151
treatment before scheduling the surgery. This simulation can also help the surgeon
choose the appropriate instruments and techniques to increase predictability and
reduce surgical time. The virtual simulation is of the great importance for orthognathic surgery, which mainly includes bilateral sagittal split osteotomy, genioplasty
and LeFort I osteotomy. Additive manufacturing technologies from polymers in
orthognathic surgery is used for 3D printed model fabrication, implant trimming,
occlusal splints, osteotomy/cutting guides, repositioning guides and spacers (Lin
et al. 2018).
Bone grafting is a common procedure in oral and maxillofacial surgery. Despite
the large number of polymeric materials and various additive manufacturing techniques proposed by different research groups, only a few synthetic polymers have
so far had successful clinical applications, namely: PEEK and PMMA (Cristache
et al. 2018a). In addition, the most documented materials used in the clinical setting
for autologous bones, cranial reconstruction, post trauma, and tumor resection or
congenital deficiencies have been titanium (Ti), HA, PEEK and PMMA (MartinezSeijas et al. 2018). In line with this, van de Vijfeijken et al. (2019) replaced PMMAbased cranioplasty after 15 years with 3D-printed PEEK, due to its fracture. The
fractured piece was compared to a freshly prepared PMMA sample cured for 30 min
at atmospheric pressure and 2.2 bar, observing that the sample after 15 years under
in vivo conditions showed a significant increase in porosity, while no changes in
molecular weight or flexural strength were observed. However, the 2.2 bar cured
sample had significantly greater flexural strength (van de Vijfeijken et al. 2019).
7.3.3 3D Printed Polymers for Maxillofacial Prosthodontics
Maxillofacial prostheses are used to replace missing facial and body tissues due to
congenital malformation, disease, surgery or trauma. The manufacture of such a
device is considered more of a work of art, and requires a lot of time and effort to
reproduce. The facial prosthesis is conventionally manufactured from a pigmented
silicone rubber, with a color matching the surrounding tissues, based on
poly(dimethylsiloxane) (PDMS), which has good biocompatibility, chemical resistance, durability, mechanical properties, is physiologically inert and thermoset in a
wide range of temperatures. Depending on the polymerization reaction of the crosslinker with PDMS chains, the silicon elastomer used for the manufacture of facial
prostheses can be heat vulcanized (HTV) or room temperature vulcanized (RTV)
(Huber and Studer 2002). Due to the lack of high-quality, color-matched elastomeric silicones with printing properties suitable for facial prostheses, 3D printing
technology is used to print the prostheses using hard materials to manufacture a
2-part mold, or the mold is printed directly on moldable wax and the final prosthesis
is fabricated from conventional silicone (Unkovskiy et al. 2017). For example,
Jindal et al. (2016) developed direct printing materials and technique by customizing a fused deposition modelling printer by replacing the heated nozzle and print
bed, and making it suitable for the proposed two -component RTV silicones with
7 3D Printing-Processed Polymers for Dental Applications
treatment before scheduling the surgery. This simulation can also help the surgeon
choose the appropriate instruments and techniques to increase predictability and
reduce surgical time. The virtual simulation is of the great importance for orthognathic surgery, which mainly includes bilateral sagittal split osteotomy, genioplasty
and LeFort I osteotomy. Additive manufacturing technologies from polymers in
orthognathic surgery is used for 3D printed model fabrication, implant trimming,
occlusal splints, osteotomy/cutting guides, repositioning guides and spacers (Lin
et al. 2018).
Bone grafting is a common procedure in oral and maxillofacial surgery. Despite
the large number of polymeric materials and various additive manufacturing techniques proposed by different research groups, only a few synthetic polymers have
so far had successful clinical applications, namely: PEEK and PMMA (Cristache
et al. 2018a). In addition, the most documented materials used in the clinical setting
for autologous bones, cranial reconstruction, post trauma, and tumor resection or
congenital deficiencies have been titanium (Ti), HA, PEEK and PMMA (MartinezSeijas et al. 2018). In line with this, van de Vijfeijken et al. (2019) replaced PMMAbased cranioplasty after 15 years with 3D-printed PEEK, due to its fracture. The
fractured piece was compared to a freshly prepared PMMA sample cured for 30 min
at atmospheric pressure and 2.2 bar, observing that the sample after 15 years under
in vivo conditions showed a significant increase in porosity, while no changes in
molecular weight or flexural strength were observed. However, the 2.2 bar cured
sample had significantly greater flexural strength (van de Vijfeijken et al. 2019).
7.3.3 3D Printed Polymers for Maxillofacial Prosthodontics
Maxillofacial prostheses are used to replace missing facial and body tissues due to
congenital malformation, disease, surgery or trauma. The manufacture of such a
device is considered more of a work of art, and requires a lot of time and effort to
reproduce. The facial prosthesis is conventionally manufactured from a pigmented
silicone rubber, with a color matching the surrounding tissues, based on
poly(dimethylsiloxane) (PDMS), which has good biocompatibility, chemical resistance, durability, mechanical properties, is physiologically inert and thermoset in a
wide range of temperatures. Depending on the polymerization reaction of the crosslinker with PDMS chains, the silicon elastomer used for the manufacture of facial
prostheses can be heat vulcanized (HTV) or room temperature vulcanized (RTV)
(Huber and Studer 2002). Due to the lack of high-quality, color-matched elastomeric silicones with printing properties suitable for facial prostheses, 3D printing
technology is used to print the prostheses using hard materials to manufacture a
2-part mold, or the mold is printed directly on moldable wax and the final prosthesis
is fabricated from conventional silicone (Unkovskiy et al. 2017). For example,
Jindal et al. (2016) developed direct printing materials and technique by customizing a fused deposition modelling printer by replacing the heated nozzle and print
bed, and making it suitable for the proposed two -component RTV silicones with
7 3D Printing-Processed Polymers for Dental Applications