Is it necessary to remove the removable orthodontic retainer when fasting if it leads to excessive saliva and swallowing it?

It is not obligatory to remove a removable orthodontic retainer for fasting, because nothing descends from it into the stomach, and increased saliva secretion due to it does not invalidate the fast. Scholars have permitted a fasting person to place a coin in their mouth as long as they do not taste it in their throat, and a jaw retainer is even more permissible due to necessity. Swallowing saliva does not harm the fast.