrylic resins

The high recurrence rate of common denture stomatitis after antifungal treatment is still concerning. This condition is caused by low patient compliance and incomplete local elimination of the main etiological factor - Candida albicans, often associated with other microorganisms, such as Streptococcus species. Impregnating denture materials with antimicrobials for local delivery is a strategy that can overcome the side effects and improve the efficacy of conventional treatments (topical and/or systemic). In this work, we describe the development of three hard autopolymerizing reline acrylic resins (Kooliner, Ufi Gel Hard, and Probase Cold) loaded with different percentages of chlorhexidine (CHX). The novel formulations were characterized based on their antimicrobial activity, mechanical, morphological and surface properties, in-vitro drug release profiles, and cytotoxicity. The addition of CHX in all resins did not change their chemical and mechanical structure. Among all the tested formulations, Probase Cold loaded with 5 wt% CHX showed the most promising results in terms of antimicrobial activity and lack of serious detrimental mechanical, morphological, surface, and biological properties.

Structural Characterization and Optimization of a Miconazole Oral Gel

The development of semisolid formulations, gels in particular, has raised the attention of scientists more and more over the last decades. Because of their biocompatibility, hydrophilic nature, and capacity of absorbing large quantities of water, hydrogels are still one of the most promising pharmaceutical formulations in the pharmaceutical industry. The purpose of this study is to develop an optimal formulation capable of incorporating a water-poorly soluble active ingredient such as miconazole used in the treatment of fungal infections with Candida albicans and Candida parapsilosis. A D-optimal design was applied to study the relationship between the formulation parameter and the gel characteristics. The independent parameters used in this study were the Carbopol 940 concentration (the polymer used to obtain the gel matrix), the sodium hydroxide amount, and the presence/absence of miconazole. Ten different dependent parameters (Y1-Y10) were evaluated (penetrometry, spreadability, viscosity, and tangential tension at 1 and 11 levels of speed whilst destructuring and during the reorganization of the gel matrix). The consistency of the gels ranged from 23.2 mm (GO2) to 29.6 mm (GM5). The least spreadable gel was GO7 (1384 mm²), whilst the gel that presented the best spreadability was GO1 (3525 mm²). The viscosity and the tangential stress at the selected levels (1 and 11) varied due to the different compositions of the proposed gels. The gels were also tested for drug content and antifungal activity. All determinations had satisfying results; the drug content was within limits accepted by Ph. Eur. 10 and all formulations containing miconazole exhibited antifungal activity. An optimal formulation with miconazole was attained, consisting of 0.84% Carbopol 940 and 0.32% sodium hydroxide.

Tissue Conditioner Incorporating a Nano-Sized Surface Pre-Reacted Glass-Ionomer (S-PRG) Filler

We aimed to evaluate the properties of a novel tissue conditioner containing a surface pre-reacted glass-ionomer (S-PRG) nanofiller. Tissue conditioners containing 0 (control), 2.5, 5, 10, 20, or 30 wt% S-PRG nanofiller or 10 or 20 wt% S-PRG microfiller were prepared. The S-PRG nanofillers and microfillers were observed using scanning electron microscopy. The ion release, acid buffering capacity, detail reproduction, consistency, Shore A0 hardness, surface roughness, and Candida albicans adhesion of the tissue conditioners were examined. The results indicated that the nanofiller particles were smaller and more homogeneous in size than the microfiller particles. In addition, Al, B, F, and Sr ions eluted from S-PRG were generally found to decrease after 1 day. Acid neutralization was confirmed in a concentration-dependent manner. The mechanical properties of tissue conditioners containing S-PRG nanofiller were clinically acceptable according to ISO standard 10139-1:2018, although the surface roughness increased with increasing filler content. Conditioners with 5-30 wt% nanofiller had a sublethal effect on C. albicans and reduced fungal adhesion in vitro. In summary, tissue conditioner containing at least 5 wt% S-PRG nanofiller can reduce C. albicans adhesion and has potential as an alternative soft lining material.

Should local drug delivery systems be used in dentistry?

