Desenvolvimento de cimentos á base de aluminatos de estrôncio/cálcio para endodontia.

Abstract

The objective of this work is the development of a new cement applied in endodontics based on calcium aluminate and strontium, with adequate physical, chemical, mechanical and biological properties, such as: short setting time and easy workability as well as bioactive properties. The aluminates were obtained by the combustion synthesis of solution because it is a simple and efficient method to obtain nanoscale materials. The reagents used for the synthesis were calcium nitrate tetrahydrate, aluminum nitrate nonahydrate and strontium carbonate, as sources of calcium, aluminum and strontium, respectively. Urea was used as fuel and nitric acid was used for the dissolution of strontium carbonate in strontium nitrate. After the synthesis, the materials were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy with Field Emission (SEM-FEG), Specific Surface and Particle Size. In the synthesis of the calcium aluminate, a single crystalline phase was obtained for dodecalcium

heptaluminate (C12A7) and in the synthesis of the strontium aluminate the tri- strontium aluminate (S3A) was obtained as the main phase, both aluminates

presented a submicron structure with specific surface area of 1,3 and 0,2 m2 /g and average particle size, after grinding, of κ,2 and 3,1 ȝm, respectively. The following step was the preparation of calcium and strontium aluminous cements in the following compositions: CS1 (100% C12A7), CS2 (80%C12A7 + 20%S3A), CS3 (60%C12A7 + 40%S3A), CS4 (40%C12A7 + 60%S3A), CS5 (20%C12A7 + 80%S3A) and CS6 (100%S3A), having been analyzed: radiopacity, workability with the use of additive and final setting time. The CS5 cement showed radiopacity greater than 3 mm in the aluminum scale, being in compliance with ISO 6876-2012. Another characteristic evaluated was the workability of CS5 cement when it was hydrated with water (CS5A) and with the addition of polyethylene glycol 4000 (PEG) as plasticizer and curing retarder in the following compositions: CS5B (20% PEG in mass/volume), CS5C (30% PEG in mass/volume) and CS5D (40% PEG in mass/volume), where it was observed that the cements hydrated with the PEG additive showed good workability, CS5C cement hydrated with 30% by mass/volume of PEG, with short setting time, of approximately 60 minutes. This cement had low temperature of hydration reaction, sufficient compressive strength for the purpose of its application, the in vitro biodegradation test evidenced the release of ions Sr2+, Ca2+ and Al3+ , responsible for the alkaline pH of the medium, which favored the antimicrobial activity against all the bacteriological strains. It also presented bioactive capacity and satisfactory cell adhesion and development in vitro. With the results presented, it can be concluded that the CS5C cement becomes very promising for potential application in endodontics.