Page 91 - IJB-9-2

International Journal of Bioprinting Steam-sterilized and degradable FFF-printed PLA/PHA surgical guides

Finally, it is not possible to draw any firm conclusions the model . Sun et al. reported angular deviations of 3.22
[33]
regarding potential dimensional changes in surgical guides, ± 1.55° after in vitro implantation using FFF-printed PLA
especially since the studies often do not clarify the question guides and of 2.74 ± 1.24° after the implantation using
of their clinical relevance. Eventually, the dimensional light-cured 3D-printed guides (material jetting) ; both
[27]
changes are probably affected by different factors, such as values were higher than those reported in our study (0.38
the type (temperature, pressure, and duration) of steam ± 0.53° and 0.72 ± 0.55°).
sterilization as well as the material used, which makes a Pieralli et al. used an experimental lignin-based
final statement difficult. Nevertheless, this question should filament for FFF printing of guides in combination with
[20]
be investigated for the different materials used, since the steam sterilization. Their results showed angular deviations
manufacturing process itself can lead to dimensional of 1.9±0.8° – even lower than those measured by our
changes as can be seen in an in vitro study by Herschdorfer
et al. who investigated the accuracy of implants placed group. Regarding translational deviations at the implant
with 3D-printed surgical guides (SLA, material jetting) base, they measured deviations in the three directions of: x
[20]
measured by angle deviation, entry point offset, and apex (0.3 ± 0.1 mm), y (0.1 ± 0.2 mm) and z (0.0 ± 0.1 mm) .
offset after scanning with a laboratory scanner. They found The calculated 3D deviation would therefore be 0.316 ±
the angle deviation without any further sterilization steps 0.245 mm, showing a higher accuracy in comparison to
[20]
to be 1.1–1.3°, the entry offset 0.19–0.23 mm, and the apex the PLA/PHA guides used in our study .
offset 0.32–0.36 mm . Guides printed with material jetting techniques such
[26]
One of the main challenges of healthcare these days is as MED610 were shown to have very low deviation values
[24]
to reduce the environmental burden of the fast-growing after steam sterilization and other resin-based prints
[34]
medical sector. As in other areas, the aim is to ensure also showed similar results . In both studies, very large
that the materials used are degradable or recyclable, or to guides incorporated with more than five teeth were printed.
replace materials currently in use with those possessing Furthermore, they did not investigate the effect of steam
these characteristics. In the surgical area, drilling or cutting sterilization on the accuracy of implant placement, which in
guides are commonly used aids that increase the accuracy authors’ opinion is a basic requirement for the indented use.
and safety in surgeries. Most resins used to produce In other studies, accuracy measurement of MED610
3D-printed materials can be potentially toxic and non- and other resins showed in vivo angle deviations of 2.72
biodegradable. Since the materials have to conform to the ± 1.42° and 3.85 ± 1.83° and a deviation at the implant
ISO standard 10993 for biological evaluation of medical base of 0.75 ± 0.34 mm and 1.05 ± 0.59 mm [28,29] , which
devices, the number of materials suitable for intraoral use were higher that the values measured in our study (angular
is limited . deviation: 1.10 ± 0.77° and deviation at the implant base:
[21]
Using PLA/PHA together with FFF is a not regular 0.36 ± 0.17 mm).
procedure in the medical field even though it reaches Comparing in vitro with in vivo results is difficult
accuracy levels comparable to those of established materials because of patient- and situation-related factors that affect
like resins in combination with digital light processing implant placement such as intraoral space and mobility.
(DLP) or material jetting [20,27] . Both techniques are already Based on a meta-analysis, the mean deviation and angular
established in the medical sector [28,29] . deviation in implant placement were 0.85 mm and 2.39°,
[35]
In this study, a combination of PLA and PHA was respectively ; clinical studies reported mean deviations
chosen because they could become more stable when of 1.40 mm and an angular mean deviation of 3.98°. The
heated during steam sterilization. Preliminary, unpublished authors did not report any problems arising from this
studies indicate that steam sterilization has no negative deviation. Keeping this in mind and considering the high
effect on the biocompatibility in terms of cytotoxicity of deviation values in clinical studies as well as the comparable
printed PLA/PHA guides and show only slight deviations low deviation values measured in other in vitro studies
from the original STL dataset after printing. which were similar to those measured in our study, it can
be concluded that even after sterilization, the PLA/PHA
Implant deviations at the implant base and the apex
using PLA/PHA and MED610 surgical guides were shown guides would still attain a sufficient accuracy level.
to be comparable to deviations in other studies using Main limitations of the present study were the in vitro
digital light processing or SLA printing techniques with design, which could have led to an overestimation of
resins (PLA/PHA: 0.38 ± 0.53 mm; DLP: 0.99 ± 0.57 mm; accuracy. An in vitro model does not fully reflect the clinical
SLA: 1.25 ± 0.49 mm) [20,30-32] . FFF-printed PLA was shown situation since implant placement is much easier and the
in a study that it did not reach the accuracy for fitting on model’s structure differs from human bone. Furthermore,

Volume 9 Issue 2 (2023) 83 https://doi.org/10.18063/ijb.v9i2.655