In dentistry, the use of biomaterial-based drug delivery systems (DDS) aiming the release of the active compounds directly to the site of action is slowly getting more awareness among the scientific and medical community. Emerging technologies including nanotechnological platforms are offering novel approaches, but the majority are still in the proof-of-concept stage. This study critically reviews the potential use of DDS in anesthesiology, oral diseases, cariology, restorative dentistry, periodontics, endodontics, implantology, fixed and removable prosthodontics, and orthodontics with a special focus on infections. It also stresses the gaps and challenges faced. Despite numerous clinical and pharmacological advantages, some disadvantages of DDS pose an obstacle to their widespread use. The biomaterial's biofunctionality may be affected when the drug is incorporated and may cause an additional risk of toxicity. Also, the release of sub-therapeutic levels of drugs such as antibiotics may lead to microbial resistance. Multiple available techniques for the manufacture of DDS may affect drug release profiles and their bioavailability. If the benefits outweigh the costs, DDS may be potentially used to prevent or treat oral pathologies as an alternative to conventional strategies. A case-by-case approach must be followed.

Sustained release varnish containing chlorhexidine for prevention of Streptococcus mutans biofilm formation on voice prosthesis surface: an in vitro study

OBJECTIVES

In this study, we aimed to develop a novel, sustained release varnish (SRV) for voice prostheses (VP) releasing chlorhexidine (CHX), for the prevention of biofilm formation caused by the common oral bacteria Streptococcus mutans on VP surfaces.

METHODS

This study was performed in an in vitro model as a step towards future in vivo trials. VPs were coated with a SRV containing CHX (SRV-CHX) or SRV alone (placebo-SRV) that were daily exposed to S. mutans. The polymeric materials of SRV were composed of ethylcellulose and PEG-400. Biofilm formation was assessed by DNA quantification (qPCR), crystal violet staining, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and kinetics experiments.

RESULTS

The amount of DNA in the biofilms formed by S. mutans on VP surfaces coated once with SRV-CHX (1.024 ± 0.218 ng DNA/piece) was 58.5 ± 8.8% lower than that of placebo-SRV-coated VPs (2.465 ± 0.198 ng DNA/piece) after a 48-h exposure to S. mutans (p = 0.038). Reduced biofilm mass on SRV-CHX-coated VPs was visually confirmed by CLSM and SEM. CV staining of SRV-CHX single-coated VPs that have been exposed to S. mutans nine times showed a 98.1 ± 0.2% reduction in biofilm mass compared to placebo-SRV-coated VPs (p = 0.003). Kinetic experiments revealed that SRV-CHX triple-coated VPs could delay bacterial growth for 23 days.

CONCLUSIONS

Coating VPs with SRV-CHX has an inhibitory effect on biofilm formation and prevents bacterial growth in their vicinities. This study is a proof-of-principle that paves the way for developing new clinical means for reducing both VPs' bacterial biofilm formation and device failure.

Characterization and Physical and Biological Properties of Tissue Conditioner Incorporated with Carum copticum L

Aim

One of the main problems in dentistry is the injury caused by the long-term application of an ill-fitting denture. The existence of multiple microorganisms along with the susceptibility of the tissue conditioners to colonize them can lead to denture stomatitis. This study is aimed at developing a tissue conditioner incorporated with Carum copticum L. (C. copticum L.) for the effective treatment of these injuries.

Materials and Methods

The Carum copticum L. essential oil composition was determined by gas chromatography-mass (GC-mass) spectrometry. The antimicrobial activity of the essential oil against the standard strains of bacterial and fungal species was determined by broth microdilution methods as suggested by the Clinical and Laboratory Standards Institute (CLSI). The physical and chemical properties of the prepared tissue conditioner were investigated by viscoelasticity, FTIR assays, and the release study performed. Furthermore, the antibiofilm activity of the Carum copticum L. essential oil-loaded tissue conditioner was evaluated by using the XTT reduction assay and scanning electron microscopy (SEM).

Results

The main component of the essential oil is thymol, which possesses high antimicrobial activity. The broth microdilution assay showed that the essential oil has broad activity as the minimum inhibitory concentration was in the range of 32-128 μg mL^-1. The viscoelasticity test showed that the essential oil significantly diminished the viscoelastic modulus on the first day. The FTIR test showed that Carum copticum L. essential oil was preserved as an independent component in the tissue conditioner. The release study showed that the essential oil was released in 3 days following a sustained release and with an ultimate cumulative release of 81%. Finally, the Carum copticum L. essential oil exhibited significant activity in the inhibition of microbial biofilm formation in a dose-dependent manner. Indeed, the lowest and highest amounts of biofilm formation on the tissue conditioner disks are exhibited in the Streptococcus salivarius and Candida albicans by up to 22.4% and 71.4% at the 64 μg mL^-1 concentration of C. copticum L. with a statistically significant difference (P < 0.05).

