AUGUSTA — A former bookkeeper for Augusta Orthodontics pleaded guilty Tuesday to embezzling about $120,000 in cash from the practice during the past six years.

Celine M. Davis, 47, formerly of West Gardiner and now of Lewiston, will be sentenced on the theft conviction in December.

In the meantime, Davis will work on arranging to pay back an estimated $70,000 from her retirement funds, attorneys told a judge Tuesday in Kennebec County Superior Court.

Davis remains free on $5,000 unsecured bail.

Under the terms of the plea agreement, Davis will receive a sentence of five years in jail — with all but six months suspended — followed by probation if she pays back a large portion of the stolen funds.

Otherwise, the sentence is to be five years in jail, with a cap of nine months on the unsuspended portion, and probation.

Assistant District Attorney Brad Grant said that Davis had been a trusted employee of the practice and was responsible for taking payments from customers and entering those payments into the computer.

Grant said the embezzlement scheme was uncovered when a customer complained about an erroneous bill.

He said the computer software showed multiple transactions had been voided once the receipts were made.

Grant said Davis admitted immediately she had taken more than $80,000 from the firm. Computer records tabbed the missing money at $120,000.

Dr. Darryl Zeleniak, who operates Augusta Orthodontics, said Davis had worked there for more than 16 years. He said she was fired in February.

“She was handling the books and the insurance,” he said Tuesday. “A glitch in the computer system allowed her to take cash and hand out receipts and then delete and void the transaction.”

Zeleniak said his wife, Karen Zeleniak, who also works at the practice, began to look into the matter in December after the client reported getting an incorrect balance on her bill.

“This one person (Davis) forgot to change it and Karen was able to find the whole sequence of voids and adjustments,” Darryl Zeleniak said.

It is at least the second time this year an embezzlement in an orthodontist’s office has reached court.

In May, Sandra Wallace — an office manager who embezzled more than $64,000 from a Rockland orthodontist by writing checks to herself during a four-year period — was sentenced in U.S. District Court to a year and a day in federal prison followed by three years of supervised release.

She pleaded guilty to one count of embezzlement in connection with health care fraud and was ordered to make restitution.