Chipping of ceramic‐based dental materials by micrometric particles

Abstract

Chipping caused by micrometric particles poses a threat to the structural integrity of modern dental prosthetic materials. It can degrade their fracture strength and cause wear of both artificial crowns and antagonist teeth. Here, surface chipping of the main types of commercial ceramic-based dental materials at the microcontact/particle level is investigated by means of indentation tests. Conical tips of different sizes (radii 20 and 200 μm) under axial and sliding loading are employed to simulate individual microcontacts. Both decreasing particle size and adding a lateral contact force decrease the chipping load below typical bite forces. Specific damage mechanisms are identified as predominantly brittle fracture in ceramics with small, equiaxed crystals, with significant quasiplastic damage in ceramics containing large, elongated crystals and composites. Critical loads for the occurrence of chipping are quantified (lowest values in equiaxed glass-ceramics; greatest in zirconia) and analyzed within the framework of fracture mechanics. The brittleness index (BI) is proposed as a simple indicator of the resistance to chipping of dental materials-the lower the BI, the greater the resistance. Special attention is paid to the effect of the materials' microstructure, which can result in transformation toughening (as in zirconia) or quasi-plastic behavior (as in lithium disilicate), both highly beneficial to increasing the chipping resistance. Finally, practical implications for the selection of current dental materials as well as for the development of novel materials with improved durability are discussed.

Effect of Post-Processing Heat Treatment on the Micro-Contact Damage of Zirconia-Reinforced Lithium Silicate Dental Materials

“…Elastic modulus, hardness and indentation fracture toughness values of 99 ± 6 GPa, 6.2 ± 0.2 GPa, and 0.70 ± 0.03 MPa•m 1/2 , respectively, were measured through Hertzian and Vickers tests in both as-received and heat-treated materials. In comparison to other dental glass-ceramics, ZLS materials generally exhibit improved mechanical properties, except for fracture toughness [4,6,7,17]. Lithium disilicate glass-ceramics, with their larger, interconnected crystals, demonstrate significantly higher toughness [7,17].…”

“…Test surfaces were subsequently examined by optical microscopy. For each test, critical chipping load was calculated from the corresponding microscopy image using the sliding speed and loading rate (more details in [6]).…”

“…Modern dental prosthetic crowns predominantly utilize ceramic materials and their composites, chosen based on aesthetic and mechanical requirements, often involving tradeoffs. Among available options, dental zirconias are renowned for their superior strength and wear resistance, albeit potentially presenting challenges in machinability and aesthetics compared to less robust materials such as glass-ceramics or ceramic-polymer composites [1][2][3][4][5][6][7][8].…”

“…A gap in the literature exists regarding the systematic examination of how post-processing treatments may impact the contact damage (e.g., fracture-induced chipping) of ZLS dental materials, beyond conventional mechanical property measurements. This is relevant because dental prosthetic crowns experience cyclic contacts against opposing dentition during chewing, involving a complex combination of axial and lateral forces, occasional bite overloads, and exposure to aggressive media where micron-sized abrasive particles may be present [6,10,11]. Mechanical degradation in the form of fracture and wear in turn has the potential to compromise the performance, strength and durability of the crown.…”

Effect of Post-Processing Heat Treatment on Micro-Contact Damage of Zirconia-Reinforced Lithium Silicate Dental Materials

“…Modern dental prosthetic crowns predominantly utilize ceramic materials and their composites, chosen based on aesthetic and mechanical requirements, often involving tradeoffs. Among available options, dental zirconias are renowned for their superior strength and wear resistance, albeit potentially presenting challenges in machinability and aesthetics compared to less robust materials such as glass-ceramics or ceramic-polymer composites [1][2][3][4][5][6][7][8][9][10][11].…”