A horizontal root fracture is a crack that runs across the root of a tooth, perpendicular to its long axis, dividing the tooth into two segments. Unlike a vertical root fracture, a horizontal fracture frequently has a favorable outcome and the tooth can often be saved. This is because the fracture occurs entirely within the bone, which provides natural stabilization and allows the tissues to attempt repair. The prognosis is generally good, provided that immediate and appropriate treatment is initiated.
How the Fracture Location Affects Tooth Survival
The single most significant factor determining the long-term survival of a tooth with a horizontal root fracture is the exact location of the break along the root. The root is conceptually divided into thirds: the apical (tip) third, the middle third, and the coronal (neck) third. The closer the fracture line is to the tooth’s crown, the worse the prognosis becomes.
A fracture in the apical third, nearest the tip of the root, has the best chance for successful healing and survival. This area is deeply embedded in the jawbone, resulting in minimal mobility of the coronal fragment and a lower risk of bacterial contamination. The chance of long-term tooth survival at this location is reported to be around 89%.
Fractures in the middle third have a moderate prognosis, with a reported 10-year survival rate of approximately 78%. Though still favorable, the increased distance from the supportive bone leads to more mobility in the crown segment, which can disrupt the healing process.
The worst prognosis belongs to fractures located in the coronal third, closest to the gumline. The lack of surrounding bone and higher susceptibility to movement and bacterial ingress leads to a survival rate that can be as low as 33% to 67%. Determining the fracture’s exact position requires specialized imaging, typically involving multiple X-rays taken at different horizontal angles to accurately pinpoint the fracture line and assess any displacement.
Immediate Treatment: Repositioning and Stabilization
Immediate management focuses on mechanically reducing and stabilizing the fractured segments to allow biological healing. If the coronal fragment is noticeably displaced, it must be gently moved back into alignment as quickly as possible. Repositioning is often accomplished manually, using light finger pressure to guide the segment back into the socket.
Stabilization is achieved using a flexible splint, known as splinting, which connects the injured tooth to adjacent healthy teeth. A flexible, non-rigid splint is preferred because it minimizes disruptive movement while permitting the slight physiological movement necessary for tissue repair.
The duration of stabilization depends on the fracture’s location. For apical and middle third fractures, the splint is maintained for about four weeks. If the fracture is in the coronal third, the splinting period is extended significantly, sometimes up to four months, due to increased mobility and poorer support. An immediate post-treatment X-ray confirms correct alignment.
Monitoring the Tooth and Healing Outcomes
Long-term success relies on the body’s ability to biologically repair the damage, a process monitored over several years. The primary goal is to maintain the vitality of the pulp tissue within the root, which is responsible for the healing response. Healing outcomes are classified into four types, the most favorable being healing by calcified tissue.
Calcified healing occurs when hard tissue, resembling cementum or bone, forms a bridge across the fracture line, fusing the two segments. Radiographically, the fracture line remains visible but the fragments are held tightly together. Other successful healing types include the interposition of connective tissue or the interposition of bone and connective tissue.
The least favorable outcome, failure to heal, involves the growth of granulation tissue, which often signals pulp necrosis and inflammation in the fracture gap. A regular follow-up schedule tracks the healing process and detects potential complications. These appointments, which include clinical examinations, pulp vitality tests, and radiographic checks, are typically scheduled at four weeks, six to eight weeks, six months, one year, and then annually for up to five years.
The main complication is pulp necrosis, or nerve death, in the coronal segment, which occurs in about 25% of cases. Signs of pulp necrosis include a change in the tooth’s color, a small gum boil, or a negative response to vitality testing.
If pulp necrosis is confirmed, the tooth can still be saved by performing a root canal treatment. This procedure is usually restricted to the coronal fragment up to the fracture line. The apical segment often maintains its vitality because its blood supply remains intact, allowing it to function normally.