Do You Measure Where the Condyle Goes from Centric Relation?

The BiteFX Blog for All Things Relating to Occlusion

Do You Measure Where the Condyle Goes from Centric Relation?

Posted by Doug Brown on Fri, Oct 07, 2011 @ 05:17 PM

delicious

We were exhibiting at the International Academy of Gnathology meeting last week so I had the opportunity to sit in on some of the very interesting presentations they had on their program. One of the presentations in particular has set me thinking so I thought I’d share its challenge on our blog. It was given by Dr. Tom Basta, one of the directors of the Foundation for Advanced Continuing Education and titled “Occlusion – Myths & Realities”.

Dr. Basta presented on a number of topics but one stood out to me as I’ve heard a lot of discussion on the topic and was convinced I understood the answer. The topic was: Where does the condyle (or condylar axis) go when a patient encounters a posterior interference in closing from centric relation (CR)?

As someone who was trained as a mathematician (I’m not a dentist, though I’ve now been involved in animating the concepts around occlusion for several years) it has always frustrated me that there is a debate in this area as we are talking about a relatively simple application of high school geometry. We are taking an inflexible object (the jaw) and translating and rotating it by measurable amounts. What happens to the condylar axis is well-defined – i.e. there’s only one answer assuming we agree on two facts: where the jaw starts (CR) and where it ends up in its position of maximum intercuspation (MIP). As far as I can tell everyone agrees on where those two positions are. Some may take longer before they are confident they have found the true CR position and have not found a “CR du jour” position (Dr. Basta’s expression) which is close but not the fully seated position that can be established if the lateral pterygoid muscles are given longer to relax. For the debate I’m considering in this article it actually doesn’ t matter whether you start with a confidently established CR or a quickly established “CR du jour”.

In case you are not aware, I’d summarize the debate I am talking about as a discussion between the following two positions:

After encountering a posterior interference the jaw slides down and forwards from CR to MIP.
OR
After encountering a posterior interference the jaw pivots about that point of contact so that the condylar axis moves down and backwards from CR to MIP.

Using slightly crude diagrams:

Jaw in centric relation	Is maximum intercuspation: Down and forwards or ...	Down and backwards?

I’ve heard dentists from both “camps” swear that the majority of their patients exhibit the behavior which they believe happens. How can that be? Surely they have not both attracted patients whose anatomies match their beliefs? That is not credible. Those who argue for “opinion” #1 say that they see the teeth slide forwards and there are no muscles that support the rotation believed to happen for “opinion” #2. Those who argue for “opinion” #2 say that they see the condyle pivoting down and back so that’s what happens.

I’ll give the mathematical answer to this debate in a future article and provide you with the mathematics to prove what happens – along with ways you can prove to yourself what’s happening with each patient’s condyle. However, for now I just want to share one thing that Dr. Basta communicated in his presentation and ask you one question.

What I liked most about Dr. Basta’s presentation is that he, and his FACE partner Dr. Jeff Brucia, take measurements so that they can establish precisely where the condylar axis goes. They do this using physical equipment which is fixed to the patient’s skull and jaw. Consequently they have hundreds of measurements of what happens to the condylar axis. This seemed like a pretty good way of verifying the answer to me!

Therefore my question to you is:

Do you measure where the condylar axis goes when the patient’s jaw moves from CR to MIP?

If you don’t make that measurement, what makes you confident about your opinion of what happens to the condylar axis?

In my next blog I’ll explain why it is unwise to take a firm opinion on this subject without taking the appropriate measurements.

PS – Add your answers to the comment area below. And you might amplify your answers by telling us what you measure and how you measure it. Would also be good to know if you keep a record of these measurements so you have a database of results (even if it’s contained in a filing cabinet).

