I am planning to get SmileDirect to fix my bottom teeth shift after braces. Will a Dr be able to put in a bonded retainer?

I do not know your situation exactly, but I would highly recommend you NOT use Smile Direct.  #1 There will be no direct supervision of your case during treatment ( you should be seen by a trained a qualified dentist every 6 weeks or so.) and no one has considered your periodontal health or anything else about your dental health which could adversely effect the longevity and long term stability of your teeth.  #2. Smile direct uses NO attachments on your teeth which are needed for many of the movements required to properly align and rotate teeth.  #3  Align/ Invisalign have hundreds of Patents on their technology which has been constantly been improving for 22 years. which Smile Direct does not have #4 MOST IMPORTANTLY - Without constant supervision of your case you may end up wth a resulting dental health problem you did not expect or desire.I ALSO WOULD NOT RECOMMEND A BONDED RETAINER BUT RATHER VIVERA RETAINERS WHICH ARE IN MY EXPERIENCE OF DOING ORTHODONTICS FOR MORE THAN 30 YEARS BY FAR THE BEST SYSTEM.  (Vivera is a retention system which gives you 3 sets of retainers which you wear at night, which do not touch your gum tissue nor interfere with any aspect of maintaining the health of your teeth. They are comfortable and  you can order more of if you ever need to without causing any relapse of the orthodontic care and result you have attained)