when using the entitydata command to add an atribute to an item on the ground i used this command by the way:

/entitydata @e[type=Item,c=1] {Item:{tag:{AttributeModifiers:[{AttributeName:"generic.maxHealth",Name:"generic.maxHealth",Amount:20,Operation:0,UUIDLeast:941137,UUIDMost:134331}]}}}

it will reset the items atributtes such as attack speed and armor values on that item