Tooth sensitivity can be classified into two categories: one may indicate a problem with the tooth's nerve and blood supply (the root canal); and the other may be caused by the exposure of dentine, resulting in dentine hypersensitivity.
What is dentine hypersensitivity?
Dentine hypersensitivity is a short, sharp pain caused by exposure of the dentine, which cannot be explained by any form of disease such as dental decay. Dentine hypersensitivity is a condition that can affect up to one in every second person at some time in their lives. This condition is estimated to affect about 1 in 3 adults in Australia.
Dentine hypersensitivity most commonly affects people in their twenties and thirties, despite the fact that older groups tend to show more exposed dentine. This may be for several reasons, including the main fact that the tubes that make up the spongy dentine fill with mineral deposits which partially close the tubes, therefore reducing sensitivity. Age changes to the dentine also make it less likely to cause sensitivity.
What does dentine hypersensitivity feel like?
Dentine hypersensitivity can be best described as a short, sharp pain arising from exposed dentine due to a loss of the surface of the tooth (enamel or cementum). When the problem that causes dentine hypersensitivity is removed, there should not be any more pain. The most common complaint is sensitivity to cold; however the pain may also be caused by:
Acidic foods and drinks (e.g. fruit and wine)
Dentists blowing air on the tooth
Brushing too hard in the sensitive area, or rubbing the area with a fingernail or toothpick
Breathing through the mouth, particularly in winter
Structure of a tooth showing exposed dentine
Dentine is the highly porous part of the tooth under the hard outer enamel surface. The dentine is made up of thousands of microscopic tubules. When the dentine is exposed the nerve tissue in the tooth becomes susceptible to triggers such as cold, air, acid, touch and heat.
What is actually causing pain?
Dentine is actually made up of a lot of tiny tubes that go from the inside of the tooth, to the outside of the dentine. These small tubes contain something called dentinal fluid. Various stimuli displace the dentinal fluid inwardly or outwardly. The movement of the dentinal fluid activates the nerve endings at the pulp/dentin interface, which causes the pain felt by the person. Anything that increases dentinal fluid movement or dentinal permeability increases sensitivity.
Structure of dentine tubules
What causes dentine hypersensitivity?
Too little or too much brushing
Very strong brushing of teeth, especially in people who have slightly crowded teeth, or even a lack of brushing that results in lots of plaque and calculus developing, will cause the gums to shrink around the tooth. Shrinkage of the gums will expose cementum and root dentine, which may cause sensitivity.
Abrasion cavities have been created at the necks of the teeth by strong brushing
Low level of dental hygiene
Poor dental hygiene will lead to gum disease, and will lead to gum shrinkage. Bacteria (in plaque and calculus) also release acids around the tooth, which may also lead to sensitivity.
Bone loss from gum disease has caused the roots of these lower teeth to become exposed
Dental erosion can be caused by diet, medications, drugs, reflux or regurgitation of stomach acids. This leads to a loss of some of the tooth structure, which may expose dentine. This process can lead to severe dental wear if combined with clenching or grinding, or even brushing immediately after exposure to acids.
Acid erosion has caused a loss of enamel on the surfaces of all of these teeth. The yellow colour of the dentine is now clearly visible
The teeth have become very worn and large amounts of dentine are now exposed
As individuals age, there is a tendency for the gums to shrink and expose dentine
While sensitivity can occur due to a variety of factors, a number of patients who undergo whitening treatments will experience bleaching-related sensitivity. This is usually a short-term issue and can be managed by your dentist.
Once your dentist confirms that you have dentine hypersensitivity he or she may recommend that you brush your teeth with a desensitising toothpaste. There are several excellent brands now available and your dentist will advise you based on your individual needs. He or she may also advise you to avoid or minimise factors like hard or incorrect brushing and frequent intake of acidic foods or drinks. Your brushing technique may be corrected if necessary.
If there has been damage to the tooth or root surface by any of the factors previously discussed, your dentist may recommend sealing or covering the damaged or exposed area of dentine. This can be done with a number of very effective and tooth-coloured materials.
Controlling dentine hypersensitivity
Stop brushing too hard and using incorrect brushing techniques as they can damage your teeth and gums
Always use a soft toothbrush. Brushing your teeth with a soft brush minimises damage to your teeth and gums. Using a hard brush may harm your teeth and gums
Reduce the frequency of taking acidic foods and drinks by confining these to main meals
Use a straw to drink acidic beverages
Rinse the mouth with water and avoid brushing for at least 30 minutes after taking acidic foods or drinks
Continue good oral hygiene habits
Visit your dentist if you have any sensitivity
Use a desensitising toothpaste if advised by your dentist
Diagram showing correct toothbrushing technique
Diagram showing the pH of a range of food and drinks