A dental crown can help to protect an endodontically treated tooth from fracture.

After your tooth's root canal treatment has been completed, your dentist may feel that a dental crown should be placed. If so, at least a part of the reasoning for this opinion will probably be based upon the dentist's determination that the strengthening effect that a dental crown can provide for a tooth (protection from fracture) is needed.

How might performing endodontic treatment weaken a tooth?

When root canal therapy is performed the structural integrity of a tooth can become compromised, possibly significantly so. This weakening effect has to do with the "access cavity" the treating dentist or endodontist must create in order to perform their root space treatment. (The term access cavity refers to that portion of a tooth that must be removed in order for the dentist can gain access to the inner aspects of the tooth.)

When a dentist begins the process of creating an access cavity, they will first identify characteristic landmarks on the tooth's surface. These landmarks provide hints for the dentist as to where the openings to the tooth's root canals will be found inside the tooth. In some cases these landmarks will be spot-on and the canals will be easily found. In other cases, and for various reasons, the dentist may have trouble locating the root canal openings. If so, they will need to carefully remove more and more tooth structure until they are located.

Creating the access cavity for endodontic therapy can weaken a tooth.

In some cases the total amount of tooth structure that the dentist has had to remove to create the access cavity can be fairly significant. And as a result the overall structural integrity of the tooth will be weakened. This weakening effect can be further amplified in situations where tooth structure was lost previously (such as due to tooth decay or fracture).

In those cases where the dentist feels that a substantial amount of weakening effect has taken place, they will be concerned that the tooth might crack or break when placed under a normal functioning load. If so, the integrity of the root canal filling, or the tooth itself, might be placed at risk. As a solution, a dentist will often recommend that a dental crown should be placed. Dental crowns provide a strengthening effect for the teeth on which they are placed and can help to prevent tooth fracture.

Will your "root canalled" tooth need the protection of a dental crown?

You'll have to rely on the judgement of your dentist and their evaluation of your specific situation in regard to this matter. It is possible that endodontically treated anterior teeth, especially ones that have conservative access cavities and no other history of loss of tooth structure (such as a previous filling), might be successfully restored with the placement of a white filling (dental bonding). Endodontically treated posterior teeth (premolars and molars) that have modest to large access cavities, and especially those that already have had a large filling already placed, are probably best restored with a dental restoration that can predictably help to prevent tooth fracture, such as a dental crown.