Lifestyle column: Making sense of sensitivity

Richard Guyver
Richard Guyver

Tooth sensitivity is one of those conditions that is so common it is often viewed as normal.

Over 90 per cent of those who suffer do not report it as they see it as part of everyday life.

In fact about 70 per cent of the population will suffer from it at some point. In those who have had gum disease the figure is as high as 98%!

In this two-part series we will firstly look at the causes and then at what can be done.

What causes sensitivity?

The most widely accepted mechanism which causes tooth sensitivity, or to give it its proper name ‘dentine hypersensitivity’ is called the ‘hydrodynamic theory’.

Hydrodynamic theory

You are probably aware that the second layer of a tooth is called dentine. If you were to look under a microscope you would see that the dentine contains a collection of microscopic tunnels called tubules which are filled with fluid. At the depth of these tubules lie the nerve endings.

When there is movement of this fluid (hence the name hydrodynamic) it triggers the nerve to react. Many things can cause the fluid to move including temperature change e.g. from a hot drink or ice-cream (due to expansion/contraction of the fluid), mechanical (simple touch e.g. from a toothbrush bristle) or chemical e.g. sugar (causes fluid to be ‘sucked out’ of the tubule due to the process of osmosis. Osmosis is the movement of fluid from an area of low concentration to an area of high concentration.)

Why doesn’t everyone suffer?

There are two barriers that protect the dentine and its tubules from the stimuli. The enamel over the crown of the tooth and the gum over the root of the tooth.

Removing either of these barriers exposes the dentine and leads to hypersensitivity.

Gum recession can be caused by over-zealous toothbrushing, gum disease, or even as part of the natural ageing process.

Enamel wear can be caused by over-zealous toothbrushing. Acidic food and drink can have a similar effect as can wear and tear from chewing. Other factors such as night-time clenching or grinding of teeth will accelerate this process.

Think of it like an area of skin that has been scratched/scalded. For a few days after it overreacts to gentle touch and small temperature changes with an exaggerated reaction. For anyone who has been overexposed to the sun think how much cooler you needed your shower after that! The difference is the skin heals up over time, but the area of exposed dentine remains.

It has also been shown that the tubules may be different in sensitive teeth compared to non-sensitive teeth. The tubules can be larger and greater in number. This means there can be up to 100 times increase in the available fluid in some teeth, so it’s not surprising that they react differently.

As you get deeper into a tooth, perhaps with increased wear, there are even more tubules and they are even wider. Some people think they need to brush their teeth harder if they have sensitivity. If the cause is due to wearing of the tooth from over zealous toothbrushing it may actually make things worse!

What else can lead to similar symptoms?

At this point it’s worth talking a little about other things that can cause a similar reaction, particularly because the way we treat the discomfort is different depending on the cause.

Decay in a tooth is the most obvious one

Cracks in teeth are one of the greatest challenges we have to deal with, and they can lead to exactly the same symptoms

A filling which ‘leaks’ or has not been sealed in correctly could also cause the same sensation

A chipped tooth will often be sensitive for a short while.

Clenching or grinding of teeth is another cause of discomfort which can be mistaken as dentine hypersensitivity (this is in addition to it causing increased wear and the sensitivity caused by that process)

Next week we will look at what you can do to help, and what the dental professionals can do...

Richard Guyver is principal dentist at enVisage-emsworth dental practice and is author of the book Live Another 4006 Days And Improve Your Health With Dental Medicine.

Visit his website to find out more.