My son has a retainer to correct his underbite. his orthodontist now wants to do a frenulectomy, does my son need this?

No way: No way to tell without examining your son. As long as you are seeing a qualified orthodontic specialist, who limits his practice to orthodontics exclusively, you can rely on his training, experience, and expertise.

Maybe or not: The two issues (under bite and frenectomy) are not always related. A frenectomy is a proceedure to cut a piece of tissue (frenum) that is causing teeth to seperate or causing gum recession. Make sure to ask your orthodontist why the frenectomy needs to take place. If not happy, get a 2nd opinion.