Trinity Koha Dental Clinic team leader and retired dentist Sue Cole said the service was "overwhelmed" by patients needing urgent care.
Roughly 80 per cent of adults were turning up with "some degree of pain", she said.
Those seeking treatment were screened based on their level of need.
The team also regularly saw patients with swelling, infection and whose oral health was impacting their quality of life, she said.
"I am honestly, so impressed with the hardiness of some of these people. They will take out their own teeth and put up with extraordinary levels of pain," she said.
"A lot of people are putting up with unacceptable levels of pain, and that impacts on their health."
Their service aimed to provide access to those struggling to afford dental treatment.
"We never saw it as a free handout, but more seeking to empower people in their own lives."
She said the price of care was not the only barrier stopping patients from getting help, with location, fear and personal beliefs all playing a role.
"Fear is a major deterrent for a lot of our patients. They haven't been to a dentist for many years and they only remember negative experiences."
Asked about the impact the service had, she spoke of one woman who had all her front teeth restored.
"Up until that point she had been so ashamed of her mouth, after treatment she was just crying because she could smile again."
Another man asked if he could video having his teeth pulled out, saying he would then know what to do next time when he needed to do it himself.
Jenine Murray, 65, who lives on Matakana Island, had three broken fillings repaired at the Bethlehem clinic last week.
Murray receives superannuation and said before finding out about the service she had been avoiding going to the dentist because of the cost of treatment.
"I wouldn't have gone. I would have just put up with it - the broken teeth and stuff," she said.
"Amazingly, I hadn't been in any pain. But I got concerned it was eventually going to lead to decay which would be another huge cost."
She recently came across Trinity Koha on social media, saying her initial reaction was "is this for real or is it a joke?"
"With the whole free dental thing, for myself, I didn't think I deserved it," she said.
"Then I got a response from them and they put me on the list."
She described the service as "marvellous" and couldn't put in words what it meant to her to receive free dental work.
"The whole thing has just brought really good balance in terms of my health. It honestly means such a lot. I didn't even know what to say."
She felt as though dental treatment was often put "at the bottom of the list" by many because of the cost, saying the charity's work was needed to help increase accessibility.
"It's a service that is one of a kind. It truly is an awesome thing," she said.
"If it was affordable I think more people would make that trip to the dentist. But I know a lot of our whanau members they won't go - because it's too expensive."
Her cousin, who had been in ongoing pain, also had five teeth extracted at the clinic.
YSA managing director Marty Emmet said the level of need for their service was "pretty unrelenting".
He said the charity could run clinics "non-stop" but there were not enough dentists available to volunteer their time.
