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

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

En face OCT imagistic evaluation and laser microspectral analysis for assessing microleakage at the prosthetic interfaces

The microleakage at the prosthetic interface, for example between the metallic framework and the veneering part of the fixed partial prostheses (FPP's) is a common problem in dentistry. Optical tomographic techniques are of particular importance in the medical imaging field, because these techniques can provide non-invasive diagnostic images. En-face OCT is preferred for microscopy as it can provide real time images with similar orientation as that of microscopy images. The purpose of this study is to detect and analyze the possible defects at the interface of several FPP's using en face optical coherence tomography (efOCT) and laser microspectral analysis, a method which allows to investigate small quantities of materials of around 0.1 μg and to establish the content of atoms and molecules and to perform semi-quantitative and quantitative analysis. By this method it is possible to establish trace elements, i. e. with concentration of ppm (parts per million). The advantages of the OCT method consist in non-invasiveness and high resolution. En face OCT investigations permit to visualize a more complex stratified structure at the interface metallic framework/veneering material

IMAGING EVALUATIONS OF UNICA CERAMICS UNDER THERMAL CYCLE CONTROL CONDITIONS

Aim of the study: To evaluate the efficacy of Optical Coherence Tomography (OCT) in non-invasively monitoring temperature variations during ceramic sintering for dental prosthetics, emphasizing the importance of precise temperature control for optimal material properties and structural integrity. Materials and Methods: The study utilized OCT to examine 17 metal-ceramic restorations at various sintering temperatures (standard, 80°C below, and 50°C above the standard). The method involved generating 61 cross-sectional images per prosthesis to identify defects and structural changes. Results: OCT revealed significant insights into the impact of temperature deviations on ceramic microstructure, including uniform grain sizes at standard temperatures and areas of reduced retention at elevated temperatures, highlighting the technology’s potential in quality control. Conclusions: OCT offers a rapid, accurate, and non-destructive means to assess sintering temperatures and detect defects in dental ceramics, facilitating improvements in dental prosthetics’ fabrication process. The study advocates for OCT’s integration into routine dental laboratory practices to enhance prosthesis quality and reliability