Produção de scaffolds de fosfatos de cálcio por transformação pseudomórfica do gesso.

Abstract

This work aimed to study the hydrothermal Pseudomorphic transformation of scaffolds obtained by 3D printing and slip casting, in a particularly useful stage for bone regeneration. The 3D printing system for x60 ProJet printers (3D Systems, Inc.) prints three-dimensional ceramic pieces in the compound VisiJet PXL (80-90% CaSO4.½H2O). The printed parts are essentially composed of calcium sulfate dihydrate (CaSO4.2H2O, gypsum), which is an inappropriate material for bone implants due to their higher resorption rate. In the study, we investigated a technical solution to the above problem. Pseudomorphic hydrothermal processing plaster parts in a useful calcium phosphate phase, which is recognized as useful for bone regeneration, maintaining the size and morphology of the starting piece was studied. Due to the unavailability of a ProJet x60 series printer in CERTBIO´s Lab and acess to a partnership as well, only the exploration phase to the methodology of adjustments was fulfilled for scaffolds obtained from the 3D printer. Therefore and because of the compound VisiJet PXL be expensive, the proposed study was continued by making scaffolds of Orthodontic Plaster (Plaster orthodontic diamond, GSE) by the slip casting method, the future idea to use this material to replace the composed VisiJet PXL. The scaffolds were characterized before and after the hydrothermal synthesis as: qualitative and quantitative composition of crystalline phases (X-ray diffraction, XRD - Rietveld refinement); microstructure (scanning electron microscopy, SEM); Semi-quantitative elemental composition (energy dispersive X-ray spectroscopy, SDS). After determining the optimum synthesis time, the samples were characterized in terms of resistance to axial and diametrical compression; and apatite surface forming ability in vitro. The hydrothermal synthesis was carried out by immersing the plaster scaffolds in a solution of 1 M (NH4)2HPO4/1.33 M NH4OH in an L/S ratio of 10 ml / g in an autoclave at 120°C and 203 kPa (2 atm) for at least three hours. Neither the form nor size significantly altered during the process. The composition of the treated scaffolds for three hours was 74% CO3-HAp and 26% β-TCP, and its compressive strength and diametral were 6.5 ± 0.7 and 5.3 ± 0.7 MPa, respectively. By extrapolating the time of synthesis for six hours the increase in β-TCP composition (63% C-HAp and 37% β-TCP) was observed. Based on these results, it was concluded that this is a viable alternative for the manufacture of two-phase scaffold (C-HAp / β-TCP) from precast pieces of gypsum.