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. 2019 Apr;92(2):172-177.
doi: 10.15386/mpr-985. Epub 2019 Apr 25.

A comparative evaluation of fracture load of monolithic and bilayered zirconia crowns with and without a cervical collar: an in vitro study

Mainak Kanti Saha  1 , Surbhi Bansal  1 , Vandana Pathak  1 , Shivani Bhardwaj  1 , Astha Chauhan  2 , Amit Singh Nirwan  3
Affiliations

A comparative evaluation of fracture load of monolithic and bilayered zirconia crowns with and without a cervical collar: an in vitro study

Mainak Kanti Saha et al. Med Pharm Rep. 2019 Apr.

Abstract

Introduction: The use of zirconia based all-ceramic restorations are preferred nowadays owing to superior biologic and esthetic properties. However, these restorations have also reported higher incidences of fracture and chipping. The clinical success may be enhanced by optimizing the core design, through the introduction of monolithic zirconia, or the layered crowns can be strengthened by adding the cervical collar to them.

Objective: This study was performed with the objective to compare and evaluate the fracture load of monolithic and bilayered zirconia crowns with and without a cervical collar.

Methods: A prospective observational study was carried out to compare 45 fabricated zirconia crowns of three different designs on a customized metal mould. The samples were oriented on the metal mould and subjected to confocal microscope for the evaluation of marginal integrity followed by cementing the crown on the metal mould and subjecting it to the universal testing machine for the analysis for the flexural strength. Data were analyzed using one way Anova and t- test for inter and intra groups. The significance level was set at P ≤ 0.05.

Results: The monolith zirconia crowns and layered zirconia crowns with cervical collar reported more flexural strength.

Conclusion: The amount of force required to fracture the zirconia crowns was higher in the case of monolith zirconia crown and layered zirconia crown with cervical collar as compared to the layered zirconia crown without cervical collar.

Keywords: bilayered; flexural strength; monolithic; zirconia.

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Figures

Figure 1
Figure 1
Custom made metal mold.
Figure 2
Figure 2
Zirconia crowns. Group 1: bilayered zirconia crowns with standard coping for core veneer crowns with additional 1 mm cervical zirconia collar. Group 2: monolithic anatomic contour crown. Group 3: bilayered zirconia crowns with standard coping for core veneer crowns.
Figure 3
Figure 3
Confocal Microscopic analysis of Zirconia crowns to evaluate for the marginal integrity. (a) shows the evaluation of cement space under the confocal microscopy prior to cementation of the crown to the metal mold (b) shows evaluation of cement space under the confocal microscopy after the cementation of the crown to the metal mold. It was seen that there was minimum or no discrepancies in cement space both before and after cementation hence marginal integrity of the crown was maintained both before and after cementation.
Figure 4
Figure 4
Samples placed in water assembly for Testing of flexure strength.
Figure 5
Figure 5
Mean values of the force ( Newtons).
See this image and copyright information in PMC

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