Sides of bridge between teeth forming bonds (10)
I believe the answer is:
debentures
'bonds' is the definition.
(debenture is a kind of bond)
'sides of bridge between teeth' is the wordplay.
'sides of' suggests removing the centre (only the letters on the sides remain).
'between' is an insertion indicator.
'teeth' becomes 'dentures' (I have seen 'False teeth' mean 'dentures' so perhaps 'teeth' could also mean 'dentures').
'bridge' with its middle taken out is 'be'.
'be' inserted inside 'dentures' is 'DEBENTURES'.
'forming' acts as a link.
(Other definitions for debentures that I've seen before include "Bonds" , "Shares" .)