Dental Case Selection

This was a case that came in to us with a problem! The Upper Left central had been root treated and another dentist and laboratory had made a metal free crown.

In this case the patient was insistent on metal free as they had been researching online (sometime the internet is not helpful!) - and as you can see the root treatment shows through and makes the whole crown look grey - I'm sure it looked great on the model, but in the mouth... not so great, so how do we get around this problem?

As we have discussed in previous blogs, covering a dark tooth with a root treatment and metal free crown is very difficult, so in this case we opted for a totally opaque core.

There aren't many opaque metal free substructures around, so we used Vita Inceram Zirconia - this is a material developed by Vita many years ago before the 'true' zirconia ceramics came out. Vita Inceram Zirconia is a combination of alumina and zirconia which results in high strength and an almost opaque core.

We rarely use this material now as we're not often asked to make an opaque metal free crown (usually a porcelain fused to metal crown is used), however you need to ensure that any laboratory you do decide to use has a detailed knowledge of materials available in order that they can advice as to the best restoration for any case.

Here's the result, still a little greynes showing through, but overall a much improved result.

What experiences do you have of trying to mask dark underlying teeth with metal free? What worked? And what didn't?

Can YOU spot the crown?

Here is an interesting case you will like. So first up a question... which tooth is a crown? 

We've shown this case many times during presentations and lectures and most people can correctly identify the Upper Right Central as a crown - it has that slightly brighter and more opaque look to it and lacks an element of vitality.

This aesthetic effect is common with porcelain fused to metal crowns and is caused by the inability for the restoration to allow light to pass through, as it does with a natural tooth.

Even if the shade of the restoration is perfect and the shape, contour and morphology are great this 'bright' effect is often difficult... no, let's say often impossible, to overcome.

OK, so here is the truth about this case.... both centrals are crowns, except one has a root treated tooth with gold post and core.

When we started this case we didn't know that the Upper Right Central had this underlying core, so we didn't take this in to account when making the 2 metal free crowns.

So, the 2 crowns are made together, the same shade and same morphology, yet one looks bright... all caused by the root treated tooth underneath.

What lessons should be learnt?

1. Dentists - Always tell the laboratory the condition of the underlying tooth with metal free crowns
2. Technicians - If the dentists doesn't tell you what the underlying tooth condition is, ask!
3. Dentists - Translucent Metal free is not the be all and end all. So be case selective about the material used.
4. Technicians - have a variety of restorations available with a variety of opacity levels, this way you can inform the dentist as to the best restoration for each individual case
5. Dentists - Send photos of preps, this gives the technician the best chance of choosing the best restoration
6. Dentists - prescribe a crown if necessary, but tell the technician the clinical situation around which you need to fit it. Tell the technician the requirements for strength, bonding technique and what the underlying tooth is... then let your technician inform you as to the best restoration
7. Technicians - Keep up to date with restoration options, know the issues facing a dentist and be prepared to offer an alternative if you feel the prescription may be less than perfect.

 To discuss restoration options for your patient, please call Keith on 01707 663293 for a friendly chat.

Are Zirconia Crowns Better than PFM?

Many dental practices will charge a higher fee for Zirconia crowns to the patients as this is often seen as a 'better' or 'private' option. I disagree.

PFM is a perfectly good option and is the ideal choice in many cases.

Here is an example. This patient wanted a crown on the upper right central to replace an old crown that didn't match the surrounding dentition.

The dentist wanted a metal free crown as this was perceived to be the best, however upon attendance at the surgery I noticed a metal post and core and advices that a PFM would be the best option.

The patient and dentist were concerned, but I insisted and this was the result.

A nice crown that matches.

Metal free are, by their nature, more translucent. In situations with natural teeth underneath this is fine, but with darker teeth or root treated teeth the cores can show through.

So long as the technician uses a ceramic margin that incorporates a fluorescent shoulder porcelain the aesthetics of the crown should be fine. Also required is around 1.5-2mm of labial reduction to ensure the opaque doesn't show through.

So are zirconia crowns better than PFM?, Well yes, sometimes and in with the right cases.

To recognise this fact as a laboratory we charge the SAME for all our crowns, this way there is never a temptation to chose one option over another. We believe this provides the best result for the patient.

When would you use a PFM over a Zirconia crown?