Dear Doctor,

I HAVE a problem of grinding my teeth at night. I am also worried about the condition of my teeth, when the enamel of my teeth wears out, will it grow back?
Caroline, Lagos

Answer
You are not alone  with this problem. Nocturnal grinding (known as bruxism) is a common condition. Most people who grind their teeth while sleeping are quite unaware of it, and only find out because their sleeping partners complain of the noise. Visit your dentist to find out whether the habit is causing any damage to the enamel of your teeth.

Unfortunately, enamel can’t grow back so any damage done is permanent, although modern dental treatments can help to repair it. It is important to tell your dentist about any other dental or facial symptoms especially waking with an aching jaw, or if you have noticed a clicking jaw joint. In most cases, bruxism doesn’t usually cause much damage to the enamel, and it is more a matter of irritation to those you sleep with.

Causes are varied but stress plays a part in most cases. For most people, treatments aimed at reducing stress will help stop the problem.

Tolerance to noise

What is the noise level a human can be exposed to before any damage is done to their hearing? Also, what is the legal level of background noise?
John, Aba

Answer
Damage to hearing depends not only on the level of noise but how long it lasts. So hearing can be damaged by very sudden short bursts of extremely loud noise, such as an explosion, or by prolonged exposure to lower levels of noise, such as if you work in a factory surrounded by machinery without ear protection. As a general rule, any noise above 90 decibels (dB) risks injury to the ears and the louder the noise the shorter exposure needed for damage.

Hearing of high pitch notes is lost first, and as damage persists lower tones are also lost. From 90dB to 120dB, deafness and pain may be temporary. But ringing in the ears, or tinnitus, may persist and be a sign that damage has been done. Above 120dB, injury is very likely indeed.

Experts should assess the noise to find its source and see whether individual restrictions apply or where controls may be brought in to resolve one-off noise problems.

Pregnancy and alcohol

Dear Doctor,
W HAT are the effects of heavy drinking in pregnancy? I want to scare my sister who’s still drinking a lot even though she is four months pregnant.
Chioma, Lagos

Answer
You have good reason to be concerned as drinking even small amounts of alcohol during pregnancy may affect the unborn child. The baby is exposed to greater amounts of alcohol for longer than the mother. This leads to particular group of problems known as foetal alcohol syndrome.

This consists of growth problems, learning difficulties, restlessness, irritability, etc. All these problems are permanent, although surgery can correct some features. Scaring your sister may just drive her away from you, at a time when she really needs you. Try to be supportive and understanding while guiding her towards more expert help.