Publication: Desarrollo y caracterización de dos materiales biocerámicos basados en β-CaSiO₃ (Wollastonita) para el tratamiento pulpar del diente temporal y permanente joven
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2016-07-04
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Universidad Complutense de Madrid
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Abstract
El empleo de la wollastonita ha sido ampliamente documentado en la literatura como sustituto óseo, siendo un material accesible, económico, biocompatible, bioactivo y osteoinductivo. Los cementos en base a wollastonita se presentan mezclando una fase solida (polvo) con una fase líquida para formar una pasta manejable, la cual se transforma en una masa dura en pocos minutos (mediante fraguado o desecación). El objetivo de nuestro trabajo está enfocado a mejorar y desarrollar nuevos cementos donde se emplea la wollastonita como fuente de iones calcio y sílice, para una aplicación endodóntica. Primero, el nuevo cemento fraguable fue formulado. El cemento fraguable consiste en una mezcla de aluminatos cálcicos (mayenita, Ca12Al14O33 y aluminato tricálcico, Ca3Al2O6) como componente hidráulico. El aluminato de calcio, al igual que los silicatos de calcio que componen el agregado trióxido mineral (MTA), experimenta una reacción de hidratación al mezclarlo con agua que conduce al fraguado y endurecimiento, pero a diferencia de los silicatos de calcio lo hace mucho más rápidamente. Esta mezcla de aluminatos cálcicos fue obtenida en laboratorio mediante combustión. El rápido endurecimiento del aluminato de calcio fue regulado mediante la adición de ácido cítrico, el cual actúa como inhibidor retardando la reacción de fraguado mediante el secuestro de iones calcio. Su elección está justificada por ser un compuesto económico y disponible comercialmente, estando aprobado su uso por la Agencia de Alimentos y medicamentos (FDA por Federal Drug Administration) como excipiente. Para mejorar su manejo y plasticidad se estudian distintos agentes plastificantes (polivinilpirrolidona, polietilenglicol y carboximetilcelulosa). Estos agentes también actúan como retardantes (en nuestro caso un efecto desventajoso) al disminuir la velocidad de reacción de fraguado mediante el incremento de la viscosidad del medio (efecto deseado). Todos ellos son disponibles comercialmente, estando aprobado su uso como excipientes por la FDA...
A lot of studies dealing with applications of wollastonite as bone substitute can be found in the scientific literature published in the last years. Availability, low cost, biocompatibility, bioactivity and osteoconductivity of wollastonite are the main reasons for this increasing interest. Wollastonite-based cements consist in a powder and a liquid which render a workable paste when mixed that may set or not into a hard mass after a few minutes. This work is aimed to develop and improve new cements including wollastonite in its composition as source of calcium and silicon ions, with potential application in Endodontics as pulp capping and root canal filler. First, the new setting cements were formulated. A setting cement was formulated which consisted of a mixture of calcium aluminates (mayenite, Ca12Al14O33 and tricalcium aluminate, Ca3Al2O6) as hydraulic components. Calcium aluminates, similarly to calcium silicates in Mineral Trioxide Aggregate (MTA), but very much faster, form hydrates and set into a hard mass when mixed with water. The mixture of calcium aluminates was obtained in the lab by solution combustion synthesis. The fast setting of the calcium aluminates was slowed by the addition of citric acid which forms stable soluble complexes with calcium ions and retards the precipitation of the hydrates. The choice of citric acid is supported by its low cost, availability and FDA (Federal Drug Administration) approval as excipient. In order to improve workability and plasticity of the cement paste several plasticizers were tested (polyvinylpyrrolidone, polyethylene glycol and carboxymethyl cellulose). These plasticizers act as retardants (an undesired effect in this case) because they increase the viscosity of the liquid (desired effect). All of these plasticizers are available and approved as excipients by FDA...
A lot of studies dealing with applications of wollastonite as bone substitute can be found in the scientific literature published in the last years. Availability, low cost, biocompatibility, bioactivity and osteoconductivity of wollastonite are the main reasons for this increasing interest. Wollastonite-based cements consist in a powder and a liquid which render a workable paste when mixed that may set or not into a hard mass after a few minutes. This work is aimed to develop and improve new cements including wollastonite in its composition as source of calcium and silicon ions, with potential application in Endodontics as pulp capping and root canal filler. First, the new setting cements were formulated. A setting cement was formulated which consisted of a mixture of calcium aluminates (mayenite, Ca12Al14O33 and tricalcium aluminate, Ca3Al2O6) as hydraulic components. Calcium aluminates, similarly to calcium silicates in Mineral Trioxide Aggregate (MTA), but very much faster, form hydrates and set into a hard mass when mixed with water. The mixture of calcium aluminates was obtained in the lab by solution combustion synthesis. The fast setting of the calcium aluminates was slowed by the addition of citric acid which forms stable soluble complexes with calcium ions and retards the precipitation of the hydrates. The choice of citric acid is supported by its low cost, availability and FDA (Federal Drug Administration) approval as excipient. In order to improve workability and plasticity of the cement paste several plasticizers were tested (polyvinylpyrrolidone, polyethylene glycol and carboxymethyl cellulose). These plasticizers act as retardants (an undesired effect in this case) because they increase the viscosity of the liquid (desired effect). All of these plasticizers are available and approved as excipients by FDA...
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Tesis inédita de la Universidad Complutense de Madrid de la Facultad de Odontología, leída el 5 de Febrero de 2016