Geometrical characterization of active contraction pulses in epithelial cells using the two-dimensional vertex model.

Several models have been proposed to describe the dynamics of epithelial tissues undergoing morphogenetic changes driven by apical constriction pulses, which differ in where the constriction is applied, either at the perimeter or in the medial regions. To help discriminate between these models, we analyse the impact of where constriction is applied on the final geometry of the active contracted cell, using the two-dimensional vertex model. We find that medial activity, characterized by a reduction in the reference area, generates anisotropic cell shapes, whereas isotropic cell shapes are produced when the reference perimeter is reduced. When plasticity is included, sufficiently slow processes of medial contractile activity, compared with the characteristic times of elasticity and plasticity, cells can achieve less elongated shapes. Similarly, for perimeter activity, the highest level of contraction is achieved. Finally, we apply the model to describe the apical contractile pulses observed within the epithelial enveloping cell layer during the pre-epiboly of the annual killifish Austrolebias nigripinnis. The analysis of the cell shape changes allowed a global fit of all parameters of the vertex model, with the pulses being quantitatively captured using perimeter activity and area plasticity.

Apical contacts stemming from incomplete delamination guide progenitor cell allocation through a dragging mechanism.

The developmental strategies used by progenitor cells to allow a safe journey from their induction place towards the site of terminal differentiation are still poorly understood. Here, we uncovered a mechanism of progenitor cell allocation that stems from an incomplete process of epithelial delamination that allows progenitors to coordinate their movement with adjacent extra-embryonic tissues. Progenitors of the zebrafish laterality organ originate from the superficial epithelial enveloping layer by an apical constriction process of cell delamination. During this process, progenitors retain long-lasting apical contacts that enable the epithelial layer to pull a subset of progenitors on their way to the vegetal pole. The remaining delaminated cells follow the movement of apically attached progenitors by a protrusion-dependent cell-cell contact mechanism, avoiding sequestration by the adjacent endoderm, ensuring their collective fate and allocation at the site of differentiation. Thus, we reveal that incomplete delamination serves as a cellular platform for coordinated tissue movements during development.

Morphology of the physiological apical foramen of maxillary premolars / Morfología del foramen apical de premolares maxilares

SUMMARY: The purpose of this study was to determine the shape and diameter of the physiological foramen in maxillary premolars of a Chilean population. The sample consisted of 125 extracted maxillary premolars, in which the apical three to five millimeters were cut and observed under magnification of 40x, photographed (Motic Cam), and analyzed using Motic Images Plus 2.0 ML in order to obtain measurements of the minor and major diameter of each physiological foramen. The average minor and major diameter in maxillary premolars was 0.270 and 0.413 mm, respectively. In terms of shape, 72.19 % had oval shaped physiological foramen; 18.93 % were irregularly shaped and 8.88 % were round. Oval and irregular canals are significantly more difficult to shape and require special attention in order to obtain a thoroughly disinfected root canal system.

RESUMEN: El objetivo del estudio fue determinar la forma y el diámetro del foramen fisiológico de premolares maxilares en una población Chilena. La muestra consistió en 125 premolares maxilares extraídos, a los que se cortó de 3 a 5 milímetros apicales, fueron observados bajo magnificación de 40x, fotografiado (Motic Cam) y analizados utilizando Motic Images Plus 2.0 ML para obtener las mediciones de el diámetro menor y mayor de cada foramen fisiológico. El promedio del diámetro menor y mayor en premolares maxilares fue de 0,270 y 0,413 mm respectivamente. En cuanto a la forma 72,19 % tenía el foramen fisiológico de forma oval; 18,93 % tenía forma irregular y 8,88 % fue redondo. Canales ovales e irregulares son significativamente más difíciles de conformar y requieren especial atención para obtener una adecuada desinfección del sistema de canales radiculares.

Morphology of the physiological apical foramen in maxillary and mandibular first molars / Morfología del foramen fisiológico apical en primeros molares maxilares y mandibulares

Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40x magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.