Conclusion

The obtained results showed that the Carum copticum L. essential oil-loaded tissue conditioner possessed suitable physical, biological, and release properties for use as a novel treatment for denture stomatitis.

Therapeutic Role of Nystatin Added to Tissue Conditioners for Treating Denture-Induced Stomatitis: A Systematic Review

Denture-induced stomatitis (DIS) represents a pathological condition caused by ill-fitting dentures trauma, manifested as inflammation of the palatal tissue beneath the denture. The fungal infections are the principal contributory factors to DIS. Although the aetiology of DIS is multifactorial, the Candida albicans fungal infection remains the main cause. The objective of the present systematic review was to evaluate the latest literature on the addition of nystatin into the tissue conditioners (TCs) in the management of DIS. To search the published literature about “the addition of nystatin in TCs for treating DIS”, electronic databases (PubMed (National library of medicine) and Cochrane Library (Wiley)) were searched (from 1975 until December 2020) using different keywords. Various studies described the effectiveness and efficacy of incorporating nystatin into several TCs. The present systematic review reported that the addition of nystatin is beneficial, with slight or no consequences on both the mechanical and physical features of TCs. Adding nystatin to various TCs for treating DIS can be suggested.

In vitro evaluation of physicochemical properties of soft lining resins after incorporation of chlorhexidine

STATEMENT OF PROBLEM

Incorporating chlorhexidine into soft lining materials has been suggested to reduce biofilm development on the material surface and treat denture stomatitis. However, evaluation of the physicochemical properties of this material is necessary.

PURPOSE

The purpose of this in vitro study was to evaluate the physicochemical properties of resin-based denture soft lining materials modified with chlorhexidine diacetate (CDA).

MATERIAL AND METHODS

Two soft lining resins were tested, one based on polymethyl methacrylate (PMMA) and the other on polyethyl methacrylate (PEMA), into which 0.5%, 1.0%, or 2.0% of CDA was incorporated; the control group had no CDA. The specimens were stored for 2 hours, 48 hours, 7, 14, 21, and 28 days and then analyzed for polymer crystallinity, Shore A hardness, degree of monomer conversion, residual monomer leaching, and CDA release. Data were analyzed by using a 3-way ANOVA and the Tukey HSD test (α=.05).

RESULTS

The polymer crystallinity of PEMA and PMMA did not change after CDA incorporation. Shore A hardness increased over time, but not for any CDA concentrations tested after 28 days (P>.05). Considering the degree of conversion, PMMA-based resin showed no statistically significant difference (P>.05). However, PEMA-based resin showed a significant decrease (P<.05), which was reflected in a significant increase in residual monomer leaching from PEMA-based resin with the incorporation of 0.5% and 1.0% CDA (P<.05), mainly in the first 48 hours. PMMA-based resin showed no change in monomer leaching (P>.05). For both resins, the CDA release kinetics were related to monomer leaching; for PEMA-based resin, the values were significantly higher in the first 48 hours (P<.05), and for PMMA-based resin, the values were more sustained up to the last day of analysis.

CONCLUSIONS

The incorporation of CDA did not affect the physicochemical properties of soft resins. The properties of PMMA were better than those of PEMA.

Antibacterial and antifungal impacts of combined silver, zinc oxide, and chitosan nanoparticles within tissue conditioners of complete dentures in vitro

BACKGROUND

Tissue conditioners are suitable places for colonization of microorganisms. A combination of tissue conditioners with antibacterial and antifungal materials inhibits the growth of microorganisms.

AIMS

Here, we aimed to investigate the antibacterial and antifungal effects of silver (Ag), zinc oxide (ZnO), and chitosan nanoparticles on tissue conditioners in complete dentures.

