A novel acrylic resin palatal device contaminated with Candida albicans biofilm for denture stomatitis induction in Wistar rats Denture stomatitis is the most frequent oral lesion in removable prosthesis wearers, with high recurrence rates and a complex treatment. Objective: This study describes a protocol to obtain and to contaminate a palatal device with Candida albicans biofilm that could be used for an animal model of denture stomatitis. Methodology: Acrylic resin devices (N=41) were obtained from impressions of the palates of Wistar rats with individual trays and polyether.The efficacy of microwave irradiation (MW), ultraviolet light (UV), or ultrasonic bath (US) was assessed by colony viability and spectrophotometric analyses (n=5) in order to select the most appropriate method for sterilizing the devices. Then, different devices (n=5) were contaminated with C. albicans and evaluated by CFU/mL determination, scanning electron microscopy, and laser confocal microscopy. Device stabilization was assessed with either autopolymerizing acrylic resins or a self-adhesive resin cement (n=2). The spectrophotometric data were analyzed by one-way ANOVA followed by the Tukey's HSD post-hoc test (α=0.05). Results: MW was the only method capable of sterilizing the devices, and the contamination protocol developed a mature and viable C. albicans biofilm (~1.2 x 10 6 CFU/mL). The self-adhesive resin cement was the best stabilization material. Conclusions: This acrylic resin palatal device was designed to be similar to the clinical situation of contaminated prostheses, with easy manufacturing and handling, effective stabilization, and satisfactory contamination. Thus, the acrylic device can be a valuable tool in the development of denture stomatitis in rats.

Background: Nystatin (Nys) is a fungicidal drug commonly prescribed for candidiasis disease in several administration routes. However, Nys is a class IV drug according to the Biopharmaceutical Classification System, that possesses limited bioavailability, and is used for local activity. Objective: This study developed and characterized nystatin:β-cyclodextrin (Nys:βCD) inclusion complexes and evaluated their activity against Candida spp. Methods: Complexes were characterized by physicochemical techniques and drug dissolution profiles. The susceptibility of C. albicans, C. krusei, C. parapsilosis, C. glabrata, C. guilliermondii, C. tropicalis, and C. auris was assessed using the broth microdilution method. The applicability of Nys:βCD inclusion complex was evaluated by incorporating it into a temporary soft material for denture stomatitis treatment Results: Nys was better complexed in a 1:1 molar ratio by freeze-drying and spray-drying methods. The inclusion complexes show bi-exponential release, an initial burst release followed by a sustained manner, presenting higher dissolution efficiency than raw Nys. The 1:1 freeze-drying Nys:βCD complex presents antifungal activity against all evaluated Candida strains, showing the maintenance of the drug effectiveness. The inclusion complex incorporated into a tissue conditioner material for denture stomatitis treatment effectively inhibited more than 90% of C. albicans biofilm growth during 7 and 14 days, in a half dose compared to raw Nys. Conclusion: This work represents a significant contribution to treating a wide variety of diseases caused by the Candida species, optimizing the drug bioavailability and compliance to the treatment due to improved drug solubility, dissolution, and sustained delivery.

This study compared different conditions to establish a rat model of denture stomatitis. Immunocompetent Wistar rats were divided into two groups (N = 35): Tetracycline = administration of 0.83 mg/mL of tetracycline hydrochloride seven days before induction of denture stomatitis and Amoxicillin = administration of 0.156 mg/mL of amoxicillin with clavulanic acid four days before induction of denture stomatitis. A suspension of Candida albicans was inoculated on the palate followed by the use of a palatal device contaminated with C. albicans inoculum for four days to induce denture stomatitis. As controls, some rats were not submitted to any procedure or used a sterile palatal device for four days. The development of denture stomatitis was confirmed by visual analysis, CFU/mL count, histopathological and immunohistochemical analyses, and through myeloperoxidase (MPO) and N-acetylglucosaminidase (NAG) assays. Rats were euthanized right after device removal (T0), four (T4), or six (T6) days after device removal. Tetracycline improved the development of the disease, with more severe clinical signs at T0. Similar results were observed in the CFU/mL count and in the histometric and immunohistochemical analyses. Higher MPO expression was detected in the palates of the Tetracycline group (p = 0.006). Despite the subtle differences between antibiotics, tetracycline showed better results in inducing and maintaining denture stomatitis for at least four days after device removal.

Introduction. Candida albicans can produce a complex, dynamic and resistant biofilm on the surface of dental materials, especially denture base acrylic resins and temporary soft liners. This biofilm is the main aetiological factor for denture stomatitis, an oral inflammatory condition characterized by chronic and diffuse erythema and oedema of the denture bearing mucosa. Gap Statement. There is no consensus in the literature regarding the best method to detach biofilms from dental materials. In order to assess the antifungal efficacy of new materials and treatments, the biofilm needs to be properly detached and quantified. Aim. This study compared different methods of detaching C. albicans biofilm from denture base acrylic resin (Vipi Cril) and temporary soft liner (Softone) specimens. Methodology. Specimens of each material were immersed in an inoculum of C. albicans SC5314 and remained for 90 min in orbital agitation at 75 r.p.m. and 37 °C. After the removal of non-adherent cells, the specimens were immersed in RPMI-1640 medium for 48 h. Biofilm formation was evaluated with confocal laser scanning microscopy (n=5). Then, other specimens (n=7) were fabricated, contaminated and immersed in 3 ml of sterile phosphate-buffered saline (PBS) and vortexed or sonicated for 1, 2, 5, or 10 min to detach the biofilm. The quantification of detached biofilm was performed by colony-forming unit (c.f.u.) ml−1 count. Results were submitted to one-way analysis of variance (ANOVA)/Tukey HSD test (α=0.05). Results. A mature and viable biofilm was observed on the surfaces of both materials. For both materials, there was no significant difference (P>0.05) among detachment methods. Conclusion. Any of the tested methods could be used to detach C. albicans biofilm from hard and soft acrylic materials.

This study evaluated methods for the contamination of a soft liner material (Softone™) with Candida albicans biofilm. Specimens were either submitted or not to pretreatment in artificial saliva in an orbital incubator, and then held suspended in different positions (horizontal or vertical) and different storage conditions (bacteriological incubator or orbital incubator) during biofilm formation. Eight conditions were tested. All specimens were immersed in C. albicans inoculum and stored in an orbital incubator at 75 rpm or in a bacteriological incubator, both at 37ºC for 90 min. Then, they were washed in PBS, and maintained in RPMI-1640 medium under the same conditions for 48 h. The degree of contamination was determined by the XTT assay. Data were submitted to ANOVA 1-factor/Tukey HSD test (α=0.05). Specimens held horizontally in an orbital incubator showed the highest cell viability, while the ones kept vertically in a bacteriological incubator had the lowest viability (p0.0001). The best condition for C. albicans biofilm formation was obtained when specimens were not submitted to pretreatment in saliva and were held horizontally in an orbital incubator.