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Comparison of marginal fit in zirconia-based all-ceramic frameworks (cercon) made by two approaches (Direct and Wax-up scanning)
Naser Golshah, Habib Hajimiragha, Saeed Nokar, Somayeh Zeighami,
Volume 25, Issue 1 (4-2012)
Abstract

Background and Aims: Since a large marginal opening allows more plaque accumulation, gingival sulcular fluid flow and bone loss, microleakage, recurrent caries and periodontal disease, marginal fit is of great importance in fixed restorations. The aim of this study was to compare the marginal fit of zirconium-based all ceramic (Cercon) frameworks, made by two different approaches (Direct and Wax-up scanning).

Materials and Methods: An abutment analog, with 5.5 mm width and height, was selected as an experimental model. Twenty all ceramic cores were made for this model (10 specimens per each group). In the first group (Direct), experimental models were scanned directly using Computer Aided Design/Computer Aided Manufacturing (CAD/CAM). The core was then designed with the aid of a computer and machined. In the second group (Wax-up or CAM) a wax-up pattern was made on the experimental model and then scanned and milled from Cercon blocks. The marginal discrepancy of each specimen was recorded using a stereomicroscope (SZX9, Olympus, Japan) and digital camera (Mode TK, C1380E, JVC, Japan) and then measured by Adobe Photoshop CS software. The data were analyzed using T-test.

Results: Mean marginal discrepancy of Direct group (85.2±3.95 µm) was significantly less than that of Wax-up group (120.2±6.91 µm).

Conclusion: Improved marginal fit of zirconia ceramics was found with the direct model scanning compared with that of Wax-up scanning using CAD/CAM.


A comparative evaluation of implant supported zirconia framework gap of two CAD/CAM systems
Narges Ameri , Hakimeh Siadat, Ahmad Reza Shamshiri, Marzieh Alikhasi,
Volume 29, Issue 2 (11-2016)
Abstract

Background and Aims: Marginal accuracy is a crucial factor influencing the clinical long-term reliability of implant-supported fixed dental prostheses (FDPs). The aim of this in vitro study was to evaluate the marginal fit of three-unit zirconia bridge frameworks fabricated using two different computer-aided design (CAD)/
computer-aided manufacturing (CAM) systems (AmannGirrbach and Zirkonzahn).

Materials and Methods: The master model of 3-unit FDP was made of two implant abutments (AmannGirrbach and Zirkonzahn) from canine to second premolar. Twelve frameworks were manufactured using each fabricating system from semi-sintered zirconia blanks, which had to be sintered for final density after milling. After manufacturing, the absolute marginal discrepancy in each abutment were determined by means of Video Measurement System (VMS). The data were analyzed, using independent and paired t test (P=0.05).

Results: For the premolar abutment, the absolute marginal discrepancy of frameworks fabricated by AmannGirrbach system was significantly greater than those of the other system (P=0.005). There was no significant difference between the marginal discrepancy of canine and premolar abutments (P>0.05).

Conclusion: Within the limitations of this study, it could be concluded that the marginal fit of zirconia FDPs was significantly dependent on the CAD/CAM system used, but the abutment size was not an effective factor.


Comparison between different veneering methods on failure of zirconia restorations; A review
Hoseinali Mahgoli, Somayeh Allahyari,
Volume 31, Issue 1 (6-2018)
Abstract
In recent years, the use of zirconia as a high-strength support for all-ceramic restorations has become widely accepted. The failure of zirconia restorations is mainly due to the weakness of veneering porcelain and other factors such as veneering approach. Except conventional hand layering, other methods such as pressing and digital veneering have been recently introduced and used. Meanwhile, the use of monolithic zirconia with no veneer is also a solution for reducing the rate of failure. The object of this review was to compare the failure of three available methods for veneering zirconia restorations in the literature and to compare with the monolithic zirconia. In the context of this overview, 42 articles were used between the years 2000 through the end of 2016 using the keywords of PubMed, google scholar search engines. In most articles, digital approach is the best way with low failure. mechanical properties of monolithic zirconia are reported to be higher than the zirconia veneered using hand layering method.

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