Getting straight teeth from your orthodontic treatment is only half of the battle. Keeping them straight is the other half. This process is called retention. No matter what kind of treatment you receive, retainers are the only way to minimize tooth movement after your appliances are removed. Like all other parts of the human body, everything sags and wrinkles with age, even our teeth.

There Is No “Best” Retainer
My blog has several articles about various retainer designs commonly used to retain the teeth following treatment. There is no "best" retainer. Each one has its advantages and disadvantages. Some restrict movement better than others but are harder to clean. Others are easier to clean but require more patient compliance. Perhaps the most popular one today is the vacuum-formed, clear plastic retainer, commonly called an Essix.

Back Teeth Hit First When Wearing an Essix Retainer
Essix retainers are formed by heating a sheet of clear plastic until it is soft and then "sucking it down" over a model of the teeth. This process produces a layer of plastic that is the same thickness over the front and back teeth. Because the upper and lower jaws come together in a hinge-like fashion, the back teeth hit first when covered with plastic. It is simple geometry.

Front Teeth Hit Harder Temporarily When Back Teeth Are Intruded
When patients wearing an Essix retainer sleep with their teeth apart, or at least not clenched, their teeth will feel like they are in the same position when they awake as when they go to bed. In patients who clench or grind their teeth while they sleep, the back teeth come together first and are intruded (pushed into the gums) ever so slightly. This intrusion is imperceptible when the retainers are in, but when they are first removed, the front teeth temporarily hit harder than the back ones. This temporary change in the bite usually resolves itself within 10 to 20 minutes. Although this change in the bite is microscopic, the retainers do change the bite temporarily, and patients can detect it.

Full-Coverage Retainers Provide a Layer of Protection
This transitory change in the bite is a minor disadvantage of Essix retainers. On the positive side, patients who experience this problem are usually bruxers or grinders, and the plastic that covers the chewing surfaces provides protection to the teeth that is not offered by other retainer designs. Because the changes caused by the retainers are temporary, most patients have no problem continuing to wear them once they understand why their bite feels different each morning.

Reducing the Plastic Between the Molars Minimizes the Side Effects
There are a couple of ways to reduce this side effect of vacuum-formed retainers. First, the problem is compounded when patients wear both upper and lower full-coverage retainers. The more plastic between the teeth, the more they are intruded. Replacing the lower Essix with a bonded retainer eliminates one of the layers of plastic and reduces the amount of intrusion. Second, shortening the length of the retainers so they don't extend back to the molars may also reduce this side effect.

NOTE: The author, Dr. Greg Jorgensen, is a board-certified orthodontist in the private practice of orthodontics in Rio Rancho and Albuquerque, New Mexico. He was trained at BYU, Washington University in St. Louis, and the University of Iowa. Dr. Jorgensen's 30+ years of specialty practice and 10,000+ finished cases qualify him as an expert in two-phase treatment, extraction and non-extraction therapy, functional orthodontics, clear aligners (Invisalign), and multiple bracket systems (including conventional braces, Damon and other self-ligating brackets, Suresmile, and lingual braces). This blog is for informational purposes only and is designed to help consumers understand currently accepted orthodontic concepts. It is not a venue for debating alternative treatment theories. Dr. Jorgensen is licensed to diagnose and treat patients only in New Mexico. He cannot diagnose cases described in comments nor select treatment plans for readers. Copyright laws protect the opinions expressed here and can only be used with the author's permission.