Table 1.

In vitro studies included in the review

Study (year)	Application	Materials tested	Outcomes
Stawarczyk et al. (2015) [20]	FDPs	CAD-CAM milled PEEK Pressed pellet PEEK Pressed granular PEEK (n = 15/group)	Higher mean fracture load (2.354 N) for milled FPDs than those pressed from granular PEEK (1.738 N)
Stawarczyk et al. (2013) [22]		CAD-CAM PEEK (n = 225)	Μean fracture load of 1383 N Plastic deformation starting approximately at 1200 N
Niem et al.(2019) [23]		CAD-CAM PEEK Zirconia Lithium disilicate glass-ceramic (n = 10/group)	PEEK exhibited higher modulus of resilience than lithium disilicate Comparable to that of gold alloy
Niem et al. (2019) [24]		CAD-CAM PEEK Ceramic Composite and Polymer-based materials (n = 10 /group)	Flexural strength and modulus of elasticity of PEEK not significantly influenced by thermocycling
Liebermann et al. (2016) [25]		PEEK Hybrid material Composite resins PMMA-based materials (n = 40/group)	PEEK demonstrated: The lowest solubility and water absorption Similar hardness parameters to PMMA-based materials
Taufall et al. (2016) [26]		CAD-CAM PEEK veneered with different methods (digital veneering, conventional veneering with crea.lign, conventional with crea.lign paste, and pre-manufactured veneers) (n = 30/group)	The digital veneering showed the highest fracture load resistance
Cekic-Nagas et al. (2018) [27]		CAD-CAM PEEK PMMA Composite resin and fiber-reinforced composite materials (n = 7/group)	Highest load bearing capacity for PEEK
Wimmer et al. (2016) [28]		CAD-CAM PEEK Nanohybrid composite PMMA-based material (n = 12/ group)	Significantly higher wear resistance for PEEK
Wachtel et al. (2019) [29]	IFDPs	CAD-CAM PEEK screw-retained crowns on titanium implants (n = 10)	Favorable fracture mode for PEEK compared to conventional materials Coronal displacement of bending points No screw loosening or veneer fracture
Sirandoni et al. (2019) [30]		CAD-CAM PEEK PMMA Zzirconia Co-Cr Ti	Highest deformation for PEEK and PMMA frameworks that decreased von Mises stresses in the frameworks, implants and abutments PEEK exhibited critical tensile stress values in the trabecular bone
Nazari et al. (2016) [31]		CAD-CAM PEEK Zirconia Nickel-chromium alloy (n = 10/group) 3-unit IFDPs on two implants	Failure loads: Zirconia 2086 ± 362 N nickel-chromium alloy 5591 ± 1200 N PEEK 1430 ± 262 N
Elsayed et al. (2019) [32]		CAD-CAM PEEK Zirconia Lithium disilicate crowns supported by titanium and zirconia implant abutments (n = 8/group)	High fracture resistance of PEEK crowns, comparable to zirconia and lithium disilicate
Jin et al. (2019) [33]		CAD-CAM PEEK and titanium frameworks veneered with composite resin n = 20/group	PEEK exhibited Higher shear bond strength than Ti, good marginal fit and fracture resistance (1518 N)
Preis et al. (2017) [1]		CAD-CAM PEEK Zirconia-reinforced lithium silicate ceramics Composite resins Zirconia (n = 8/group)	PEEK molar implant-supported crowns showed lower fracture resistance than zirconia crowns Total failure rate of PEEK screw-retained frameworks veneered with composite paste
Yilmaz et al. (2018) [34]		Seven different CAD-CAM HPPs 100% PEEK 80% PEEK with 20% filler 80% PEKK with 20% filler Ceramic reinforced PEEK Interlaced fiberglass and resin Fiber-composite material New generation cubic zirconia 3Y-TZP Zirconia	Higher fracture resistance for zirconia implant-supported frameworks with cantilevers than PEEK-based materials
Ghodsi et al. (2018) [35]		CAD-CAM PEEK Zirconia Composite (n = 12/group)	No clinically acceptable marginal gaps for PEEK No significant differences observed in retention forces
Zeighami et al. (2019) [36]		CAD-CAM PEEK Zirconia, Composite (n = 12/group)	Better marginal adaptation for zirconia than PEEK
Chen et al. (2019) [37]	RPDs	CAD-CAM PEEK Co-Cr Ti alloys	PEEK caused lower stresses on periodontal ligament and higher stresses on the mucosa
