MoD (Degree of Modification) = Crosslinked BDDE + Pendant BDDE
Low MoD is a filler safety requirement.
e.p.t.q. checks the total amount of BDDE combined with HA molecules(MoD ~1%) that strictly manages the safety.
BDDE is a chemical catalyst material that is essential for filler cross-linking, but it is also a risk factor that can cause allergic reactions.
Generally, free BDDE is washed after hydrolysis, but the BDDE attached to HA molecules remains in the HA filler.