The soldiers are accused of involvement in setting Rodrigo Rojas and Carmen Quintana alight with gasoline. Mr Rojas later died of his injuries.
Six officers were charged with murder, the seventh as an accomplice.
They were arrested after an ex-soldier changed his testimony, echoing witness accounts of the soldiers’ actions.
Ms Quintana, a student of psychology, said that she and Mr Rojas, a Chilean-born American photographer and student, were detained by a military patrol during a protest against the Pinochet government on 2 July 1986.
She said the soldiers set the two on fire, and then dumped them on the outskirts of Santiago.
Despite the seriousness of their injuries, the students managed to get help and were taken to a hospital.
Mr Rojas died four days later. He had been visiting Chile from the US where he lived with his mother, a Chilean political exile.
Official accounts of the incident at the time said the two victims accidentally set themselves on fire while constructing a burning barricade to hold back law enforcement officials.
The attack was condemned by foreign governments and human rights groups in Chile and abroad.
The case was reopened this week after a military conscript, Fernando Guzman, changed his previous testimony.
He said the officers intentionally set the two teenagers on fire before abandoning them in a ditch 20km (12 miles) outside the Chilean capital, Santiago.
He said he and his family had been threatened and ordered to keep silent about what had happened.
Ms Quintana, who is now an official at the Chilean embassy in Canada, said: “The truth has come late, and I hope that justice comes too. I congratulate this former conscript for his bravery, and for finding the courage to tell the truth.”
Mr Rojas’s aunt, Amande de Negri, told Chilean TV: “That someone would break the silence is something we always hoped for, and finally it happened.”