ceramic restorationAll ceramic restorations can break, even IPS e.max lithium disilicate, which has a flexural strength of 400 mPa. The two most common reasons for ceramic restoration failure are:

  1. Microcracks that are created in the ceramic restoration at the time of occlusal adjustment. Using a diamond or stone that is too coarse or at too high of an RPM speed, will cause excessive trauma, vibration, and heat, which cause the microflaws. The ceramic restoration may fracture immediately at the time of adjustment or cracks will propagate over time, which will ultimately cause chipping or catastrophic failure of the restoration.
  2. When the ceramic restoration is thinner than manufacturer recommendation, cracking, chipping or fractures can occur. Ivoclar recommends the following thickness be maintained to minimize the risk of failure:
    1. A minimum of 1.5 mm thickness in the central groove and cusp tips for onlays and crowns.
    2. A 1.0 mm shoulder preparation with a rounded internal line angle for crowns.

Additional causes of ceramic restoration failure are:

  1. Microcracks are created in the ceramic at the time of fabrication due to improper handling, grinding, or polishing. This may occur in the laboratory or during chairside milling.
  2. Inaccurate internal fit of the restoration (between the restoration and the tooth), which causes high spots where pressure during try-in or seating can cause ceramic trauma. The high spots may be caused by:
    1. Inaccurate scanning/impressing
    2. Inaccurate margin trimming
    3. Inaccurate milling
    4. Adjusting of the ceramic during fitting on the die or tooth
    5. Abrasion of the die material resulting in an improper fit of the ceramic on the tooth
  3. Excessive occlusal load applied at the time of try-in to check occlusion or during the cementation process.

You should always handle ceramic restorations with care during every stage of the fabrication, try-in, or insertion process. The techniques to use for adjustment and polishing will be discussed in my next article. 


Commenter's Profile Image David Fox
October 2nd, 2014
nice,clear, and concise
Commenter's Profile Image David Wilcox
October 2nd, 2014
Great Article! One Unrelated Question - Is there a way to prevent the marginal fracture like the onlay in #31 above?
Commenter's Profile Image Lauren Semerad
October 8th, 2014
What burs/brands do you recommend to adjust eMax and bruxzir crowns? Thanks!
Commenter's Profile Image Bharat Katarmal
October 15th, 2014
Very good information.. Thanks
Commenter's Profile Image Bob Winter
October 20th, 2014
Lauren: the process and armamentarium that I use for adjusting ceramic crowns will be explained in my next article. David: to minimize the chance of marginal fractures the ceramic should be at least the minimum thickness recommended by the manufacturer, and be careful during adjustment to minimize micro cracks.
Commenter's Profile Image Klara
February 1st, 2015
Helpful as usual , thanks.
Commenter's Profile Image Colin Pech
February 15th, 2015
If micro cracks are propagated post pressing or milling; would these crack "heal" if the restoration was re-fired in a porcelain oven prior to final cementation?
Commenter's Profile Image Michael Klotz
February 20th, 2015
I have also found that margins can break if the technician uses ceram in the marginal ridge areas. Ask your technician to make your inlays and onlays monollithic so that you don't see this type of complication.
Commenter's Profile Image Thomas Katz
February 22nd, 2015
Great info. Most Docs have their assistant remove spruce and try in crowns. Be SURE to communicate this info to them and monitor how this is being done if you experience failures and don't know why.
Commenter's Profile Image Louise First
February 23rd, 2015
Why not use a PFM and gold on second molars? That would solve all of the above problems.