The dental student was at an Octagon bar early on August 7.
The 18-year-old victim was heading to the dance floor area when Sorensen knocked his drink out of his hand.
The victim did not think the act was deliberate and requested an apology.
Sorensen had other ideas.
The court heard he grabbed the victim by the shoulders and pulled him towards him "with force", headbutting him.
The blow left the victim unconscious, bleeding from his mouth.
Sorensen immediately examined him, de Jager said, and advised him to go to hospital for treatment.
The victim was diagnosed as having fractured roots to his front top two teeth. He required a wire to hold them in place and also needed 20 stitches to his gums and mouth.
Medical professionals were still unsure whether the teeth would have to be removed.
The psychological damage was just as pronounced, the victim told the court in a statement.
He said he experienced "vivid replays" of the event and would lie awake at night.
He was normally a person who could forgive but struggled to come to terms with what he described as an "aggressive, forceful attack".
The scars would remain for the rest of his life, he said.
Sorensen's case for a discharge was significantly bolstered by support from academics, including Professor Joanne Baxter, who noted the defendant had been the "worthy recipient" of three scholarships.
Emeritus Professor John Broughton was similarly glowing.
He said Sorensen was a man of "very high moral and ethical principles" and had shown remarkable leadership qualities.
The defendant would "rise to a position of leadership in the New Zealand dental health sector", Broughton predicted.
The university's faculty of dentistry dean Professor Michael Morgan wrote that a violence conviction to Sorensen's name would create a high risk of him being shunned by the dental council.
Judge Bouchier granted the discharge without conviction on the proviso the defendant pay $2000 to the victim.