Influence of the Type and Thickness of Cervical Margins on the Strength of Posterior Monolithic Zirconia Crowns: A Review

Abstract

Objective The aim of this research is to review the literature for the influence of the thickness and shape of cervical margins on the strength of posterior monolithic zirconia crowns. Materials and Methods Studies to assess the fracture resistance of monolithic zirconia crowns with different types of cervical margins, published from 2014 to 2020, were searched using the electronic database PubMed and Google Scholar using the following keywords: “monolithic zirconia,” “translucent,” “shoulderless,” and “margin preparation design.” Results Analysis of studies has shown that overall the design of the margin would have a significant effect on the strength of these crowns. Monolithic zirconia crowns with a knife-edge margin have shown a breaking load higher than the maximum chewing force of humans. Conclusion It would be safe to suggest the utilization of posterior monolithic zirconia crowns with vertical preparation. As the new translucent monolithic zirconia crowns are recent, further studies would be needed to guide the selection of the appropriate minimum thickness of the knife-edge margin to meet the clinical guidelines for their use.

Influence of the Operator`s Experience, Working Time, and Working Position on the Quality of the Margin Width: In Vitro Study

“…The fracture resistance of all-ceramic restorations, especially in the case of posterior crowns is a controversial topic in the research literature. According to Camille Haddad and Kathy Azzi, the marginal design of the abutment significantly affects the resistance of these aesthetic restorations [ 21 ]. Beuer et al reported that the shoulder margin provided a higher fracture resistance than the deep chamfer and chamfer margins [ 22 ].…”

“…The heavy chamfer finish line is recommended for posterior aesthetic restorations since it improves the biomechanical performance of posterior single zirconia crowns [ 25 ]. In an article-type review performed by Camille Haddad and Kathy Azzi, the conclusions showed that the monolithic zirconia crowns with knife-edge margins displayed superior fracture resistance at maximum occlusal forces compared to other types of finish lines [ 21 ].…”

Evaluation of the machinability and machining accuracy of polymer-based CAD/CAM blocks using merlon fracture test model

“…Based on the results of the machinability and machining accuracy tests of polymer-based CAM blocks using the merlon fracture test model specified in ISO 18675, the two null hypotheses established before the experiments were rejected. It was found that the thickness of dental prostheses manufactured in dental clinics is generally 0.5 mm or higher 43,44) ; however, the marginal area of the dental prostheses -prone to chipping and microfractures-should be 0.5 mm thick or lower. Therefore, the thicknesses considered in this study (0.1, 0.2, and 0.3 mm) are appropriate for evaluating the machinability to simulate the condition of dental prosthesis fabrication.…”

Influences of Different CAD/CAM Ceramic Compositions and Thicknesses on the Mechanical Properties of Ceramic Restorations: An In Vitro Study

“…A ceramic thickness in the range of 0.5–1 mm can be used for the fabrication of veneers [ 30 ], while a thickness of at least 1.5 mm has shown to be appropriate for the fabrication of full-coverage CAD/CAM ceramic restorations [ 12 , 31 ]. Previous studies demonstrated an acceptable fracture resistance of monolithic zirconia crowns with a 0.5 mm thickness fabricated on the posterior molars [ 32 , 33 ]. However, further research using other types of ceramics, such as ZLS, ALD, LD, and LE, is still required.…”