METHODS

The growth of four microorganisms in six different concentrations of Ag, ZnO, and chitosan nanoparticles was investigated after 24 and 48 h. Nanoparticles were synthesized using optical sequestration and approved by scanning electron microscope, x-ray diffraction, and infrared (FT-IR) methods. Nanoparticles were combined at 0.5, 0.25, and 0.25 ratios (chitosan, Ag, and ZnO, respectively) with 0.625, 1.25, 2.5, 5, 10, and 20 mass percentages. Tissue conditioners with nanoparticles were entered to test tubes containing microorganisms, and the growth rate was measured using the turbidity method by spectrophotometer after 24 and 48 h of incubation at 37 °C.

RESULTS

Growth inhibition of Candida albicans occurred at 2.5% concentration. However, the growth inhibition of Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa occurred at 5% after both 24 and 48 h. Also, the optimum nanoparticle concentration for Candida albicans was found to be 1.25% for both timings. On the other hand, the optimum nanoparticle concentration for Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa was 2.5% for both time scales.

CONCLUSIONS

The combination of Ag, ZnO, and chitosan nanoparticles inhibited the growth of fungi and bacteria in tissue conditioners. These nanoparticles inhibited the growth of fungi more effectively than bacteria.

Evaluation of the physical and antifungal effects of chlorhexidine diacetate incorporated into polymethyl methacrylate

This study aimed to evaluate the physical properties and antifungal activities of polymethyl methacrylate (PMMA) acrylic resins after the incorporation of chlorhexidine diacetate salt (CDA).

To study the effect of Cocos nucifera oil when incorporated into tissue conditioner on its tensile strength and antifungal activity: An in vitro study

Aim:

This study aims to test the tensile strength and growth of Candida albicans on Viscogel tissue conditioner when incorporated with coconut oil (CCO) and to compare its efficacy with other antifungal agents.

Settings and Design:

Evaluative - In-vitro study design.

Materials and Methods:

Fifty dumbbell-shaped samples (n = 10) of Viscogel tissue conditioner were fabricated according to ASTM standard and were classified into 5 groups (10% CCO, 30% w/w tea tree oil, 5% w/w fluconazole, 0.03% w/w silver nanoparticles, and plain tissue conditioner). These samples were compared and evaluated for their tensile strength. Further to test the antifungal activity, a total of 60 samples (n = 15) were fabricated, each group (n = 15) was further divided into three subgroups (n = 5), namely 24-h, 3-day, and 5-day period, which were inoculated in sabouraud dextrose agar plate to test for the growth of C. albicans.

Statistical Analysis Used:

Oneway ANOVA and post hoc Tukey honestly significant difference test.

Results:

10% w/w CCO yielded a mean tensile strength of 20.06 as compared to the plain tissue conditioner which showed a mean tensile strength of 17.81. Similarly, 10% w/w CCO incorporated into Viscogel tissue conditioner showed a significant reduction in the colonization of C. albicans on the 5^th day.

Conclusions:

10% w/w of CCO when mixed with Viscogel tissue conditioner showed a significant reduction in the growth of C. albicans, and addition of the same increased the tensile strength of the tissue conditioner.

Antifungal activity and Shore A hardness of a tissue conditioner incorporated with terpinen-4-ol and cinnamaldehyde

PURPOSE

This study investigated the anti-Candida activity and the Shore A hardness of a tissue conditioner (Softone™) modified by incorporation of terpinen-4-ol and cinnamaldehyde.

MATERIAL AND METHODS

Agar diffusion, microdilution, and mechanism of action methods were performed to determine to evaluate the antifungal activity of phytoconstituents. Then, phytoconstituents in varying concentrations were incorporated into the tissue conditioner. The anti-Candida effect of the modified conditioner was evaluated through agar punch well and biofilm formation methods. Shore A hardness of the experimental liners was evaluated after baseline, 24 h, 48 h, 4 days, and 7 days immersion on artificial saliva.

RESULTS

The phytoconstituents incorporated into Softone showed completely inhibited fungal growth in concentrations of 20-40% and did not present significant antifungal activity until their concentrations where higher than 5%. There were differences between non-modified Softone and M5, M10, C10, and T10% (p < 0.05). The groups containing 10-40% of cinnamaldehyde incorporated into Softone were able to completely inhibit the biofilm. Concentrations below 40% of terpinen-4-ol showed unsatisfactory biofilm inhibition. The T40% and C40% groups presented the lowest Shore A hardness values. Hardness values from groups T40% at 7 days (p = 0.476); C40% at 4 days (p = 0.058); and T20% (p = 0.058), C20% (p = 0.205), T30% (p = 0.154), and C30% (p = 0.874) after 48 h did not differ from the control group.

