Optical Properties and Color Stability of Dental PEEK Related to Artificial Ageing and Staining

Abstract

Considering that the processes of PEEK discoloration caused by either intrinsic or extrinsic factors require elucidation, the aim of this study was to investigate the long-term effect of the combined action of ageing and immersing solutions on the optical properties and color stability of PEEK material, related to surface processing (polishing or glazing). (2) Methods: This study aims to determine the influence of different ageing and staining protocols on optical properties, color changes, and surface roughness of a reinforced PEEK material (bioHPP, Bredent, Senden, Germany). For ageing, specimens were submitted to 5000 cycles in a 55 °C bath and a 5 °C bath filled with distilled water. For staining, thermal cycling was performed in a hot coffee bath (55 °C) and a bath filled with distilled water (37 °C) and in a cold juice bath (5 °C) and a bath filled with distilled water (37 °C). Translucency (TP) and opalescence (OP) parameters were determined, the total color change value (ΔΕ*) was calculated, specimens’ surface roughness was analyzed, and statistical analyses were performed. (3) Results: The mean TP values of the studied samples were in the interval of 1.25–3.60, which is lower than those reported for natural teeth or other aesthetic restoration materials. The OP values of PEEK were registered in the range of 0.27–0.75, being also lower than those of natural teeth or other aesthetic restoration materials. OP has a very strong positive relationship with TP. The mean registered Ra values for all subgroups were below 0.13 µm. Artificial ageing and staining in hot coffee proved to increase the roughness values. (4) Conclusions: The glazing of PEEK has a favorable effect on surface roughness and opalescence, irrespective of the artificial ageing or staining protocols. Artificial ageing damages the color stability and roughness of PEEK, regardless of surface processing, and decreases the translucency and opalescence of glazed surfaces. Immersion in hot coffee leads to perceivable discolorations.

Applications and Clinical Behavior of BioHPP in Prosthetic Dentistry: A Short Review

“…Rasheed et al state that the shear bond strength of PEEK is similar to that of zirconia, showing the advantage that with the right surface treatments it is also the best adhesive solution [12,27]. Furthermore, the PEEK crowns showed minimal abrasion, better stress modulation through plastic deformation, and good color stability, which makes it a promising alternative to zirconia for fabrication of the crown [28][29][30][31]. PEEK has a low specific weight that permits the fabrication of lighter prostheses, providing high patient satisfaction and comfort during function [32].…”

Clinical Applications of Polyetheretherketone in Removable Dental Prostheses: Accuracy, Characteristics, and Performance

“…PEEK is widely used to fabricate removable restorations, which are often manufactured using the conventional lost-wax technique, via heat-pressing pellets or granules, or using CAD/CAM techniques, which can be classified as subtractive or additive (3D printing) techniques [ 7 , 10 ].…”

“…Polishing removable dental prostheses to obtain a smooth surface and to provide a superior tongue feel is important [ 10 , 31 , 32 ]. Batak et al [ 8 ] used a contact profilometer to compare the Ra values of differently milled PEEK and its composite materials and investigated the effect of polishing on the Ra values of the polymer surfaces.…”

“…Even if sufficient polishing is achieved on the laboratory side, the surface of a prosthesis may need to be adjusted due to malocclusion and would then need to be polished to be smooth again. Moreover, artificial aging has been proven to increase roughness values [ 10 ]. Therefore, more effective and convenient chairside polishing protocols should be designed.…”

“…Discoloration, as one form of esthetic failure, is a relevant clinical problem [ 48 ]. The discoloration of dental prostheses after long-term use may be caused by intrinsic factors and extrinsic factors [ 10 , 48 ]. Intrinsic factors include water absorption, the dissolution of the matrix composition or fillers, chemical reactions, and the restoration of the manufacturing mode [ 49 ].…”