Root canal treatment (RCT) involves cleaning and sealing the internal root canal system to eliminate bacteria and prevent infection when the pulp is irreversibly infected or inflamed. A dental crown, a custom-made cap that fully encircles the tooth, is the final step in this process. Its purpose is to restore the tooth’s natural shape and function while providing a protective shield against chewing forces.
The Vulnerability of a Tooth After Root Canal Treatment
A tooth that has undergone endodontic therapy is structurally compromised, even after the infection is cleared. Removing the vascular pulp tissue means the dentin loses its internal moisture source. This process, often called devitalization, leaves the tooth more brittle and less resilient over time, similar to dried wood.
The procedure also requires creating an access cavity through the top of the tooth. This preparation, combined with the loss of structure from decay or fracture, significantly reduces the tooth’s resistance to pressure. When the access cavity extends into the main cusps, the tooth walls are weakened and lack the support needed to withstand routine biting forces.
Risk of Catastrophic Tooth Fracture
Skipping the protective crown leaves the weakened tooth susceptible to mechanical failure from routine eating forces. Back teeth, such as molars and premolars, bear the highest chewing load, making them vulnerable. For these teeth, the risk of fracturing can be up to six times greater compared to an untreated tooth.
When a crown is absent, the remaining thin walls are unsupported against the inward pressure exerted during chewing. This strain can lead to a crack extending from the chewing surface down the side of the tooth. While minor surface fractures might be repairable, a vertical root fracture is severe. This type of crack travels down into the root, often making the tooth completely unrestorable and necessitating its removal.
Pathway to Re-Infection
Neglecting the crown also risks the failure of the root canal seal. After the canals are cleaned and filled, a temporary filling is placed in the access cavity. This temporary material is not designed to withstand long-term exposure to the oral environment and will degrade or leak over time.
Once the seal fails, bacteria and saliva can seep back down through the access cavity into the root canal system. This process, known as coronal leakage, reintroduces microorganisms into the canals, leading to recurrent infection. The resulting contamination can cause an abscess to form at the root tip, which may present with pain, swelling, or appear as bone loss on an X-ray.
Necessary Treatments Following Tooth Failure
When a root canal-treated tooth fails due to fracture or severe re-infection, corrective treatments are more involved than placing the original crown. If the tooth has a vertical root fracture or severe re-infection, it must be extracted to prevent further damage to the jawbone. Extraction is a permanent outcome that requires replacing the missing tooth.
The primary options for replacing a lost tooth are:
- A dental implant.
- A fixed bridge.
- A removable partial denture.
A dental implant involves a surgical procedure to place a titanium post into the jawbone, followed by a crown, making it the most complex option. A fixed bridge requires reducing the size of neighboring healthy teeth to support the replacement tooth. Delaying the protective crown often results in the future need for these invasive and financially demanding procedures.