Bacterial-derived extracellular polysaccharides reduce antimicrobial susceptibility on biotic and abiotic surfaces.

OBJECTIVE: Extracellular biofilm matrix plays a role in reducing bacterial susceptibility against antimicrobials. Since the surface where biofilm is growing modulates microbial accumulation and bacterial-derived exopolysaccharides (EPS) synthesis, this study compared the role of EPS to reduce antimicrobial susceptibility on biotic (dental surface) and abiotic (titanium (Ti) material) surfaces and the effect of remaining matrix-enriched biofilms to promote bacterial recolonization. DESIGN: 48 h Streptococcus mutans UA159 strain biofilms were grown on enamel and Ti surfaces. The medium was supplemented with 1% sucrose, substrate for EPS synthesis, or with 0.5% glucose + 0.5% fructose as control. Chlorhexidine (CHX) 0.2% was used for antimicrobial treatment. Biofilms were collected and the following analyses were considered: viable bacterial counts, biofilm pH, EPS content, and biofilm structure by scanning electron microscopy and confocal laser scanning microscopy (CLSM). Substrate surfaces were analyzed by 3D laser scanning confocal microscope. RESULTS: Enamel surface showed a higher amount of EPS content (p < 0.05), which may be explained by the higher bacterial biomass compared to Ti material. EPS content reduced bacterial susceptibility against antimicrobial treatments for both substrates, compared to EPS control (p < 0.05). However, sucrose-treated cells presented the same magnitude of reduction for Ti or enamel. Interestingly, matrix-enriched biofilms favored bacterial recolonization for both substrates. CONCLUSION: The surface where the biofilm is growing modulates the amount of EPS synthesized and matrix content plays a key role in reducing antimicrobial susceptibility and promoting bacterial recolonization.

Smile Transformation with Composite Resin by Semi-Direct Technique: a Case Report / Transformação Do Sorriso Com Resina Composta Por Técnica Semi-Direta: Relato De Caso

Composite veneers stand out in modern dentistry for their practicality, time-saving and excellent optical properties. This work describes the operative steps for the realization of veneers in composite resin in an academic clinical environment using a semi-direct technique. A 21-yearold female patient attended the clinic-school complaining of aesthetic dissatisfaction with her smile. In the clinical dental evaluation, multiple diastemas were observed in the upper anterior teeth, and resin cement residues from orthodontic bracket bonding. In addition, the patient expressed an interest in having bigger and whiter teeth. In view of the complaints reported by the patient, the following treatment sequence was proposed: 1. Removal of residual resin cement from all teeth; 2. Tooth whitening; 3. Confection of composite resin veneers using the semi-direct technique on the upper teeth (canine to canine). The die stone that had already been made for the home bleaching procedure was used for esthetic rehabilitation. The 6 veneers were made using a nanoparticulate resin. The veneers were cemented and adjusted. The 12-month follow-up showed an excellent marginal adaptation and an excellent aesthetic and function quality. The semi-direct technique may be considered a therapeutic option based on the conservation of sound tooth structure, minimal emotional stress during clinical work and excellent final optical and mechanical properties. Simplicity and practicality of the technique allow reproducibility and excellent results at a lower cost when compared to dental ceramics. (AU)

As facetas em resina composta destacam-se na odontologia moderna por sua praticidade, economia de tempo e excelentes propriedades ópticas. Este trabalho descreve as etapas operatórias para a realização de facetas em resina composta em ambiente clínico acadêmico utilizando a técnica semi-direta. Paciente do sexo feminino, 21 anos, compareceu à clínica-escola com queixa de insatisfação estética com seu sorriso. Na avaliação clínica odontológica, foram observados múltiplos diastemas nos dentes anteriores superiores e resíduos de cimento resinoso proveniente da colagem de braquetes ortodônticos. Além disso, a paciente manifestou interesse em ter dentes maiores e mais brancos. Diante das queixas relatadas pela paciente, foi proposta a seguinte sequência de tratamento: 1. Remoção do cimento resinoso residual detodos os dentes; 2. Clareamento dental; 3. Confecção de facetas de resina composta pela técnica semi-direta nos dentes superiores (canino a canino). O modelo de gesso já confeccionado para o clareamento caseiro foi utilizado para a reabilitação estética. As 6 facetas foram confeccionadas utilizando resina nanoparticulada. As facetas foram cimentadas e ajustadas. O seguimento de 12 meses mostrou uma excelente adaptação marginal e uma excelente qualidade estética e funcional. A técnica semi-direta pode ser considerada uma opção terapêutica baseada na conservação da estrutura dentária sadia, mínimo estresse emocional durante o trabalho clínico e excelentes propriedades ópticas e mecânicas finais. A simplicidade e praticidade da técnica permitem reprodutibilidade e excelentes resultados a um custo menor quando comparado às cerâmicas odontológicas. (AU)