CONCLUSIONS

Cinnamaldehyde incorporated into Softone inhibited Candida biofilm formation at concentrations of 10-40%, being more effective than terpinen-4-ol modification despite of halo inhibition observed by both products.

CLINICAL RELEVANCE

All modifications showed a very similar pattern of hardness being useful for clinical practice.

Peel bond strength and antifungal activity of two soft denture lining materials incorporated with 1% chlorhexidine diacetate

Two soft denture lining materials (SC-Soft Confort and TS-Trusoft) were investigated with and without the addition of 1.0% of chlorhexidine diacetate (1.0% CHX). To assess peel bond strength, specimens (75×10×6 mm) were submitted to a peel test at 10 mm/min immediately and after 24 h. To evaluate Candida albicans growth inhibition, disc of specimens (10×3 mm) were immersed in a solution with 3×10⁶ CFU/mL of C. albicans, and spectral measurements were made following immersion in MTT solution for 2, 4, and 6 days. The agar diffusion test was performed by investigating the diameters of inhibition zones around the disc of specimens (10×3 mm)after 48 h. Data were submitted to statistical analysis (α=0.05) and the failure modes were visually classified. The incorporation of 1.0% CHX significantly decreased the peel bond strength for TS (p=0.001) and SC (p=0.005) for immediate test and for TS after 24 h (p=0.010), but not for SC. C. albicans growth was decreased for both materials over time (p<0.05). SC presented inhibition zones approximately 2.0 times larger than TS. The incorporation of 1.0% CHX inhibited fungal growth without impairment to the peel bond strength for SC after 24 h.

Antifungal and Mechanical Properties of Tissue Conditioner Containing Plant-Derived Component: An In Vitro Study

PURPOSE

To evaluate the antifungal activity and mechanical properties of a novel antifungal tissue conditioner containing Juncus powder.

MATERIALS AND METHODS

Juncus powder was mixed with GC tissue conditioner at concentrations of 2.5%, 5.0%, and 10.0% by mass. The cylindrical specimens of Juncus-mixed tissue conditioner (dimensions: 10 mm in diameter and 2 and 6 mm in height for antimicrobial and mechanical tests, respectively) were prepared. The specimens placed on the bottom of the 24-well tissue culture plate were cultured with Candida albicans CAD1 for 2 and 4 days. The proliferation of the C. albicans in the wells was determined by measuring the optical density of fungal culture, and the surface of the specimens were also observed by scanning electron microscopy (SEM). To assess the mechanical properties of the specimens, the fluidity and hardness of Juncus-mixed tissue conditioner were measured using the methods certified according to ISO 10139-1.

RESULTS

Juncus-mixed tissue conditioner significantly exhibited growth inhibitory effect in a Juncus concentration-dependent manner after both 2- and 4- day cultures. SEM observation showed that the amount of C. albicans on Juncus-mixed specimens drastically decreased, and biofilm formation was markedly inhibited. Moreover, both mechanical properties were found to be within the ranges regulated and specified by ISO.

CONCLUSION

These findings demonstrated that the tissue conditioner including Juncus powder has a significant growth inhibitory effect against C. albicans, and it is suggested that the application of Juncus-mixed tissue conditioner may prevent denture stomatitis and oral candidiasis in denture wearers.

Role of antifungal medicaments added to tissue conditioners: A systematic review

PURPOSE

The aim of this review is to investigate the current state of knowledge on the incorporation of antifungal agents into the tissue conditioners for the treatment of denture induced stomatitis.

STUDY SELECTION

Studies reporting the incorporation of antifungal/antimicrobial agents in to tissue conditioners were included in the review. In order to search the studies on the topic "incorporation of antifungal agents in tissue conditioners for the treatment of denture induced stomatitis" ISI web of science, PubMed/MEDLINE, and Google-Scholar databases were searched from 1970 up to and including July 2015 using various keywords such as antifungal agents, tissue conditioners, Candida albicans, denture stomatitis, etc.

