Anna Rosemond was drawn to the advertisements for SmileDirectClub, which promises to straighten teeth for under $2,000 — about a third the cost of traditional braces — in as little as six months and all from the comfort of home.”It seemed like a really simple, easy way that they were offering people to straighten their teeth,” said Rosemond, of Richmond, Virginia.Rosemond ordered one of the kits and took an impression of her teeth with the putty and tray she received.To get started, SmileDirectClub customers either can get a 3D image of their teeth in one of their SmileShops or have an at-home kit sent to them. A few weeks later, she received dental aligners and followed the instructions to send in photos of her mouth every 90 days. SmileDirectClub told her the treatment would be reviewed remotely by one of its 250 dentists and orthodontists. All of her care was done online, she said.One of several photos of her mouth that Rosemond submitted to SmileDirectClub, which were said to be used to monitor her treatment.Courtesy of Anna RosemondAfter a year, Rosemond was in pain.”I really noticed that things didn’t feel right with the bite,” Rosemond said. “My head was hurting frequently.”She’d been assured that she’d be able to get in touch with her assigned dentist, but after multiple attempts, she said she was never connected, nor given contact information. So she consulted an outside orthodontist, who diagnosed her with a crossbite, or misalignment, possibly caused by the aligners. What’s more, her orthodontist said the crossbite was causing other symptoms: strain in her neck and jaw muscles, which led to migraines.Rosemond, who says she tried SmileDirectClub because of the money she thought she’d save, wound up spending thousands on traditional braces to fix her teeth.While SmileDirectClub, the largest at-home dental alignment company, and others promise to leave patients smiling, an NBC News investigation into a growing list of complaints found that this new trend in straightening teeth is leading to painful problems for some people.The Better Business Bureau reports more than 1,800 complaints nationwide involving SmileDirectClub. Most of the complaints involve customer service issues — such as broken aligners, delivery issues and payment problems — but dozens describe concerns about treatment results: complaints like broken teeth and nerve damage.Last month, nine members of Congress asked the Food and Drug Administration and the Federal Trade Commission to investigate SmileDirectClub “to ensure that it is not misleading consumers or causing patient harm.”Let our news meet your inbox. The news and stories that matters, delivered weekday mornings.And in January, in an effort to protect patients, a law went into effect in California requiring all teledentistry patients to get an X-ray before undergoing online aligner treatment. Virginia is considering similar rules.Dr. Chung Kau, chairman and professor of orthodontics at the University of Alabama in Birmingham, said moving teeth without in-person supervision can lead to permanent harm.Problems with a person’s bite aren’t just cosmetic. “If you can’t get a proper bite, that affects the entire function of your jaw,” Kau said. “You could get migraines, jaw joint problems, disintegration of your joints.”This harm is irreparable. I want to state that.“This harm is irreparable. I want to state that,” he said. “It’s because things like bone loss, disease, loss of a tooth — you can’t put it back in the mouth.”That’s what happened to Tom Harwood, 40, of Winnemucca, Nevada. Harwood told NBC News that his dentist said the SmileDirectClub aligners moved his teeth so fast that it caused some of them to detach from the bone.“Now I stand to lose two to three of my bottom teeth and two to three of my front teeth,” Harwood said. “Every day I wake up — it feels like I’m being punched. It’s just an all day type pain.”Harwood said that he stopped his treatment after about 3 months, before the 90-day mark when customers are asked to send photos of their mouths to SmileDirectClub to monitor progress. He also said that he tried to get in touch with his assigned dentist, but that he was unable to do so.It’s important for teeth straightening patients to see an orthodontist regularly to make sure their bite is correct and their mouth is healthy overall, Kau said.Regular visits with an orthodontist help ensure everything is on track, Kau said. “Every visit that we spend with a patient, we’re constantly making adjustments so we can get the best, optimal care for the patient,” he said.SmileDirectClub said that they can’t comment on individual cases like Rosemond’s and Harwood’s because of privacy concerns, but the company’s chief legal officer, Susan Greenspon-Rammelt, said the company has helped more than 750,000 people with its network of licensed dental professionals. “They’re subject to the same standards of care that a doctor in a traditional setting is,” she said.But NBC News found complaints related to poor patient outcomes, including problems with bite and spacing.Greenspon-Rammelt said that SmileDirectClub’s network of dentists, not the company itself, is responsible for treatment plans, but said that undesirable results could occur if patients aren’t adhering to the program correctly. “That could be because they weren’t following the instructions for use, they didn’t come in for a midcourse correction when they were advised to do that, they didn’t follow up with the dental team,” she said.SmileDirectClub reviews all patient scans before sending the first treatment kits, and only sends them to patients that they think are good candidates, Greenspon-Rammelt said, adding that 95 percent of people reviewed for treatment are accepted. All customers are required to see a dentist within six months before starting, which Greenspon-Rammelt says offers proof that their teeth are healthy enough for the treatment.Rosemond eventually got braces to correct her crossbite and straighten her teeth.Courtesy of Anna RosemondBut NBC News hidden cameras recorded employees at SmileDirectClub shops in Ohio, New Jersey and Alabama advising potential customers they didn’t have to see a dentist before starting treatment.One employee said “it’s not mandatory” to see a dentist first. Another said, “that’s what the scans are for.” Kau, however, said the scans are just a map of the teeth and don’t provide a full picture of someone’s oral health.“That may be a Smile guide who didn’t actually have or remember the proper training,” Greenspon-Rammelt said in response to the videos.Another employee said that the home impression kits used by thousands of customers who never set foot in a SmileDirectClub shop may not be reliable, and that “anything could go wrong.” Greenspon-Rammelt characterized that statement as a “personal opinion” of the employee, not of the company.If customers can show the treatment didn’t work and want a refund outside the return window, SmileDirectClub requires they sign a confidentiality agreement, raising the possibility that there may be more complaints than have been made public.Greenspon-Rammelt responded that in many instances, by the time such customers are asked to sign the confidentiality agreement, “they’ve already gone out there, they’ve put this on social media, they’ve filed complaints,” Greenspon-Rammelt said.Harwood refused to sign that confidentiality agreement and was unable to get his money back.“It was basically like, here’s your money back, but you can’t ever talk about us,” he said. “It’s not right. There are so many people out there putting their trust in a company that should be doing right by you, and they’re not.”Follow NBC HEALTH on Twitter & Facebook.