When a tooth is heavily filled, had root canal treatment and insufficient tooth structure remains for an onlay, a full crown is needed. Crowns again are much stronger and longer lasting than fillings. Crowns can be made of Gold, Porcelain Fused to Metal, or All - Porcelain or Zirconium.
A Crown fits over the existing natural tooth and replaces the natural crown, the part of the tooth seen above the gums.
Different Types of Crowns
Porcelain Fused to Metal crowns have a good combination of good appearance, high strength and excellent fit. They are often a good option for back teeth such as molars
All ceramic or zirconium crowns are good for some situations where extremely high aesthetics are required
Gold crowns wear the most like natural teeth, and have the best fit. They do not look natural, but have an excellent fit and shine. They are the best choice for very high stress situations like the very back teeth.
Cerec onlays and crowns are a viable option occasionally but will not be as aesthetic or strong and require more of the tooth to be removed than other onlays or crowns. We prefer to use a more accurate lab constructed crown wherever possible.
Construction of an onlay or crown involves 3 stages.
1. Preparation of the remaining structure of the tooth to provide a sound base to "cap' or "shoe"
2. An i tero scan or Impression is taken and a temporary crown for protection of the tooth while the final onlay/crown is constructed.
3. Bonding or cementation of the lab constructed tooth (usually 1 to 3 weeks, depending on the type)
Cerec or E4D onlays or crowns are an option for urgent situations where the patient can have a restoration placed the same day. However our experience is that the cost is the same but the quality is inferior (materials used, shape, greater amount of sound tooth structure removed), so we avoid this option if possible.
The key to long lasting teeth is strengthening weakened or cracked teeth before they split in an unrestorable way through the root or under the gum.
Cracks also can sometimes unfortunately extend into the pulp or "nerve", causing the tooth to become "non-vital"(i.e dead). The non-vital pulp will need to be removed and replaced with inert material. This is called Endodontic or Root canal treatment. (You know it as the treatment that gets the bad press in all movies with a dentist involved :-)
Bridges repace one or more missing teeth. They consist of an artificial tooth anchored to the natural teeth on each side of the gap. If a tooth is lost through an accident, or is too badly decayed to save with a crown, a bridge may be the treatment of choice. You can also ask your dentist about implants, which are another way of replacing missing teeth.
The steps in preparation and fitting a bridge are similar to those for a crown. The teeth on either side of the gap are shaped in order to fit crowns over them. Crowns and bridges require regular flossing and brushing, with extra attention around the margins where decay is more likely. Special devices including floss threaders and "superfloss" are available for cleaning under bridges.
Inlays and Onlays
Inlays can be made to replace medium to large sized fillings in almost any tooth. They can be made of gold or porcelain.
- Inlays/Onlays feel very natural and smooth
- The materials are very stable and biologically neutral.
- They are more expensive than amalgam or resin initially, but last longer.
We rarely use inlays at Kawanadental as a well constructed, nano composite direct bonded filling is a more cost effective, stronger and better alternative.
Onlays are a more extensive repair that covers the tooth cusps. Cracked teeth are now becoming more common as we try to keep our teeth longer. An onlay puts a cap, like a thimble over the weakened structure. It is much stronger than any simple filling and actually increases the strength of the tooth.
For crowns and onlays
Why can’t I just have a filling?
Fillings can be made from various materials and are good for fixing decayed sections of a tooth where “cavities” have occurred. They are not good for repairing cracks, broken cusps, extensive decay, or severely damaged old fillings. There has to be enough of the natural tooth left to support a filling. If not, a crown or onlay is typically the only answer.
I have been told that I have a defective filling and need to have a crown or onlay. My tooth doesn’t hurt. Why bother?
Basically it's a strength issue. If you have been recommended a onlay or crown it's because the remainder of the tooth is at risk of breaking.... possibly unrepairably (i.e extraction).
Sometimes a crown or onlay may reduce the risk of a pulp/nerve dying, requiring endodontic treatment.