Page 168 - IJB-9-5

International Journal of Bioprinting Guide about the effects of sterilization on 3D-printed materials for medicine

Given the biocompatibility and heat-resistance, a practical point of view. This is in accordance with
both MED610 and Surgical Guide resins stand as good previous works . For instance, Msallem et al. found
[54]
[55]
options to produce surgical guides and positioning guides that SLS PA12 is the most accurate material and has better
in contact with mucous for less than 24 h (following heat resistance when they compared the mechanical
biocompatibility testing). MED610 has a good mechanical performance of a 3D-printed dry human bony mandible,
resistance after being sterilized by HPO and AU121, and made of polyamide (PA) (SLS), White V4 resin (SLA),
thus, it is a more solid option. This result is in line with VERO (MJ), PLA (FFF) and four other binder jetting
Gielisch et al. who compared the behavior of polylactide/ materials, sterilized by different methods.
[46]
polyhydroxyalkanoate (PLA/PHA) surgical guides printed Additionally, it is important to highlight that PA12
by FFF and MED610 guides printed by MJ in fully is commonly used in surgical guides because according
guided dental implant placement before and after steam to EN ISO 10993-1, PA12 is a material that is chemically
sterilization, and the study found significant deviations in and physically durable and biocompatible . However, it
[56]
angles and accuracy in the PLA/PHA guide as compared to has a main drawback, which is the dust formed at where
the MED610 guide. MED610 and Surgical Guide resin can mechanical friction forces are applied.
also be used for the production of custom-made medical
devices to support treatments with materials needing skin PA12 represents a good candidate of hard and
or mucous contact for less than 24 h [47,48] . resistant material for the production of patient-specific
cutting and positioning guides, as well as custom-made
VERO and Durable, although do not have
biocompatibility tested for mucous contact, are good medical devices.
alternatives to produce material that do not have to be 4.2. Tissue-material-mimicking comparison
in contact with patients, such as anatomical models and Producing anatomical models is a common application
material for education and simulation purposes. Durable of 3D printing in healthcare sector. These models are
is normally used for low-friction assemblies and impact- usually used for training, simulation or enhancing the
resistant applications; however, very few information comprehension and communication between patients
regarding its biocompatibility and sterilization resistance and clinicians. However, most of the present 3D-printable
is provided by the manufacturer . VERO is used for the materials are far from being mechanically comparable to
[49]
production of custom-made bone and tissue simulators, the behavior of human tissues and therefore lack a certain
such as the case presented by Lioufas et al. . tactile realism. Figure 10 shows the comparison of different
[50]
4.1.3. Liquid resin flexible/elastic materials (SLA, MJ) data obtained from different research papers [57-62] with the
SLA and MJ flexible materials such as Elastic Clear (MJ) or mechanical properties of the 3D-printed materials used
Elastic 50 and Flexible 80 (SLA) are normally used for the in this work. The Surgical Guide resin material is the best
production of anatomical models mimicking vessels or soft material for mimicking hard tissues such as the bone.
tissues . According to the presented results, overall, the However, the analyzed materials were unable to mimic the
[51]
elastic materials become harder after different sterilization softness of tissues such as those in liver or heart. This means
methods are applied. This is consistent with Told et al. that for these tissues, it is necessary to find softer materials
[37]
and Fuentes et al. . Although the main application of which have been previously analyzed by Tejo-Otero
[53]
[62]
elastic materials is the production of anatomical models et al. . Figure 12 shows a comparison of Shore hardness
for surgical training and education, most of them fail in between the elastic materials shown in the present paper and
mechanically mimicking the behavior of real human tissue those in other studies, in which the Shore hardness of soft
(Figure 10). Moreover, there is still a lack of mucous- tissue has been investigated [62-65] . The Shore hardness values
biocompatible soft materials, which could have an of the elastic materials fall within the range of Shore A, while
important impact on the improvement of patient-specific those of the soft tissues fall within the range of Shore 00.
temporary implants, such as stents. This implies that, even if the mentioned materials are closer
to other materials in terms of hardness/softness, they are
4.1.4. Powder polymeric material (SLS) not the best materials used for mimicking soft tissues. This
Powder polymeric materials printed using SLS technology shows that in tissue-mimicking applications, other softer
tend to have good resistance to heat. According to this materials, such as hydrogels or silicones, must be used.
work, PA12 could be sterilized following any of the
studied sterilization processes (HPO, AU121, and AU134); 4.3. Contribution of the current work
although few mechanical properties were affected, their This current work presents practical testing complemented
minor changes were not found to be significant from with a literature review, bringing in new insights into

Volume 9 Issue 5 (2023) 160 https://doi.org/10.18063/ijb.756