Patients of an Auckland-based orthodontist are thousands of dollars out of pocket and left with problematic teeth after the practice suddenly shut down and the dentist vanished.

Some were told Saad Al-Mozany at the Orthodontic Institute had not paid rent for his practice in a year and his licence had been suspended, the Health Practitioners Disciplinary Tribunal has heard.

The father of one patient who paid up to $5000 for treatment said his son had two entirely healthy teeth removed, received no effective treatment for around two years, and now has permanent gaps in his smile.

One patient signed a settlement letter, effectively silencing her complaints, in order to receive a refund. She received nothing.

"I was told that he had run away and disappeared," her evidence said.

Another patient paid more than $8000 for Invisalign treatment, which involves using clear, removable aligners to move teeth, but it was not completed.

Al-Mozany, whose interim name suppression lapsed on Monday, has not attended the tribunal hearing.

He has been charged with professional misconduct in relation to 12 patients between January and December 2018, by the Professional Conduct Committee.

Eight patients are providing evidence to the tribunal panel in a hearing set down for three days in Auckland.

The registered dentist allegedly used the same excuses on different patients for frequently missing appointments, such as having his house in Sydney burgled or complications with his new child.

One patient called the owner of the building which the Orthodontic Institute used, who told her Al-Mozany had not paid rent in a year and suggested she transfer her treatment elsewhere.

She had turned up to an appointment in December 2018 to find the door locked and no one inside.

"[Another orthodontist] told me that the locks ... had been changed by the landlord and that they could not get in to get my aligners."

Another claimed she did not hear from Al-Mozany for up to five months at a time, despite repeated efforts to call, email and see him in person.

All patients of Al-Mozany giving evidence have permanent name suppression.

Saad Al-Mozany, specialist orthodontist, faces one charge laid by the Professional Conduct Committee. (Photo / Supplied)

One, who demanded a refund after she stopped receiving aligners, was given a settlement agreement by Al-Mozany to sign.

It read: "The patient agrees to not follow through with any further claims to the respective bodies, on the basis that the orthodontist agrees to refund the monies paid for her treatment."

It also said to "remove any disparaging or negative comments on social media".

She signed it but received no refund. She had paid Al-Mozany a total of $6,900.

"He didn't give me a refund and then I could not contact him," her evidence said.

She said he lied to her and gave a lot of excuses about why her aligners hadn't turned up.

She reported Al-Mozany for fraud in October 2018 to the Dental Council, and tried to track him down by calling a dental centre in Australia.

"I was then told by [the centre] in Australia that he had been suspended and was under investigation in Australia," she said in her evidence to the tribunal.

"I was told that he had run away and disappeared.

"My teeth are going back to the days before I had the treatment. It looks horrible and not straightened."

A man who had numerous appointments cancelled was told by Al-Mozany's receptionist that he "was busy with his family" and that "they had a new baby, and he had some other family commitments".

"At the end of 2018 ... [another orthodontist] called me and told me that Dr Al-Mozany's licence had been suspended and that he was not treating patients anymore.

"For over six months my braces' wires were not changed because I was looking for an orthodontist and also I was hoping I could get my refund back from Dr Al-Mozany. I got nothing.

"I was very frustrated by my experience ... I wasted over a year and paid around $3000 for treatment which had no benefit."

All patients said they have still not been reimbursed by Al-Mozany, and they have had to pay various other orthodontists to "start over" with treatment.

The father of one patient said the practice's failure to notify when appointments had been cancelled "was dysfunctional in the extreme".

When he visited another orthodontics next door, staff there talked about how a "stream of dissatisfied patients had been in, only to find discarded mail on the floor, the doors closed and no one in attendance, with endless answer phone promises that the receptionist would respond ASAP".

Anita Miller from the Professional Conduct Committee said the accounts of complainants are "strikingly similar" and patients had "serious concerns" about their treatment considering they had paid Al-Mozany, in full, in advance.

The committee said Al-Mozany had breached his professional and ethical obligations.

The tribunal hearing continues today.