Marginal accuracy of four‐unit zirconia fixed dental prostheses fabricated using different computer‐aided design/computer‐aided manufacturing systems

Abstract

Besides load-bearing capacity, marginal accuracy is a further crucial factor influencing the clinical long-term reliability of fixed dental prostheses (FDPs). The aim of this in vitro study was to evaluate the marginal fit of four-unit zirconia bridge frameworks fabricated using four different computer-aided design (CAD)/computer-aided manufacturing (CAM) systems. Ten frameworks were manufactured using each fabricating system. Three systems (inLab, Everest, Cercon) processed white-stage zirconia blanks, which had to be sintered to final density after milling, while with one system (Digident) restorations were directly milled from a fully sintered material. After manufacturing, horizontal and vertical marginal discrepancies, as well as the absolute marginal discrepancy, were determined by means of a replica technique. The absolute marginal discrepancy, which is considered to be the most suitable parameter reflecting restorations' misfit in the marginal area, had a mean value of 58 mum for the Digident system. By contrast, mean absolute marginal discrepancies for the three other systems, processing presintered blanks, differed significantly and ranged between 183 and 206 mum. Within the limitations of this study, it could be concluded that the marginal fit of zirconia FDPs is significantly dependent on the CAD/CAM system used, with restorations processed of fully sintered zirconia showing better fitting accuracy.

Microfractures in metal-ceramic and all-ceramic implant-supported fixed dental prostheses caused by superstructure fixation

“…The choice of zirconia material in this study, i.e., HIP zirconia ceramic versus presintered zirconia ceramic, had no effect on strain development in the all-ceramic frameworks. This result contradicted a study conducted by Kohorst et al 25) and a review published by Abduo et al 2) , which claimed that restorations made from fully sintered zirconia showed better fitting accuracy.…”

“…The contradicting results by Kohorst et al 25) as well as Vigolo and Fonzi 15) might be explained by the different study designs. In the current study, assessment was based on strain development, and hence fitting accuracy, using strain gage measurements 11) .…”

“…In the current study, assessment was based on strain development, and hence fitting accuracy, using strain gage measurements 11) . In the aforementioned studies 15,25) , assessment was based on marginal fit using gap measurements. As shown by Hegde et al 4) , microgap measurements had no correlation with increasing misfit and that the presence or absence of a microgap was not necessarily indicative of passivity.…”

Trueness of four different milling procedures used in dental CAD/CAM systems

“…The quality of the analysis is correlated to the number of measurement points [29]. Due to the necessary cutting process, there is a loss of information in the analogue twodimensional (2D) replica technique [20], and an evaluation based only on 2D is disadvantageous [30]. Analyses based on micro-computed tomography are also used [9,31].…”

Aesthetic All-ceramic Restorations: CAD-CAM System

“…Other investigations (Kohorst et al, 2009) in vitro assessed the marginal adjustment of four Zirconia bridges manufactured by 4 different systems of manufacturing assisted by computer (CAM). Three systems (inLab, Everest, Cercon) are presintered and had to be sintered to the final density after the milling, while with a system (Digident) the restorations were directly done with a material completely sintered.…”