Jacobus van Nierop, 51, ripped out healthy teeth and left dozens of patients in a remote French village with broken jaws, recurrent abscesses and septicaemia.
Van Nierop was hired in 2008 by a head-hunter to work near the rural area of Chateau-Chinon in central France. He was initially welcomed by locals who were sorely lacking in medical services. A neighbour recalled the arrival of a smiley, larger-than-life character, with a "big 4x4, a big dog, a big cigar".
But by 2011, the authorities were starting to question some of his accounting, and patients were starting to compare notes on his dentistry.
Sylviane Boulesteix, 65, visited the dentist in March 2012 to have braces fitted.
An 80-year-old, Bernard Hugon, said the dentist left "pieces of flesh hanging everywhere" after tearing out a tooth.
"Every time, he would give us what he called 'a little prick' and we were asleep, knocked out," said Nicole Martin, a retired teacher who lost several teeth to abscesses caused by the horrific operations. "When it was over, we would find a Post-it note saying to come back for an appointment the next day or the day after," she added.
In early 2013, Martin set up a victims' group to press charges, and it soon swelled to 120 members.
Fled to Canada
In June of that year, police arrested Van Nierop but left him free pending trial, and he fled the country the following December.
He was eventually tracked down to a small Canadian town in New Brunswick and arrested under an international warrant in September 2014.
Local media reported that he tried to slit his throat when police came for him.
Van Nierop tried to block his extradition, first to the Netherlands and then France, claiming to suffer from "psychological problems" including gender identity issues and suicidal tendencies, but he was eventually placed in a prison psychiatric unit in the Loiret department, south of Paris.
"He claimed to have killed his first wife, he played crazy, he said he was trans-sexual. He tried everything" to avoid extradition, Martin said.
Already under investigation in The Netherlands
According to Dutch media, Van Nierop had already come under investigation at home over his working practices before coming to France.
Van Nierop is charged with aggravated assault, as well as fraud over claims that he tried to rip off patients and insurance companies, and faces up to 10 years in prison and a 150,000 euro fine if found guilty.