It is difficult to know what you are referring to by "bite plate". My assumption is that you are talking about a night guard (a device worn, generally at night, to protect your teeth from the effects of clinching and grinding). If you had the night guard fitted before orthodontic treatment began...
A retainer can be made that has a fake tooth attached to it as a temporary solution. In order to make sure that the other teeth don't tip into the open space, the retainer must be worn full time (of course, it can be taken out for eating and brushing). This is a great option to maintain...
Unfortunately, the narrow palate should have been addressed BEFORE any teeth were moved and certainly before any teeth were extracted. You are now left to deal with a grossly underdeveloped palate that is causing a narrow smile, narrow face, compromised airway and most likely a compromised TMJ...
