Rachel Barnes, of Sportswood Close, and Rachel Barton, of Crowder Crescent, performed the £30 procedure at the Flutter Fairy beauty salon in Hackenthorpe on May 1 this year.
The two women, however, were not authorised to carry out the service which, under the Dentistry Act 1984, must be carried out by a qualified dentist.
The court heard how the victim, Courtney Eadon, aged 19, was left with badly swollen lips after a tooth-whitening lamp used by Barnes and Barton caused a burning sensation and left her in agony.
After Ms Eadon complained that the lamp was hurting her and she was in pain, the defendants responded by offering her a glass of water.
Neither of the defendants were in court to hear proceedings and were dealt with in their absence.
Both women do own businesses but do not own the business in which the procedure was carried out, the court heard.
Magistrates imposed a fine of £750 on Barnes as well as a £75 victim surcharge.
On Barton, the bench imposed a £500 fine and a £50 victim surcharge.
Both women must pay an equal share of the £2745.30 costs the General Dentistry Council had incurred in prosecuting the case and Ms Eadon was also awarded £130 in compensation.
Imposing the fines, the Magistrates said: “This type of matter doesn’t come before the courts very often but when it does it needs to be dealt with in a robust manner.
“We are dealing with protecting the public from harm and individuals who offer a treatment for which they are not authorised need to be punished in an appropriate way.”
“The public have been put at risk - in particular the complainant who has suffered harm - and Miss Barnes had been warned on a prior occasion that she should not engage in this type of activity.”
“We believe the financial penalty and the costs we have ordered should act as reassurance to those qualified individuals who offer services to the public which carry the risk of harm.”