Development of Bioabsorbable Interference Screws: How Biomaterials Composition and Clinical and Retrieval Studies Influence the Innovative Screw Design and Manufacturing Processes - Biologically Responsive Biomaterials for Tissue Engineering - page 129

Fig. 6.18 SEM investigation of the biocomposite materials (70% PDLLA + 30% b-TCP) used for
manufacturing innovative interference screw
for the innovative interference screw presented in Fig. 6.11 a composite material
type PDLLA 70% and b -TCP 30%.
The obtained composite biomaterials were characterized in terms of composi-
tional FT-IR spectroscopy on a JASCO 6200 spectrophotometer equipped with a
Type A Golden Gate ATR accessory (SPECAC).
Spectra were recorded on dry samples, using a resolution of 4 cm −1 and an accu-
mulation of 60 spectra. Figure 6.17 shows the FT-IR spectra characteristic of com-
posite materials developed and confirms the presence of specific structural units of
the monomer used in the organic phase (band at 1,748 cm −1 corresponding to stretch-
ing vibrations of the C=O group; bands at 2,941 and 2,995 cm −1 are attributed to the
C-H group of PDLLA) and the characteristic groups of b-TCP in range of 1,100-
1,000 cm −1 attributed to phosphate groups.
The biocomposite material structure was analyzed in detail by SEM using a
Philips XL 30 ESEM microscope and worked at 25 kV and 0.7 Torr (samples not
requiring coverage). The results obtained are shown in Fig. 6.18 and a relatively
uniform distribution of bioceramics in polymer matrix could be observed.
Also, the EDAX profiles of the bioceramics particle (Fig. 6.19 ) con fi rm the pres-
ence of b-TCP and the convenient report Ca:P.
According to the previous considerations, for the manufacturing of the innova-
tive interference screw we choose several manufacturing processes: machining,
rapid prototyping (indirectly by building the mold as a negative of a prototype screw
manufactured using a Fused Deposition Modeling (FDM) screw prototype), and
microinjection molding.
Procedure FDM was developed in 1988 for obtaining prototypes in various sizes
made by wax, polyester, polypropylene, and elastomer. Through this process,
filaments of thermoplastic material, heated to a temperature above the melting
point 1°C, are sent to a pressurized pump and then extruded through a nozzle mov-
ing in XY plane following cross-sectional shape of the model and thus filling a
layer. In the next stage of the process, the platform lowers and the extrusion head
make a second layer over the first. Lamellar support structures are also built along