What is the difference between fixed retainer and removable retainer?

January 23, 2021

  

The developing phase of human dentition can many times result in poor alignment of the teeth. This is commonly seen when the milk teeth are gradually replacing the permanent teeth. The malalignment can lead to improper bite, forwardly or backwardly placed teeth, etc. One of the most common treatment options are braces.

Braces have a direct effect on the bone surrounding the teeth. The movements of the teeth caused by the braces changes this bony architecture. A major role is played by the gingiva (gums) and certain fibres surrounding the teeth. These fibres can be imagined as elastic threads that help in the controlled movements of the teeth. The total time till which braces should be worn depends on the severity of malalignment.

Once the treatment gets over, and the teeth are in their desired position, it is important to stabilize them in those areas. As stated before, the fibres of the gingiva and the ligament surrounding the teeth can be visualised as elastic bands. Once the braces are removed, these bands can recoil and push the teeth away from their desired positions. This is called relapse.

Relapse occurs as a result of failure of teeth stabilization. However, eruption of third molars, growth of the upper and lower jaws, age-related facial growth, tongue pressure and abnormal bite force are other factors that result in relapse of malalignment. In order to prevent this relapse, dentists give an appliance that helps in retaining the position of the teeth permanently. These are called retainers.

Retainers are always a part of the treatment protocol when it comes to malaligned teeth. The dentist will explain the patient about the retainers the same day he or she explains to the patient about the braces. After the braces are removed, the dentist will give a retainer based on the patient's condition, positioning of the teeth and patient compliance. The two broad classifications of retainers are removable and fixed.

Removable Retainers

These are retainers that have a plate and wire component in them. They can be removed and hence oral hygiene can be maintained. These retainers are not recommended to be worn while eating. In some cases these retainers should be worn only at night. However, the time period of wearing these retainers can often be ignored by the patient. Thus, there is a chance of relapse while wearing these retainers. The wire component of these retainers can be adjusted if at all there is a need for some subtle tooth movements.

Advancements in removable retainers include Vacuum-formed Retainers (VFRs) and Thermoplastic retainers. These have a more aesthetic value as they are made from clear plastic. They give full coverage to the teeth, even on the chewing surface. Just like the conventional retainers, eating should be avoided while wearing those retainers. These retainers also help in some movement of the teeth if needed.

Fixed Retainers

Fixed retainers are, as the name suggests, ones that cannot be removed after being placed. These retainers have a wire which is fixed by means of a tooth-colored material called composite, on the back surfaces of the front teeth. The wires used can be smooth, multi-stranded or flexible. Fixed retainers assure better fixation of the teeth in the desired area. The patient does not have to worry about removing it or wearing it at particular time periods like removable retainers. However, fixed retainers can lead to accumulation of plaque and calculus. It is thus a challenge for the patients to maintain their oral hygiene in those regions. In order to do this, a soft-bristled toothbrush is used with mild to moderate force. Mouthwashes can also be used for avoiding build-up of plaque. It has been reported that some fixed retainers can cause unwanted teeth movement. This can occur if the composite has detached and the wire is not attached properly to the tooth surface.

Dual Retention

Dual retention is when fixed and removable retainers are used at the same time. Once the fixed retainer is placed, patients are advised to wear the removable retainer at night. This ensures that even if one form of retainer fails, the other will always be there as a backup.

Retainers may need the additional support of a few minor surgical procedures that do not allow the unwanted movements of the teeth. A treatment called pericision can be done where fibres of the gingiva around the neck of the teeth are removed. However, this procedure is carried out only if there is a better underlying bony support and the patient is capable of maintaining good oral hygiene. Another method is called Interproximal Reduction where the enamel (first and the hardest layer on the tooth) near the contact points of two adjacent teeth is removed. This procedure helps the teeth is compensating for any unwanted movements.

A patient is asked to wear the retainer at least for a year. There is no ideal time limit for the total time till which the patient should wear a retainer. Irrespective of the duration, the important role that the patient should play in fixating his or her teeth is by wearing the retainer regularly while simultaneously maintaining good oral hygiene.

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