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Scanning Electron Microscopy Analyses of Dental Implant Abutments Debonded from Monolithic Zirconia Restorations Using Heat Treatment: An In Vitro Study

https://doi.org/10.3390/prosthesis4030041

“The aim of this in vitro study is to present a debonding protocol developed to remove a screw-retained, monolithic, zirconia restoration from its titanium-base abutment, and to microscopically evaluate the abutment integrity at both the prosthetic and connection levels. Materials and Methods: A total of 30 samples were tested. Each sample consisted of a monolithic zirconia restoration bonded on a titanium link abutment. Five different shapes were designed and fabricated. Randomly, one-third of the Ti-link abutments were subjected to an anodizing process. Then, all the zirconia samples were bonded to the Ti-link abutments according to a pre-established protocol. Forty-eight hours later, the samples were debonded according to the experimental protocol. The outcomes were evaluated by a visual inspection with an optical microscope, scanning electron microscopy (SEM), and chemical composition analysis. Results: Thirty samples were collected and visually analyzed. Seven samples were randomly evaluated via scanning electron microscopy. In all the examinations, no relevant changes were reported. Chemical composition analysis also relieved no changes in the chemical structure of the titanium. Conclusions: The titanium-base abutments do not alter the structure and properties of the material, not creating phase changes or the birth of oxides such as to induce fragility. Further clinical studies with longer follow-up periods are needed to confirm these preliminary results.”

“The SEM analyses were performed in two centers, one public centre in Warsaw (Warsaw University of Technology, Warsaw, Mazovia, Poland) and another private centre in Villafranca d’Asti, Italy (R&D Nobil Metal SpA). All the collected data were analyzed at the Department of Medicine, Surgery, and Pharmacy, University of Sassari, Italy.”

As no damages were found under stereomicroscopic analysis, the samples proceeded directly to the SEM inspection. More details can be found in the SEM images presented in Figure 6a–d. A conical part of the TBAs is compared in Figure 6a,b. As can be noticed, the contrast on the part after the thermal exposure is visibly less prominent, which may be related to a lower conductivity of the specimen or the presence of a very thin layer, which can hinder the escape of secondary electrons during observations. Both features can be linked to the presence of an oxide layer established during the thermal exposure of TBA. Higher magnification of the TBA in its initial condition reveals the patterns from the manufacturing process—the machining. The cementing and removal of the zirconia did not change those patterns, as seen in Figure 6d, but some slight changes on the surface can be noticed. Similar results were found for the anodized TBAs compared with the control and the new titanium-base abutment (Figure 7).
Figure 6. Test (a,c) and control (b,d) TBAs at 30× (a,b) and 500× (c,d).
Figure 7. Anodized (a,c) and control (b,d) TBAs at 85× (a,b) and 300× (c,d). The black spot in Figure 7d is related to the electric charge in the dust on the specimen’s surface.

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