La información relacionada a la anatomía del foramen fisiológico apical es limitada. Conocer su diámetro y forma contribuye al trabajo clínico, específicamente en los procedimientos de limpieza y conformación del tercio apical. El objetivo de este estudio ex vivo fue determinar los diámetros menor, mayor y la forma del foramen fisiológico apical en las raíces de primeros molares maxilares y mandibulares. Se realizó un estudio descriptivo sobre 89 primeros molares recientemente extraídos. Se seccionaron las raíces a 3­5 mm del ápice y fueron preparadas para su análisis bajo magnificación de 40X. Se midieron los diámetros mayor y menor de cada foramen fisiológico mediante el programa Motic Images plus 2.0 ML. La forma de los forámenes fue determinada de acuerdo a la diferencia entre diámetro mayor y menor, clasificándose como redondo, oval o irregular. Un total de 174 forámenes fisiológicos fueron analizados. El promedio del diámetro menor y mayor fue entre 0,24­0,33 mm en primeros molares maxilares y entre 0,25­0,33 mm en primeros molares mandibulares. En molares maxilares, la forma del foramen más común fue la oval (50%), luego irregular (32%) y redonda (18%). En molares mandibulares, la forma oval también fue la más frecuente (59%), seguida por la irregular (23%) y redonda (18%). Los hallazgos de este estudio en relación a morfología de los forámenes fisiológicos apicales en primeros molares, permite al operador facilitar la elección de instrumentos del calibre adecuado para realizar con éxito la terapia endodóntica.

Morphology of the Physiological Apical Foramen in Maxillary and Mandibular First Molars.

Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40× magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.

Influência da espessura de dentina, da constrição apical e do diâmetro do forame apical na precisão de leitura com localizadores foraminais eletrônicos / Influence of dentin thickness, apical constriction and diameter of the apical foramen in the accuracy of readings with electronic apex locators

Este trabalho teve como objetivo avaliar a influência da espessura de dentina radicular apical, da constrição apical e do diâmetro do forame apical na precisão de leituras realizadas com os localizadores foraminais eletrônicos Mini Apex Locator e Root ZX II®. Foram utilizados 30 incisivos inferiores permanentes unirradiculados de humanos, extraídos, com raízes íntegras e ápices completamente formados e portadores de um único canal. Por meio de um paquímetro, as espessuras radiculares dos dentes foram medidas, no sentido mésio-distal a 1,0 e a 4,0mm aquém do forame apical. Após a abertura coronária, uma lima tipo K no 10, munida de limitador de penetração, foi introduzida no canal radicular até que sua extremidade pudesse ser visualizada na altura do forame, com o auxílio de um microscópio óptico com aumento de 7,8X. Dessa medida, subtraiu-se 1,0mm, estabelecendo-se o comprimento de trabalho. A dilatação do canal radicular foi feita, inicialmente, com brocas de Gates Glidden, em ordem numérica decrescente, da número 5 até a número1, até 4,0mm aquém do forame apical. Os dentes foram fixados em um modelo experimental especialmente desenvolvido para permitir a medição com os localizadores foraminais eletrônicos. Tal modelo era constituído por dois segmentos de PVC: um de menor calibre, com diâmetro correspondente a meia polegada por 2,0cm de comprimento, com as duas extremidades abertas e outro, de maior calibre, com uma das extremidades fechada e com diâmetro interno equivalente ao diâmetro externo do primeiro segmento (3/4 de polegada). No segmento de maior diâmetro, foi feito um orifício lateral que permitiu o posicionamento do eletrodo labial do localizador foraminal eletrônico e, para a medição, no seu interior, foi colocado alginato e, então, encaixado o componente de menor diâmetro, fazendo com que o ápice radicular ficasse imerso no alginato. Foram realizadas as leituras com os localizadores, iniciando-se com a lima tipo K no 10 e seguindo-se...

This study evaluated the influence of the apical root dentin thickness, apical constriction and diameter of the apical foramen in the accuracy of readings obtained using the electronic apex locators Mini Apex Locator and Root ZX II ®. The study was conducted on 30 extracted human single-rooted permanent mandibular incisors, with intact and completely formed roots and presenting a single canal. The root thickness of the teeth was measured with a pachymeter in mesiodistal direction, at 1.0 and 4.0mm from the apical foramen. After coronal opening, a 10 K file with a stop was introduced in the root canal until its end could be observed at the level of the apical foramen, with aid of a light microscope with 7.8X magnification. One millimeter was subtracted from this measurement for establishment of the working length. Enlargement of the root canal was initially performed using Gates Glidden burs, in decreasing order, from number 5 to number 1, up to 4.0mm beyond the apical foramen. The teeth were fixated in an experimental model especially designed to allow the measurement with the electronic apex locators. This model was composed of two PVC segments: one smaller, with diameter corresponding to half inch with 2.0cm length, with both ends open; and the other, with larger diameter, with one end closed and internal diameter similar to the external diameter of the first segment (3/4 inch). In the segment with greater diameter, a lateral orifice was made to allow positioning of the lip electrode of the electronic apex locator. For the measurement, alginate was poured and the component with smaller diameter was fitted, so as the root apex was immersed in alginate. Readings were performed using the electronic apex locators, initiating with a 10 K file and following the sequence of instrumentation and measurement up to 130 K file. The 10 K file was used in all diameters. After this stage, the root canals were overinstrumented, i.e. the file tip was introduced until 1.0mm...