Tags: Occlusion, Centric Relation

Comments

Great topic Doug. The other way to look at this is to question what the posterior tooth interference really is. For the condyle to move downward and forward, there is a slide that the lateral pterygoid must continue to contract to clear. But if the condyle is moving downward and backwards, then the posterior interference is acting as a fulcrum. When we use Condylar Position Indicators on articulators we see both phenomenon occur. I'd love to hear your take on this Doug, because while I "see" it on an articulator, I can't quite wrap my head around what muscle force vector would allow for a fulcrum.
Lane

Posted @ Friday, October 07, 2011 7:02 PM by Lane Ochi

Interesting blog. from where i sit both situations occur. you can even have both situations occuring in the same patient. a slide on one side and a fulcrum on the other. unless co =cr, the mandible has to move out of cr when the teeth come together. The avoidance of the posterior interferences determines the amount of the cranial base to mandible discrepency, and which direction this occurs.

Posted @ Thursday, October 13, 2011 8:20 AM by mark luttrell

Lane - I'll explain more of this in my next blog on the subject which will include a video presenting the math. My main response to your question on what muscle vector would allow the fulcrum is that that question is saying "How does it happen?" which needs to be asked AFTER we answer the question "What happens?"

What happens is based on observation and measurement. It should not be influenced by our ability or inability to explain how it happens.

Posted @ Wednesday, October 19, 2011 11:34 AM by Doug Brown

Mark - good comment.

When you say you see a fulcrum occur, what exactly do you see? When I hear "fulcrum" I imagine the jaw rotating about a fixed point, but if you are seeing a slide on one side, the other side must move (translate) too, though possibly to a lesser amount and in a different direction (for example the right side slides forward and the left side moves left and forwards as the jaw rotates around the left condyle).

So I'm concluding that when you say "fulcrum" you are probably saying that there appears to be more rotation than translation, not that there's rotation about a static point of contact. Is that correct?

Posted @ Wednesday, October 19, 2011 11:46 AM by Doug Brown

Doug,

You have picked out an interesting topic for discussion. People that record and measure condyle position definitely are going to be the only people to see the back and down movement of the condyle. People that try to explain condylar movement by purely a muscle vector of force model may have over simplified the biology of the system The how and why we see the backward and downward condylar movement are open to discussion . The osseous anatomy of the fossa on the medial aspect limits the condyle to one uppermost midmost position in CR or Adapted Centric Posture(ACP). The question now needs to be asked is how often do we see the condyle move back and down when the condyle/disc assembly is anatomically intact and there has been no dental intervention on the teeth. Most of the time when I see the condyle move back and down there has been stretching of the collateral ligaments and an anterior disc displacement. The amount, size, and position of the deranged disc or the hypertrophy of the retrodiscal tissue can effect the condylar position irregardless of the vector of force of the muscles. What about restorative dentistry and force directed orthodontics which introduce distalizing forces on the condyle. I think this topic is worthy of input from many camps. I would like to hear more from FACE, more from OBI, more from Roth-Williams and more from the TMD docs that have restorative backgrounds. I have never been a blog person but I feel I owe you this response because you are a fellow student of the stomatognathic system and bring a curious mind to the controversy.

Posted @ Sunday, October 23, 2011 11:29 AM by Dick Schirmer

Dick - appreciate your contribution to the discussion and agree it will be great to hear from others. I'll be collecting some of that input myself directly so will either include it in future blogs or in comments on this blog.

My focus initially is on WHAT happens, based on observed movement of the lower teeth. Once it is clear what happens, then we work out HOW/WHY it happens - a topic that is debatable, but should be based on observed data.

Posted @ Monday, October 24, 2011 12:06 PM by Doug Brown

There appears to be an assumption that CR is a significant position for the healthy function of the patient (as opposed to a reference point for restorative dentistry). I'm not sure I agree with this, and, as malocclusion cannot be defined in anything other than functional terms, I am less concerned with shifts from CR to CO.See Ackerman, Ackerman and Kean, A Philadelphia Fable: How Ideal Occlusion Became the Philosopher’s Stone of Orthodontics, Angle Orthodontics;
77:1, Jan. 2007, pp 192-3. for a review of this.
BTW, the mandible and joint complex are NOT rigid under functional loading. I look forward to seeing the maths.

