Why You Shouldn't Use Your Whitening Trays as Retainers
If your retainer has become too worn to work as effectively as it should, or you have misplaced it, you may be wondering if your whitening trays could perhaps do the same job. The truth is that even if used on a temporary basis, a whitening tray would serve as a poor substitute for your orthodontic retainer. Though whitening trays might look similar in form, that's about as far as the similarities go.
In fact, by relying on your whitening tray to do the job of your retainer, you may be putting all the good work previously achieved by your orthodontic treatment at risk. This is true for several reasons.
Whitening Trays are Made of Softer Material
Retainers are usually made of inflexible medical grade plastic and are designed to be rigid so that your teeth remain in the positions they were moved into during your orthodontic treatment. Whitening trays on the other hand, are made of soft, flexible plastic and so have little to no retention capability.
Likewise, whitening trays sold in pharmacies are not designed for your specific bite, therefore they will likely be loose. For the purpose of whitening teeth, they may be adequate even if the fit isn't perfect, but as far as retaining teeth goes, they are almost useless.
Retainers are a Much Better Fit
Because your orthodontist designed your retainers for your specific bite, naturally, they are a much better fit. Although in the early stages post-orthodontic treatment, there may still be some movement--even with the retainers, a well-made retainer should ensure that your teeth don't relapse.
Although whitening trays custom made by your dentist for your specific bite may be slightly more effective, because they are made of soft plastic, their retention capability is limited.
Teeth Shift More in the Period Just after Braces
Once your braces come off, it takes your periodontal ligaments, and jawbone about a year to adjust to the changes in the position of your teeth. After this time, the bone around your teeth solidifies. Subsequently, as long as you wear your retainer for the time recommended by your orthodontist, the position of your teeth should remain stable.
Wearing a whitening tray instead of a retainer in this period then, will likely lead to your teeth gradually shifting toward their former positions.
Although, in an emergency, a whitening tray is better than nothing, the sooner you can see an orthodontist to get a replacement retainer, the better. Otherwise, you may lose weeks or even months of progress.