Is Your Zirconia Crown Safe? The Truth About Glazing and Long-Term Wear
"Discover how glazing impacts the flexural strength of translucent zirconia crowns and what it means for your dental health."
In modern dentistry, yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has become a popular alternative to metal alloys due to its superior light permeability and biocompatibility. This material integrates well with soft tissues and boasts exceptional mechanical and physical properties.
Early Y-TZP products were primarily used as frameworks for anterior and posterior teeth, often layered with a veneering ceramic. These restorations, however, were prone to chipping due to the cohesive failure of the veneering ceramic layer. As a solution, translucent monolithic Y-TZP products have been developed, offering better aesthetics and eliminating the need for a ceramic veneer. These crowns also require less tooth removal, preserving more of your natural tooth structure while ensuring optimal function and aesthetics.
However, the long-term performance of dental zirconia is a topic of ongoing research, particularly concerning low-temperature degradation (LTD), a process that can affect the material’s structural integrity over time. Surface glazing is a common technique used to enhance the aesthetic appeal of zirconia crowns, but questions remain about how this process, combined with LTD, influences the material's flexural strength—its ability to withstand bending forces without fracturing.
Zirconia’s Growing Clinical Role
Zirconia is widely used in contemporary restorative dentistry because of its mechanical strength, biocompatibility, and aesthetic properties. New zirconia crown materials reflect varied technological approaches and are expected to support further clinical advancements. However, stable long-term performance remains challenging because zirconia is chemically inert and resistant to acid. A 2024 prospective recall report documented failures and complications involving zirconia crowns placed on teeth and dental implants.
Understanding Flexural Strength and Zirconia Crowns
Flexural strength is a critical property for dental crowns, as it indicates how well a crown can withstand the forces of chewing and biting. Zirconia, known for its high flexural strength, is often chosen for dental restorations because of its durability. However, the flexural strength of zirconia can be affected by several factors, including the manufacturing process, surface treatments like glazing, and environmental conditions within the mouth.
- Glazing: A surface treatment applied to enhance aesthetics.
- Low-Temperature Degradation (LTD): A process that can weaken zirconia over time.
- Flexural Strength: The ability of a crown to withstand bending forces.
Glazing Effects Depend on Zirconia Type
Research on glazing does not point to one universal effect on zirconia strength. One study notes that a previous investigation found increased flexural strength in 3Y-TZP after glazing and conventional sintering, while most other researchers reported decreased flexural strength under those conditions. Another in vitro study specifically evaluated glazing dwell time and cooling duration in high-translucency 3Y-TZP. Research on repeated firing found that glazing and firing significantly compromised the flexural strength of 5Y-PSZ, whereas 4Y-PSZ showed the highest stability.
Comparing Zirconia With Alternatives
Zirconia has been introduced as an abutment material for dental implants as an alternative to titanium, partly in response to aesthetic demands. Evidence comparing the survival of zirconia crowns with metal-ceramic crowns is described as sparse, limiting firm conclusions about comparative survival. Comparative discussions also consider zirconia alongside PFM, lithium disilicate, and metal alloys, with attention to strength, aesthetics, cost, and clinical indications.
The Bottom Line: What This Means for Your Dental Work
For patients considering or already having translucent zirconia crowns, understanding the balance between aesthetics and long-term durability is key. Glazing can enhance the appearance of your crown, but it's important to be aware of its potential impact on flexural strength. While LTD remains a concern, ongoing research helps refine our understanding and improve the performance of zirconia restorations. Consulting with your dentist about the best surface treatments and maintenance practices will ensure the longevity and safety of your zirconia crowns.
Clinical Lessons From Zirconia’s Evolution
Zirconia crowns made their debut in dentistry a little over ten years ago, and early clinical problems included chipping of veneering porcelain. Subsequent review work describes clinical revelations and in-office recommendations intended to support more favorable outcomes with zirconia ceramic crowns. Zirconia laboratory costs are reported to be much lower than those for PFM or lithium disilicate crowns, potentially reducing costs for dentists, technicians, and patients.
Adoption Brings New Questions
The use of all-ceramic restorations has grown steadily, with zirconia showing a significant increase in adoption. A 2017 survey of 1,000 German dentists reported that approximately 60% of posterior crowns were all-ceramic and 48% of posterior fixed dental prostheses were zirconia-based. Modern reviews attribute zirconia’s role in restorative dentistry to its high strength, biocompatibility, and improved aesthetic performance, while also examining materials, microstructure, digital fabrication, and optical capabilities.
Evidence From Real-World Patients
A recent scoping review examined 779 zirconia implants in 459 patients. The available clinical literature increasingly includes patients with selected systemic and local risk factors. However, the review does not provide definitive conclusions for specific risk groups. Instead, it offers an overview of how the evidence base for zirconia implants is evolving in real-world clinical practice.