Page 168 - IJB-8-1

Optimization of 3D Printing Parameters of PLA/HA Bone Plates
high biocompatibility and biodegradability. It is often in bone plate printing, such as the HA content, layer
used to make degradable scaffolds, bone plates, and other thickness, printing speed, and filament feeding speed,
implants. The bone plates are different from long-term were optimized by an orthogonal experiment. Combined
orthopedic implants such as artificial joints and cages, with the analysis of the internal defects, the temperature
some non-degradable bone plates need to be removed of the printing process, and the printing pressure, the
after the fracture is healed, which will make the patients influence of the process parameters on the bending
undergo another operation. Degradable bone plates do not strengths of the bending specimens were studied.
need to be removed after fracture healing, but common
degradable materials, such as PLA, have poor mechanical 2. Materials and methods
properties, and the acid products produced by degradation According to the stress characteristics of the plate, the
process can easily lead to aseptic inflammation [19,20] . The influence of the process parameters on the bending
strength of a composite composed of bioceramic particles mechanical properties of the plate was analyzed. To
as the reinforcing phase in PLA is higher than that of pure simplify the analysis process, the influence of the screw
PLA. Hydroxyapatite (HA) is a widely used biodegradable holes in the plate samples was not considered.
bioceramic. The addition of HA can not only improve the
bone integration ability and biocompatibility of implants, 2.1. Materials
but also produce a slightly alkaline environment in the PLA filament and two kinds of PLA composite filaments
degradation process, which helps to reduce the occurrence of with different HA contents (HA mass ratios in 10%
aseptic inflammation. Huang et al. grafted poly (D-lactide) and 20%) were used to prepare samples for bending
(PDLA) oligomers onto HA nanorods (HA-PDLA), and the experiments. The average size of HA particles is 15 μm.
HA-PDLA hybrids were mixed with poly (L-lactide acid) The diameter of the filaments is 1.75mm, which were
(PLLA) to improve the tensile strength and the elongation . supplied by Shaanxi Jugao AM medical corporation.
[21]
Shikinami et al. investigated the forged composites of raw
HA particles and PLLA (PLLA/F-u-HA) bone rods that 2.2. Experimental setup
exhibited bioactivity and biodegradation . The strength
[22]
stability, bioactivity, and biodegradation properties were (1) Printing platform
ideal for bone repair. Takayama et al. studied the effects of The 3D printer used in this study is shown in Figure 1A.
a bimodal distribution of micro-HA and nano-HA (nHAP) It consisted of a three-axis closed-loop servo motion
particles on the mechanical properties, such as the bending system, a hotbed, a nozzle, and a temperature control
strengths, modulus, and mode I fracture energies of PLLA/ system. The hotbed was the substrate for the molten
HA composites . The bending properties and fracture filament deposition, which was installed on the worktable
[23]
energies were effectively improved using a bimodal that was controlled by the motion control system for X-Y
distribution instead of a monomodal distribution. Nejati
et al. prepared nHAP/PLLA composite scaffolds with A B B
porosities of 85% . Experimental results showed that the
[24]
cell affinity and compatibility of the material were superior
to those of pure PLLA and PLLA micro composites.
PLA and bioceramic particles were mixed in
different proportions to make different composite
filaments, which could be conveniently used to make a
composite model by a fused deposition modeling (FDM)
printer. In the FDM printing process, minimizing the
voids and improving the adhesion between deposited
lines are the keys and challenges for improving the C D D
printing quality [25,26] . The process parameters are among
the main factors affecting the mechanical properties of
FDM printed parts [27-29] . There are relatively many studies
on the relationship between the process parameters and
mechanical properties of printed parts [30-34] , but there are
few studies on the formation mechanism of the internal
microscopic defects of printed parts and their influence
on the mechanical properties of the parts. Figure 1. (A) 3D printing platform. (B) Mechanical test machine
In this study, a PLA/HA composite plate was and 3D full-field strain measurement setup. (C) Printing temperature
proposed. The important process parameters involved measurement setup. (D) Printing pressure measurement setup.

154 International Journal of Bioprinting (2022)–Volume 8, Issue 1