RESULTS

Various studies reported the efficacy and effectiveness of adding conventional organic antifungal medicines (nystatin, azole group derivatives and chlorhexidine, antimicrobials/antifungals other than organic (silver zeolite, silver nano-particles, photo-catalysts and metallic oxides) and natural and herbal antimicrobials (tea tree oil, lemongrass essential oil and origanum oil) into various tissue conditioners. The review literature reported that incorporation of antifungal agents into tissue conditioners is effective with minimal or no effects on physical and mechanical properties of tissue conditioners.

CONCLUSIONS

Incorporation of different antifungal medicaments to commercially available tissue conditioners can be recommended for the management of denture induced stomatitis.

Advances in Soft Denture Liners: An Update

Soft denture liners are used in complete and partial removable dentures to distribute functional loads homogeneously on the denture-bearing tissues. These materials are recommended in cases of irregular bone resorption, bony undercuts, thin atrophic mucosa, immediate prosthesis, healing after implant placement, and for patients with bruxism and xerostomia. The resilient lining materials can be categorized as plasticized acrylic resins or silicone elastomers. The plasticized acrylic resin comprises of acrylic polymers and copolymers, a liquid containing an acrylic monomer and plasticisers, such as ethyl alcohol and/or ethyl acetate responsible for preserving the material softness. The silicone elastomers, consisting of dimethylsiloxane polymers, with a chemical composition similar to that of the silicone impression materials devoid of leachable plasticisers, retain their elastic properties for prolonged periods. Most of the currently available materials have several disadvantages, including color stability, long-term resiliency, abrasion resistance, bond strength and porosity. Several modifications have been done recently to overcome of these disadvantages of the soft liners. The current review summarizes the recent developments in soft liners.

Resins-based denture soft lining materials modified by chlorhexidine salt incorporation: an in vitro analysis of antifungal activity, drug release and hardness

OBJECTIVES

To evaluate the in vitro growth inhibition of Candida albicans, the rate of chlorhexidine release and shore A hardness from resins-based denture soft lining materials modified by chlorhexidine diacetate (CDA) or chlorhexidine hydrochloride (CHC) incorporation.

METHODS

Resin discs were prepared from soft denture liners based on poly (methyl methacrylate) (PMMA) or poly (ethyl methacrylate) (PEMA) containing 0.5, 1.0 and 2.0 wt.% of CDA or CHC. For antifungal activity resin discs were placed on agar plates inoculated with C. albicans, after 48 h at 37°C the diameters of inhibition zones were measured. For the chlorhexidine release, discs were immersed into distilled water at 37°C, and spectral measurements were made after 48 h. Shore A hardness was evaluated at the baseline, 2 and 7 days, using 6mm thick rectangular specimens also immersed into distilled water at 37°C. Data were statistically processed by SigmaStat software using ANOVA and all pairwise multiple comparison procedures was done using the Holm-Sidak method, with α=0.05 (p<0.001).

RESULTS

CDA added to PMMA soft liner and PEMA soft liner had a dose-related inhibitory effect on C. albicans and on chlorhexidine release rate (p<0.001). The PMMA and PEMA hardness increased statistically by time but not for the different CDA concentrations. CHC had no inhibitory effect on C. albicans.

SIGNIFICANCE

Chlorhexidine diacetate released from resins-based soft lining materials can be convenient to reduce the biofilm development on the material surface and treat denture stomatitis, without depending on patient compliance.

Effect of antimicrobial agents incorporated into resilient denture relines on the Candida albicans biofilm

OBJECTIVE

The antimicrobial action of five drugs incorporated in temporary denture relines on the fungal biofilm was evaluated.

MATERIALS AND METHODS

A Candida albicans biofilm (SC5314) was formed on specimens (10 × 1 mm) of materials (Trusoft and Softone) modified or not (control) by the drugs (nystatin, miconazole, ketoconazole, itraconazole, and chlorhexidine diacetate). Cell viability was determined spectrophotometrically by the tetrazolium salt reduction assay (XTT) after 24 h, 48 h, and 7 and 14 days of incubation. The minimum inhibitory concentrations (MICs) were those which inhibited 90% or more of fungal growth. Fungal susceptibility was confirmed by confocal laser scanning microscopy analysis.

RESULTS

The MICs of drugs incorporated in the materials were 0.032, 0.256, 0.128, 0.256, and 0.064 g ml(-1) for nystatin, miconazole, ketoconazole, itraconazole, and chlorhexidine, respectively. Images from nystatin, chlorhexidine, and ketoconazole demonstrated no viable cells.

