A frequent mishap with firing lithium disilicate is the loss of contacts. Quite a few people have reported that contacts were perfect at try-in stage, but after crystallization they were light or even open. This phenomenon is caused by a lack of support of the material while it is in the oven. The material distorts enough to render weak contacts.
Adequate support is necessary, but I like to cross the line and go against manufacturers’ recommendations when they advise using the issued pegs when placing the material in the oven – especially for larger crowns like those meant for abutments on implants, as there is a much larger surface area to address.
This photo shows how I load the internal of the crown with Quick-Peg or object fix-like material and then place the restoration on a bed of the same material, making sure that the contact areas are supported. I then place my glaze and stains on the occlusal and buccal/lingual walls. I am not concerned about the contacts areas, as these will be addressed with a quick polish on a high-speed electric handpiece.
This technique has worked well for me for more than five years, and I no longer have to contend with distorted contacts.
