A root fracture is a crack in the part of the tooth you cannot see, the root that sits under the gum and inside the bone. Where the crack runs matters more than almost anything else. A horizontal root fracture, which crosses the root sideways, can often heal and keep the tooth for years. A vertical root fracture, which splits the root lengthways, usually means the tooth cannot be kept. Telling the two apart needs an X-ray and sometimes a 3D scan, because they can feel almost the same from the outside.
Key takeaways
- A root fracture sits below the gum line, so you often cannot see it, only feel it.
- Horizontal fractures often have a fair to good outlook, especially when the crack is near the tip of the root.
- Vertical root fractures usually have a poor outlook and often end in removal of the tooth.
- Around 59 percent of horizontal root fractures keep their nerve alive without root canal treatment when managed early.
- Only an X-ray, and sometimes a cone beam (3D) scan, can confirm the type and position of the fracture.
The one thing that decides the outlook: which way the crack runs
When a tooth root cracks, the single most useful question is whether the fracture runs across the root or down it. A horizontal (or transverse) fracture usually follows a knock to the mouth, such as a fall or a sporting impact, most often in an upper front tooth. A vertical fracture usually develops slowly in a tooth that has already had root canal treatment or carries a large post and crown. The direction of the crack shapes the whole plan, so this is what your dentist works out first.
Horizontal root fracture
A horizontal fracture splits the root into an upper piece nearer the crown and a lower piece nearer the tip. The closer the break is to the tip of the root, the better the outlook, because more of the root stays anchored in bone. Fractures near the gum line are harder to keep because the upper piece tends to wobble.
The reassuring part is that many of these teeth heal on their own. Research suggests roughly 59 percent of horizontal root fractures keep a living nerve without ever needing root canal treatment, and the lower (apical) piece rarely dies. Pulp death in the upper piece happens in around a quarter of cases. Because of this, the modern approach is often to splint the tooth, watch it, and only carry out root canal treatment if signs of nerve death appear.
How a horizontal fracture is managed
If the upper piece is loose, the dentist gently repositions it and fixes the tooth to its neighbours with a flexible splint, usually for about four weeks. You eat soft food, keep the area very clean, and return for review. Many of these teeth settle and stay in use for years. Some need root canal treatment later, limited to the upper piece, if the nerve does not survive.
Vertical root fracture
A vertical root fracture runs the long way down the root, from the inside out. It is most common in teeth that have already had root canal treatment, often years earlier, and in teeth carrying a large post. The crack lets bacteria seep alongside the root, which slowly destroys the bone next to it.
The signs can be vague and easy to confuse with other problems: dull pain on biting, a gum boil or small pimple that comes and goes, and a deep, narrow gum pocket beside one root. Plain X-rays often miss the crack, so a cone beam (3D) scan is frequently needed. In up to two thirds of root-filled teeth with a vertical fracture, there is localised swelling, a sinus tract, tenderness, and a deep isolated pocket.
The hard truth is that the outlook is usually poor. Because the crack runs the full length of the root and lets bacteria in, the tooth normally cannot be sealed or repaired predictably. Most vertical root fractures end in removal of the tooth or the affected root. Catching it early matters, because a long-standing fracture destroys more bone, which can make later options such as an implant more complex.
Horizontal vs vertical root fracture at a glance
| Feature | Horizontal root fracture | Vertical root fracture |
|---|---|---|
| Usual cause | A knock or fall, often a healthy front tooth | Slow split in a root-filled or heavily restored tooth |
| Direction of crack | Across the root | Lengthways down the root |
| Typical symptoms | Loose or sore tooth straight after injury | Vague bite pain, recurring gum boil, deep narrow pocket |
| How it is found | X-ray soon after the injury | Often needs a 3D (cone beam) scan |
| General outlook | Fair to good, better nearer the root tip | Usually poor |
| Common plan | Splint, monitor, root canal only if needed | Remove the tooth or the affected root |
When to see a dentist quickly
After any blow to the mouth, see a dentist promptly even if the tooth looks intact, because a root fracture hides below the gum. Book a prompt check if a tooth feels loose, sits slightly out of line, hurts to bite on, or develops a gum pimple that keeps returning. Early assessment gives a horizontal fracture the best chance of healing and stops a vertical fracture from quietly destroying bone. If part of the tooth has broken away above the gum as well, read our guide on a crown-root fracture, and if the tooth has been pushed out of position, see tooth luxation injuries.
Frequently asked questions
Can a cracked root heal by itself?
A horizontal root fracture can heal, often with new hard tissue bridging the two pieces, especially when the break is near the root tip and the tooth is splinted early. A vertical root fracture does not heal, because the crack runs the full length of the root.
Will I always need a root canal?
No. Many horizontal fractures keep a living nerve and never need root canal treatment. Treatment is started only if the nerve in the upper piece dies. Vertical fractures are different, as root canal treatment alone rarely saves them.
Why was my X-ray normal if the tooth still hurts?
A fine vertical crack often does not show on a standard X-ray because of the angle. A cone beam (3D) scan gives a clearer view and is frequently needed when a vertical root fracture is suspected.
What happens if the tooth has to come out?
Once the tooth is removed and the area heals, the gap can be restored in several ways. Our overview of healing after an extraction explains what to expect in the first days, and your dentist can talk through replacement options.
Talk to the team at Lumi Dental
If you have had a knock to the mouth or a tooth that hurts to bite on, the team at Lumi Dental can examine it, take the right images, and explain your options clearly. Lumi Dental does not list its own prices here. For current offers see our current deals, ask for a written quote, or book a visit with a general dentist in Melrose Park.
This article is general information only and is not a substitute for personal dental advice. Please see a dentist about your own situation.