CONCLUSIONS

The antimicrobials incorporated in the resilient materials inhibited fungal growth during 14 days, with lower MICs for nystatin and chlorhexidine.

Prevention and treatment of Candida colonization on denture liners: a systematic review

STATEMENT OF PROBLEM

Denture liners are well known for their poor physical properties that favor the accumulation of plaque and colonization by Candida species, which can irritate the oral tissues and lead to denture stomatitis.

PURPOSE

A systematic review was conducted to determine the feasibility of a prevention protocol for Candida colonization in denture liners and an effective treatment after the fungi has colonized the material.

MATERIAL AND METHODS

Clinical and in vitro investigations that assessed the treatment and/or prevention of Candida colonization and biofilm formation in denture liners were selected according to the PRISMA statement. Seven electronic databases were searched from 1950 to April 2012 with the keywords "denture liner" OR "reline*" OR "tissue conditioner" AND "Candida" OR "denture stomatitis" OR "oral candidiasis" OR "antifungal agents" OR "denture clean*".

RESULTS

The incorporation of nystatin (in general, 500 000 units) into tissue conditioners to prevent the onset of the disease and immersion in sodium hypochlorite for disinfection were the methods most often described in this systematic review, and both methods were able to prevent or inhibit Candida colonization, depending on their concentrations. The 0.5% sodium hypochlorite concentration can disinfect tissue conditioners and denture liners. Microwave irradiation has also been described an alternative method of disinfection. Because of a lack of standardized results (especially with regard to the method used to perform microbial counts), a meta-analysis could not be performed.

CONCLUSIONS

The literature suggests that the use of 0.5% sodium hypochlorite can help disinfect denture liners and tissue conditioners. The incorporation of nystatin in those materials is also able to treat or prevent oral candidiasis. However, as most of the studies were in vitro, there is insufficient reliable evidence to truly provide recommendations regarding the ideal cleaning method or whether the addition of antifungal agents is worthwhile. Well-designed randomized controlled trials are needed to provide answers to these questions.

Effects of undecylenic acid released from denture liner on Candida biofilms

Denture liners (DL) are easily colonized by Candida spp. In an attempt to prevent biofilm colonization, manufacturers have incorporated undecylenic acid (UDA) into DL. In this in vitro study, the effects of UDA released from DL on Candida biofilms were investigated. The concentrations of UDA released from commercial DL were determined by gas chromatography-mass spectrometry (GC-MS). Minimum inhibitory concentration (MIC) and minimum fungistatic concentration (MFC) tests were performed for C. albicans or C. glabrata, with UDA for comparison with the concentrations released from DL. Specimens of DL with (experimental group) and without UDA (control group) were fabricated, and Candida biofilms were developed on DL surfaces. Biofilms were evaluated by cell counts, metabolic activity, structure, and secretion of proteinase or phospholipase. The concentrations of UDA released were within the MIC and MFC ranges. In the presence of UDA, C. albicans biofilms were thinner and had lower numbers of viable and active cells, although no significant enzymatic changes were observed relative to the control group (p > 0.05). In contrast, C. glabrata biofilms exhibited higher cell counts and greater metabolic activity and also increased proteinase activity in the presence of UDA relative to the control group (p < 0.05). Overall, UDA did not prevent Candida biofilm formation.

One-pot synthesis of a new antifungal polymerisable monomer and its characterisation by coordination-ion spray mass spectrometry

We have investigated the synthesis of a new antifungal agent with a polymerisable moiety for the prevention of denture stomatisis. Nystatin (antifungal polyene) is modified in one step by reaction with isocyanatoethylmethacrylate to afford a new polymerisable antifungal agent in good yield (90%). In order to prove the monografting of the acrylate derivative and to localise the new group in the skeleton of the molecule, a rapid and efficient analytical method involving electrospray ionisation mass spectrometry (ESI-MS) was developed for the study. In view of the structures of such antifungal agents, their complexation with metal cations was investigated by Coordination-Ion Spray Mass Spectrometry (CIS-MS). This mass spectrometry study covers two aspects: improving the MS signal to overcome the low ionisation efficiency in ESI-MS and exploring the complexation behaviour of the induced structure to optimise the antifungal properties.