Influência da espessura de dentina, da constrição apical e do diâmetro do forame apical na precisão de leitura com localizadores foraminais eletrônicos / Influence of dentin thickness, apical constriction and diameter of the apical foramen in the accuracy of readings with electronic apex locators

Este trabalho teve como objetivo avaliar a influência da espessura de dentina radicular apical, da constrição apical e do diâmetro do forame apical na precisão de leituras realizadas com os localizadores foraminais eletrônicos Mini Apex Locator e Root ZX II®. Foram utilizados 30 incisivos inferiores permanentes unirradiculados de humanos, extraídos, com raízes íntegras e ápices completamente formados e portadores de um único canal. Por meio de um paquímetro, as espessuras radiculares dos dentes foram medidas, no sentido mésio-distal a 1,0 e a 4,0mm aquém do forame apical. Após a abertura coronária, uma lima tipo K no 10, munida de limitador de penetração, foi introduzida no canal radicular até que sua extremidade pudesse ser visualizada na altura do forame, com o auxílio de um microscópio óptico com aumento de 7,8X. Dessa medida, subtraiu-se 1,0mm, estabelecendo-se o comprimento de trabalho. A dilatação do canal radicular foi feita, inicialmente, com brocas de Gates Glidden, em ordem numérica decrescente, da número 5 até a número1, até 4,0mm aquém do forame apical. Os dentes foram fixados em um modelo experimental especialmente desenvolvido para permitir a medição com os localizadores foraminais eletrônicos. Tal modelo era constituído por dois segmentos de PVC: um de menor calibre, com diâmetro correspondente a meia polegada por 2,0cm de comprimento, com as duas extremidades abertas e outro, de maior calibre, com uma das extremidades fechada e com diâmetro interno equivalente ao diâmetro externo do primeiro segmento (3/4 de polegada). No segmento de maior diâmetro, foi feito um orifício lateral que permitiu o posicionamento do eletrodo labial do localizador foraminal eletrônico e, para a medição, no seu interior, foi colocado alginato e, então, encaixado o componente de menor diâmetro, fazendo com que o ápice radicular ficasse imerso no alginato. Foram realizadas as leituras com os localizadores, iniciando-se com a lima tipo K no 10 e seguindo-se...

This study evaluated the influence of the apical root dentin thickness, apical constriction and diameter of the apical foramen in the accuracy of readings obtained using the electronic apex locators Mini Apex Locator and Root ZX II ®. The study was conducted on 30 extracted human single-rooted permanent mandibular incisors, with intact and completely formed roots and presenting a single canal. The root thickness of the teeth was measured with a pachymeter in mesiodistal direction, at 1.0 and 4.0mm from the apical foramen. After coronal opening, a 10 K file with a stop was introduced in the root canal until its end could be observed at the level of the apical foramen, with aid of a light microscope with 7.8X magnification. One millimeter was subtracted from this measurement for establishment of the working length. Enlargement of the root canal was initially performed using Gates Glidden burs, in decreasing order, from number 5 to number 1, up to 4.0mm beyond the apical foramen. The teeth were fixated in an experimental model especially designed to allow the measurement with the electronic apex locators. This model was composed of two PVC segments: one smaller, with diameter corresponding to half inch with 2.0cm length, with both ends open; and the other, with larger diameter, with one end closed and internal diameter similar to the external diameter of the first segment (3/4 inch). In the segment with greater diameter, a lateral orifice was made to allow positioning of the lip electrode of the electronic apex locator. For the measurement, alginate was poured and the component with smaller diameter was fitted, so as the root apex was immersed in alginate. Readings were performed using the electronic apex locators, initiating with a 10 K file and following the sequence of instrumentation and measurement up to 130 K file. The 10 K file was used in all diameters. After this stage, the root canals were overinstrumented, i.e. the file tip was introduced until 1.0mm...