The Hows and Whys of Orthodontics

Part 2

What is normal function?

We will divide the function of these muscles into 4 main sections:

  • Swallowing
  • Breathing
  • Talking
  • Chewing.


Between the ages of 18 months to 2 years, the child should develop an adult swallowing pattern. This means the tongue should brace itself against the roof of the mouth with the teeth touching slightly and the whole swallow should start with the tongue pushing against the palate with the throat taking over the peristaltic wave. There should be no movement of the facial muscles while swallowing.

This is the natural balanced situation which allows the jaws and teeth to develop correctly. Unfortunately, this is not the type of swallow that develops in many cases.

Very often, we see an infantle swallow which, in some cases, presents with the tongue pushing against the front teeth and the facial muscles contracting to push the food to the back of the throat. In this situation, the tongue is not supporting the roof of the mouth and the lips and cheeks are pushing in with extra force. This makes the arch narrow and the teeth crooked. In severe cases, this may lead to an open bite.

Another common situation is where the tongue lies on top of the lower teeth and holds the teeth apart when swallowing. This leads to an increased overbite and because of the strong lip pressure needed to swallow like this, it may cause the front teeth to point backwards. Very often in these cases, tooth imprints may be seen on the side of the tongue.

It is felt that these changes in the swallowing pattern may be due to changes in the feeding habits of babies, through the use of bottles and soothers instead of breast feeding.


Breathing and facial posture have a profound effect on the development of the face and jaws. Correct breathing should be carried out through the nose, with the lips lightly touching and the tongue against the roof of the mouth using the diaphragm to move the air in and out of the lungs. In this situation, the head is upright and the muscles of the head and neck are in balance, with all the power for the breathing coming from the diaphragm.

Unfortunately, many children breath through their mouths which significantly changes the balance of the muscles of the head, neck, face and shoulders. The muscles of the upper thorax (chest area) are used instead of the diaphragm.

The reasons for mouth breathing are multi-factorial:

  • large tonsils and adenoids, ear infections, grommets
  • respiratory infections (colds and flu )
  • structural blockages in the nose

Plus, of course, the most common cause - that of allergies

Some research has shown that the indoor living environment of modern man may be the major cause of mouth breathing and therefore malocclusion. The hypothesis states that the air inside a building is full of dust, which is the most common allergen. As we all know, babies are born with an under-developed immune system. The dust, which is mainly protein, causes an allergic reaction, which leads to inflammation of the lining of the nose (rhinitis). This causes the child to breath through their mouth because their nose is blocked, starting the myriad of problems at a very young age.

How can breathing through your mouth cause problems with teeth and jaws?

One point to remember is that the roof of the mouth is made from the same bone as the floor of the nose. For a child to start mouth breathing, it takes more than just opening the mouth. If you have had first aid training you may remember that when giving mouth-to-mouth resuscitation, the head has to be tipped back to open the oral airway. This is what the child must do to breathe through their mouth.

This has the effect of pulling the tongue back and downward on to the floor of the mouth, making it much more difficult for it to sit up against the roof of the mouth. The muscles also pull the lower jaw back preventing it from developing into its correct forward position.

The child cannot spend their life with their head tipped back looking up at the ceiling so they bend their neck to bring their eyes level with the horizon, placing an extra strain on the muscles of the neck and shoulders.

When you consider that the average weight of the head is 10 to 15 pounds, and that the strain of supporting your head is multiplied by three for every inch the head is held forward of its neutral position, you can appreciate the huge strain that the muscles of the head and neck are put under.

The change in load and alignment of the muscles prevents the child from using the diaphragm to breathe and so the muscles of the chest and upper thorax are recruited. Correcting these problems not only requires orthodontics and orthopaedics, but also myofunctional therapy (training of the lips, cheeks and tongue) and breathing exercises.

A few pointers to look out for in your child are:

  1. An open mouth posture, (slack jaw and tongue showing)
  2. Tired eyes with dark shadows, (veinous pooling)
  3. A short upper lip, large lower lip (usually pouting and dry)
  4. History of recurrent colds, sore throat or ear infection
  5. The need to have grommets fitted
Where to find us
Based in Argyll, on the West Coast of Scotland, Stewart Wright currently practices two days per week in Oban.