One of the most common questions I get asked is: “Which material should I use when restoring a patient with a worn dentition?”

I think the answer to this question has become easier as ceramics have evolved. Today, our selection mainly includes three materials: lithium disilicate, translucent zirconia and high-strength zirconia. The key to clinical success is knowing when and how to use different materials.

To begin, we first need to understand that we choose materials differently depending on where the restoration is in the mouth. In the posterior, the restoration needs to be strong, while in the anterior, the restoration needs to be esthetic Typically, the most esthetic restorations have at least the incisal 1/3 cut back and layered by hand. This creates a much more esthetic restoration, compared to just an external stain or glaze, as the technician can layer translucency and characterization into the incisal edge. In turn, layering the incisal edge will create the “weak link” of the restoration.

No matter how strong the base ceramic material is:

  • Lithium disilicate = 500 MPa
  • Translucent zirconia = 500-800 MPa
  • High strength zirconia = 1000-1400 MPa

It is the veneering ceramic (approximately 89 MPa) that typically fails. In the posterior, where forces are higher and strength is important, it is preferable to use materials in their monolithic form – meaning the restoration is the same material through and through with no layered or veneering ceramic added.

In general, when choosing a material in the posterior it is important to remember that with less thickness, the strength of the material will need to be higher. But as the strength of the material goes up, the esthetics of the material goes down (Figs. 1- 2). In a worn dentition patient, I’m OK with sacrificing esthetics, since an opaque restoration is better than a fractured restoration.

However, if you want to enhance the esthetics of monolithic restorations, there are a few options. The restorations can be externally stained or glazed, milled with a multilayer block/puck (zirconia) or pressed with a multilayer ingot (lithium disilicate).

Initial presentation and preparation.
Monolithic restorations using a variety of restorative materials were fabricated and tried in to compare fit and esthetics.

Greggory Kinzer, D.D.S., M.S.D., is a member of Spear Resident Faculty.


Comments

Commenter's Profile Image Victor K.
February 7th, 2020
What are your thoughts on materials like Enamic? My concern with a material like Zirconia is the wear against the opposing tooth
Commenter's Profile Image Sam G.
February 12th, 2020
What would be the best material for cementation?
Commenter's Profile Image Michael S.
February 21st, 2020
Nice Article Gregg! In regards to the question on Enamic. It's a nice idea to have a "hybrid" of ceramic/composite... but I would say that it behaves much more like a composite than a ceramic. Although the resilience of the material is quite high, the low modulus makes it more prone to debonding in many clinical scenarios and it has trouble retaining it's polish... and needs quite a bit of maintenance compared to a glass ceramic or zirconia.