* Portugal defender dismissed for butt on Mueller
* Latest in string of incidents of violent conduct (Adds background)
SALVADOR, Brazil, June 16 (Reuters) - Portugal defender Pepe faces the possibility of a three-match ban for violent conduct after being sent off in the first half of Monday's World Cup Group G game against Germany.
Pepe, who has a long history of losing his cool and lashing out at opponents, leant into Germany striker Thomas Mueller with his head, making contact and applying pressure in a needless altercation that could bring him a stiff punishment.
The Brazil-born centre back had caught Mueller in the face in an innocuous-looking challenge but took umbrage as Mueller went down, returning to the forward and thrusting his forehead against the German's.
Serbian referee Milorad Mazic had no hesitation in dismissing Pepe in the 37th minute.
A red card brings a mandatory one-game ban at the World Cup but that is usually extended in the case of a sending-off for violent play.
Pepe's latest episode of violent conduct follows a series of similar incidents in recent years playing for his club Real Madrid, including one in a La Liga match against Getafe in April 2009 which earned him a 10-game ban.
With the scores level at 2-2 and three minutes left in the clash at the Bernabeu, Pepe pushed Getafe's Francisco Casquero and the referee awarded a penalty.
Pepe then kicked Casquero on the ground and a second swipe saw him rake his studs over the midfielder's back. In the ensuing melee he struck another Getafe player, Juan Albin, in the face.
He was shown a straight red card, having already picked up a yellow earlier in the match.
He was red-carded in a bad-tempered Champions League semi-final against Barcelona in 2011 for a studs-up lunge on Barca full back Dani Alves and earned wide condemnation for stamping on Lionel Messi's hand in another Real-Barca game in 2012. (Additional reporting by Iain Rogers,; Reporting by Mark Gleeson,; Editing by Ed Osmond; email@example.com; +55 21985471451; Reuters Messaging: firstname.lastname@example.org; To sign up for our Global Sports Forum chatroom, click on https://forms.thomsonreuters.com/global_sports_forum)