Experimental animal models for denture stomatitis: A methodological review.

Denture stomatitis is the most prevalent form of oral candidiasis and the most frequent oral lesion in removable prosthesis wearers. It is characterized by an inflammatory response of the denture-bearing mucosa, especially the palatal mucosa, and its clinical signs include chronic edema and erythema, and papillary hyperplasia. Despite having a multifactorial etiology, its main etiological agent is the infection by Candida albicans. Given its high treatment failure rates, an in vivo model of denture stomatitis should be established to test alternative treatments. The aim of this study is to review the existing denture stomatitis models and to provide an overview of the main methodological differences between them. Over the last 40 years, different animal models were developed in order to study denture stomatitis etiopathogenesis and to assess novel therapies. Many approaches, including the use of antibiotics and immunosuppressors, have to be further investigated in order to establish which protocol is more appropriate and effective for the development of an animal model of denture stomatitis.

Is there an optimal method to detach Candida albicans biofilm from dental materials?

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.

The effect of stainable drinks followed by simulated brushing on the roughness and stainability of acrylic resins polymerized with different cycles.

STATEMENT OF PROBLEM: No information is available on roughness and stainability of acrylic resins polymerized by experimental microwave cycles after immersion in stainable liquids and simulated brushing. PURPOSE: The purpose of this in vitro study was to evaluate the effect of stainable drinks and brushing on roughness and stainability of acrylic resins (Vipi Cril [CA] and Vipi Wave [MA]) polymerized with different cycles. MATERIAL AND METHODS: CA and MA specimens (n=5; diameter, 20 mm; thickness, 3 mm) were made using 4 methods recommended by the manufacturer (water bath polymerization and microwave polymerization cycles) and experimental at 550 W or 650 W for 3 or 5 minutes (M550/3 and M650/5), respectively. After storage in distilled water at 37°C for 48 hours (T0), the specimens were stored in water, coffee, or red wine (37°C) for 36 days with simulated brushing (54 000 cycles, T1). Roughness (Ra) and stainability (ΔE/National Bureau of Standards) were measured at T0 and T1. Roughness and stainability data were analyzed by 3-way repeated measures and 2-way ANOVA, respectively, followed by the Bonferroni test (α=.05). RESULTS: After storing in coffee and brushing, CA showed the highest (M550/3=2.33 ±0.72 µm) and the lowest roughness (water bath polymerization=1.22 ±0.58 µm), whereas roughness of MA specimens processed by M650/5 increased (1.57 ±0.59 µm). Storing in wine and brushing increased roughness (1.75 ±0.32 µm) in the M550/3 group. No staining was observed on MA after brushing regardless of the polymerization cycle. All values were acceptable (ΔE≤3.3), except for MA (microwave polymerization), which showed National Bureau of Standards=4.49 (appreciable change) after storing in wine and brushing. CONCLUSIONS: A slight increase in material roughness was observed after staining and brushing. Only MA polymerized following manufacturer cycles showed relevant stainability after immersion in wine and brushing.

Knoop microhardness of conventional and microwaved denture base acrylic resins.

BACKGROUND: Microwave polymerization reduces the time of acrylic resin processing, but it is important to select a proper cycle to avoid overheating, porosity, and impairment to the materials' properties. AIMS: To evaluate the microhardness of conventional (Vipi Cril-VC) and microwaved (Vipi Wave-VW) acrylic resins after microwave polymerization cycles and the cycles recommended by the manufacturer. It was also evaluated the effect of thermocycling on the microhardness of these materials. METHODS AND MATERIALS: Specimens (n = 10) were made: 1. WB (water-bath recommended for VC polymerization); 2. M630/25 (10 min at 270 W; 5 min at 0 W; 10 min at 360 W: recommended for VW polymerization); 3. M550/3 (3 min at 550 W); and 4. M650/5 (5 min at 650 W). After 48 h in distilled water at 37°C, specimens were subjected to Knoop test under 25 g during 5 s. The same specimens were submitted to thermocycling (5,000 cycles; 5°C and 55°C; 60 s) and the microhardness was again measured. The results were analyzed by repeated measures one-way analysis of variance/Bonferroni for each material (α = 0.05). RESULTS: For both materials, no difference was obtained for groups polymerized using the cycles recommended by the manufacturer (VC = 19.8 ± 0.9 KHN; VW = 21.0 ± 1.6 KHN) and M650/5 (VC = 19.9 ± 1.5 KHN; VW = 20.9 ± 0.8 KHN). After thermocycling, microhardness decreased in experimental cycles for VC (M550/3 = 17.0 ± 1.9 to 14.6 ± 1.2 KHN; M650/5 = 19.9 ± 1.5 to 17.8 ± 0.8 KHN) and in all microwave cycles for VW (M630/25 = 21.0 ± 1.6 to 18.3 ± 0.9 KHN; M550/3 = 17.5 ± 3.0 to 15.7 ± 2.0 KHN; M650/5 = 20.9 ± 0.8 to 18.2 ± 2.0 KHN) (P = 0.000). The lowest hardness was observed for both resins processed by M550/3 (P = 0.001). CONCLUSIONS: Both materials could be polymerized in microwave during 5 min showing hardness similar to the cycles recommended by the manufacturer. Thermocycling did not decrease the hardness of VC polymerized with both cycles recommended by the manufacturer and VW polymerized with the water-bath conventional cycle.

