Page 617 - IJB-10-3

International Journal of Bioprinting Wireless module system applied on 3D-printed implant

To place the developed WMS within the 3D-printed 3. Result
implant, an openable back cover was designed on the Under 50 N/100 N/200 N load conditions, the strain values
implant lingual side. Two screws with a diameter of 2.5 mm derived from the FE analysis and the signal data log system
and length of 3.1 mm were used to secure the back cover were recorded as -82.95 ue/-165.90 ue/-331.81 ue and
to the supporting beams inside the implant. Additionally, -78.17 ue/-161.49 ue/-319.67 ue, respectively. Based on the
a 6 mm hole was also made in the center of the back cover FE analysis results as reference, the percentage errors for
to allow Bluetooth signals to transmit to a mobile phone the strain values measured by the signal data log system
application (Figure 3).
were 5.76%/2.66%/3.66% across the corresponding load
A metal 3D printer (AM400, Renishaw, Gloucestershire, conditions. Furthermore, a linear regression plot was
UK) with titanium alloy powder (Ti6Al4V powder with created correlating the strain values from the signal data
average grain size of 30 μm) was used to manufacture log system with the applied loads (Figure 5a), resulting in
the implant. The 3D printing machine was operated an R value of 0.9991.
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with a laser power of 400 W, a scanning rate of 0.6 m/s,
exposure time of 125 s with a spot diameter of 70 μm, The voltage values obtained from the WMS under
and an accuracy of ±25 µm in the laser beam movement 50 N/100 N/200 N loads were recorded as -912.87 uV/-
and positioning. The implants were then acid-etched to 1828.75 uV/-3386.46 uV, respectively. After plotting the
remove residual sandblast particles and cleaned using power-voltage results through linear regression (Figure 5b),
2
ultrasonic oscillations. 11,15 an R value of 0.9927 was obtained. Further analysis
involved performing a linear trend analysis between the
2.4. In vitro biomechanical fatigue tests voltage values measured by the WMS and the strain values
The uniaxial strain gauge was glued to the inner right obtained from the signal acquisition system. The outcome
buccal wall of the 3D-printed implant at halfway up its is depicted in Figure 5c, presenting the derived equation
height. The strain gauge axis was oriented perpendicular for converting strain values to voltage values as y = 10.166x
to the occlusal surface. Simultaneously, the strain gauge − 147.39 (where x = strain and y = voltage variation).
wires were soldered to the corresponding Bluetooth chip Based on the derived voltage conversion equation, the
pins. The WMS (comprised of the chip and battery) was voltage values obtained from point A in the validation
placed within the implant and the back cover secured in experiment can be converted into strain values using the
place with screws (Figure 4a). formula provided in material mechanics. Simultaneously,
The corresponding remaining mandibular plastic bone a comparison can be made with the strain results obtained
models were duplicated in acrylonitrile butadiene styrene from the signal data log system at point B. The theoretical
(ABS-P430; Stratasys, Ltd., Minnesota, USA) using a 3D strain value at point A was expected to be twice that of
printer (Dimension 1200es SST, Stratasys, Ltd., Minnesota, point B. From Table 2, it was observed that the maximum
USA). The 3D-printed metal implant included WMS was error percentage was 17%.
fixed onto the remaining mandibular ABS bone model with Biomechanical fatigue test results indicated that
bone screws (Tandry Locking Bone Plate System ψ2.4 mm average strain values obtained by the WMS were 146.96
L18 mm, All Micro Precision Co., Ltd., Taiwan) as the test ue ± 66.14 ue/230.49 ue ± 134.92 ue /336.80 ue ± 117.04
sample. The samples were clamped upside down onto a test ue when 200 N/300 N/400 N were applied on the molar,
machine (Instron E3000, Instron, Canton, MA, USA) and while the corresponding strain values on the premolar
the condyle head fixed in an embedded resin block to apply a were 248.19 ue ± 86.21 ue /316.30 ue ± 41.23 ue /402.82
force to the mandible angle according to the Wiebke Schupp ue ± 93.73 ue. From the stress–strain relationship plot in
test method and the work of other scholars (Figure 4a). Figure 6a, it can be observed that the strain decreased as
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The testing sample received cyclic loads ranging from 20 the applied load diminished. However, strain was lower
N to 200 N, 30 N to 300 N, and 40 N to 400 N, applied when the same load was applied on the molar compared to
separately to the right mandibular molar/premolar area of that on the premolar.
the mandibular bone model at a frequency of 3 Hz until
the sample exhibited noticeable failure or reached 250,000 Moreover, the corresponding average fatigue loading
cycles (Figure 4b). This was performed to simulate the cycles for 200 N/300 N/400 N obtained applied on the
mandibular occlusal conditions 6 months after surgery. premolars were 182,591 ± 63,633/38,354 ± 10174/13,416
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Three test samples were processed for each load value and ± 5072, and on the molars were 250,000 ± 0/210,324 ±
position. Gauge strain values captured by the WMS were 56,111/82,681 ± 11,887, respectively. As depicted in the
analyzed, and the sample failure locations were recorded. stress–fatigue cycles relationship plot in Figure 6b, it was
noted that fatigue loading cycles increased as the applied

Volume 10 Issue 3 (2024) 609 doi: 10.36922/ijb.2553