Our experiences with full ceramic
So far we have registered 13 cases of a construction ruptures, from those 7 were caused by incorrect indication / glass abutment, inlay bridge and too many pontiacs and in two cases it was because of the abutment tooth was loosened/. The cases of an incorrect indication were our mistake and currently we do not make full ceramic in questionable cases.
Further we know about 17 cases of chipping which can be caused by many things. But often we don’t even find out about small cases of chipping because not even the patients themselves notice it.
Comparing lithium-silicate ancd zirconia
|Strength||800 - 1 200Mpa||300Mpa|
|Indication||minimum restrictions||single crowns, facets, onlays|
|Preparation||shoulder or knife edge||only shoulder|
|Fixation||the same as with PFM||adhesive|
Number of prosthetics made in JSLAB since 1994
|JSLAB||PFM (Porcelain Fused to Metal)||Zirconia full ceramic|
|total made||58 230||12 100|
|failure of framework||5||13|
The zirconia framework may fail especially when too much pressure is used while putting it on. Zirconia has one big disadvantage – it is not flexible, so if there are inaccuracies and the framework does not fit, the dentist may use too much pressure trying to make it fit and it often cracks.
With PFM (Porcelain Fused to Metal) the ceramic part will come off.
The solution for chipping
It is very difficult to repair ceramic teeth at the dentist’s office. Without using a sandblaster the repair is only temporary and the broken tooth, that is the chipping, needs to be repaired again in a few weeks. But it is not necessary to remove the whole bridge.
We have a simple solution for you. All you need to do is file down the ceramic from the tooth all the way to the metal part. On the edge, if there is not enough space, you can even file the metal part, only the connectors should not be weakened too much. After that you can take an impression as usual and send it to the dental lab.
In the dental lab we will create a dental crown based on the precise impression which you will not cement as usual. You will cement the new crown, made from PFM or full ceramic over the current framework which stayed in the mouth.
We have been successfully using this method for 15 years. The repair is permanent, esthetically perfect, the broken tooth is stronger than before because the layer of ceramic is smaller and the patient saved money compared to making a whole dental bridge. If the work was under warranty then both the dental lab and dentist’s office will save a lot on costs compared to the usual procedure, which is making the dental bridge all over again.
On the photo you can see the difference in shade between PFM and full ceramic. We did not have a chance to see the patient before making the crown. Even though the PFM crown is put over metal framework, the result is more natural than the original bridge. The difference is also probably caused by a different kind of ceramic used on the bridge which was not made by us.
The reason why we almost never have returns
1. PFM (Porcelain Fused to Metal) and full-ceramic are as strong as thick is the layer of ceramic that you use. The less ceramic the better. Ideally the layer at the edge of the frontal teeth should be about 1mm. Everywhere else we try to have about 0,5mm, in case of full-ceramic on zirconia we try to have only zirconia in the place of the occlusion.
2. The CAD software helps us design the framework in an anatomical shape in reduced size. CAD/CAM metal framework are homogeneous, do not have inner tension and do not contain oxides which makes the bonding of ceramic stronger.
3. On metal framework we use a special bonding material and firing with the material NP primer.
4. On zirconia framework we use a special bonding material and firing with the material Zirkonia adhesor.
5. We facet with the Heraceram ceramic. This natural ceramic contains leucites which prevent from cracking. Thanks to this feature, leucite ceramics are twice as strong as ceramics which do not contain leucites.
Our modeling of zirconia framework