1. Slow rate of tooth movments.

Normally tooth movment should proceed at 1 mm per month in children and less in adults. If progress is slow , check the following.

  • Is the patient wearing the appliance full-time? If the appliance is not being worn as much as required, the implications of this need to be discussed with the patient and the parent. If poor cooperation continues, resulting in a lack of progress, consideration will have to be given to abandoning treatmen
  • Are the springs correctly positioned? If not, explain again to the patient the purpose of the spring and show them how to insert the appliance correctly.
  • Are the springs underactive, overactive, or distorted? If the springs were correctly adjusted at the patient’s last visit, check that the patient is not using them to remove the appliance or putting it in their pocket during meals.
  • Is tooth movement obstructed by the acrylic or wires of the appliance? If this is the case, these should be removed or adjusted.
  • Is tooth movement prevented by occlusion with the opposing arch? It may be necessary to increase the bite-plane or buccal capping to free the occlusion.

2. Frequent breakage of the appliance.

The main reasons for this are as follows:

  • The appliance is not being worn full-time.
  • The patient has a habit of clicking the appliance in and out .
  • The patient is eating inappropriate foods whilst wearing the appliance. Success lies in dissuading the patient from eating hard and/or sticky foods altogether. Partial success is a patient who removes their appliance to eat hard or sticky foods!

3. Appliance quickly becomes loose fitting

The most common cause of this is a patient who is clicking the appliance in and out. This habit can also lead to intrusion of the teeth, which are clasped by the appliance and to frequent breakages. The patient’s close family are often very grateful if the habit is stopped, as the clicking noise that it generates can be very irritating.

4. Excessive tilting of tooth being moved.

Removable appliances are only capable of tilting movements. However, this is exaggerated by the following:

  • The further that the spring is from the centre of resistance of the tooth the greater is the degree of tilting. Therefore a spring should be adjusted so that it is as near the gingival margin as possible without causing gingival trauma.
  • Excessive force is being applied to the tooth, as this has the effect of moving the centre of resistance more apically.

5. Anchorage loss.

This can be increased by the following:

  • Part-time appliance wear, thus allowing the anchor teeth to drift forwards.
  • The forces being applied by the active elements exceed the anchorage resistance of the appliance. Care is required to ensure that the springs, etc. are not being overactivated or that too much active tooth movement is being attempted at a time.

6. Palatal inflammation.

This can occur for two reasons:

  • Poor oral hygiene. In the majority of cases the extent of the inflammation exactly matches the coverage of the appliance and is caused by a mixed fungal and bacterial infection . This may occur in conjunction with angular cheilitis. Management of this condition must address the underlying problem, which is usually poor oral hygiene. However, in marked cases it may be wise to supplement this with an antifungal agent (e.g. nystatin, amphotericin, or miconazole gel) which is applied to the fitting surface of the appliance four times daily. If associated with angular cheilitis, miconazole cream may be helpful.
  • Entrapment of the gingivae behind the upper incisors during overjet reduction between the incisors themselves and the acrylic of the bite-plane . A mistake commonly made during overjet reduction is to trim away the fitting surface of the appliance to allow for palatal movement of the incisors only, forgetting that space should also be created for retraction of the palatal gingivae. To prevent this from occurring, it is necessary to achieve good over-bite reduction in the initial stages of appliance therapy and trim the acrylic as shown in  during overjet reduction.

7. Lack of overbite reduction.

Lack of progress with overbite reduction can be a problem in patients who are not actively growing vertically, such as adults or those with a horizontal direction of mandibular growth. In these cases it may be necessary to proceed onto fixed appliances. In children, the most common reason for lack of progress with overbite reduction is that the appliance is not being worn during meals. Patients should be advised that their treatment will be quicker and more successful if they wear their appliance for eating, and that adaptation will be enhanced if they start with softer foods.

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