Effect of incorporating antifungals on the water sorption and solubility of interim resilient liners for denture base relining.

STATEMENT OF PROBLEM: Incorporating antifungals into interim denture resilient liners has been proposed to prolong their clinical longevity and to treat denture stomatitis. However, information is lacking on the effect of this addition on water sorption and solubility. PURPOSE: The purpose of this in vitro study was to evaluate the addition of minimum inhibitory concentrations (MICs) of antifungals for Candida albicans biofilm on the water sorption (WS) and solubility of interim denture resilient liners. MATERIAL AND METHODS: Disk-shaped specimens (n=10; 50×0.5 mm) of tissue conditioner (Softone) and resilient liner (Trusoft) were created either without (control) or with the incorporation of 1 of the 3 following drugs at MICs (g of drug per g of resilient material powder): nystatin (Ny, 0.032g/g), chlorhexidine diacetate (Chx, 0.064g/g), and ketoconazole (Ke, 0.128g/g). Specimens were dried; immersed in water for 24 hours and 7 or 14 days; weighed, dried, and weighed again. Data (µg/mm(3)) were analyzed by 3-way ANOVA followed by the Tukey-Kramer honest significant differences test (α=.05). RESULTS: At the 14-day interval, only the addition of Chx (483.0 ±61.0 µg/mm(3)) increased the WS of the tissue conditioner compared with the control group (244.0 ±42.0 µg/mm(3); P<.001). For all periods, the solubility of both materials increased with the addition of Chx (27.7 ±6.1 µg/mm(3)) and Ke (30.9 ±5.3 µg/mm(3)) compared with the control group (22.5 ±6.0 µg/mm(3); P<.001). CONCLUSIONS: After 14 days, the addition of Ny and Ke at MICs in both Softone and Trusoft and addition of Chx in Trusoft did not affect WS. The solubility of the 2 interim materials was not altered by the addition of Ny for up to 14 days.

Effect of denture-coating composite on Candida albicans biofilm and surface degradation after disinfection protocol.

INTRODUCTION: Denture stomatitis is the most common pathology affecting denture wearers and its main cause is colonisation of dentures with Candida albicans. OBJECTIVE: This study investigated the effectiveness of two commercial composite surface sealants (Biscover(®) LV and Surface Coat(®)) to reduce C. albicans biofilm colonisation on denture resin, as well as their surface integrity after disinfection cycles with 1% sodium hypochlorite solution. METHODS: Heat-cured acrylic resin specimens were manufactured (10 mm × 10 mm × 1 mm). The specimen surfaces were mechanically polished to simulate rough or smooth denture surfaces. Four surface-treatment groups were tested: smooth surfaces [0.3 µm of mean roughness (Ra)]; rough surfaces (3 µm of Ra); rough surfaces treated with Biscover(®) LV; and rough surfaces treated with Surface Coat(®). Specimens of each group were randomly divided to undergo immersion in distilled water or 1% sodium hypochlorite for 30 or 90 cycles each. Specimens of all groups in each immersion solution were tested using a crystal violet (CV) staining assay for biofilm quantification and by scanning electron microscopy for visual analyses of surface integrity and biofilm structure. CV assay data were analysed using one-way analysis of variance (ANOVA) followed by Tukey's multiple comparison test (P < 0.05). RESULTS: The effectiveness and surface integrity of Biscover(®) LV-treated surfaces were similar to those of smooth surfaces, whereas Surface Coat(®) -treated surfaces presented a similar performance to rough surfaces in all solutions and cycles. CONCLUSION: These results suggest the possibility of clinical use of Biscover(®) LV for denture coating on surfaces in which mechanical polish is not indicated, such as the fitting surface.

Effect of the addition of antimicrobial agents on Shore A hardness and roughness of soft lining materials.

