Micro-CT evaluation of the presence of voids in endodontic obturation / Evaluación microtomográfica de la presencia de vacíos en la obturación endodóntica

ABSTRACT Identifying the presence, size, type and location of voids in an endodontic obturation is of great clinical importance because it enables evaluation of the three-dimensionality of the sealing techniques, which can be related to the success of the endodontic treatment. Aim To analyze by micro-CT the presence of voids in lower single-rooted premolar root canal obturations prepared using the single cone and ultrasound vibration technique. Materials and methods Twenty extracted single-rooted lower premolars were selected, and the root canal prepared surgically and chemically. In GROUP 1 - Without Vibration, the canal was obturated with a single cone and bioceramic, without applying vibration. In GROUP 2 - With Vibration, the gutta-percha cone inside the root canal was held with a cotton plier to which ultrasound vibration was applied for 3 periods of 3 seconds each. A micro-CT scanner was used to acquire and reconstruct images for analysis. Results No significant difference was found between obturation techniques, though there were differences between thirds, with the cervical third having a higher percentage of voids than the middle and apical thirds. Conclusions The results suggest that the volume of closed, open and total voids does not differ between treatments with and without ultrasound vibration. In the cervical third, the highest volume of voids was related to oval geometry in the teeth evaluated.

RESUMEN La presencia de vacíos en la obturación endodóntica, su tamaño y el tipo y localización tiene gran importancia clínica ya que permite evaluar la tridimensionalidad de las técnicas de sellado y relacionarlas con el éxito del tratamiento endodóntico. Objetivo analizar mediante microtomografía la presencia de vacíos en la obturación del conducto radicular de premolares inferiores unirradiculares, utilizando la técnica de cono único y vibración con ultrasonido. Materiales y Método se seleccionaron 20 premolares inferiores unirradiculares a los que se les realizó la preparación quirúrgica y química del conducto radicular. Se realizó la obturación con cono único y biocerámico GRUPO 1- sin vibración. En el GRUPO 2 - con vibración se aplicó vibración por ultrasonido, se tomó del cono de gutapercha colocado en el interior del conducto con pinza de algodón que fue vibrada durante 3 períodos de 3 segundos cada uno. Las mismas fueron adquiridas y reconstruidas en un microtomógrafo para posterior análisis de las imágenes obtenidas. Resultados No se evidenciaron diferencias significativas entre ambas técnicas de obturación comparadas, pero si entre los tercios analizados, siendo el cervical el que mayor porcentaje de vacíos presenta en comparación a los cortes correspondientes al tercio medio y apical. Conclusiones Los resultados sugieren que el volumen de vacíos cerrados, abiertos y total no varía en los tratamientos donde se aplica vibración por ultrasonido. En el tercio cervical, el mayor volumen de vacíos se relaciona con la geometría oval que presentaron las piezas dentarias evaluadas en este estudio.

Protocolo para la medición de espacios vacíos dentro de la obturación endodóntica con microtomografía / A protocol for the measurement of voids within the endodontic filling with microtomography

La microtomografía es un estudio que utiliza la ra-diación X para obtener imágenes de tamaños de mi-lésimas de milímetros y de alta resolución. Las imá-genes 2D son procesadas por diferentes softwares para lograr obtener volúmenes capaces de ser ana-lizados tridimensionalmente. La microtomografía es el estudio de elección a la hora de evaluar caracte-rísticas muy pequeñas con gran precisión. La obtu-ración endodóntica buscar lograr un sellado que no tenga espacios vacíos dentro de la masa de obtura-ción. Esto es importante debido a que los poros pue-den permitir, si están en contacto con la pared den-tinaria, la entrada de microorganismos al conducto radicular. El objetivo de este trabajo fue describir el procedimiento para el análisis y visualización de los espacios vacíos dentro de la obturación endodónti-ca, utilizando la microtomografía de rayos x, y esta-blecer un protocolo para ser utilizado por cualquier investigador(AU)

Microtomography is a study that uses X-radiation to obtain high-resolution images of sizes of thousandths of millimeters. The 2D images are processed by different software to obtain volumes capable of being analyzed three-dimensionally. Microtomography is the study of choice when evaluating very small features with great precision. Endodontic filling seeks to achieve a seal that does not have voids within the filling obturation. This is important because the voids can allow, if they are in contact with the dentin wall, the entry of microorganisms into the root canal. The objective of this work was to describe the procedure for the analysis and visualization of voids within the endodontic filling using microtomography and to establish the protocol to be used by any researcher (AU)

