A French court sentenced a father-and-son dentist team to years in prison on Thursday for removing teeth from hundreds of patients and fitting costly dental bridges that left many disfigured and in pain.

Lionel Guedj, 42, established his surgery in a poor neighborhood of Marseille's southern city and ran it for six years with the help of his father, Carnot Guedj, before being charged with deliberate violence causing mutilations in 2012.

During their April trial, prosecutors claimed Lionel Guedj performed an estimated 3,900 root canal operations on the perfectly healthy teeth of 327 patients, necessitating their extraction and replacement with bridges.

That saw him become France's highest-paid dentist in 2010 when he billed some 2.9 million euros ($2.9 million).

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He fitted 28 times more bridges than the average dentist, according to France's national health service, which bore a portion of the cost of the fraudulent operations. The son told the court, "Never, but never, did I intend to injure or cause pain."

But presiding judge Celine Ballerini said Thursday the two men had set up a "systematic" scheme that had "destroyed" the lives of patients who could no longer bear to smile and suffered "intolerable pain".

Lionel Guedj was sentenced to eight years in prison, and his father five years. Both had been booed as they approached the Marseille courthouse.

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To applause from the dozens of victims in attendance, the judge ordered both men directly to prison, regardless of whether they decide to appeal. Many former patients were outraged that the couple had remained free since being charged. Several people testified that the mutilations caused intense pain and social isolation.

"I had lost half my teeth by the time I was 45, and at 55 I no longer had any, only implants," Ouassila, who declined to give her full name, said ahead of the ruling.