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Title: 1743 - In Vivo Low Thermal Degradation of Monolithic Zirconia Restorations

Authors:

Vinciane Koenig (Presenter)
Dental Biomaterials Research Unit (d-BRU), University of Liège (ULiège)

Claudine Wulfman, Unité de Recherches en Biomatériaux Innovants et Interfaces (URB2i) – EA442, Université Paris Descartes
Nathalie Dupont, Dental Biomaterials Research Unit (d-BRU), University of Liège (ULiège)
Sandrine Bekaert, Dental Biomaterials Research Unit (d-BRU), University of Liège (ULiège)
Stéphane Le Goff, Unité de Recherches en Biomatériaux Innovants et Interfaces (URB2i) – EA442, Université Paris Descartes
Maher Eldafrawy, Dental Biomaterials Research Unit (d-BRU), University of Liège (ULiège)
Guillaume Martin, Dental Biomaterials Research Unit (d-BRU), University of Liège (ULiège)
Alain Vanheusden, Dental Biomaterials Research Unit (d-BRU), University of Liège (ULiège)
Amélie Mainjot, Dental Biomaterials Research Unit (d-BRU), University of Liège (ULiège)

Abstract:

Objectives: To evaluate In vivo low thermal degradation (LTD) of zirconia monolithic implant and tooth restorations, particularly in-mouth zirconia crystalline microstructure changes, as well as influence of occlusal stress and glaze protection on this process. Secondary objectives included the investigation of restorations’ general clinical behaviour and material wear.

Methods: 75 posterior monolithic zirconia crowns and bridges (total: 101 tooth elements) (Lava Plus, 3M ESPE) were included. On each element, several areas were determined: submitted and non-submitted to mastication mechanical stress, glazed and non-glazed. Before prosthesis placement, ex vivo analyses regarding LTD and wear were performed using Raman spectroscopy, SEM analysis and 3D laser profilometry. After placement, restorations were clinically evaluated following FDI criteria, complemented by the analysis of fracture clinical risk factors. Clinical evaluation and ex vivo analyses were repeated after 6 months and then each year for up to 5 years.

Results: Elements were evaluated at baseline (n=101), 6-months (n=101) and 1-year (n=96) follow-up. 59.6% of patients suffered from bruxism. The element transformation rate (TR), defined as the percentage of elements in which transformation was detected, was 17.8% at baseline (due to occlusal grinding) and 41.1% at 1 year. Elements showing a monoclinic volumetric fraction > 50% (Cri-TR), was of 7.9% at baseline and 8.4% at 1 year. 14.5% of buccal/palatal and 7.6% of occlusal contact point areas (OCA) exhibited transformation. Monolithic zirconia restorations showed a survival rate of 93.3% and a success rate of 84.0% after a mean observation period of 391.2 ± 58.3 days. No significant zirconia wear was observable, unlike glaze, which wore out.

Conclusions: TR and Cri-TR increase indicated that zirconia LTD developed In vivo after one year. Yet, this process had no impact on the clinical performance of restorations. Pull-out process of transformed zirconia grains could explain the lower TR of OCA compared to buccal/palatal areas.

Student Presenter

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: None

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