X-rays Of Teeth Needing Root Canal

Written & Reviewed by Dr David Chen

There are many conditions that affect your teeth which require root canal treatment. Each one of them will present with unique radiographic characteristics that look different on x-rays. Their radiographic appearance is used as one of the diagnostic tools to determine if it needs a root canal.

Tooth conditions that needs root canal:

  • Pulp decay
  • Tooth abscess
  • Dying tooth
  • Filling close to nerve
  • Irreversible pulpitis
  • Recurrent infection

The x-rays of these teeth will look different but they all need root canal treatment. I will show you what each of them look like on periapical or bitewing x-rays.

Are you ready to see what they look like?

Pulp decay x-ray

Untreated cavities will progress through the stages of tooth decay and eventually reach the nerve. Once the pulp has been infected, the only viable treatment left would be nerve treatment.

Below is an x-ray of a tooth with pulp decay that needs a root canal.

periapical x-ray of a large cavity into the pulp
large cavity on molar into pulp

As you can see in the image above, there is a large black area in the tooth. That dark spot is indicative of tooth decay and it is right next to the tooth nerve.

X-ray of tooth abscess

A tooth with an untreated infection will eventually develop a tooth abscess. Some tell-tale signs are severe pain, swelling, or even a pimple on the gums (gum boil). Aside from the distinctive physical characteristics, it also has a unique radiographic one as well.

Below is an x-ray of an abscessed tooth needing a root canal.

front-tooth-periapical-pathology - marked
Periapical abscess outlined on x-ray

Essentially what it looks like on a radiograph is a big dark spot that surrounds the root tip. That radiolucency signifies that the jaw bone is becoming less solid. The bone is supposed to be radiopaque because it is solid. Basically, the abscess is dissolving the bone in your jaw.

Can you guess what treatment this condition needs? That’s right, a root canal.

X-ray of dying tooth

Believe it or not but your teeth are alive which means that they can die. There are many signs and symptoms of a dying tooth.

  • Decreased sensitivity to cold.
  • Tooth discoloration – it is becoming more yellow or darker than the adjacent teeth.
  • Constricted canals on an x-ray.

Below is an x-ray of a dying tooth that needs a root canal.

dead-front-tooth-constricted-canal - traced out
outlined constricted canals

Dying teeth have a very interesting radiographic presentation because the canals are constricted. The radiograph above shows two upper front teeth side by side, one that is healthy and one that is about to die.

  • The healthy tooth has wide canals extending to the apex of the root.
  • The dying tooth has barely visible canals!

You should get the root canal done as soon as you can before the canal completely disappears and becomes obliterated.

Filling close to pulp x-ray

The bigger the cavity is the closer the dental filling will be to the tooth nerve. Of course if it is into the pulp it will need a root canal but sometimes it may still need one if it is close enough. Your pulp prefers a certain amount of buffer distance away from foreign objects. If it is too close it will cause irritation and inflammation.

Below is an x-ray of a tooth with a filling that is close to the nerve, thus requiring a root canal.

x-ray of filling that is close to nerve needing root canal

The x-ray above outlines where the tooth nerve is, which fillings are deep, and which fillings are shallow. That is to give you an idea of what they look like on a radiograph.

Irreversible pulpitis x-ray

Irreversible pulpitis is when an unhealthy nerve can no longer recovery from it’s injury. It is characterized by an unbearable toothache. Here are some descriptions of what it feels like.

  • Severe tooth pain that comes and goes.
  • Wakes you up in the middle of the night.
  • Spontaneously hurts even if you’re not eating.

Below is an x-ray of a tooth with irreversible pulpitis which will need root canal treatment.

pa x-ray of irreversible pulpitis

Unfortunately for teeth with irreversible pulpitis, the x-rays often don’t show anything especially if it just started. The periapical x-rays will look normal so they’re not that helpful in the diagnosis.

The diagnosis for this tooth condition will rely on clinical examination techniques:

  • Percussion – percussing the tooth involves tapping it with the back of a dental mirror.
  • Palpation – palpating the tooth to see if it is pressure sensitive.
  • Vitality testing – cold testing or electric pulp testing to verify health status.
  • Reported symptoms – the history of the symptoms gives clues as to what it could be.

Ultimately, this condition will require immediate root canal treatment for pain relief.

Recurrent infection x-ray

If there is a dark halo around your tooth root in the x-ray after a root canal, it may indicate a recurrent infection. That means the root canal treated tooth got re-infected and the root canal has failed.

What it looks like on an x-ray is a dark halo that surrounds the root tip of a root canaled tooth. I’ve attached x-rays of what this condition looks like and outlined one of them to show you.

This condition is called a recurrent infection because these teeth have already been treated by a root canal once before. There could be many reasons as to why it happened but the bottom line is that the infection returned.

This tooth will need a second root canal which is called a root canal retreatment.


Depending on the condition, the teeth will have their own distinct appearance on x-rays but ultimately they all require root canals. However there are some commonalities with their radiographic appearance.

Common signs:

  • Black spot
  • Dark spot
  • Shadow
  • Halo
Tooth conditionX-ray Appearance
Pulp decayDark spot into pulp
Tooth abscessBlack circle around root tip
Dying toothConstricted canal
Filling close to nerveWhite object close to pulp
Irreversible pulpitisLooks normal
Recurrent infectionHalo around root tip with root canal
Radiographic description of tooth conditions needing a root canal

Essentially they’re all radiolucent attributes or descriptions. Put more simply, if you see darkness on an x-ray, that is a bad sign and you should ask your dentist what it is.

Or perhaps you’re reading this article because you wanted to verify their recommendation to do a root canal on one of your teeth. Nonetheless, hopefully you found your answer here.


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