An autopsy report says Finley Boyle suffered a heart attack that was likely caused by the sedatives and local anesthesia that were administered to her.
The report says Finley received five drugs in preparation for cavity fillings and root canals. The medical examiner noted her teeth were in good shape.
Her death is classified as accidental.
The girl lapsed into a coma Dec. 3 in the office of Dr. Lilly Geyer at Island Dentistry for Children. She died Jan 3.
Finley's parents filed a negligence lawsuit claiming the staff was not properly trained to monitor vital signs.
The dentist's attorney calls the allegations unproven.
(The Associated Press contributed to this report)