crowns

What is a crown?

A crown is a custom made protective covering which fits over the remaining tooth structure and restores its function and appearance.

When is a crown required?

There are a variety of situations in which teeth require a crown. Here are the most common:

1) Large filling:

When more than 50-75% of the natural tooth is missing a direct filling isnt strong enough to have a long term chance of lasting. Direct fillings (composite/amalgam etc) dont add any strength to the remaining tooth and very often there is only a thin shell left which is prone to breaking. Crowns add significant strength and bracing back to the tooth and have the best chance of lasting the longest of any restoration.

2) Root canal treated teeth:

Research has confirmed that teeth that have had root canal treatment are much weaker than ‘vital’ teeth which still have an intact blood supply hydrating them. They are more brittle and without the nerves the awareness of how hard you are chewing on the tooth is much reduced. In fact the superior seal and strength provided by crowns (‘coronal seal’) is the biggest factor in the success of the root canal treatment long term.

3) Cracked tooth syndrome:

Teeth commonly develop internal cracks over time which can result in sharp pain on chewing and sensitivity to temperature. In order to prevent the crack from spreading, the tooth from breaking or the central live part (pulp) from dying a crown is used. This holds the tooth together and redistributes biting stress evenly throughout the tooth, eliminating the pain and allowing the tooth to be saved. A two stage process is often involved whereby a metal band is cemented around the tooth until it settles completely then the final crown made.

4) Excessive wear of teeth:

There are many causes of tooth wear, which can act alone but usually occur in combination. Irreversible damage and shortening occurs over time, which leads to closing down or collapse of the bite; this in itself speeds up the process.  Common causes of wear include grinding and clenching habits (see section about this topic on this website) and erosion by acid.  The origin of the acid is commonly dietary, acid reflux or bulimia. In addition to addressing the above causes, crowns may be required to prevent further tooth loss and restore the bite.

5) Undesirable appearance of teeth:

Crowns and strong ceramic veneers can be used to dramatically improve the shape, alignment and shade of teeth. Spaces can be closed and harmony restored while maintaining a very natural appearance.

6) Crowns on dental Implants:

Crowns can be attached to titanium implants, either by a screw or cement, in order to replace a missing tooth/ teeth. This restores aesthetics and brings the tooth/teeth back to function.

What types of crowns are available?

Many different materials are used to make crowns, each with their own profile of advantages and disadvantages. They are each designed for specific situations.  In recent times there have been major developments in materials with many new more durable tooth coloured ‘all ceramic’ materials becoming available.  Crowns can be made from gold alloy, other metal alloys, porcelain fused to gold alloy, all ceramic, zirconia and more.
Gold is still the longest lasting in all the studies and is the most conservative to the remaining tooth. Porcelain and all ceramic crowns have the aesthetic advantage and can be colour matched very precisely. We will discuss all the options and what is best for your individual situation so you can make an informed choice. The process is the same regardless of the material.

What is the procedure for making a crown?

Two visits are required; the first is longer and involves preparing the tooth. The second is shorter and involves fitting the crown.

Visit one: Preparing the tooth

Topical anaesthetic gel then local anaesthetic is given if required to numb the tooth and surrounding gum area.
The correct shade of the tooth is determined. This may require a visit to the technician depending on the situation.
The minimum amount is removed from the outer surface of the tooth to make room for the crown to sit.
An impression (mould) is taken of your teeth using very accurate silicone rubber. The putty is placed into an impression tray which is placed over your teeth in order to take an impression.  An impression is also taken of the opposing teeth, so the technician can see how you bite together and design the crown to fit exactly into your bite.
A temporary crown is made and cemented onto the prepared tooth with temporary cement to protect it while your crown is being made. The impression will be sent to the dental laboratory where my technician will construct your crown by hand. This usually takes around two to three weeks.

Visit two: Cementing the crown

Topical gel then local anaesthetic is given if needed to numb the tooth and surrounding gum area.
The temporary crown is removed and the tooth cleaned thoroughly to remove all the temporary cement.
Your new crown is tried in, making sure that the fit is perfect and that you are happy with the appearance. Once it has passed all the tests, the crown will then be permanently cemented in place. The bite is checked carefully. Occasionally this needs minor adjusting.

Looking after crowns:

It is essential to care for crowns by making extra effort to brush and floss them very well; crowns dont prevent teeth from developing decay (caries). It is also critical to avoid very hard or sticky foods; although they are the strongest way to restore a tooth they are still subject to fracture or loosening. If it is clear there is an ongoing grinding or clenching habit it is worth considering making a guard (occlusal splint) to wear at night. This will protect the crown and teeth, increasing their longevity.