A Connecticut dentist was responsible for the death of a patient who flat-lined while he was performing a full-mouth extraction, officials said in a year-long investigation into the woman's death.

Rashmi Patel, 45, was charged Tuesday with criminally negligent homicide for the 2014 death of 64-year-old Judith Gan at the Baystate Medical Center in Springfield, the Hartford Courant reported.

Patel failed to "properly respond to J.G.'s oxygen desaturation and/or respiratory distress and or/cardiopulmonary distress" during the full-mouth extraction. Gan died on Feb. 17, according to charging documents obtained by the Hartford Courant.

Investigators said Patel was in the middle of extracting 20 teeth from Gan's mouth when the low-oxygen alarm on his monitoring equipment went off. Gan, who had a history of heart problems, started making gurgling noises and then stopped breathing.

"The assistant begged [Patel] to stop working, and finally ran out and called 911, but the patient had already flat-lined," state health officials said in the documents.

Patel turned himself in to police and is now out on $25,000 bail. He is expected to appear in court Feb. 24.

The dentist has a history of malpractice accusations, including one involving another patient who ended up in the hospital after choking on a throat pack, the newspaper reported. The patient survived.

Patel was also sued for malpractice in 2011 after a different patient said he severely damaged her mouth and teeth during a reconstructive session. The suit was settled for an undisclosed amount.

Paul Knag, the dentist's lawyer, said his client denounces the charges against him and said his monitoring equipment was not working. Though his license was briefly suspended, the Dental Commission found no fault in Patel's actions and did not take away his license, Khag said.

"The state's seeking of criminal charges is contrary to this evidence and inconsistent with the decision of the Commission not to revoke his license," the lawyer told the Hartford Courant.

"Dr. Patel disputes the charges and urges that the charges be dropped."