Robert Hunter was told by a judge that the case was the most serious he had ever heard and should act as a warning to parents.
Hunter admitted 15 charges of causing or inciting a child to engage in sexual activity and 14 of making indecent photos of children.
Teesside Crown Court heard how he pretended to be a 14-year-old boy to persuade girls to expose themselves on a webcam.
On occasions, he also convinced his victims - some as young as 11 - that he was the teenage heartthrob Justin Bieber.
Hunter, of Brough Court, Middlesbrough, used social networking sites and an online music site to target the schoolgirls.
Prosecutor Richard Bennett told the court that girls across Europe, Asia, the US, Canada, the UK and Australia were targeted.
One 11-year-old victim was threatened that her parents would be told what she has been doing if she did not comply with his requests.
He threatened to kill the brother of one girl if she refused his demands, Mr Bennett told Judge Peter Bowers.
More than 800 films and stills taken from the online chats were discovered on Hunter's computer and on disc.
His barrister, Tamara Pawson, told the court that he knows he has a problem and wants to receive treatment.
Judge Peter Bowers accused Hunter of "gross exploitation" and told him: "I don't know what damage you've done."
He added: "The deceits you used were elaborate, persistent and clever at times.
"It represents callous - almost sadistic - exploitation of young girls. Their feelings were manipulated and their naivety and vulnerability undermined and used by you for your own benefit and personal gratification.
"This is one of the most serious cases of internet abuse the courts have dealt with in this area.
"It is certainly a salutary warning to all parents of teenage children and what is capable of being done on the internet and how it can be abused."
Miss Pawson said: "He knows what he did was wrong and knows that he needs punishment."
Article from the Northern Echo