A dentist has been accused of sexually molesting a 14-year-old girl and locking her in a wooden cage at his home in Indiana, US.

Alan Friz, 57, faces 26 counts of sexual misconduct, neglect and criminal confinement after the girl told officers she had been locked up every night since September and deprived of food and water.

She alleged Friz had also been touching her breasts since she was 13 years old.

Friz's wife, Aimee, 36, has also been charged with 22 counts of neglect and criminal confinement, the Dubois County Free Press reported.

According to court documents seen by the newspaper, the pair were arrested after the Dubois County Sheriff's Department received reports of an unruly "mentally retarded" child at the Friz residence, west of Huntingburg.

When officers arrived they were told a scuffle had broken out between the teenage girl and her grandfather after he had confiscated a ball she was playing with and wouldn't give it back.

The girl was later interviewed by the Division of Family and Children during which she alleged Alan Friz had touched her breasts on several occasions in the past year.

This included, she claimed, an incident when he entered her room, turned the light off and touched her breasts until some of the other children at the residence entered and turned on the lights.

She went on to claim she had been kept locked in a cage nightly since the beginning of September. Investigators say they found a 4-by-8 feet wooden cage with a padlock and chain in a closet of a bedroom in the home.

It was said to have been labeled with the teen girl's name above the entrance and contained a mattress as well as a pan for the girl to use as a toilet.

According to court documents, Alan Friz admitted the girl was kept in the cage overnight but said it was to protect his wife and other children since the girl had allegedly made threats to harm them.

His wife told deputies the girl had threatened to kill her and her unborn child. She said the married couple were trying to find help for the teen on their own.

The pair made their first appearance at Dubois County Circuit Court on Thursday (5 October).

Alan Friz subsequently appeared on Monday (9 October) after further charges of sexual misconduct were made against him.

He reportedly nodded forward, half closed his eyes and became unresponsive as the allegations were read out by the judge. Proceedings had to be stopped as police officers checked on his condition but were allowed to continue after he was given the all-clear following a medical.

Judge Verkamp set bond at $10,000 for Aimee Friz and for $25,000 for Alan Friz. He also ordered them to not contact the alleged victim and banned them from leaving the state.