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Why Candid Doesn't Offer Night Wear Only Clear Aligners

A statement from Dr. C. Lynn Hurst, co-founder and Chief Dental Officer of Candid.

Dr. C. Lynn Hurst
Chief Dental Officer, Candid

You may have noticed other companies advertising new night wear only aligners recently and asked: why isn’t Candid offering a similar product? The answer is, because there is no peer-reviewed evidence that they work. Yet, our reasoning goes further than that. From a clinical perspective I have concerns about what could go wrong if aligners are worn too few hours in a day. 

Let me explain.

For starters, it helps to know a little about how regular clear aligners work. They gently move your teeth into place using light continuous force. When this type of pressure is applied to a tooth, the first phase of tooth movement is a release of prostaglandins, the body’s inflammatory response, which typically lasts 2-3 days. This first phase is the uncomfortable phase of tooth movement, which prepares the body for bone remodeling. 

The second phase of tooth movement is bone remodeling through osteoclast and osteoblast cells found in bone, specifically alveolar bone. The third and final phase of tooth movement is healing, where the new immature bone created as a result of tooth movement becomes mature bone. This period of bone healing will last for 3-6 months and is the reason wearing retainers (post-tooth movement retention) is so critical. 

Because the protocols around nighttime aligner therapy generally specify only 10 hours of wear time per day, I am concerned that you may never experience the light continuous force necessary for effective healthy tooth movement. Without a longer and more consistent wear schedule, your teeth can be left in a limbo state of inflammation. And it would take your teeth much longer to reach the healing phase, if at all. It’s kind of like breaking your arm and having the physician reset the fracture, but only wearing the cast at night, preventing proper healing. 

I am concerned about the safety implications of nighttime aligners because they would subject your teeth to an inconsistent force load. This is because when you’re wearing aligners they interrupt the contact between your top and bottom teeth. However, when you’re not wearing them the contact between your top and bottom arches can cause your teeth to shift back into their original position. Every additional hour that you are not wearing aligners increases the likelihood that your teeth may shift in an undesired direction. This ultimately leads to a prolonged duration of heavy occlusal forces, which could produce diminished treatment outcomes at best, or bone loss and root resorption at worst. In summary, this circular event of moving teeth for 10 hours, followed by subsequent exposure to counter-forces, has not been proven to be either effective or healthy.

I’ve also yet to find any scientific evidence that supports an abbreviated 10-hour wear schedule. There have been no peer-reviewed studies published to date on the efficacy of nighttime aligners. At the end of the day, we need answers to a few basic questions: What exactly is this new “nightly wear technology”? How does this approach to aligner therapy differ from standard clear aligners? And how does this type of treatment impact one’s bio-physiology?

All that aside, I’ll admit it: Nighttime aligners basically sell themselves: “Now clear aligner therapy is more accessible and convenient than ever!” “Your care, on your schedule!” But, as doctors specializing in orthodontics and dentofacial orthopedics we have a clear responsibility to our patients: do no harm. Without more evidence that nighttime aligners are safe and effective, I can’t support nighttime aligner therapy at this point in time.

Teeth straightening has come a long way since I entered practice 35 years ago. Yet while our technology and methodologies have changed, one thing certainly hasn’t: the biomechanics and biophysiology of tooth movement. Until I see evidence otherwise, we’ll stick to the science. ✧


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