Unfortunately nothing in dentistry lasts forever. Although crowns are very durable restorations and have the potential to last a long time, the average lifespan for a crown is only 8-10 years. That said, we have have seen crowns that are over 30 years old and still look as good as new.
What affects the longevity of the crown is determined by multiple factors. These factors include the condition of the tooth being crowned, the types of force the tooth will be regularly experiencing, and how well the crown is maintained. Teeth that are in better shape, receive minimal forces, and are easy to keep clean will last much longer than a tooth that has been heavily restored multiple times, takes all the chewing forces, and is hard to clean.
Factors affecting the condition of the tooth:
- Root Canal Treatment: Teeth that have had root canal treatments dry out and become brittle. This makes them more prone to cracking and breaking. Although crowns do a much better job than a standard filling at preventing a tooth from breaking, it is still possible for that tooth to break. Often teeth that have had root canal treatment also have a post in them, to make up for the extent of tooth loose from previous cavities. These posts help provide support for the crown, but also increase the stress in the roots of the tooth. This stress can eventually result in cracks and more tooth loss.
- Remaining tooth structure: A tooth tends to be crowned because the damage to the tooth has extended beyond what a filling can effectively restore with a good long term prognosis. Unfortunately this usually means there is not a lot of good solid tooth structure to which the crown can adhere. This why dentists are often proactive and recommend crowns on teeth that are not having any serious troubles. If a crown is added before a tooth breaks, or before the filling covers all surfaces of the tooth, the crown can last longer.
Factors affecting forces:
- Surrounding teeth: The more surrounding teeth that are in good condition, the better the longevity of the crown. This is because the biting force is spread across multiple teeth. If the tooth is on its own, it will experience greater forces, and have less lateral support (no neighboring teeth to rest against). Additionally, as teeth are lost, the bone support shrinks away in those areas. This increases the tooth structure above bone, and greater flexing can occur. The end result is increased risk of the tooth breaking.
Factors affecting cleanliness:
- Anatomy of crown: Depending on the design of the restoration, some crowns are easier to keep clean than others. In some cases, for added support, multiple teeth may be splinted together with crowns. This makes the area between the teeth much harder to keep clean. These sites are common places for recurrent decay and crown failure. Similarly, when crowns extend deep down in between teeth, the area becomes harder to keep clean as the floss needs to be extended deeper between the teeth than normal. Also, more of a gap between the teeth forms as the crown extends deeper down the side of the tooth. This creates a larger food trap that requires extra meticulous cleaning to help prevent decay.
- Patient oral hygiene: This is probably the biggest factor behind why crowns fail. As crowns blend with tooth structure right at or below the gumline, it is very important to be very thorough with cleaning these areas. This will involve brushing at least twice a day using a proper brushing technique to ensure the bristles of the tooth brush are reaching the edges of the crown. It will also involve proper flossing at least once a day. Effective oral hygiene habits will help protect the crowned tooth from decay.
- Regular cleanings and checkups, along with fluoride treatment: These visits will help keep the crowned tooth healthy, as well as allow the dentist to monitor the restoration. If problems do start, often a simple patch can be done to significantly extend the life span of the crown. Other times, the problem can not be fixed without a new crown, but if caught earlier, the damage to the tooth can be minimized. If decay under a crown is left too long, the tooth can decay enough that the tooth may not be fixable. Sometimes this process takes years, and in other cases it can happen in as little as 6 months (depends on oral hygiene, diet, and condition of the tooth under the crown). While regular visits help provide early detection, the regular fluoride treatments can help keep the tooth strong and reduce the risk of decay. And for those who choose to avoid the use of fluoride, there are alternatives that can and should be used for those with high potential for cavities.
So if you have had a lot of dental work in the past, and it has been a while since you have seen a dentist, or if you are unsure how often you should see a dentist for checkups, contact us today and let us help guide you.