Another Kind of Orthodontic Crowding

One of the most common reasons patients seek treatment is crowding. Although some patients have big teeth, most crowding exists because the jaws are too small. Crowding in the front of the mouth is obvious – the teeth overlap and are crooked. Crowding at the back of the mouth, especially in the lower jaw, is less obvious and commonly goes undiagnosed. This orthodontic condition is known as posterior crowding.

Problems with Lower 12-Year-Molars
When the lower jaw is smaller than the upper, the most common manifestations in the front of the mouth are excessive “overbite” and crowded teeth. Sometimes, however, crowding in the back of the mouth is not so obvious. The most common symptom of this posterior crowding is a problem with the eruption of the second molars – impaction or partial eruption. Impacted second molars are obvious on x-rays, but the crowding associated with the delayed or partial eruption of the second molars is often overlooked.

Removing Bicuspids Due to Crowding is Common
When crowding exists in both the upper and lower arches, removing bicuspids is a common approach for matching the number of teeth to the space available. The need to remove bicuspids when there is visible crowding in the front of the mouth is usually understandable. Generally, if there is crowding in both the upper and lower, removing four bicuspids not only addresses problems in the front but also helps create more room in the second molar area.

Removing Bicuspids is Not Always Possible
But what if removing lower bicuspids is contraindicated? This is the case when a patient has little or no crowding in the front, has upright front teeth that should not be moved back, or has excessive overbite. Removing lower teeth under these circumstances would only make matters worse! So, how do we deal with posterior crowing in the lower jaw when we prefer not to remove bicuspids?

Moving Lower Molars Forward is Difficult
Some doctors might still consider removing the lower second bicuspids to allow moving the lower 6-year-molars to make more room for the 12-year-molars. However, this process is long, difficult, and unpredictable. The first and second molars are twice as wide as bicuspids, have two large roots, and take much longer to move. Even if a “heroic” orthodontist succeeded in moving the lower molars forward without compromising the front teeth (i.e., using TADs), what has been gained? He still had to remove two healthy bicuspids to create the space. Is there anything more “sacred” about second molars than second bicuspids?

Treatment Options for Crowded Lower Second Molars
The second molars may remain impacted or partially erupted after orthodontic treatment if all the teeth are maintained in a small lower jaw. If that happens, what can be done? If the second molars are impacted or don’t have enough room to erupt, they can be extracted just like bicuspids or wisdom teeth. If they are fully erupted but partially covered with tissue, given time, the gingiva will usually migrate distally on its own, exposing the entire occlusal surface. If the tissue is extremely thick or just doesn’t improve on its own, a periodontist, oral surgeon, or general dentist can remove the extra tissue.

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. The opinions expressed here are protected by copyright laws and can only be used with the author's written permission.