Crown margin design and the marginal strength of multilayered zirconia: A step towards clinical relevance using the hoop-strength approach
Year: 2025
Type: article
Abstract: Objectives A demand for clinically relevant assessment of materials has been claimed mandatory for better understanding clinical design issues over pure material behavior. Here we focus on a strength test on dome-like half-spheres which serves to simulate the marginal fracture type in single crowns. On the example of a multilayer chairside zirconia material, we aimed to investigate the influence of cervical margin design on crown strength, thereby correlating numeric stress analysis with experimental strength testing assisted by fractographic post-processing. Materials and methods Ninety dome-like half-spheres were CAD/CAM manufactured in a chairside milling unit (PrimeMill, DentsplySirona) using a 4/5Y-PSZ zirconia multilayer chairside block (e.max ZirCAD MT Multi; Ivoclar). Three design variations were designed to simulate a clinical “shoulder”, “chamfer”, and “taper” preparation. A tapered (7°) hardened steel load piston was used to uniaxially load the domes to fracture by inducing radial hoop stress onto the margins. Fractographic post-processing was performed to confirm the fracture mode at cervical margins. Finite element modelling served to analyze the maximum principal stress (σ MPS ). Weibull statistics were applied on the σ MPS data. Results Characteristic fracture forces were 744.3 N for shoulder, 651.1 N for chamfer, and 551.2 N for tapered margin designs. Fracture forces translated into characteristic strength and Weibull moduli of σ MPS = 1588.8 MPa (m = 9.2), σ MPS = 1616.5 MPa (m = 11.1), and σ MPS = 1468.8 MPa (m = 7.6). Fracture initiation was confirmed in the region of dome margins. Significance The margin design had a significant influence on fracture strength, as a significant drop of σ MPS at fracture was observed for the taper design. Fractography proved the potential of the test setup to trigger marginal fractures.
Source: Dental Materials
Authors: U. Lohbauer, J. Mayer, L. Schwamberger, R. Belli, S. Wartzack
Institution: Friedrich-Alexander-Universität Erlangen-Nürnberg
Language: English
Subfield: Orthodontics
Field: Dentistry
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $4,560
OpenAlex ID: W4415313181