Best way to prevent relapse after premolar extractions?

Where to start...

I am sad that you had premolar extraction orthodontics to start because you are now faced with a myriad of possible problem, including: TMD, poor facial aesthetics (small lips, compromised facial profile, narrow smile, long face, etc.) and a compromised airway. The reason you have a difficult time retaining the teeth is because all of the issues that caused the excessive crowding you had are still present. Excessively crowded teeth are a SYMPTOM of underdeveloped dental arches (jaws). The reasons that your jaws are underdeveloped can be numerous, including too soft of a diet during jaw development, lack of breast feeding, overuse of a pacifier, thumb or finger habit, allergies, mouth breathing, etc.

When teeth were extracted in order to straighten the remaining teeth none of the underlying causes of the excessive crowding were addressed; therefore, your jaws will not only remain underdeveloped but will more than likely become even smaller and your teeth will not remain straight. You are trying to fight against nature with retainers and the retainers, more often than not, will lose this battle.

What can you do at this point? Undo the bicuspid extraction orthodontics. Go back and make your small jaws bigger. Move your retruded mandible forward. Tip your front teeth back to their ideal position, etc. You must give your tongue space to sit in the roof of your mouth at rest and then you need to train the tongue to go to that spot. If this is not done then you will never have the support of your tongue (a very strong muscle) to maintain the size of your palate.

Your incisors continuing to extrude is a clear sign that you have an improper swallowing pattern. Bone loss continuing years after extractions is very common because of your small jaws that cause clinching and grinding which leads to more bone loss and gum recession. You are also at risk for TMJ problems and sleep breathing problems.

Sorry to be the bearer of so much bad news but this can be fixed.

Good luck!