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Additional file 3 Growth curves for individual and 4-member coculture of Burkholderiaceae strains.

Background: Diode laser (DL) can be used in endodontics both for its bactericidal effect inside the root canal system (RCS) and for photobiomodulation therapy (PBMT) to accelerate the repair of periradicular bone tissue. Clinical Cases: This work presents two cases of pulp necrosis/asymptomatic apical periodontitis (AAP) that were treated with 940-nm DL, administered both to disinfect the root canal and to apply PBMT to the periradicular tissues. The cases were analysed by Cone-Beam Computed Tomography (CBCT). Discussion: DL has become widely accepted due to its high antimicrobial effectiveness and its ability to accelerate the repair of large apical lesions by biostimulation. Nevertheless, differences of opinion persist within the scientific community due to the lack of standardized endodontic protocols. Conclusions: The application of 940-nm DL, both for disinfection of the RCS and for PBMT, is an effective treatment in non-vital teeth with large periapical lesions. In both cases reported, bone neoformation were found at the 6-month check-up.

Additional file 1. Viable cell numbers of Burkholderiaceae strains from single cultures and co-culture combinations on Arabidopsis thaliana root exudates.

Additional file 2. Selection of replicates of the 4-member combination to set the next generation inocula.

Additional file 4. Graphic representation of the elbow method to discriminate number of clusters.

[eng] Bacteria and their sub-products are the main cause of the occurrence and perpetuation of endodontic infection. However, only a few bacterial species are seen as responsible of persistent endodontic infections, among them Enterococcus faecalis is the most frequently isolated species. It has several virulence factors, such as aggregation substances, enterococcal surface protein (Esp), “endocarditis and biofilm-associated pili” (ebp) and cytolysin. Moreover, its high resistance to antibacterial agents is emhanced by its ability to form biofilm. Due to the complex and unpredictable root canal morphology, the complete removal of smear layer and bacterial biofilm is difficult. Recently, laser-activated irrigation (LAI) has been introduced as an alternative to achieve a deeper cleaning and disinfection of the root canal system. Its mechanism of action is based on the generation of cavitation bubbles, through the absorption of laser energy by the irrigant. The most used lasers are from the Erbium family, Er, Cr: YSGG (2780nm) and Er: YAG (2980nm). Sodium hypochlorite (NaOCl) is considered the "gold standard" of endodontic irrigators. It has a broad antibacterial spectrum and is capable of dissolving organic tissue. It is used in a range between 0.5% and 6%, varying its degree of effectiveness. Nevertheless, at high concentrations it is toxic, causing damage to endothelial cells and the periodontal ligament cells, which generates an acute inflammatory reaction and pain. Hence, the aim of this thesis was to explore the bactericidal effect of low concentration of NaOCl activated by Er, Cr: YSGG laser-activated irrigation against E. faecalis biofilms in root canals in order to decipher if it may be similar to the one achieved by high concentrations of NaoCl. IN IN VITRO ROOT CANAL MODEL: The main objective of the first stage of this thesis was to build a laboratory model to simulate the conditions inside a single-tooth root canal. The Pasteur pipettes were inoculated with E. faecalis ATCC 29212 for 24 hours bacterial colonization and the subsequent formation of biofilm in the proposed in vitro model was demonstrated by atomic force microscope. The second essential point of this part was to determine antimicrobial capacity of Er,Cr:YSGG laser against E.faecalis. In addition, passive ultrasonic irrigation was also tested. Laser-activated irrigation demonstrated higher antimicrobial activity than passive ultrasonic irrigation. The final stage of this first part consisted in the analysis and measurement of the nano-roughness by atomic force microscopy of the cells treated and its comparison with that of untreated cells. EXTRACTED TEETH: This part was focused on the endodontic preparation of extracted human teeth. The root canals were instrumented by a crown-down / step-back technique using conventional sequence of 0.02 taper files up to the master # 55. The teeth were inoculated with E. faecalis ATCC 29212 for 10 days. The following stage was focused on the study of the antibacterial action of low concentration of NaOCl activated by Er,Cr: YSGG laser in extracted human teeth. The antimicrobial effectiveness of laser-activated irrigation was compared with passive ultrasonic irrigation activation and conventional manual irrigation. Er,Cr:YSGG laser and 0.5% NaOCl showed a considerable synergistic action. Finally, the last part was focused on the microscopic visualization of the samples, to complement the results of the microbiological count. The scanning electron microscope was used to determine the degree of effectiveness of bacterial biofilm and smear layer removal both on the dentin surface and inside the dentinal tubules. Additionally, the confocal scanning electron microscope was used to visualize the proportion of alive and dead bacteria after treatment. The results obtained in this thesis show that laser-activated irrigation is a therapeutic alternative for infections caused by E. faecalis inside of root canals., [spa] Las bacterias y sus subproductos son la principal causa de la infección endodóntica y su perpetuación. E. faecalis es la especie más frecuentemente aislada de los fracasos endodónticos. Su alta resistencia a los agentes antibacterianos viene incrementada por la capacidad para formar biofilms. Recientemente, el riego activado por láser (LAI) se ha propuesto como una alternativa para lograr una limpieza y desinfección más profunda del sistema de canales radiculares. Su mecanismo de acción se basa en la generación de burbujas de cavitación, a través de la absorción de energía láser por parte del irrigante. El objetivo de esta tesis fue explorar si el efecto bactericida de una baja concentración de NaOCl activado por el láser Er, Cr: YSGG, puede ser similar al alzanzado por altas concentraciones de NaOCl contra biofilms de E. faecalis en canales radiculares. MODELO DE CANAL RADICULAR IN VITRO: El objetivo principal de la primera etapa de esta tesis fue construir un modelo de laboratorio para simular las condiciones al interior de un canal radicular. Las pipetas Pasteur fueron inoculadas con E. faecalis ATCC 29212 durante 24 horas. Luego se determinó la capacidad antimicrobiana del láser Er, Cr: YSGG contra E.faecalis. La irrigación activada por láser demostró una mayor actividad antimicrobiana que la irrigación ultrasónica pasiva. Finalmente se realizó el análisis y la medición de la nano rugosidad mediante microscopía de fuerza atómica de las células tratadas y no tratadas. DIENTES EXTRAÍDOS: Los dientes fueron inoculados con E. faecalis ATCC 29212 durante 10 días. El láser Er, Cr: YSGG y 0,5% de NaOCl mostraron una acción sinérgica considerable. Finalmente, el microscopio electrónico de barrido se utilizó para determinar el grado de efectividad en la remoción de biofilms bacterianos y de barro dentinario. Además, se utilizó el microscopio electrónico de barrido confocal para visualizar la proporción de bacterias vivas y muertas después del tratamiento. Los resultados obtenidos en esta tesis muestran que la irrigación activada por láser es una alternativa terapéutica para las infecciones causadas por E. faecalis dentro de los canales radiculares.