A comparative evaluation of gingival microleakage and internal voids in Class II composite restoration with two different lining techniques An in vitro study

Aim: The aim of this study was to evaluate the gingival microleakage and internal voids in Class II composite restoration restored with precure and co-cure lining techniques using stereomicroscopic method. Materials and Methods: Forty-five freshly extracted permanent multirooted human molar teeth were collected and used in the study. After surface debridement and scaling of all teeth, standard Class II mesio-occlusal cavities were prepared. Forty-five samples were randomly divided into three experimental groups (n = 15), and filled according to manufacturer's instructions. Group I was precure group, Group II was co-cure group, and Group III was only bulk fill. The finishing and polishing of the restorations was done after 24 h. Then, all the specimens were subjected to thermocycling for 500 cycles. The gingival microleakage and internal voids of all the groups were evaluated using dye penetration method. Samples were then sectioned and examined under the stereomicroscope at ×40. Readings obtained were subjected to statistical analysis using SPSS ver 20.0 (IBM Corp, ARMONK USA) and Chi-square test. Results: The statistical analysis revealed that extent of microleakage was maximum in Group II (co-cure), followed by Group III (only bulk fill) and Group I (precure). The gingival voids were maximum in Group III (only bulk fill), minimum in Group II (co-cure), and least in Group I (precure). The cervical voids were maximum in Group II (co-cure) and Group III (only bulk fill), followed by Group I (precure). The occlusal voids were maximum in Group II (co-cure) and similar in Group I (precure) and Group III (only bulk fill). Conclusion: The precure lining technique was better than co-cure lining technique in terms of both microleakage and internal voids.

Momentos de "des-existir" e espaços vazios de "des-existência" / Moments of "de-existing" and empty spaces of "de-existence" / Momentos de "des-existir" y espacios vacíos de "des-existencia"

A utilização do conceito des-existir, usado por mim neste e em outros trabalhos, resulta de uma necessidade de nomear e delimitar situações em geral transitórias limitadas à esfera psíquica. Diferencia-se do conceito de matar, verbo ativo que implica na ação de um sujeito, seja em termos físicos ou metafóricos. Assim como diferencia-se também do conceito de morrer, ligado a algo mais definitivo em termos naturais ou figurados. Des-existir refere-se a uma situação momentânea, temporária e às vezes prolongada, em que o sujeito entra em processo de falência como sujeito psíquico por desinvestimento. Pode ser des-existido em diferentes graus de apagamento em um espectro que se estende entre a situação ativa de sujeito e a condição passiva de objeto da pulsão de morte (AU)

I employ the idea of de-existing, in this and other papers, as a result from an urge to name and delimit usually transient situations limited to the psychic sphere. It differs from the idea of killing, active verb that implies the action of a subject, in physical or metaphorical terms. As well as it also differs from the idea of dying, connected to something more definitive in natural or figurative terms. De-existing refers to a momentary, temporary situation, sometimes long-lasting, in which, due to disinvestment, the subject goes into a process of failure as psychic subject. It may be de-existed in different levels of effacement in a spectrum that extends between the active situation as subject and the passive condition of object of the death drive (AU)

El uso del concepto des-existir, que utilizo en este y otros trabajos, resulta de una necesidad de nombrar y delimitar en general situaciones transitorias limitadas a la esfera psíquica. Se diferencia del concepto de matar, verbo activo que implica la acción de un sujeto, ya sea en términos físicos o metafóricos. Además, también se diferencia del concepto de morir, ligado a algo más definitivo en términos naturales o figurativos. El des-existir se refiere a una situación momentánea, temporal y en ocasiones prolongada en la que el sujeto entra en proceso de desplome como sujeto psíquico debido a la desinversión. Puede ser des-existido en diferentes grados de desvanecimiento en un espectro que se extiende entre la situación activa del sujeto y la condición pasiva de objeto de la pulsión de muerte (AU)

A produção social do espaço/tempo e os vazios urbanos: o caso do assentamento 20 de novembro em Porto Alegre / The social production of space/time and the urban voids: the 20 de novembro settlement case in Porto Alegre

Localizada na Região Central da Cidade de Porto Alegre, na Rua Dr. Barros Cassal, nº 161, a propriedade onde hoje se localiza o Assentamento 20 de Novembro, após décadas de abandono e degradação foi, a partir do início deste século, palco de tensionamento por parte de organizações de moradores na luta pela moradia da Região Metropolitana. Com base em pesquisa bibliográfica e documental qualitativa, este artigo propõe a discussão da segregação socioespacial verificada nas cidades submetidas ao modo capitalista de produção do espaço e do tempo urbano. O Assentamento 20 de Novembro é aqui apresentado como situação emblemática, na forma de um estudo de caso, exemplificando a apropriação pelo movimento social de um vazio urbano como ação de resistência contra-hegemônica à financeirização do habitat, aliada à emergência de um significativo protagonismo das camadas populares no exercício de sua cidadania.

