BARBOSA, W. T.; http://lattes.cnpq.br/6689285779202999; BARBOSA, Willams Teles.
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.
