Tags
Asymmetry, Bruxism, Centric relation, Condyle (anatomy), Dentistry, Health, Radiography, Retruded Position of the Mandible, Temporomandibular joint, Temporomandibular joint disorder
Dental students are normally taught about the necessity of an overview radiograph in the screening for and in the early detection of undiagnosed hard tissue changes of the maxilla and of the mandible (neoplasms, tumors or any strange lesions). Most dental students have also been told the questionable value of the panoramic radiograph because of the superimposition of the structures due to the construction of the X-ray machine with its two axes of rotation ( focus and film in opposite directions). On the other hand the panoramic radiograph is the only routinely used radiograph in the dental practice in which comparisons between the right and the left sides of the jaws can be made, as both side are projected in the same film without any change of head position.
However,comparisons of horizontal dimensions are not possible due to the superimposition of structures.Vertical dimensions can be compared as the focus of the X-ray machine is long and narrow. From this point of view the panoramic radiograph therefore shows its strength and its unquestionable clinical value in assisting the dentist in finding the correct vertical and frontal relations between the two jaws. In other words, in evaluating the occlusion from a functional point of view the panoramic radiograph is an aid of utmost importance.
Steps in determining the vertical condylar / ramus asymmetries:
1. Determine the most posterior point of the two condyles and the mandibular angels.
2. Draw a line through the two points of each mandibular side. This line we have named ” the ramus tangent “.
3. Draw new lines through the points perpendicular to ” the ramus tangent” and do so also between the most superior point of the condyle and “the ramus tangent “.
4.Measure the condylar heights ( CH )and measure the ramus heights( RH ).
At a vertical mandibular asymmetry you most often will find a difference in vertical height between the two condyles as the ramus portion of the mandible is a most stable part of the mandible and is less reacting on traumata etc during growth and development.
In evaluating the condylar asymmetry it was suggested ( Habets LLMH,Bezuur JN,Naeije M, Hansson TL. The Orthopantomogram,an aid in diagnosis of temporomandibular joint problems 2. The vertical symmetry. J Oral Rehabil 1988;15:465-471) to measure the condylar heights on ” the ramus tangent “. The condylar asymmetry,expressed in percentage is calculated accordingly, ( Right-Left/Right+Left)x100%. An asymmetry bigger then 3% is to be considered a true morphological asymmetry.
If you want to estimate the vertical difference in mm between the two condylar heights you absolutely need to adjust for the magnification of the machine used.
From many years of daily clinical experience it seems as if a condylar asymmetry might be a major reason for an asymmetrical stomatognathic system and its asymmetrical function. The ” shorter condyle ” side is most often found on the mediotrusive side at laterotrusive bruxing. When there is a lateral slide between the retruded contact position of the mandible ( RCP } or the centric relation ( CR ) and the intercuspal position ( ICP ) or the centric occlusion ( CO ) the slide seems to be most often directed towards the ” shorter condyle “side. It seems consequent that a condylar asymmetry most likely will result in an asymmetrical function, bruxism with orofacial pain of either mainly arthrogeneous origin or of mainly myogeneous origin.
To recognize a condylar asymmetry, when present, is therefore in my opinion of utmost importance for the registration of the mandibular position used in diagnostics and in the treatment ,topics to which I will return within shortly.
HAPPY NEW YEAR!
Jamie said:
Hi torelhansson,
I just discovered your blog, it is presented very nicely and dealing with condylar asymmetry specifically is very interesting.
I am 22 years old and have had TMJ symptoms for a few years. My facial symmetry is slightly off (it is minor, but looking carefully reveals the right side of my jaw is slightly lower than the left, along with a noticeable occlusal cant), leading me to believe this could be the source of my TMD. I have begun seeing a TMJ specialist who has given me a repositioning splint.
Anyway, I am wondering whether this asymmetry stems condylar asymmetry, or whether my dislocated TMJ disc could be another reason for this minor facial imbalance.
Also, if it is the case that condylar asymmetry is the culprit, is there any non-invasive procedure to fix this, or would it require surgery?
Sorry for the lengthy message!
Jamie
torelhansson said:
Hi Jamie,
Thank you for your question.To diagnose a condition like yours can not be done from just a letter. However,it is my opinion that often a TMJ disk displacement is linked to a condylar asymmetry i.e. the shorter ” condyle side ” is unstable. I suggest that you discuss it with your dentist and that your dentist have a panoramic x-ray taken in which he/she easily can analyze the vertical dimensions of the two condyles. If there is a difference your dentist most probably can provide you with an occlusal stability through reversible means in form of a splint which in my view should be made around the ” higher condyle ” side. It is also my opinion that you will need to wear this splint 24hours per day during 6 months before irreversible treatment should be considered.Again these are just my thoughts and are in no way meant to substitute for a diagnosis or treatment plan between you and your dentist.
Thank you for reaching out via the blog.
Tore L.Hansson
jamie said:
Hi,
It’s been a while since my previous message but I managed to dig up a letter which included a photograph of an X-ray similar to the one described on this page. I have been wearing the splint for around 5 months now and my TMD symptoms are not improving, while my cant is exactly the same as before. It should be clear from the photo that the splint is more built up on the right side (left on the photo) as this seems to be the side with the longer condyle. Here are the photos:
http://cantedjaw.imgur.com
My dentist did not mention anything to do with my canted jaw as being a problem, but looking at the x-ray myself it looks as if there is condylar asymmetry. However, my maxilla also looks canted on one of the photos, which I did not notice before.
It looks like my entire jaw is crooked and I doubt this could be solved without surgery. Do you have any opinion on treating this cant?
Thank you
torelhansson said:
Reblogged this on Tore L. Hansson.