Why are Holding Arches important?

Why is it important to keep baby teeth and hold space if they are lost?

 

One of the first things many parents run into at their child’s dental visit besides regular cleanings and the occasional filling, is the question of removing baby teeth v. putting more money into saving them.  They may also be told that space must be maintained following loss of a specific baby tooth.  Before getting upset and thinking your Dentist or Pedodontist is trying to pile on to your child’s treatment plan, I want to explain the sequence of how permanent teeth erupt and how the baby teeth are important in the eruption of adult teeth (and overall alignment of teeth).

 

So generally lower baby teeth erupt from front to back with lower incisors erupting first (usually around 8mo to 12mo) and baby second molars erupting at around age 2yrs.  The chart below gives an overall summary (note the wide varied eruption estimates revealing a wide range of “normal” eruption pattern.

You will notice that there are no baby premolars (bicuspids); there are only 20 baby teeth (10 upper, 10 lower) as opposed to 32 adult teeth (16 over 16).  This will play a part in development as I explain later.  But for now, the important thing is that most children will have their full complement of baby teeth from age two forward.

 

When the permanent teeth begin to erupt at around age 6, the first to erupt are usually the same as the primary teeth; that is the lower front baby teeth get loose (ideally) and the lower permanent incisors erupt to take their place (usually starting out behind the baby teeth only to be pushed forward into the arch by the tongue).

 

What parents may not realize is that the next permanent teeth to come in actually come in behind the last baby molars around age 6 to 7. The importance of this may escape most people but what this means is that all of the space for the future permanent teeth is set by the time the permanent 1^st molars erupt around age 6 to 7; permanent canines and premolars won’t erupt for another 4 to 5 years.  Any loss of space from permanent molars drifting forward will increase crowding of future teeth and can reach the point of requiring removal of teeth to align.

 

Also, since the permanent premolars develop under baby molars (remember, no baby premolars), it turns out that the baby teeth actually hold more space (termed the “Leeway Space”) since the premolars are smaller than baby molars overhead.  In fact, maintaining this Leeway space can make save up to 3mm per side and can make the difference in a borderline extraction case of braces later of whether we remove permanent teeth or not.  Holding this space can also help to prevent severe crowding and/or impaction of teeth as they try to erupt.

 

To illustrate this, consider the following patient where an upper left baby 2^nd molar was removed early and inadequate efforts were made to hold space (there is actually a bar attempting to hold space however these un-lateral bars are insufficient to hold space in my experience as this demonstrates).

 

Notice the space on the right in front of the banded tooth; this space of 3mm is left over from a 10mm tooth that was removed.  The bar was placed late and space continued to be lost.

 

 

 

In the radiograph, you can see the severe crowding under the lost space (in fact there is crowding throughout the arch due to a general narrowness and under-development of the arches).

Following expansion of the upper arch to restore the arch size and an early effort to re-open some of the lost space, you can still see the lingering effect of this lost space as the premolar erupts more into the roof of the patient’s mouth.

 

It may seem unfair that that the molars will drift forward when baby teeth are lost however this is why the baby molars are larger than the underlying premolars; because the permanent teeth drift forward, Leeway space is always lost during the natural eruption of teeth so having extra space gives time for the premolar to erupt before it gets blocked.

For this reason, anytime a baby molar (especially a baby 2^nd molar) is lost before the permanent teeth are ready to erupt or even if we need to use the Leeway space, your dentist or Orthodontist will likely recommend a “Holding Arch” to maintain the Leeway space.

 

 
In the lower arch, the holding arch is a bilateral holding arch from permanent molar to permanent molar.

 

In the upper arch, we generally prefer a wire running across the roof of the mouth extending from molar to molar.

Believe it or not, a simple holding arch as those shown above can easily prevent the need to remove permanent teeth later and can reduce crowding significantly.  So when your Dentist, Pedodontist or Orthodontist recommends a holding arch, you can be sure they are looking out for the best interests of your family.  Likewise, if there is a chance to save a baby tooth with a Stainless Crown and baby root canal (pulpotomy) instead of removing it and having to place a holding arch, you can see it may be worth the cost, especially if that tooth in question is supposed to be there for a few more years.

 

If you have questions or comments concerning this or any orthodontic question, please feel free to make a complimentary new-patient appointment at either my Steiner Ranch location or my North-central Austin location on West 35^th street and MoPac.

 

Dr. James R. Waters 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 and is a Diplomate of the American Board of Orthodontics.  Dr. Waters and his wife of 20 years live in Austin, TX with their 4 children where he has a thriving, multi-faceted Specialist practice with locations in Steiner Ranch and North-Central Austin.  You can learn more about Dr. Waters at BracesAustin.com.