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Orthodontics/Class III Underbite


My daughter who will be 6 in Dec was diagnosed with a Class III Underbite when she was very young.  Our primary dentist said he would suggest an orthodontic consult around age 5 or 6. He was unsure if they would actually start treatment, but he said he wouldn't want us to miss the boat just incase they suggested early treatment.  

I have a consult with a orthodontist and I was informed over the phone that they will be taking a Panoramic X-Ray.  I found it odd that this was told to me when making the appointment, when they didn't even ask why I was seeking ortho consult.  

I work as a CT Tech and am very familiar with radiation, etc.  

I am trying to find out medically, is a panoramic x-ray necessary for Class III underbite early treatment?  

And I'm hoping that we can talk with the doctor first, as if treatment is not necessary at this time I would prefer not to have the panoramic film done.  Many office like to get all that stuff done, then you sit with the doctor.

Please advise.

Dear Dawn.

First I apologize for the delay in replying as I have once again been traveling and out of town.

In answer to your question about the radiographs, you have some excellent concerns. Let me first explain some of the fundamental concerns about a Class III bite.

A Class III bite, much like a Class II bite, can be due to a dental-based (tooth) discrepancy, a skeletal-based (jaw bone size) discrepancy, or a combination of each of the two preceding. As I am sure you are aware, a Class III bite is one in which the lower teeth and/or jaw is displaced relatively forwards of the lower teeth and or jaw. Now this "under-bite relationship, assuming it is primarily skeletally based,  can be due to  1) Normal Upper jaw and overly large ( and forward projecting) lower jaw; 2) Normal Lower jaw but undersized ( and retro positioned) upper jaw; or 3) A combination of an undersized upper and over-sized lower jaw. All three combinations can result in an "under-bite: which is often noted as a Class III condition.

I will not get into the nuances of a pseudo Class III  condition where the upper and lower jaw are just fine and it is simply a matter of poorly positioned or improperly inclined teeth creating the under-bite condition. Dental or tooth based Class III determinations commonly utilize the relative positions of the upper and lower adult first molars and/or the upper and lower adult canines.

Assuming some form of skeletal Class III condition exists, it is a common treatment strategy to "develop" the upper jaw to help equalize things. The upper jaw is very commonly under-sized, and therefore lacking in sufficient anterior front to back dimension, as well as in sufficient transverse side to side dimension. In other words the upper jaw is very very commonly small front to back and left to right.

Now, fnally getting to your question of radiographic diagnostics. A panoramic radiograph will help to identify the extent of the likely crowding, including possible common impactions such as "jammed" upper abut canines which often in a poor vertical orientation or are "too squeezed" for room to erupt normally. A panoramic is helpful for this and very recommended.

A second type of radiograph to help determine the extent of the anterior-posterior discrepancy is called a cephalometric  or lateral head plate x-ray. The soft tissue profile of the face ( as seen from the side) as well as the hard tissue skeletal profile underneath the skin can be examined using such a cephalomteric radiograph. Subsequent diagnoses and treatment plans using reverse head gear, face masks, and other orthopedic types of intra-oral ad extra-oral appliances can then be developed.

A third Xray is called a Frontal radiograph and it can help determine how narrow the upper (and lower) jaws are. Transverse measurements for example can be made using a variety of anatomical points on the upper jaw, such as the left and right "jugal points".

In the ultimate analysis, treating the Class III condition may require addressing transverse as well as anterior-posterior discrepancies of the upper jaw. An extra-oral face mask can help with Anterior-posterior issues, where as an intra-oral fixed Hyrax palatal expander may hep with transverse shortcomings. It has been suggested in the clinical orthodontic literature that simultaneous transverse expansion be done along with Anterior posterior orthopedic appliances such as a face mask to take advantage of the plasticity of the upper jaw. These approaches are generally valid for growing children where the many bone sutures have not yet fused. An adult with such severe Class III discrepancies is generally a candidate for surgical orthognathics combining surgery to the jaw and orthodontics.

I hope that this has not been too complex. I would recommend the Cephalometric and panoramic work up. An alternative would be a 3D type xray. I appreciate your concern regarding dosages of radiation, and I can not give you advice on this because there are so many different machines and digital imaging products. As a whole, 3D type CT scans do appear to generally have a higher dosage impact.

Please check with your orthodontist. It may be worth while getting several orthodontic consultations from different doctors. This is an area of early treatment using orthopedic approaches to correct Cass III skeletal discrepancies where you will find a diversity of opinions for sure.

And finally, what I write here are only my opinions based on very limited information. My comments should not be viewed as any form of diagnosis, definitive or otherwise,  or any form of  treatment recommendation.  Indeed, in the ultimate analysis all final decisions, particularly clinical ones, should  only be made by qualified doctors who have had a chance to see you in person and who have had an opportunity to take and analyze proper diagnostic records.

Good luck Dawn and feel free to write again.  


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Paul Supan, DDS, MA, MPH


First may I say please set your questions to Public so other readers can benefit from the response. Also, if you look at my comprehensive answers, they are not short 1 or 2 paragraph quickie replies that anyone can type out in < 5 minutes. Instead I often will ask other colleagues in other specialties for their advice in order to provide you the questioner with a more interdisciplinary perspective. This all takes time. I ask for readers to therefore allow 5-7 days. You will be rewarded with a very detailed response.

Because of the nature of Orthodontic questions, any pictures of the teeth and X-ray images would be very helpful. If you write to me and explain that you have crooked overlapping front teeth can be interpreted in many many ways, and my goal is to provide a specific response that meets your needs.

I hold double specialty credentials. I am Board Certified in Orthodontics and Board Eligible in Dental Public Health. I welcome questions regarding Braces, Invisible Braces, & Invisalign, as well as issues involving combination Cosmetic Dentistry and Orthodontic treatment. Orthodontics alone sometimes is not enough to achieve that perfect smile. Gingival (gum) re-contouring, tooth reshaping, bonding and other services are sometimes needed. I also have substantial experience in the areas of Infection Control and Sterilization in the Dental Environment. My personal websites and are non-commercial for information purposes only and may provide you with some background to more precisely frame your question for

Please allow a week for a reply. I am in full time Private Practice, lecture on occasion, and am involved in many volunteer activities. I am therefore not always able to respond to questions straight away. Your understanding is appreciated.


Board Certified Orthodontist (ABO Diplomate) with over 25 years of Private Practice experience. Second Specialty Certificate in Dental Public Health with research experience at NIH, and Epidemiology Training & Research at Harvard, NIH, and the Centers for Disease Control (CDC) in Atlanta. Postgraduate Masters degree from the Harvard School of Public Health, as well as a Master of Arts Degree in Education.

American Dental Association, American Association of Orthodontists, Academy of General Dentistry, College of Diplomates of the ABO, OSAP - Office Sterilization & Asepsis Procedures Organization, Others

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BS College of William & Mary, DDS Medical College of Virginia, Masters of Public Health (MPH) Degree Harvard School of Public Health. Dental Public Health Specialty Certificate from NIH. Orthodontic Specialty Certificate from University of Rochester Eastman Dental Center. USPHS clinical research experience at NIH, and Epidemiology Training & Research at Harvard, NIH, and the Centers for Disease Control. Fellow of the Academy of General Dentistry (FAGD), and Fully Board Certified Diplomate of the American Board of Orthodontics. Board Eligible in Dental Public Health. Visiting Adjunct Associate Professor at the Meharry Medical College School of Dentistry, Nashville, Tennessee.

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