underobturation

Underobturation refers to a root canal filling that does not extend to the apical constriction or fails to adequately fill the prepared canal, leaving voids and an incomplete seal. In endodontics, an ideally obturated canal should occupy the canal space from a close coronal start to the apical terminator, with a dense, continuous fill and proper sealer. Underobturation is commonly associated with persistent or recurrent endodontic infection and can compromise treatment success.

Causes of underobturation include inaccurate working-length determination, inadequate canal negotiation or instrumentation, ledge formation or canal blockage that prevents complete cleaning and filling, fractured or separated instruments, improper obturation technique, and insufficient irrigation or drying. Complex canal anatomy and operator experience can also contribute.

Diagnosis is usually based on radiographic assessment, where the obturation ends short of the apex and may show voids or poor adaptation. In cases with inconclusive radiographs or suspected complexity, cone-beam computed tomography can provide three-dimensional evaluation of filling length and canal filling quality.

Management typically involves retreatment to remove the existing obturation material, re-clean and re-shape the canal, and re-obturate to an appropriate apical length with an effective seal. When nonsurgical retreatment is not feasible, surgical options such as apical surgery may be considered. Ensuring a good coronal seal after obturation is also important to prevent reinfection.

Prevention focuses on accurate working-length determination (often with an apex locator and radiographs), careful canal instrumentation, proper cleaning and drying, and selecting an obturation technique that reliably fills to the appropriate length with a dense fill and minimal voids.