La percepción de seguridad de los habitantes en sus entornos residenciales más inmediatos se nutre de diversos factores tanto personales como del territorio y de las relaciones sociales entre vecinos. Este trabajo explora mediante el método estadístico de Regresión Lineal Multivariada los principales determinantes de la percepción individual de seguridad. Esta metodología se aplica con una perspectiva multinivel que considera el nivel de determinantes individuales (sexo, edad, años de educación, ingreso del hogar), como el nivel de determinantes de las relaciones sociales y del territorio residencial del individuo. Los resultados a nivel de variables individuales son coherentes con la evidencia previa. Diversas variables asociadas a la interacción social en el barrio inciden en la percepción de seguridad. En particular, confianza e interacción entre vecinos junto a la antigüedad de los barrios son relevantes en la determinación de la percepción de seguridad. El rol de las señales de desorden físico no parece relevante. La presencia de programas de seguridad ciudadana a nivel municipal en el territorio es significativa, indicando la relevancia de estas iniciativas en frenar el temor de las comunidades. The sense of security of inhabitants within the immediate residential surrounding is nurtured by personal and land factors and social relationships among neighbors. By using multivariate linear regression, this paper explores the main factors that determine the individual perception of security. This methodology is applied with a multilevel perspective that considers individual determinants (age, education, household income) and determinants regarding social relationships and the residential area of the individual. The results at variable level are consistent with previous evidence. Different variables related to social interaction within a neighborhood have impact on the sense of security. Particularly, trust and interaction among neighbors and the age of neighborhoods are important elements that determine the sense of security. The role played by physical disorder does not seem relevant. The presence of security programs at municipal level is important as it reveals the relevance of these initiatives.

Financial incentives linked to test performance have been a topic of study in contexts where they exist only for a single test or year. This paper explores a policy's randomized setting in which monetary rewards are attached to exams for multiple years, with the control group never being incentivized. I link the program's rich administrative data with that of a separate set of non-incented math and language exams spanning four consecutive years. Firstly, no effects on grade retentions and small ones on exam abstentions are found. Regarding tests scores, results show no impact in the first year, suggesting evidence from previous literature of immediate effects in incented tests may not reflect students' cognitive development. For the second year, positive impacts emerge, opposing the notion that financial rewards contemporaneously crowd out intrinsic motivation. For the third and final years, although incentives persist, the effects do not, gradually fading away in language and instantly disappearing in math. Incentivos financeiros atrelados à performance em provas educacionais são um tema de estudo previamente abordado em contextos onde existem apenas para um único teste ou durante um único ano. Este artigo explora um ambiente aleatorizado de uma política pública onde prêmios monetários são atrelados a provas por múltiplos anos, período no qual o grupo de controle nunca é incentivado. Eu vinculo os dados administrativos do programa aos de um conjunto de provas de português e matemática que cobrem quatro anos consecutivos e não são ligados à política. Primeiramente, nenhum efeito em reprovações e efeitos pequenos em faltas nas provas são identificados. Em relação às notas, os resultados não demonstram impacto no primeiro ano, sugerindo que achados da literatura sobre efeitos imediatos não refletem o desenvolvimento cognitivo dos alunos. No segundo ano, efeitos positivos são encontrados, em contraste à ideia de que prêmios financeiros reduzem a motivação intrínseca. Para o quarto e quinto ano, apesar dos incentivos persistirem, os efeitos desaparecem, de forma gradual nas notas de português e instantaneamente nas de matemática.

A literatura acadêmica já fornece evidências de que a centralização de admissões no ensino superior tem consequências relevantes de curto e longo prazo, tanto a nível educacional quanto no mercado de trabalho, incluindo mudanças na composição de alunos, no retorno salarial e na desigualdade de renda. Entretanto, seu efeito na acumulação de capital humano é pouco explorado. O presente artigo ajuda a preencher essa lacuna, investigando como a introdução de um novo sistema de admissões centralizadas para instituições públicas no Brasil impactou a retenção de alunos em cursos que adotam a plataforma. Para este fim, utilizamos dados administrativos em painel, explorando a variação temporal na adoção do novo sistema. Os resultados indicam que a centralização reduz a retenção de alunos em programas que adotam plataforma, ao passo que a taxa a qual esses alunos mudam de curso aumenta. Entretanto, a interação da centralização com políticas de ação afirmativa atenua a queda de retenção observada. De maneira geral, os efeitos documentados sugerem que a centralização de admissões impacta significativamente a progressão de alunos, que, em torno, pode ser um canal importante de transmissão desses efeitos para o mercado de trabalho.