Candida albicans adherence to an acrylic resin modified by experimental photopolymerised coatings: an in vitro study.

PURPOSE: This study evaluated whether photopolymerised coatings containing zwitterion or hydrophilic monomers would reduce the adhesion of Candida albicans to an acrylic resin. MATERIALS AND METHODS: Disc-shaped samples (n = 468) were fabricated with rough or smooth surfaces. The samples did not receive any surface treatment (control) or were coated with one of the following experimental coatings (2-hydroxyethyl methacrylate - HE; 3-hydroxypropyl methacrylate - HP; and 2-trimethylammonium ethyl methacrylate chloride - T; and sulfobetaine methacrylate - S). The concentrations of the constituent monomers were 25, 30 or 35%. The water contact angles of the samples were measured, and half of the samples were exposed to saliva. The adherent yeast cells were counted after crystal violet staining. RESULTS: For the smooth samples, the groups S35, HP35 and HE35 showed significantly lower number of adhered Candida than control, in the absence of saliva. There were no significant differences among the experimental and control groups for the rough samples, but the saliva decreased the cell numbers for groups S25, S30 and HP30. The photoelectron spectroscopy analysis confirmed the changes in the chemical compositions of the experimental samples. CONCLUSIONS: The experimental photopolymerised coatings changed the chemical composition and decreased C. albicans adhesion in the groups S35, HP35 and HE35, suggesting that they should be further investigated.

Effect of experimental photopolymerized coatings on the hydrophobicity of a denture base acrylic resin and on Candida albicans adhesion.

OBJECTIVE: This study investigated the effect of experimental photopolymerized coatings, containing zwitterionic or hydrophilic monomers, on the hydrophobicity of a denture base acrylic resin and on Candida albicans adhesion. METHODS: Acrylic specimens were prepared with rough and smooth surfaces and were either left untreated (control) or coated with one of the following experimental coatings: 2-hydroxyethyl methacrylate (HE); 3-hydroxypropyl methacrylate (HP); and 2-trimethylammonium ethyl methacrylate chloride (T); and sulfobetaine methacrylate (S). The concentrations of these constituent monomers were 25%, 30% or 35%. Half of the specimens in each group (control and experimentals) were coated with saliva and the other half remained uncoated. The surface free energy of all specimens was measured, regardless of the experimental condition. C. albicans adhesion was evaluated for all specimens, both saliva conditioned and unconditioned. The adhesion test was performed by incubating specimens in C. albicans suspensions (1×10(7)cell/mL) at 37°C for 90min. The number of adhered yeasts were evaluated by XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-5-[{phenylamino}carbonyl]-2H-tetrazolium-hydroxide) method. RESULTS: For rough surfaces, coatings S (30 or 35%) and HP (30%) resulted in lower absorbance values compared to control. These coatings exhibited more hydrophilic surfaces than the control group. Roughness increased the adhesion only in the control group, and saliva did not influence the adhesion. The photoelectron spectroscopy analysis (XPS) confirmed the chemical changes of the experimental specimens, particularly for HP and S coatings. CONCLUSIONS: S and HP coatings reduced significantly the adhesion of C. albicans to the acrylic resin and could be considered as a potential preventive treatment for denture stomatitis.

Efetividade de vernizes fotopolimerizáveis experimentais na redução da hidrofobicidade e adesão de candida albicans em uma resina para base de prótese / Effectiveness of experimental light-cured varnishes in reducing the hydrophobicity and adhesion of candida albicans to a denture base acrylic resin

