In the Premier League fixture between West Bromwich Albion and Arsenal on New Year's Eve, Dean gave the Baggies a last-minute penalty, which was converted to deny Arsenal all three points at The Hawthorns.
Wenger disputed the decision and after questioning the standard of refereeing, the Frenchman was handed a three-match touchline ban, which was completed at the weekend.
However, the FA has revealed the written reasons for the punishment, with the Gunners manager said to have claimed that Dean had frequently given decisions against his team, as well as acting in an 'aggressive' manner towards the official.
As well as the report, a written testimony from Dean read: "As we've entered the dressing room after the game Mr Wenger stood behind us in the doorway and told the West Brom steward to 'let him in'.
"He was very aggressive leaning towards me, pointing aggressively at me saying 'you're not honest' on numerous occasions. I replied 'so you're calling me a cheat'. He replied 'I maintain what I say, you're not honest'.
"He then said 'you've done this to us many times before, you're supposed to be professional, you're a disgrace'. He was then ushered out of the room by the West Brom safety officer."
Wenger will return to the dugout when Arsenal play host to Crystal Palace on Saturday afternoon.