The answer to this question is a big “NO”, to understand why your old retainer cannot straighten back your teeth now after months or years of use you need to know How and Why retainers are made. Dental Retainers after Orthodontic treatment are not meant to pull or push teeth into position but they are made to maintain their position after completing Orthodontic treatment. There are three types of Orthodontic Retainers – Removable Hawleys Retainer, Removable Clear Plastic Retainer and Bonded Lingual retainer. Of the three only Hawleys Retainer when Activated can produce a minor force which can be used to achieve only a specific type of movement which we will be discussing later in the post. If you are given a Clear Plastic retainer or Bonded Lingual Retainer, you cannot use them to achieve any type of movement whatsoever.
There are different types of Orthodontic Tooth movements which require different amounts of forces. Intrusion or moving the tooth into the socket requires the least amount of force – 15-25 grams while Bodily movement of the tooth requires the most amount of force which is 100-150 grams. Such amounts of force cannot be achieved by Removable Appliances such as Retainers or any Removable Orthodontic appliances.
One main factor for using your old Retainer to straighten back your teeth is that it just wont fit now. Your Retainer is made to exact dimensions of the position of your teeth after completing your Orthodontic treatment. Not that your teeth have either drifted or changed position, the retainer cannot be seated properly which makes it virtually impossible to use them.
Retainers do not apply precise force and position which does not allow predictable tooth movement. To achieve movement of teeth, you need to apply specified amount of force for a certain period of time and at an exact position on the tooth, all of which are not possible with Retainers or any Removable appliances.
The only case in which a Retainer “MIGHT” work is in cases of Interdental spacing or spaces between the upper or lower front teeth. In such cases if there is marginal tooth movement or spaces forming again, you can try to use the Orthodontic Retainer to bring back the teeth to their original position.
So it is best to visit your Dentist or Orthodontist again to access the amount of Relapse which has happened and check whether any Removable appliance can be used to treat it. In some mild cases of Interdental spacing we use Activated Hawley’s appliance to close interdental spaces. This appliance needs constant activation in regular intervals to help in closing spaces.