149
PEEK is another polymer usually used in prosthodontics due to its good biocompatibility, and mechanical and physical properties. PEEK is a semi-crystalline thermoplastic biomaterial with the chemical formula of (-C 6 H 4 -O-C 6 H 4 -O-C 6 H 4 -CO-) n ,
and is part of the poly(aryl ether ketone) (PAEK) family. 3D-printed PEEK-based
fixed crowns and bridge frameworks have been successfully developed to replace
the metal structures. YM values of reinforced PEEK have ranged from 15 to 83 GPa,
e.g. carbon-fiber reinforced PEEK (18 GPa) (Sandler et al. 2002), glass-fiber reinforced PEEK (12 GPa) (Lee et al. 2012), thus being recommended as an ideal material for prosthetic reconstructions (Rho et al. 1993; Cavalli et al. 2004; Chun et al.
2014). However, due to its grayish brown color it is not suitable for aesthetic reconstructions without a resin composite coating. For this reason, air abrasion with and
without silica coating has been suggested to increase the adhesion of the composite
material (Stawarczyk et al. 2013). Etching with sulfuric acid has also been proposed
due to its chemical alterations on the PEEK surface, being more suitable for bonding with hydrophobic resin composites (Schmidlin et al. 2010; Najeeb et al. 2016).
In this sense, Stawarczyk et al. (2015) tested in vitro the mechanical resistance of a
three-unit fixed dental prosthesis manufactured from PEEK reinforced with 20 wt.%
inorganic fillers using different techniques based on CAD-CAM milled and pressed
from PEEK granules and pellets. These authors obtained a mean fracture load of
2354 N for CAD-CAM milled prosthesis, 2011 N for PEEK pellets and 1738 N for
granular PEEK (Stawarczyk et al. 2015). These values were significantly higher
compared to lithium disilicate glass ceramic (950 N), In-Ceram Alumina (851 N),
In-Ceram Zirconia (841 N), zirconia (981–1331 N) and PMMA composites (from
268 N to 467 N) (Beuer et al. 2008; Kolbeck et al. 2008; Stawarczyk et al.
2012, 2015).
Among the additive technologies, FDM 3D printing is mostly used to print customized PEEK parts (Honigmann et al. 2018). Polymers are also used for 3D printing models with various applications, such as functional models, study/diagnosis
models for treatment planning or didactic models, among others. An important
advantage of the RP models is the production of multiple copies without distortions
of the anatomy. Depending on the use of the model, specific requirements are
imposed. Models can be produced directly, using data acquired with intraoral scanners, and indirectly by scanning an impression. The dental prosthesis can be manufactured without a working model, but the fit between the abutment and the crown
cannot be assessed before insertion into the oral cavity. In addition, if the dental
crown/bridge need to be customized by ceramic layering, a working model is
mandatory.
Accuracy is mandatory for working models. Several studies carried out on orthodontic models have shown favorable results with printed polymers. Keeping this in
view, Hazeveld et al. (2014) compared three RP techniques for the manufacture of
polymeric molds: 3D printing (Z-Corp, Rock Hill, USA), DLP (Envisiontec,
Gladbeck, Germany), and jetted photopolymer (Objet Geometries, Rehovot, Israel).
These authors found that all three RP techniques were acceptable in terms of precision and reproducibility for their appropriate clinical use (Hazeveld et al. 2014). In
the same lines, Rebong et al. (2018) compared the dimensional accuracy of three
7 3D Printing-Processed Polymers for Dental Applications
PEEK is another polymer usually used in prosthodontics due to its good biocompatibility, and mechanical and physical properties. PEEK is a semi-crystalline thermoplastic biomaterial with the chemical formula of (-C 6 H 4 -O-C 6 H 4 -O-C 6 H 4 -CO-) n ,
and is part of the poly(aryl ether ketone) (PAEK) family. 3D-printed PEEK-based
fixed crowns and bridge frameworks have been successfully developed to replace
the metal structures. YM values of reinforced PEEK have ranged from 15 to 83 GPa,
e.g. carbon-fiber reinforced PEEK (18 GPa) (Sandler et al. 2002), glass-fiber reinforced PEEK (12 GPa) (Lee et al. 2012), thus being recommended as an ideal material for prosthetic reconstructions (Rho et al. 1993; Cavalli et al. 2004; Chun et al.
2014). However, due to its grayish brown color it is not suitable for aesthetic reconstructions without a resin composite coating. For this reason, air abrasion with and
without silica coating has been suggested to increase the adhesion of the composite
material (Stawarczyk et al. 2013). Etching with sulfuric acid has also been proposed
due to its chemical alterations on the PEEK surface, being more suitable for bonding with hydrophobic resin composites (Schmidlin et al. 2010; Najeeb et al. 2016).
In this sense, Stawarczyk et al. (2015) tested in vitro the mechanical resistance of a
three-unit fixed dental prosthesis manufactured from PEEK reinforced with 20 wt.%
inorganic fillers using different techniques based on CAD-CAM milled and pressed
from PEEK granules and pellets. These authors obtained a mean fracture load of
2354 N for CAD-CAM milled prosthesis, 2011 N for PEEK pellets and 1738 N for
granular PEEK (Stawarczyk et al. 2015). These values were significantly higher
compared to lithium disilicate glass ceramic (950 N), In-Ceram Alumina (851 N),
In-Ceram Zirconia (841 N), zirconia (981–1331 N) and PMMA composites (from
268 N to 467 N) (Beuer et al. 2008; Kolbeck et al. 2008; Stawarczyk et al.
2012, 2015).
Among the additive technologies, FDM 3D printing is mostly used to print customized PEEK parts (Honigmann et al. 2018). Polymers are also used for 3D printing models with various applications, such as functional models, study/diagnosis
models for treatment planning or didactic models, among others. An important
advantage of the RP models is the production of multiple copies without distortions
of the anatomy. Depending on the use of the model, specific requirements are
imposed. Models can be produced directly, using data acquired with intraoral scanners, and indirectly by scanning an impression. The dental prosthesis can be manufactured without a working model, but the fit between the abutment and the crown
cannot be assessed before insertion into the oral cavity. In addition, if the dental
crown/bridge need to be customized by ceramic layering, a working model is
mandatory.
Accuracy is mandatory for working models. Several studies carried out on orthodontic models have shown favorable results with printed polymers. Keeping this in
view, Hazeveld et al. (2014) compared three RP techniques for the manufacture of
polymeric molds: 3D printing (Z-Corp, Rock Hill, USA), DLP (Envisiontec,
Gladbeck, Germany), and jetted photopolymer (Objet Geometries, Rehovot, Israel).
These authors found that all three RP techniques were acceptable in terms of precision and reproducibility for their appropriate clinical use (Hazeveld et al. 2014). In
the same lines, Rebong et al. (2018) compared the dimensional accuracy of three
7 3D Printing-Processed Polymers for Dental Applications