NHS Greater Glasgow and Clyde said half of Harry Robertson's 3000 patients who had been warned there was a "slight risk" they may have been exposed to the disease have come forward.
The former dentist worked in Paisley and Dumfries for nearly a decade. Patients in the NHS Greater Glasgow and Clyde and NHS Dumfries and Galloway areas have been warned as a precaution of "a very slight risk that they might have been exposed to the virus".
A letter was sent to all Mr Robertson's former NHS patients, but 250 NHS patients and 230 private patients have not yet been traced.
He treated people at Kelburne Dental Surgery in Paisley between January 2004 and March this year, and provided locum Sunday emergency cover at Nithbank Hospital, Dumfries between April 2004 and 2007.
The helpline has been set up to allow people to voice their concerns and to arrange to be tested for HIV.
Dr Syed Ahmed, NHS Greater Glasgow and Clyde Consultant in Public Health Medicine, said: "The vast majority of patients involved have received a letter from NHS Greater Glasgow and Clyde or NHS Dumfries & Galloway."