Tribst et al. (2020) [38]		PEEK Polyamide Polyoxymethylene Gold alloy Titanium CoCr	Polyoxymethylene and PEEK exhibited the lowest retentive forces
Peng et al. (2019) [39]		PEEK CoCr alloy	No significant difference in the long-term deformation
Muhsin et al. (2018) [40]		CAD-CAM PEEK granular PEEK Co-Cr casting alloy (n = 10/group)	Higher retentive force for milled PEEK clasps than thermopressed clasps Higher retentive forces for PEEK clasps at deeper undercuts with a thicker clasp design than Co-Cr clasps after 3 years of fatigue simulation
Negm et al. (2019) [41]		CAD-CAM Milled PEEK Thermo-pressed PEEK (n = 10/group)	Higher fit and trueness for directly milled frameworks
Arnold et al. (2018) [42]		CAD-CAM Milled PEEK Cast metal frameworks with different techniques (n = 12/group)	PEEK RPD frameworks have better precision and fit than metal frameworks fabricated using different techniques
Hada et al. (2020) [43]	Complete denture framework	PEEK Fiber-reinforced composite Nano-zirconia cobalt-chromium-molybdenum alloy (n = 6group)	PEEK provides lower reinforcement than the other materials
Emera et al. (2019) [5]	Double-crown-retained Removable Dental Prostheses	Zirconia or PEEK primary crowns Zirconia or PEEK secondary crowns	Telescopic attachments fabricated from zirconia primary crowns and PEEK secondary crowns exhibited the lowest stresses transmitted to the implants
Schubert et al. (2019) [44]		Implant-supported zirconia primary crowns with electroformed secondary crowns or CAD-CAM PEEK secondary crowns (n = 10/group)	Stable retentive force values over 10 years of simulated aging for PEEK secondary crowns
Merk et al. (2016) [45]		Zirconia primary crowns Secondary PEEK crowns of different taper and manufacturing methods; milled from PEEK blanks; thermo-pressed from PEEK pellets; thermo-pressed from granular PEEK (n = 10/group)	Fabrication method and taper angle had no consistent effect on retentive forces within different groups
Stock et al. (2016) [46]		Zirconia primary crowns Secondary PEEK crowns of different taper and manufacturing methods; milled from PEEK blanks; thermo-pressed from PEEK pellets; thermo-pressed from granular PEEK (n = 30/group)	Milled 0° tapered PEEK crowns presented the lowest retention force Milled 2° tapered PEEK crowns had the highest retention force values Retention force of pressed PEEK not influenced by the taper angle Decrease of retention after the first twenty pull-off cyclew for pressed PEEK
Wagner et al. (2018) [47]		PEEK telescopic crowns and cobalt chrome copings of different taper and manufacturing methods (n = 10/group)	Stable retention load values for each test group
Stock et al. (2016) [48]		Milled PEEK primary and cobalt-chromium (CoCr), zirconia (ZrO2) and galvanic (GAL) secondary crowns with three different tapers (n = 30, 10/taper)	Milled PEEK can be used as primary crown material with high retentive forces in combination with secondary zirconia, cobalt-chromium or electroformed crowns
Benli et al. (2020) [11]	Occlusal splint	CAD-CAM PEEK Vinyl acetate Polymethyl methacrylate Polycarbonate Polyethyleneterephthalate (n = 12/group)	After chewing simulation PEEK occlusal splints exhibited lower loss of volume and lower roughness alteration compared to other CAD-CAM materials
Benli et al. (2020) [49]	Intra-radicular posts	Milled PEEK Glass-fiber Cast-metal (n = 20/group)	PEEK posts exhibited the highest tensile bond strength and the lowest surface roughness
Kaleli et al. (2018) [9]	Implant abutments	PEEK and zirconia customized abutments	Finite element analysis showed higher stress values in restorative crowns for PEEK abutments
Abdullah et al. (2016) [50]	Provisional crowns	PEEK VITA CAD Temp Telio CAD-Temp Protemp 4	PEEK demonstrated superior fit and fracture strength than other materials