Nottingham Police have confirmed they are investigating whether there is a link between a 23-year-old woman's death and the treatment she received from dentist Desmond D'Mello.
Around 22,000 people have been told to undergo checks for a series of blood-borne diseases such as hepatitis and HIV following concerns of "multiple failures" in cross-infection control measures at the D'Mello's Daybrook practice in Gelding, Nottinghamshire.
The dentist was suspended after a whistleblower told NHS England how D'Mello would not change his gloves or wash his hands between seeing patients or even sterilise his equipment before each use.
An inspection by the Care Quality Commission also found D'Mello used the staff toilet room to store equipment where they were at risk of being contaminated by bodily fluids.
One woman who had received treatment at the Daybrook Dental Surgery died less than a month later. Police are now investigating whether there is a link.
Police have ruled out a connection between the death of a second woman and her treatment at the surgery.
A spokesperson added: "We are making further enquiries, on behalf of the Coroner, into the death of a woman in August 2013. The 23-year-old had received treatment at the former Daybrook Dental Surgery, in Mansfield Road, earlier that month. Detectives are now working to establish if there are any links between the death and the dental treatment she received."
NHS England has opened up a hotline to anyone who might be concerned following the revelations about D'Mello.
Dr Doug Black of NHS England added: "I would like to stress again that the risk is low but would encourage anyone affected to contact the advice line.
"We have written separately to the 166 patients who were filmed without consent to explain what has happened, and offer assurances about the video footage, which remains securely stored while this investigation is running."
HIV and sexual health charity Terrence Higgins Trust reassured there is a very small chance anyone could have contacted HIV as a result of being seen by D'Mello. The dentist has already been tested and is not HIV positive.
Rosemary Gillespie, chief executive at the Terrence Higgins Trust, said: "NHS England has confirmed that the dentist in this case does not have HIV. The suggested risk is likely to relate to dental equipment not being properly sterilised between appointments.
"It is right that these patients have been recalled, but we would reassure anyone who has been contacted that there is next to no risk of HIV being passed on in this way."
A dedicated advice line has been set up on 03330 142479 for guidance on how to access additional support and is available 8am to 8pm, seven days a week.