Carmen Beatriz Borges Fortes

Antimicrobial activity of (2-(methacryloyloxy)ethyl)trimethylammonium chloride against Candida spp.

BACKGROUND Candida-associated denture stomatitis is the most common manifestation of oral candidal infection, caused mainly by Candida albicans. Several authors have attempted to add antifungal agents or antiseptics to denture temporary soft lining materials or to denture acrylic resins, without relevant results. Therefore, the investigation of a quaternary ammonium functionalized compound [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT), which copolymerizes with methacrylates and which could act as a fungal inhibitor, is of paramount importance. AIMS To evaluate the in vitro activity of MADQUAT against Candida species. METHODS Thirty-one Candida strains were used to determine the in vitro antifungal activity of this compound. The minimum inhibitory concentrations and minimum fungicidal concentrations of MADQUAT and nystatin were determined. RESULTS MADQUAT showed antifungal properties at concentrations of 6.25 to > 100mg/ml, and fungicidal activity between 25 and > 100mg/ml. The quantitative determinations of the fungistatic and fungicidal activity of MADQUAT showed fungistatic activity against all Candida albicans, Candida krusei and Candida parapsilosis strains, revealing fungicidal activity against some strains of the other species. CONCLUSIONS MADQUAT has antifungal activity against Candida spp. Moreover, the sensitivity to this substance varies across the different species in terms of MIC values and fungicidal or fungistatic activity.

Effect of different curing condition on material properties of acrylic resin for orthodontic appliances

Abstract The aim of this study was to evaluate the influence of different curing conditions on degree of conversion, glass transition temperature (Tg), microhardness and impact strength of an autopolymerizing acrylic resin. Twenty-one acrylic resin baseplates with wire clasps simulating removable appliances were produced according to three curing conditions and allocated in three groups (n = 7): Group A—curing in air during 1 h at room temperature and pressure; Group M—treated as in Group A plus additional heating by microwave energy (500 W; 3 min); Group TP—curing in water at 50 °C, during 15 min under 20 psi pressure. Microhardness was measured using a Knoop microhardness indenter, and the degree of conversion and Tg were determined by differential scanning calorimetry (DSC). For impact strength test, 12 non-notched specimens were fabricated per group according to ASTM D256 standard. Data were analyzed statistically by one-way ANOVA and Tukeys test (p < 0.05). Group TP presented the highest microhardness means (p < 0.05), followed by Groups M and A. Group TP showed statistically significant differences on impact strength means (p < 0.05) compared to Groups M and A, which, in turn, did not differ significantly to each other (p > 0.05). No significant differences were found among the Tg values of the three groups (p > 0.05). A better performance may be expected when autopolymerizing acrylic resins are cured under controlled heat and pressure conditions.

Microbiological evaluation of peracetic acid for disinfection of acrylic resins

PURPOSE: The aim of this study was to assess the efficacy of peracetic acid (PAA) for the disinfection of dental acrylic resins experimentally contaminated with Candida albicans, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. METHODS: Fifteen materials were used for each type of resin (thermosetting, self-curing and microwave-curing). Each material was placed in a test tube containing culture medium with a suspension of each microorganism and then incubated. The materials were rinsed and transferred to other tubes containing 50 mL of water for 5 min, 0.2% peracetic acid for 5 min or glutaraldehyde for 30 min. The materials were placed in the culture agar and incubated. Microbial growth was determined by colony counting after plating. RESULTS: Candida albicans growth was inhibited by peracetic acid and glutaraldehyde treatments. The number of colonies on resins treated with saline was greater than 105 CFU/mL. In resins infected with E. coli, S. aureus and P. aeruginosa the colony growth was not inhibited by saline and peracetic acid, but it was totally inhibited by glutaraldehyde. CONCLUSION: Surface disinfection using peracetic acid effectively inhibited C. albicans growth on all acrylic resins.

Effects of postpolymerization microwave irradiation on provisional dental acrylics: physical and mechanical properties

Background This study aimed to evaluate the effects of microwave irradiation on the physical and mechanical properties of poly(methyl methacrylate) (PMMA) provisional resins. Methods Twenty bars and 20 disc-shaped specimens were fabricated for each selected provisional restorative material (Dencor and Duralay). Test groups were subjected to microwave irradiation (3 minutes at 600 W) after polymerization. Bar specimens were subjected to a flexural strength test. Disc-shaped specimens were used to evaluate microhardness. Backscattered Raman spectroscopy was employed for each group to define the degree of conversion of the monomer/polymer. The frequency bands corresponding to C = C and C = O groups were used to determine the conversion of methyl methacrylate (MMA) monomers into polymers. Glass transition temperature was determined using a differential scanning calorimeter. Results Microwave irradiation of both tested autopolymerizing PMMA provisional materials resulted in a statistically significant increase in microhardness, degree of conversion and glass transition temperature values. Also, the results demonstrated a significant increase in flexural strength after postpolymerization microwave irradiation for the Dencor specimens. Conclusions It is concluded that mechanical and physical properties are positively influenced by microwave irradiation.