PURPOSE: While the incorporation of antimicrobial agents into soft denture liners has been suggested as a reliable alternative treatment for denture stomatitis, it may affect the liner's properties. The effect of addition of antimicrobial agents for the treatment of denture stomatitis on the surface roughness and Shore A hardness of soft lining materials was evaluated. MATERIALS AND METHODS: The test groups comprised specimens (36 × 7 × 6 mm(3) ) of soft materials (Softone and Trusoft) without (control) or with incorporation of drugs (nystatin, miconazole, ketoconazole, chlorhexidine diacetate, and itraconazole). Hardness (Shore A) and roughness (Ra) were evaluated after immersion of specimens (n = 10) in distilled water at 37°C for 24 hours, 7 and 14 days. Data were analyzed by 3-way ANOVA/Tukey's test (α = 0.05). RESULTS: After 14 days, an increase (p < 0.05) was observed in the hardness of soft materials with time for the modified specimens, except for itraconazole. Addition of drugs increased the Softone roughness only for the addition of miconazole and chlorhexidine (p < 0.05), and did not increase the roughness of Trusoft with time. Only chlorhexidine and itraconazole altered the roughness compared to the control for each material (p < 0.05). CONCLUSIONS: The smallest changes of hardness and roughness with time in the modified groups compared to controls were observed for itraconazole groups for both materials.

Peel bond strength of resilient liner modified by the addition of antimicrobial agents to denture base acrylic resin

In order to prolong the clinical longevity of resilient denture relining materials and reduce plaque accumulation, incorporation of antimicrobial agents into these materials has been proposed. However, this addition may affect their properties. OBJECTIVE: This study evaluated the effect of the addition of antimicrobial agents into one soft liner (Soft Confort, Dencril) on its peel bond strength to one denture base (QC 20, Dentsply). MATERIAL AND METHODS: Acrylic specimens (n=9) were made (75x10x3 mm) and stored in distilled water at 37ºC for 48 h. The drug powder concentrations (nystatin 500,000U - G2; nystatin 1,000,000U - G3; miconazole 125 mg - G4; miconazole 250 mg - G5; ketoconazole 100 mg - G6; ketoconazole 200 mg - G7; chlorhexidine diacetate 5% - G8; and 10% chlorhexidine diacetate - G9) were blended with the soft liner powder before the addition of the soft liner liquid. A group (G1) without any drug incorporation was used as control. Specimens (n=9) (75x10x6 mm) were plasticized according to the manufacturers' instructions and stored in distilled water at 37ºC for 24 h. Relined specimens were then submitted to a 180-degree peel test at a crosshead speed of 10 mm/min. Data (MPa) were analyzed by analysis of variance (α=0.05) and the failure modes were visually classified. RESULTS: No significant difference was found among experimental groups (p=0.148). Cohesive failure located within the resilient material was predominantly observed in all tested groups. CONCLUSIONS: Peel bond strength between the denture base and the modified soft liner was not affected by the addition of antimicrobial agents.

Peel bond strength of resilient liner modified by the addition of antimicrobial agents to denture base acrylic resin.

UNLABELLED: In order to prolong the clinical longevity of resilient denture relining materials and reduce plaque accumulation, incorporation of antimicrobial agents into these materials has been proposed. However, this addition may affect their properties. OBJECTIVE: This study evaluated the effect of the addition of antimicrobial agents into one soft liner (Soft Confort, Dencril) on its peel bond strength to one denture base (QC 20, Dentsply). MATERIAL AND METHODS: Acrylic specimens (n=9) were made (75x10x3 mm) and stored in distilled water at 37 ºC for 48 h. The drug powder concentrations (nystatin 500,000 U--G2; nystatin 1,000,000 U--G3; miconazole 125 mg--G4; miconazole 250 mg--G5; ketoconazole 100 mg - G6; ketoconazole 200 mg--G7; chlorhexidine diacetate 5%--G8; and 10% chlorhexidine diacetate--G9) were blended with the soft liner powder before the addition of the soft liner liquid. A group (G1) without any drug incorporation was used as control. Specimens (n=9) (75x10x6 mm) were plasticized according to the manufacturers' instructions and stored in distilled water at 37 ºC for 24 h. Relined specimens were then submitted to a 180-degree peel test at a crosshead speed of 10 mm/min. Data (MPa) were analyzed by analysis of variance (α=0.05) and the failure modes were visually classified. RESULTS: No significant difference was found among experimental groups (p=0.148). Cohesive failure located within the resilient material was predominantly observed in all tested groups. CONCLUSIONS: Peel bond strength between the denture base and the modified soft liner was not affected by the addition of antimicrobial agents.