Abstract
Calibration loss of ovens used in sintering metal ceramic prostheses leads to stress and cracks in the material of the prostheses fabricated, and ultimately to failure of the dental treatment. Periodic calibration may not be sufficient to prevent such consequences. Evaluation methods based on firing supplemental control samples are subjective, time-consuming, and rely entirely on the technician’s skills. The aim of this study was to propose an alternative procedure for such evaluations. Fifty prostheses were sintered in a ceramic oven at a temperature lower, equal to or larger than the temperature prescribed by the manufacturer. A non-destructive imaging method, swept source (SS) optical coherence tomography (OCT) was used to evaluate comparatively the internal structure of prostheses so fabricated. A quantitative assessment procedure is proposed, based on en-face OCT images acquired at similar depths inside the samples. Differences in granulation and reflectivity depending on the oven temperature are used to establish rules-of-thumb on judging the correct calibration of the oven. OCT evaluations made on a regular basis allow an easy and objective monitoring of correct settings in the sintering process. This method can serve rapid identification of the need to recalibrate the oven and avoid producing prostheses with defects.
Highlights
Dental ceramic materials are essential in producing prostheses to replace missing teeth or damaged dental structures
The aim of this paper is to evaluate the utility of an established biomedical imaging technique, optical coherence tomography (OCT), in establishing the correct settings used by ovens
The following aspects were determined for the groups of samples studied: Group N: a normal distribution of the reflectivity could be noticed (Figure 4(c1))
Summary
Dental ceramic materials are essential in producing prostheses to replace missing teeth or damaged dental structures. Non-metallic materials manufactured by heating raw minerals at high temperatures [1]. The issue is that materials like ceramics and glasses are brittle: they display a high compressive strength but a low tensile strength; they may be fractured under a low strain of only 0.1 to 0.2% [2,3]. Dental ceramics present disadvantages due mostly to their inability to withstand the functional (especially mastication) forces that are present in the oral cavity [3]. Shear Bond Strength Tests of Zirconia Veneering Ceramics after Chipping Repair.
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