Dentists and dental assistants from across metro Atlanta will provide free services this weekend in Cobb County, organizers said Monday.

The third annual Free Dental Day will be held Saturday from 4 a.m. to 4 p.m. at Marietta Family Dental Care, 4720 Lower Roswell Road. The event is part of the global Dentistry from the Heart campaign held in other parts of the United States, Canada, Ireland, Australia and Puerto Rico.

Dr. Michael Mansouri has organized the Marietta event annually since 2011 and said more than 500 people have been helped with services valued at more than $250,000.

Mansouri said volunteers realize many people on tight budgets usually put off tending to medical and dental needs, especially if they have little or no insurance. The dentist recalled one of the 300 patients last year had been in an auto accident and showed up with a neck brace determined to get a tooth extracted.

“People are neglecting themselves,” Mansouri said. “Part of our mission is to encourage other practices to hold similar events in their community.”

Eighteen dentists and more than 120 other dental professionals will perform cleanings, extractions and fillings on a first-come, first-served basis on Saturday. People have lined up as early as 7 a.m. the day before the event, the dentist said. By 3 a.m. the day of the event, there are usually at least 200 people in line.

“I want to encourage people that if they want be seen they need to be here at least by three or four in the morning,” Mansouri said.

Other free dental services also have been offered across metro Atlanta. Thousands waited in line last November at Woodstock First Baptist Church, which teamed up with Georgia Mission of Mercy for a two-day free dental clinic. The goal was to serve 2,000 with more than $1 million in services.

Only the first 150 people are guaranteed service at Saturday’s event in Marietta, while the next 150 to 200 have a good chance of being seen. People joining the line Saturday afternoon, however, have a little to no chance of getting in, Mansouri said.

Only adults age 18 and older will be seen Saturday. “Children need a little more time and patience, and we really want to maximize the amount of time we will have to see patients,” the dentist said.

Mansouri has been a dentist for about 10 years and practices with his wife, Dr. Azita Mansouri, at their three locations.

“We want to help as many people as needed and give back to the community,” he said.