Myths about root canal treatment: Placing a dental crown on a tooth will cause it to need root canal treatment.
Dental crowns do not cause teeth to need root canal treatment but there definitely can be a relationship that does exist between these two, on a number of levels.
Teeth that have had root canal treatment are often best restored by way of placing a dental crown.
It's common that root canal treatment and dental crown placement is performed, in tandem, for a tooth. This is because the strengthening effect of placing a dental crown on a tooth that has had root canal treatment (especially a molar) can be an excellent way to protect it from subsequent fracture or breakage. Additionally, dental crowns also provide a substantial seal for a tooth, therefore protecting the root canal work from contaminates that may try to seep back in (a process called coronal leakage). It is, however, factors associated with having had or having had a need for root canal treatment that necessitates the need for the dental crown, not the other way around.
There is a correlation between teeth that have had a dental crown placed and those teeth that will be diagnosed as needing root canal treatment sometime during the patient's lifetime.
Dental crowns provide a way by which a dentist can rebuild teeth that have experienced significant damage (such as that caused by tooth decay or fracture). As it happens, these same types of events can also damage a tooth's nerve and therefore create a need for root canal treatment. It's not the placement of the crown that has caused a need for the endodontic treatment but instead the events that have lead up to the need for the placement of the dental crown that have caused the need for both. There can be a lot of gray area associated with the crown placement / root canal treatment relationship. The need for both may be diagnosed together or at least during a similar time frame. In other cases a crowned tooth's need for root canal treatment may not become evident until a later point in time, possibly even years later.
In some instances you might make the case that the crown placement process has precipitated the need for root canal treatment. But, in general, it is typically not the original causative factor. A realistic estimate might be that between 4 and 8% of crowned teeth will, at some point, require root canal treatment (Whitworth [2002]).
