What are the material options for a crown?

1. All metal

• This option is usually for the back teeth , but I have had patients who like to have a gold tooth in front - My dearest grandad had a front gold tooth, it was a status symbol and was a symbol of being wealthy in the 60's/70's. Johnny Depp had a few of his front teeth done as gold for the movie 'POTC'.

Fig 1: Gold front teeth

It can be either be as

• Non-precious metal (less than 33% gold) - which looks silver in colour.

• Semi-precious containing (up to 60% and more of gold). This is a very good option for restoring teeth and requires minimal preparation.

• Evidence - Metal Crown - 97% survival at 9 years and 94.9% at 25 yrs . This was a study by a single prosthodontist in private practice, and the crowns were precious metal crowns that are not routinely used anymore due to the high costs of pure gold. And as patients are very conscious of their smile and mouth, are not very keen on having a metal crown. (Donovan.et.al 2004)

Fig 2 : Non-Precious metal crown - Old fillings removed , changed to white and prepared as core, and restored with Non-precious metal crown, as a milled crown for holding a chrome denture.

Fig 3 :Precious metal crowns (Gold) as the most conservative preparation and option for a patient with severe erosion after suffering from Bulimia for many years, treated as a part of generalised rehabilitation of most her teeth in the teeth.

2. Metal Ceramic Crowns(MCC)/Porcelain Fused to Metal Crown (PFM)

• This is usually used to mask the colour of a dark tooth, or if the tooth has a cast metal post, or patient is a bruxist (grinder)

• This requires more tooth preparation but can lead to a pleasing result.

• The metal is usually layered using feldspathic porcelain.

• This is cheaper than and all white material

• MCC- 97% survival rate in 10 years and 85% survival rate in 25 years. (Walton et al 2013)

• MCC- 94.7% survival rate at 5 years - A Systematic Review (Sailer.et.al - 2015)

Fig 4 : MCC /PFM-Patinet was unhappy with the current appearance of teeth, requested to improve her smile as she had a teeth grinding habit and could not have the more conservative veneer option, so decided on MCC crowns for her. The teeth where her teeth meet is kept as metal to avoid wear of the opposing teeth and reduce the preparation for it.

3. All-Ceramic Crowns (ACC)

• this is usually used for very aesthetic cases. There are two types of commonly used full porcelain crowns.

• ACC - 95.6% survival rate at 5 years. - A Systematic Review (Sailer.et.al - 2015)

A. Zirconia

• this is stronger material but this has a dull lifeless look to it , so will mostly need to be layered if used in teh front of the mouth.

• This is usually used on the back teeth/bridges or

• Also for people who need strong material due to their bruxism (grinding habit).

• 
  

B. Lithium –Di-silicate (commonly known as E-max made by ivoclar)

• this is a very aesthetic material that can be made to look very lifelike if the underlining teeth are not discoloured

• For this we need sufficient enamel to bond this restoration to.

• This is comonly used for smile makeovers - for crowns and veneers and onlays in the posterior teeth.

• ACC (Emax) – survival rate 97.8 % in 5 years and 92.6 % in 10 years - A systematic Review (Peiger.et al.- 2014)

Fig 5: Zirconia Crowns -The upper central incisors were broken at gum level, and all teeth had severe erosion, so all the teeth were crown lengthened, and the central incisors were root canal treated, and built up with a metal post and core. To cover up the gold colour of the metal we used Zirconia crowns.

Figure 6 : Emax Crowns -Young patient with localised severe erosive wear, as the patient was not keen on a gold crown, we did minimal preparation and used E-max crowns to restore her teeth 2 molar teeth.

Each material has advantages and disadvantages, and it is a decision made between the patinet , the dentist and the lab technician to see what will work the best in a clinical situation.