Louisa, I am in an email group of several hundred dentists and raised this very subject recently.I was particularly keen to get the views of dentists who were parents of young children.
There is no universally accepted view on the damage done to teeth by dummies or thumbsucking. Prolonged use of dummies/ thumb can definately distort the growing jaws and teeth, but will not inevitably do so.
There is no doubt many children ( and therefore their parents!)are greatly pacified by dummies so you have to balace the possibility of damage to teeth with the benefits of a quiet life! The generally accepted age at which you should get your child off the dummy (dentally speaking) is by about age three, so purely from a dental viewpoint your little boy is still very young for you to worry too much. Thumbsucking should ideally stop by age five, or roughly when school starts. I should stress I give these time guidelines as an ideal; you will notice I am somewhat silent on HOW to get your child off the dummy/thumb, but there are others on mumsnet more qualified and experienced than me for this . One friend of mine got her four year old off dummies by leaving them all out for Santa. It worked a treat for him.
One of the dentists in the email group posted the following message and I thought it was appropriate to reproduce it here, with his permission.
"Although dummies can be a comfort to babies and young children, they
are also damaging to the successful development and positioning of their
teeth, especially if used over a period of several years.
Unfortunately the time when parents are most likely to feel their child
needs a dummy is also the time when the baby teeth are erupting and the
shape of the dental arch is being formed. The excessive sucking action
on a dummy can lead to the upper teeth being pushed forward quite a
considerable way, leading to a 'bucked tooth' appearance.
Another disadvantage of the use of a dummy is that it can very easily
lead onto thumb sucking. This will also cause a 'buck toothed'
appearance if allowed to continue, and if not checked, increases as the
child grows. It is not possible to remove a child's thumb!
We generally advise that if a dummy has to be used it is a special
orthodontic one. These have a specially adapted flatter teat, so causing
less harm. They can be readily purchased at the chemist.
We stress that the child MUST be weaned off the dummy as soon as
possible and NOT encouraged to suck the thumb as a replacement.
By the age of 3 a child should NOT have a dummy and if possible it
should be discarded much earlier or ideally NOT USED AT ALL.
Now, having said that, there is a further consideration on the
differences between a thumb and a dummy . If you have ever watched a child with a dummy, it
becomes evident very quickly that a considerable amount of force can be
put on the dummy by the child biting hard and, ergo, on to the teeth. In
some cases, I believe, although I have not tried this and I would urge
you not to try this at home, children, that you could probably grasp the
dummy hard, pull it up gently and lift the child bodily off the ground.
Is it any wonder that the teeth are moved orthodontically when you have
constant orthodontic forces continually at work?
The difference between this and the thumb is that there is a limit which
a child is prepared to put on biting a thumb - it is a self-limiting
action. Bite too hard, and it hurts. I believe that this is a factor in
favour of preferentially allowing a child to suck a digit instead of
providing a functional appliance (otherwise known as a dummy)."
Hope this helps.