Fracture surface characterization of clinically failed all-ceramic crowns

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Ceramics

Background:

• Dental ceramic restorations are prone to fracture, impacting clinical success.
• Understanding fracture mechanics is crucial for improving material durability and longevity.
• Fractographic analysis provides insights into failure origins and mechanisms.

Purpose of the Study:

• To establish a protocol for retrieving and analyzing failed ceramic restorations.
• To compare fracture surface features of clinically failed restorations with laboratory-tested specimens.
• To identify factors influencing the fracture initiation sites in dental ceramics.

Main Methods:

• Retrieved and analyzed 10 fractured Dicor and 12 fractured Cerestore crowns.
• Utilized optical microscopy for fractographic analysis of clinical failures.
• Fabricated and fractured control disks of the same ceramic materials using bi-axial flexure.
• Compared fractographic features between clinical failures and laboratory specimens.

Main Results:

• 90% of Dicor and 75% of Cerestore crowns were suitable for fractographic analysis.
• Dicor crowns predominantly failed along the internal surface.
• Cerestore crowns mostly failed at the porcelain/core interface or within the core.
• Critical flaw sizes in Dicor crowns ranged from 127 to 272 microns.
• Estimated failure stresses for Dicor crowns were 65-94 MPa; for Cerestore crowns, 15-68 MPa.

Conclusions:

• Fracture initiation in dental ceramics is governed by the location and size of critical flaws.
• Specimen thickness does not appear to be the primary determinant of fracture initiation.
• The developed protocol aids in understanding clinical failure mechanisms of ceramic restorations.