Armed vs unarmed Char denied DEX?

[Hayato Ken]

Do armed characters gain an advantage versus oponents who are unarmed?
Wether it is improved unarmed strike, catch off-guard or disarm that creates the situation does not matter so much i believe.
The questions is more, if oponents are then denied their DEX to AC or something else.

[Quatar]

If the unarmed character does NOT have Improved unarmed strike (IUS), they provoke an AoO each time they use their unarmed strike.
If they don't have IUS they also do not threaten and can not do AoO themselves.

But other than that, no. Full dex to AC.

[blackbloodtroll]

If you have the Catch off guard feat, and are using an improvised weapon, then yes. Otherwise, no, they keep the dex.