A horizontal root fracture is a serious traumatic dental injury involving a break in the tooth’s root, the portion embedded in the jawbone below the gum line. This injury often leads to instability and potential complications for the tooth’s long-term health. Because the fracture occurs within the bone, it requires immediate, specialized attention to properly diagnose the damage and initiate a treatment plan aimed at saving the tooth.
What Exactly Is a Horizontal Root Fracture
A horizontal root fracture is a break in the tooth’s root that runs perpendicular or oblique to the long axis, dividing the tooth into two segments. This trauma involves the dentin, the cementum, and the pulp, which contains the tooth’s nerves and blood vessels. The break occurs entirely within the alveolar bone.
The primary cause of this injury is high-impact trauma, such as a direct blow to the mouth from a sports accident, a fall, or a motor vehicle incident. Although these fractures account for a small percentage of all dental injuries, they most commonly affect the upper front teeth, which are exposed to frontal impact forces. The impact causes a compression injury, separating the root into a coronal segment (nearest the crown) and an apical segment (nearest the root tip).
Identifying the Injury
A patient with this injury may experience clinical signs, including pain upon chewing, increased tooth mobility, and displacement of the tooth crown. Bleeding from the gingival sulcus, the space between the tooth and the gum, is also a common indicator of underlying damage. The tooth may also be highly sensitive to percussion.
Confirming a horizontal root fracture often presents a diagnostic challenge because the fracture line can be difficult to visualize on a standard two-dimensional X-ray. Since the X-ray beam must pass perfectly through the plane of the fracture, multiple periapical radiographs taken at different angles are often required to reveal the break. Cone-Beam Computed Tomography (CBCT) is frequently used to overcome this difficulty, providing a three-dimensional view that significantly increases the accuracy of fracture detection and localization.
Treatment Approaches Based on Fracture Location
The treatment approach is determined by where the fracture occurs along the root, as this dictates the stability and potential for healing. Repositioning the displaced coronal fragment as soon as possible is the first step, followed by stabilization. Stabilization is typically achieved using a non-rigid or semi-rigid splint, which connects the injured tooth to its healthy neighbors for several weeks to months.
Apical Third Fractures
Fractures in the apical third generally have the most favorable prognosis because the coronal segment is firmly supported by surrounding bone and is less mobile. These fractures often require minimal intervention, such as repositioning and short-term splinting for about four weeks, or sometimes only monitoring if there is no displacement. The location near the root tip also limits the risk of bacterial contamination from the mouth.
Middle Third Fractures
A fracture located in the middle third of the root has a good prognosis, provided the coronal segment is promptly repositioned and stabilized, usually with a splint for two to four months. This longer stabilization period allows the surrounding periodontal tissues time to reorganize and begin healing. If the pulp tissue in the coronal segment dies after the trauma, endodontic therapy is performed only on the coronal fragment, leaving the apical fragment intact.
Cervical Third Fractures
The cervical third presents the poorest prognosis due to the high degree of fragment mobility and increased risk of bacterial infection. Treatment involves immediate repositioning and stabilization, but extraction of the coronal fragment is often necessary if the fracture is severely displaced or if contamination leads to persistent infection. Specialized surgical procedures may be attempted to save the tooth, but the long-term success rate remains the lowest for this location.
Long-Term Outlook and Monitoring
The long-term outlook for a horizontally fractured tooth depends on the biological response at the fracture site. The most successful outcome is healing by hard tissue union, where the fragments fuse with calcified material, resulting in a solid bridge between the two pieces. Healing may also occur with the interposition of connective tissue or a combination of bone and connective tissue, which stabilizes the fragments but leaves a visible gap on an X-ray.
Regardless of the initial success, long-term monitoring is necessary to detect any signs of failure. Clinical and radiographic follow-up appointments check for changes in the tooth’s color, mobility, and the pulp’s response to stimuli. The most common sign of late-stage failure is pulp necrosis in the coronal fragment, which occurs in about 22% of cases, requiring secondary root canal treatment to prevent infection and inflammatory root resorption.
Inflammatory root resorption is a destructive process where the body attacks the tooth structure, often signaling that the pulp tissue has died. If this occurs, endodontic therapy is initiated to remove the necrotic tissue from the coronal part of the tooth, with the goal of preserving the apical segment. Successful healing is defined by the tooth remaining functional, asymptomatic, and stable within the dental arch.