Toothache - Causes

Authored by Dr Ben Williams, 19 May 2017

Reviewed by:
Dr Hayley Willacy, 19 May 2017

A tooth is made of three layers:

  • Enamel: the hard outer layer of teeth above the gum.
  • Dentine: the slightly softer layer under the enamel.
  • Pulp: nerves and blood vessels in the centre of a tooth.

The dentine is made of a densely packed set of microscopic tubes leading from the enamel to the pulp. If the dentine loses its protective covering of enamel then harmful things like germs (bacteria), toxins and hot, cold or sweet stimuli are able to pass along the tubes of the dentine and exert a damaging and painful effect on the living pulp underneath.

The pulp responds to these harmful stimuli by becoming inflamed (this is called pulpitis) as it tries to repair and defend itself.

There are two types of pulpitis:

  1. Reversible pulpitis: the damage to the pulp is not extensive and has the potential to heal if the tooth receives appropriate dental treatment.
  2. Irreversible pulpitis: the inflammation and damage within the pulp is too extensive for the pulp to survive even with prompt dental treatment.

Tooth decay (dental caries) is the most common cause of pulpitis. When we eat sugary food and drinks, the bacteria in our mouths consume the sugar and release acid. Over time the acid can dissolve a hole in the enamel layer of our teeth which allows the bacteria and their toxins to enter the softer layer of dentine and pass through it to irritate the pulp.

A side-effect of pulpitis is an increase in blood pressure around the nerves within the pulp. In cases of irreversible pulpitis the raised pressure inside the tooth limits the amount of blood that can enter the tooth. Without sufficient blood entering the tooth, the pulp will die painfully due to a lack of oxygen.

Apart from tooth decay, other possible causes of pulpitis include:

  • Loose, leaking or lost fillings.
  • Gum wear, called 'recession'. This is caused by tooth brushing too hard which exposes the sensitive dentine of the tooth root.
  • Having sensitive teeth. Avoid brushing too hard or consuming many acidic things in your diet. Both of these can thin the protective insulating layer of enamel.
  • Having a dental filling placed close to the pulp.

To understand the effect of temperature on the pulp, think about the sensation of biting into ice cream. When the dentine is exposed, sweet things and room temperature drinks can feel like ice cream sensitivity.

The following conditions may feel like toothache but do not actually involve the pulp:

  • Periodontal infections: these are infections which develop in the space between the tooth and gums. If you have gum disease, you are likely to have deeper spaces, called pockets, between the gums and teeth. Germs (bacteria) can multiply in these pockets and cause infections which may be painful and lead to bone loss.
  • Pericoronitis: this is an infection around a partially erupted tooth. Any tooth can be affected but most frequently it is the wisdom teeth. Your dentist will usually clean around the area to remove food and bacteria. You may need painkillers and antibiotics if the infection shows signs that it is spreading to other areas.
  • Trauma: biting on an unexpected hard piece of food can cause the bone and ligaments around teeth to become bruised and painful to bite on to for several days. A soft diet and avoiding chewing on the tender teeth for a day or two usually resolve this problem.
  • Sinusitis: the roots of upper back teeth can be closely related to the air spaces - sinuses - in the upper jaw on either side of the nose. If the sinuses become inflamed and infected the increased pressure can push on the tooth nerves as they enter the root tip. This causes pain that feels like pulpitis. Over-the-counter decongestants may reduce the symptoms.

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