Concrescence: What It Means When Two Teeth Fuse Together

Concrescence is a dental anomaly where the roots of two or more fully formed teeth are joined by cementum, the hard tissue covering the root. Because this fusion occurs below the gumline, it often goes unnoticed and is discovered by chance during routine dental check-ups.

Defining Dental Concrescence

Dental concrescence is the fusion of the roots of at least two separate, fully formed teeth by cementum alone, occurring after the crowns have fully developed. The union is limited to the cementum layer and does not involve the underlying dentin. This characteristic is what distinguishes it from other developmental anomalies.

Concrescence is classified as either true or acquired. True concrescence happens during tooth development when forming roots are so close that cementum deposition bridges the gap between them. Acquired concrescence occurs after teeth have fully formed, often as a response to chronic inflammation that triggers hypercementosis, an overproduction of cementum that fuses the roots.

Concrescence should be differentiated from two similar conditions: fusion and gemination. Fusion is the joining of two separate tooth buds early in development, resulting in a single, oversized tooth where the dentin is also connected. Gemination occurs when a single tooth bud attempts to divide, creating a large tooth with a split crown but a single root system.

Origins and Formation of Concrescence

The specific cause of concrescence is often unknown, but several factors are recognized as contributors. Trauma to the jaw can displace developing tooth buds or trigger an inflammatory response leading to the condition. Severe crowding is another factor, as lack of space can force the roots of adjacent teeth into direct contact, creating an environment for fusion.

The biological process involves cementoblasts, the cells that create cementum. Chronic inflammation or infection near a tooth’s root tip, sometimes from deep decay, can stimulate these cells to produce excessive cementum. If neighboring tooth roots are close enough, this new cementum can span the gap and fuse them together.

This process can also be triggered by the resorption of the thin bone plate separating adjacent tooth roots. Once inflammation or pressure removes this bone, cementum-producing cells can connect the two root surfaces. Many cases are considered idiopathic, arising from an unknown origin.

Detection and Diagnostic Clues

Concrescence is asymptomatic and does not cause pain or visible changes, so it is often discovered incidentally during routine dental examinations. The most definitive identification method is through dental radiographs, such as periapical or panoramic X-rays.

On a radiograph, the affected tooth roots appear in direct contact, lacking the clear, dark line of the periodontal ligament space that surrounds a normal root. The thin white line of the lamina dura, which outlines the socket, will also be absent between the fused roots, making them appear merged. The cementum at the union may also look visibly thicker than on other parts of the root.

This anomaly is most commonly observed in the maxillary (upper jaw) molars, particularly between the second and third molars, but can occur elsewhere. It can also happen between a regular tooth and a supernumerary (extra) tooth. While radiographs are the primary tool, a tooth failing to erupt or unusual tilting might prompt investigation. Advanced imaging like Cone-Beam Computed Tomography (CBCT) can provide a 3-D view to confirm the diagnosis.

Clinical Impact and Approaches

Concrescent teeth present challenges for dental procedures, especially tooth extractions. Attempting to remove one fused tooth without awareness of the condition can damage the adjacent tooth or fracture the surrounding alveolar bone. In the upper jaw, this could fracture the maxillary tuberosity. To avoid these complications, a planned surgical extraction that involves carefully sectioning the teeth is often required.

Orthodontic treatment is also complicated, as the fused teeth act as a single unit, resisting movement and potentially disrupting the treatment plan. Similarly, if one tooth needs endodontic (root canal) treatment, the shared root structure can make it difficult to access and clean the canal system, compromising the outcome.

If concrescent teeth are healthy and asymptomatic, no immediate treatment is necessary beyond regular monitoring with check-ups. Good oral hygiene is important, as the fusion site can accumulate plaque, increasing the risk for gum disease and cavities. Should intervention be needed for decay or infection, a dentist will develop a plan to manage the unique challenges.