Located in the city of Porto Alegre in its downtown area, on Doutor Barros Cassal Street, between Farrapos and Alberto Bins Avenues, the property where is located The Vinte de Novembro Settlement, after decades of abandonment and degradation, was from the beginning of this century, the scene of occupations by organizations of residents in the fight for housing in the metropolitan area. Based on bibliographical and qualitative documentary research, this article proposes the discussion of the socio-spatial segregation verified in cities subjected to capitalist mode of urban space/time production. The Vinte de Novembro Settlement was chosen as an emblematic example of counterhegemonic resistance to the financialization of the urban habitat, with the upbringing of a significant role of the popular classes in citizenship.

Influence of voids in the hybrid layer based on self-etching adhesive systems: a 3-D FE analysis

The presence of porosities at the dentin/adhesive interface has been observed with the use of new generation dentin bonding systems. These porosities tend to contradict the concept that etching and hybridization processes occur equally and simultaneously. Therefore, the aim of this study was to evaluate the micromechanical behavior of the hybrid layer (HL) with voids based on a self-etching adhesive system using 3-D finite element (FE) analysis. MATERIAL AND METHODS: Three FE models (Mr) were built: Mr, dentin specimen (41x41x82 μm) with a regular and perfect (i.e. pore-free) HL based on a self-etching adhesive system, restored with composite resin; Mp, similar to M, but containing 25 percent (v/v) voids in the HL; Mpp, similar to Mr, but containing 50 percent (v/v) voids in the HL. A tensile load (0.03N) was applied on top of the composite resin. The stress field was obtained by using Ansys Workbench 10.0. The nodes of the base of the specimen were constrained in the x, y and z axes. The maximum principal stress (σmax) was obtained for all structures at the dentin/adhesive interface. RESULTS: The Mpp showed the highest peak of σmax in the HL (32.2 MPa), followed by Mp (30 MPa) and Mr (28.4 MPa). The stress concentration in the peritubular dentin was high in all models (120 MPa). All other structures positioned far from voids showed similar increase of stress. CONCLUSION: Voids incorporated into the HL raised the σmax in this region by 13.5 percent. This behavior might be responsible for lower bond strengths of self-etching and single-bottle adhesives, as reported in the literature.

Propriedades físicas do solo, influenciadas pela distribuição de poros, de seis classes de solos da região de Lavras-MG / Soil physical properties, influenced by pores distribution, of six soil classes in the region of Lavras-MG

A distribuição de poros dos solos condiciona seu comportamento físico-hídrico. Assim, influencia os processos dinâmicos do ar e da solução do solo, bem como a potencialidade agrícola dos mesmos. Desta forma, com o presente trabalho, objetivou-se avaliar a influência da distribuição de poros sobre as propriedades físicas de seis classes de solos, sob vegetação natural, localizados na região de Lavras (MG). Coletaram-se amostras deformadas e indeformadas da camada superficial (0-20 cm) para a caracterização física e a determinação da curva de distribuição de poros dos solos. Os resultados indicaram que as propriedades físicas dos solos não foram influenciadas pelos poros com diâmetro entre 0,03 e 0,0375 mm. Verificou-se, também, que os valores de macroporosidade foram diretamente proporcionais aos valores de condutividade hidráulica saturada dos solos estudados.

The soil pores distribution conditions its physical-hydraulic behavior. Therefore, it influences the dynamic processes of air and solution of the soil, and also its agricultural potentiality. This work aimed at evaluating the influence of pores distribution on physical properties of six classes of soil, under natural vegetation, located in the region of Lavras (MG). Disturbed and undisturbed samples were collected from superficial layer (0-20 cm) for physical characterization and determination of pores distribution curves. The results indicated that soil physical properties were not influenced by the pores with diameter between 0,03 and 0,0375 mm. It was also verified that macroporosity values were directly proportional to the hydraulic conductivity values of saturated soils.