It happens quite frequently, Doctor. We’ll have a child come into the clinic with their parents, complaining that one of their permanent teeth is quite delayed in erupting. When we take an X-ray to investigate, we sometimes find a little surprise cleverly tucked away within the bone.
This “surprise” is often the star of today’s discussion: the Retained Deciduous Root Fragment.
What Exactly Is a Retained Deciduous Root Fragment?
Simply put, Doctor, it’s a piece of a primary tooth root that, for whatever reason, didn’t undergo the normal process of resorption. Instead, it stayed behind, embedded within the jawbone, long after the crown of the deciduous tooth has naturally exfoliated. Essentially, the root fractured, and a small part of it remained lodged inside.
What It Looks Like on X-rays: Radiographic Features
To spot it quickly on a radiograph, pay close attention to these specific details:
Location
You’ll most commonly find these fragments mesial and/or distal to the second premolar. They appear more frequently in the mandible than in the maxilla. However, generally speaking, they can really show up anywhere within either jaw.
Edge
Their borders are consistently well-defined. Sometimes, you might even discern remnants of the periodontal ligament space surrounding them.
Shape
The typical shape is either linear or curved.
Internal Structure
They appear radiopaque on X-rays, and their density is quite similar to that of dentin.
Number
It’s possible to find a single fragment, but occasionally, multiple fragments can be present.
Key Insights
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The deciduous second molar is the tooth most frequently associated with this phenomenon.
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These fragments can often persist for many years without causing any symptoms whatsoever.
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Occasionally, they might impede the eruption of the permanent successor tooth that’s developing beneath them.
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It can be challenging to differentiate a retained root fragment from an enostosis (a dense island of bone) if there isn’t a clear periodontal ligament space visible around it.
Its Clinical Significance
More often than not, their discovery is an incidental finding during routine radiographic examinations. Generally, if they are asymptomatic, these fragments typically don’t require any treatment.
However, they can sometimes be responsible for a delayed eruption of permanent teeth. In extremely rare instances, a retained root fragment might even contribute to cyst formation.
A Critical Diagnostic Note
Here’s an important point, Doctor: if you’re examining an X-ray and can’t find a clear periodontal ligament space surrounding the fragment, then you’ll need to differentiate it from an enostosis primarily by its shape. A linear shape strongly suggests it’s a retained root fragment. The good news is, in either scenario—whether it’s a retained root fragment or an enostosis—neither typically requires treatment as long as they remain completely asymptomatic.