Acrylic resin disinfection by peracetic acid and microwave energy

Objective: The objective of this study was to evaluate the effectiveness of disinfection methods in microwave and immersion in peracetic acid in heat-cured, self-cured and microwave-cured acrylic resin, contaminated with Candida albicans.Methods: Five specimens were prepared for each type of acrylic resin. All were infected with Candida Albicans, incubated at 37°C for 24 hours. The group which underwent microwave energy was irradiated with a power of 840W for 1 minute and the other group underwent disinfection by soaking of 0.2% peracetic acid for 5 minutes.Results: All samples proved to be contaminated after the incubation period. After the different processes of disinfection, both immersion in 0.2% peracetic acid as microwave irradiation were effective in disinfection of the 3 types of acrylic resins contaminated by Candida Albicans.Conclusion: Concluded that soaking in 0,2% peracetic acid for 5 minutes with microwave irradiation power 840W for 1 minute are effective methods for disinfecting heat-cured acrylic resin, self-cured acrylic resin and microwave-cured acrylic resin, contaminated with Candida Albicans.

Pigment effect on the long term elasticity of elastomeric ligatures

OBJECTIVE: To evaluate the response of elastomeric ligatures in several colors for a 4 mm traction over time. METHODS: Morelli® elastomeric ligatures, were submitted to traction forces using two rods of circular cross section, until a 4 mm distance was reached, matching the approximate diameter of an upper central incisor bracket of the same manufacturer. The ligatures were kept in artificial saliva immersion at 37 oC. Forces levels were measured immediately (0 h), 2, 4, 6, 8, 10, 12, 24, 48, 72, 96 hours, 1, 2, 3, 4 weeks and results were submitted to two-way repeated-measures ANOVA statistical analysis. RESULTS: The gray samples showed the higher initial values of tensile strength. The lowest values were presented by purple, light pink, green, black and red groups. The greater tensile strength instability was presented by red, black, silver, green and gray groups. The greater tensile strength stability was presented by deep pink, dark blue, blue, purple and light pink groups. CONCLUSION: Elastomeric ligatures do not present stable behavior when suffering traction forces over time and different colors display different behaviors. Deep pink, dark blue, blue, purple and light pink groups, displayed the most stable forces, suggesting that they should be used during the treatment to obtain constant forces.

Influence of dye and nylon fibers on microwave-cured acrylic resin properties

ABSTRACT ObjectiveThe aim of this study is to analyze if both color and nylon fibers have an influence on microwave-cured acrylic resin properties.MethodsRectangular and disk-shaped specimens were prepared using acrylic resins; medium pink with and without nylon fibers and colorless without nylon fibers. To obtain the rectangular specimens, a stainless steel die was used with the following dimensions: 64 X 10 x 3 mm (± 0.5mm). To obtain disk-shaped specimens, a die 50mm (±0.5mm) in diameter and 0.5mm (±0.05mm) thick was employed. They were randomized to form groups: control (colorless acrylic) and experimental (medium pink, with and without nylon fibers), with each group consisting of ten (10) specimens rectangular in shape and five (5) disk-shaped. They were analyzed in six (6) assays (izod impact strength, n=10; Knoop hardness, n=10; glass transition temperature, n=3; water sorption and solubility, n=5; degree of monomer/polymer conversion, n=1; flexural strength and flexural modulus, n=10). All variables were subjected to the analysis of variance test followed by Tukey’s multiple comparison test, at a 5% level of significance.ResultsThe analysis of the monomer/polymer degree of conversion did not reveal any difference between the three groups of resins (medium pink, with and without nylon fibers and colorless resin); it was approximately 88%. The results did not show significant differences between the groups for each variable (p>0.05). ConclusionThe results showed that color and presence of nylon fibers in acrylic resins did not affect the properties analyzed in this study.Indexing terms: Acrylic resins. Microwave. Nylons.