Expanders used to restore ideal arch width in the non-crossbite crowded arch

For many years, expanders (RPE) have been used by orthodontists to correct misfit jaw sizes or crossbites by pushing the two bones of the upper jaw apart from each other thereby widening the upper jaw.  In turn, the lower jaw would fit better and there would now be a larger circumference in the upper arch making more room for crowded teeth.  The lower arch which may have been shifting from one side to the other due to a poor fit now would re-center itself and the remaining crowding would be treated with traditional braces.

However sometimes the upper jaw can be just as narrow and during development in the lower arch, the lower teeth become restricted within the upper arch.  Instead of a crossbite where you see a narrow upper jaw and normal sized lower jaw shifting sideways into a crossbite, the lower teeth can collapse or lean inward toward the tongue creating a smaller circumference and severe crowding (a small upper jaw can lead to a small lower arch form).  This can actually push the lower backward and restrict growth leading to severe overjet.

 

 

 

As the lower teeth lean inward, they continue to block un-erupted teeth and we start seeing impactions (un-erupted teeth locked down deep in the bone without room to erupt) which cause teeth to cross over each other and can even lead to developing roots being destroyed.

In the recent past, when there was a narrow upper jaw and lower jaw, orthodontists would remove teeth (extract all 1^st bicuspids) so that the remaining teeth would fit into the narrow arches.  Over time these cases would show a lack of lip support and through continued growth the nose and the chin would grow and the lips would appear to sink inward creating a concave or “witch” profile.

What we as orthodontists have learned from this is that when we see a narrow upper jaw with crowding of the front incisors at age 6 to 7, and we see crowding of lower incisors as they are erupting, we know if we restore the width of the upper jaw to accommodate all future teeth, we will likewise remove the constriction to the lower jaw and the tongue will push on the lower arch to upright teeth and restore adequate arch length in the lower arch as well.  In most cases, this will make future extraction of permanent teeth un-necessary and will reduce the time in future braces or may even eliminate the need for braces later.

In simpler terms, think of jaw size (or circumference around the jaw) in both the upper and lower arches versus the actual added widths of all teeth.  If the width of all teeth within an arch is greater than the circumference of bone, then they will not fit since the width of the jaws from molar to molar does not change past age six.  To see the widths of un-erupted teeth , as the permanent teeth develop long before they erupt, an orthodontist will take a panoramic x-ray.  Severe crowding would signify a lack of arch length.  This means that as soon as a child’s upper jaw is identified as narrow and crowding begins to appear in the front incisors, expansion can be used to restore arch length and thereby allow adequate space for future teeth to erupt instead of letting them crowd more and more until they become either impacted or too crowded to fix without removing permanent teeth.

 

In truth there are other factors that help determine the need and timing of expansion (RPE) since as natural mesial drift of teeth, shifting of the lower jaw, parental facial patterns and positions of teeth; a well trained certified orthodontist will help guide you during the treatment planning process but you have to see one first!  This is why the American Dental Association, American Association of Orthodontists and the American Board of Orthodontists all recommend kids see an orthodontist by age 6 to determine growth and possibly identify developing issues that will affect teeth later.    

 

Dr. James R. Waters is a practicing Board Certified Orthodontist in Austin, TX.  He is a 1996 graduate from UTHSC Dental School in San Antonio, 1997 graduate of Advanced Dentistry from the UNMC in Nebraska and the 2001 Valedictorian graduate from the prestigious Saint Louis University Orthodontic Program receiving the J.P. Marshall award for clinical excellence in 2001.  He holds a Bachelor’s Degree in Science, Doctorate in Dental Surgery, a post-doctorate certificate in Advanced Dentistry, post-doctorate Degree in Orthodontics & Dentofacial Orthopedics and a Master of Science Degree in Orthodontics.  Dr. Waters and his wife of 18 years live in Austin, TX with their 4 children where he has a thriving, multi-faceted Specialist practice.  You can learn more about Dr. Waters at BracesAustin.com.