I don’t think I’ve ever had a patient excited about having teeth removed as part of orthodontic treatment. Nevertheless, there are some mouths that just don’t have enough room for all 32 teeth (in fact, if you count wisdom teeth, less than 15% of Americans keep all their teeth). Parents seem relieved when I offer the option of an expander in the upper arch as an alternative to extractions. Can expanders also be used in the lower arch?

There is a growth plate in the palate
The anatomic feature in the upper arch that allows for the use of palatal expanders is the mid-palatal suture. In children younger than about 15 years of age, this suture or growth plate is immature and “stretchable.” If soft cartilage is present in the palate, the two halves can be slowly separated by a series of very small “activations” of an expansion screw built into the expander. In still-growing patients a gap develops between the upper two front teeth as evidence that the suture has been opened rather than the crowns of the teeth being merely tipped outward. If the mid-palatal suture has already fused however, there is no separation of the front teeth and any expansion obtained is purely dental (just tipping the teeth towards the cheeks).

There is no growth plate to stretch in the lower arch
The problem with using an expander in the lower arch is that there is no suture close to the teeth to expand. There are two growth plates in the lower jaw, but they are located up by the joints, not down by the teeth. Any expansion that takes place in the lower is strictly tooth movement. There is no problem with this as long as there is sufficient bone and gum around the roots. Terms commonly used to describe expansion in the lower arch are “uprighting” if the teeth are tipped inward initially and “flaring” if they are already upright and get pushed over the edge of the supporting bone by the treatment.

All lower "expansion" is actually just tooth movement
There are lots of ways to upright or flare the teeth in the lower arch to resolve crowding. Some orthodontists use “sagittal” appliances (removable retainers with an expansion screw built in) while others use lip bumpers. Some doctors use a wire behind the teeth with a spring on it. I have even seen banded expanders with jackscrews just like those we use in the upper. What the research shows however is that any expansion that takes place in the lower arch is accomplished by tipping teeth only and not by moving bone.

Braces provide the most predictable expansion in the lower
Understanding that the results will be the same no matter how obtained, I feel that the most efficient way to tip the teeth AND align them at the same time is with fixed appliances (braces). The expansive force comes from the wires themselves and springs that we thread over them to push the teeth apart. The bottom line is that resolving crowding in the lower arch requires either tipping the teeth or extractions. The decision to expand or extract is determined by the supporting structures (bone and gums). The shape and size of these structures are genetically determined and it is the orthodontist’s job to decide which option will produce a final result that is attractive, healthy, and stable.

Can the lower arch be expanded? Absolutely. Can expansion be used in every case to eliminate the need to have teeth removed? Nope. Ask your orthodontist if you have enough bone to allow for the flaring that will take place if teeth are not removed. If you are not a candidate for expansion, realize that the removal of teeth may be necessary for the best outcome.

NOTE: The author, Dr. Greg Jorgensen, is a board-certified orthodontist who is in the private practice of orthodontics in Rio Rancho, New Mexico (a suburb on the westside of Albuquerque). He was trained at BYU, Washington University in St. Louis, and the University of Iowa in the United States. Dr. Jorgensen’s 25 years of specialty practice and 10,000 finished cases qualify him 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 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 the state of New Mexico. He cannot diagnose cases described in comments nor can he select treatment plans for readers. Because he has over 25,000 readers each month, it is impossible for him respond to all questions. Please read all of the comments associated with each article as most of the questions he receives each week have been asked and answered previously. The opinions expressed here are protected by copyright laws and can only be used with written permission from the author.