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Family's Campus -Children aged 7 or above - Occlusion and irregular teeth - Causes of irregular teeth

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Causes of irregular teeth

  • Hereditary factors
    • Mismatch in the sizes of upper and lower jaws
      "Projected upper teeth" may be resulted if the upper jaw is much longer than the lower jaw.  "Reversed bite" may be resulted if the upper jaw is smaller than the lower jaw.
    • Mismatch in the tooth and jaw sizes
      If the tooth size is too big, or the jaw size is too small, the jaw may not have enough space for all the teeth to align, leading to crowding of teeth.  On the contrary, if the tooth size is too small, or the jaw size is too large, there will be spaces between the teeth and the teeth alignment will look unesthetic.
    • Abnormal number of teeth
      Normally one should have 28 permanent teeth (excluding the third molars).  If the number of teeth is more than that, the jaw may not have enough space for all the teeth to align properly. If there are too few teeth, there may be spaces between the teeth and the teeth alignment may look unesthetic.
  • Environmental factors

    Early loss of deciduous teeth
    If a deciduous tooth is lost prematurely, the adjacent teeth will migrate towards the space of the lost tooth, occupying the space.  The small gap prevents the succeeding permanent tooth from erupting into good position.

    • Bad habits
      Bad habits such as digit sucking and biting on a pen can induce pressure on the teeth and push them into an abnormal position.
    • Tooth decay
      Severe tooth decay in the adjacent tooth surface will cause the neighbouring tooth to tip over and take up the space, and the teeth will become irregular.
    • Gum disease
      Severe gum disease usually occurs in adults. It will result in the loss of bone support to the teeth.  The teeth will then drift to abnormal positions.
    • Loss of teeth
      Loss of teeth due to other oral diseases or traumatic injury can cause drifting of adjacent teeth.

How to avoid irregular teeth position

Irregular teeth position caused by hereditary factor is unavoidable.
To prevent irregular teeth position caused by environmental factors, you should:

  • Refrain from bad habits such as digit sucking, pen biting.
  • Receive proper oral care and treatment to prevent tooth loss and drifting of teeth.


  • Clean the teeth thoroughly, especially at areas with irregular teeth.
  • Seek professional advice from an orthodontist to see whether an orthodontic treatment is necessary.
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