Related Experiment Video
Updated: May 22, 2026

Systematic Assessment of Mammalian Skull Specimens for Dental and Temporomandibular Joint Pathology
Published on: August 22, 2022
Arrested root formation of 4 second premolars: report of a patient
Maria L Pinzon1, Siew-Ging Gong
1Department of Orthodontics, School of Dentistry, University of Michigan, Ann Arbor, USA.
Abstract:
The shape and size of tooth roots are genetically and phylogenetically predetermined. Clinical defects in root formation can manifest in the form of shortened roots caused by either root agenesis or root resorption. We report on a patient who came at age 7 years for space management. In the 2-year period after the initial visit, maxillary arch expansion was performed, followed by serial extractions of all 4 first premolars. A radiograph taken about 18 months after the serial extraction showed that although the crowns of all 4 second premolars had erupted fully into the arch, the roots were only about half of their normal length. With a family history of 1 sibling with a missing second premolar and the symmetrical distribution and pattern of the teeth in the 4 dental quadrants, we speculated that the arrested root development was due most likely to a genetic predisposition. Arrested root development is difficult to predict, but a potential warning sign is a family history of malformed or missing teeth. Proper, adequate, and accurate records continue to remain critical for both medical and legal purposes in the treatment of patients with potential problems in root agenesis.
Related Concept Videos
Tooth Anatomy
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
Teeth
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...