Foi proposto avaliar diferentes vernizes experimentais, que apresentam em sua formulação monômeros hidrofílicos ou zwiteriônicos, como método para modificar a superfície de resina acrílica para base de prótese, com o objetivo de prevenir a adesão de C. albicans. Foram confeccionados corpos-de-prova com características superficiais que simulavam a parte polida das próteses (superfície lisa) e com características superficiais que simulavam a parte interna das próteses (superfície rugosa) utilizando-se uma resina para base de prótese específica para micro-ondas (Vipi Wave). Matrizes metálicas com 10 cavidades (13,8 mm de diâmetro e 2 mm de altura) foram incluídas em mufla, entre 2 placas de vidro, para simular a superfície lisa, ou em contato com gesso para obter amostras que simulassem a superfície rugosa da prótese. Todos os corpos-de-prova foram submetidos à mensuração da rugosidade utilizando-se um rugosímetro (Mitutoyo SJ 400) com cutoff de 2,5 mm. A rugosidade superficial foi determinada (Ra-µm) pela média de três mensurações realizadas em cada amostra. Após a leitura da rugosidade, os corpos-de-prova foram divididos em grupo controle (n=72; 36 lisos e 36 rugosos), não recebendo nenhum tratamento superficial, e 12 grupos experimentais (n=72; 36 lisos e 36 rugosos) que receberam uma camada do verniz experimental sendo polimerizado em forno EDG. Os vernizes experimentais apresentaram em sua composição o monômero metil metacrilato (MMA), dois agentes de ligação cruzada (TEGDMA e Bis-GMA) e o foto iniciador MBP (4- metil benzofenona). Além desses componentes, os vernizes identificados pelos códigos P, E e T apresentaram monômeros hidrofílicos em 3 concentrações (25, 30 e 35%). O verniz identificado pelo código M apresentou um monômero zwiteriônico (MZ), nas mesmas...

The aim of the present study was to evaluate the use of different experimental varnishes containing zwitterion or hydrophilic monomers as a manner to modify the surface characteristics of a denture base resin and prevent the adhesion of C. albicans. For such purpose, specimens with surface characteristics that simulated the polished side of the dentures and the inner side of the dentures were fabricated using a microwave-polymerized denture base acrylic resin (Vipi Wave). Hollow metallic matrices with 10 cavities (13.8 mm diameter x 2 mm high) were flasked either between two glass plates, in order to produce specimens with smooth surfaces that simulated the polished side of the dentures, or in direct contact with the stone, in order to obtain specimens with rough surfaces that simulated the inner side of the dentures. All specimens were subjected to surface roughness readings in a roughness meter (Mitutoyo SJ 400) with cutoff length of 2.5 mm. Surface roughness (Ra, µm) was determined as the average of three random measurements made on each specimen. After the roughness readings, the specimens were randomly assigned to one control group (n=72; 36 smooth and 36 rough specimens), in which the specimens received no surface treatment, and 12 experimental groups (n=72; 36 smooth and 36 rough specimens) in which the specimens were coated with one of the experimental varnishes followed by polymerization in an EDG oven. The 12 experimental varnishes presented in their composition the monomer methyl methacrylate (MMA), two crosslinking agents (TEGDMA and Bis-GMA) and a photoinitiator agent (4-methyl benzophenone . MPB). In addition to these components, the experimental varnishes labeled as P, E and T presented hydrophilic monomers at three concentrations (25, 30 and 35%). The experimental varnish labeled as M presented a zwitterion...

Técnica de moldagem para implante / Molding technique for implants

Uma das etapas primordiais para o sucesso de uma reabilitação por meio de prótese fixa sobre implante é a moldagem, pois busca-se obter sempre uma adaptação precisa e passiva entre a plataforma do implante e o componente protético. Essa adaptação garantirá aintegridade do tecido ósseo e das estruturas adjacentes ao implante, frente a isso o objetivo desse artigo foi revisar e esclarecer algumas dúvidas sobre as técnicas de moldagem empregadas para a obtenção do modelo de trabalho o mais fiel possível para a confecção da prótese fixa sobre implante.

One of the main steps for the success of the implant supported prostheses is the impression technique because the accuracy to fit and the passivity of the cast metal framework are important. This fit will guarantee the health of the tissue/titanium interface and adjacent structures. Thus, the aim of this study was to review and elucidate some doubts about the impression techniques used to obtain a more accurate master cast fabrication for implant supported prostheses.