What is the importance of dental crowns after a root canal?

The process of doing the root canal weakens the already compromised tooth, so by doing a minimally invasive restoration that can spread the load of chewing the longevity of the root canalled tooth can be extended

In a normal vital tooth the dentine has a elastic/flexibility that makes the tooth resistant to compressive and tensile forces as we chew, hence making the tooth resistant to fracture. Once root canal therapy is performed the tooth becomes non-vital or dead( due to loss of blood supple) or brittle, leaving it prone to fracture. It is here that the crown protects the brittle tooth and prevents fracture, thus providing the tooth a greater life.

UNDERGOING RCT SAVES the tooth BUT to SAFE it CROWN is required.  Aesthetics is the prime reason to crown anterior tooth while prevention of tooth fracture & restoration & reinfection is prime reason to crown posterior RCT tooth. One need to acknowledge the RCT tooth in three dimension since a good amount of tooth structure loss happens for this treatment.

to avoid fructure of the filling  or the tooth

The root filled teeth are brittle and if the crown is heavily restored, remaining tooth structure is at high risk of fracture. Crowning is necessory of such teeth to prevent fracture. Moreover, in the aesthetic zone, crowning on root treated teeth is done to improve aesthetics as they go grey due to lack of blood supply. Internal bleaching is an alternative to crowning to improve tooth shade. 

Root canal treated tooth property changes with months.
It may become brittle .
Also the filling done after rct by most of dentist is silver amalgam or gic cement which may lead to micro leakage in long term and reinfect ion of Rct treated tooth.
To avoid these complications and to get abetter tooth structure and good seal its better to go for a crown.
Further details check in www.salemdental.in

By doing root canal treatment we make the tooth nonvital. So the tooth becomes brittle and prone to fractures. So to prevent it from fractures we give crowns.

root canal weakens the tooth...also the natural blood and nerve supply of the tooth are removed during root canal treatment so tooth looses its natural defenses to high pressure stimuli....also rc treated teet usually have extensive carious lesions that are to be removed and extensively restored.....these restorations may break under highly stressful conditions.....
so it is highly reccomended that in order to save the root canal tooth from high stress situations and increase its functional longevity in oral cavity it should be crowned after a successful root canal treatment.

after root canal treatment the teeth becomes non vital chances os fracture  , so it is necessary to crown it specially in posteriors

protect the remaining brittle tooth structure

Restoration of RCT teeth with a permanent coronal restoration, offering atraumatic cusp protection and optimum seal against bacterial invasion is essential for long term success. It is vitally important that the permannet coronal restoration is commeneced immediately after completion of RCT , in order to prevent fracture of compromised dentinal walls as well as microbial leakage. There is a strong evidnece in the literature confirming that root canal treated teeth, with adequate or inadequate root filling, have an improved treatment outcome with an adequate coronal restoration.