After root canal treatment, the integrity of the tooth is destroyed and the tooth is prone to splitting due to the uneven force of the filling alone. Some people have statistics: after root canal treatment, about 20% of the teeth without crown are split after one year, about 45% of the teeth are split after 3 years, about 55% of the teeth are split after 5 years, and most of the teeth split after root canal treatment are combined crown-root split, so the affected teeth cannot be retained and can only be extracted; after root canal treatment, 85% of the teeth with crown are still in use after 10 years, and 72% of the affected teeth are still functional after 15 years. After 15 years, 72% of the affected teeth are still functional. Crowning of teeth after root canal treatment can better seal the roots and prevent bacteria in the mouth from entering the roots and re-infecting the roots, causing apical inflammation.