Why do they shave hair and remove teeth before sending them into shrinking procedure?

Question

In sci-fi comedy Downsizing (2017), why do they shave hair and remove teeth before sending them into shrinking procedure?

Answer 1

The downsizing process only works on living tissues. I guess bones are sufficiently alive to not require removing. ;)

Actually, they don't remove the teeth, only the fillings. From a review in The New Yorker:

The process of shrinking works only with living tissue, which is why, to prepare for the procedure, an enema is administered, all hair is shaved off, and all fillings removed from teeth. In the processing center, a battalion of natural-sized dentists works on patients before downsizing, and a battalion of small dentists gets immediately to work on the newly downsized upon arrival

Answer 2

Fillings need to be removed because if they aren't they'll cause a catastrophic failure in the 'downsizing' procedure.

NGOC LAN: This lady Gladys alone, no have nobody. Husband die Mexico when they make small. Stupid people forget take out gold from teeth, head explode.

and

INT. DENTAL THEATER - DAY 86

A still-sedated Paul is at a station in this large room with rows of dentists’ chairs. His mouth is held open with a dental brace. A drill approaches. FILLINGS drop inside a metal pan.

_{^{Downsizing: Production script}}

I think we can assume that much the same is true of hair. It's not alive (unless it's encapsulated in living tissue?) and hence wouldn't shrink.