Can a new essix retainer fix an overbite?

Unfortunately the retainer is not designed to move teeth but rather hold them in their current position. If you need to correct the alignment of your teeth, orthodontics using conventional braces, or clear aligners may be necessary.All the best,

Usually not. A clear Essix retainer will hold your teeth in current positions only.You may ask your orthodontist how the Essix retainers will fix your overbite? Are you referring your "overbite" to which of the followings: deep bite, or open bite, or excessive overjet (too much distance between upper and lower front teeth? It is not clear what type of overbite problem you have.It should be noted that if you have an open-bite tendency prior to your orthodontic treatment, the upper and lower Essix retainers will help with this condition.