Posted @ Tuesday, October 25, 2011 4:02 AM by Andy Toy

Andy - Interesting comments and paper. My thoughts:

1. What I understand of the CR position is based on input from many dentists who say that taking that as a significant position has improved the longevity of their dentistry.

2. I would agree with the Ackerman paper that it is a pity that there appears to be no strong scientific studies to prove one view of occlusion versus another. (Though I understood that people like Bob Lee, founder of OBI, came to his conclusions on occlusion based on the study of many subjects who still had healthy dentitions in their later years.)

3. To me the Ackerman paper only says "pity there's no scientific evidence" - although it questions commonly held beliefs it doesn't give any data to back a different understanding.

4. I'd be interested to hear how you determine the mandible and joint complex are not rigid under functional loading, and to know the extent to which you believe the mandible flexes.

5. My understanding is that a lot of the damage from malocclusion occurs at night when there is no conscious guidance of the jaw so it is important to understand the nighttime positions of the jaw - possibly more so than the functional positions (which I take to mean chewing).

6. I'll publish my maths in the second half of November as I have a 2-week visit to the UK coming up and won't be able to produce the video I think that will be necessary to communicate the concepts until I return.

7. Let me know if you'd be interested in discussing this on the phone some time and I'll give you a call when in the UK.

Posted @ Wednesday, October 26, 2011 12:24 PM by Doug Brown

Thanks for the offer Doug. Please email me when you're in the UK. The science of occlusion is a difficult one to study, at least in part because there are several models or theories, so that any systematic review is unlikely to reveal anything other than 'noise'. We are testing a model based on anthropological evidence (which is probably the strongest scientific basis of all I have come across). The results in the clinical setting have triangulated well, so my cinfidence in this model is growing. We have a Biomechanics research team at Loughborough University providing further evidence to support it. Go to the websitewww.pgocclusion.com for lots more on this.

Posted @ Wednesday, October 26, 2011 2:02 PM by Andy Toy

Unfortunately, the circuitous arguments generated from personal opinions, dogmatic occlusion camps, and a complete lack of biomechanical fundamentals regarding the kinematics and sensorimotor control of the joint have lead to misguided and erroneous assumptions predicated upon ignorance.
Most dentists have not a clue as to the functional heterogeneity of the masticatory muscles. The muscles are partitioned and act in a task dependent fashion predicated on proprioceptive input from multiple receptor sources which have been integrated into shared and cross-system interactions called multisensory processing. Furthermore, the motor nuclei for the muscles are functionally partitioned, as well, creating preferential pathways for a rich repertoire of movements and interactions.
The deep masseter alone has been investigated in three regions and found by Weijs and Blanksma to have unique properties. This region of the masseter muscle forms a cruciate arrangement with the superficial masseter and along with the middle and posterior temporalis is likely to pull the condyle down and back subsequent to comminution. Gravity also plays a role as a contributor to jaw position and the inherent intra-articular pressure.
The truth lies within understanding the fundamental truth behind Posselt's envelope of motion. There are two cuspal positions. The (ICP) position occurs at the final apex of closure where the condyle/disk(if preserved) assembly is positioned against the fossa in its most anterior superior position. The RCP is a tooth bound position where the condyle disk system is relatively loaded less. That is why studies comparing CR/MIP show almost 100% discordance between the two. Nature doesn't make so many mistakes. Additionally, centric relation is considered a border position which means the assembly is articulated...loaded. Who has read the literature concerning continuous loading of a joint? Who decided this is an orthopedically stable position? Clearly, somebody who has never read about the biology of joints.
The conviction of an habitual position because it lacks coincidence with Centric Relation implicates this as the perpetrator violating this sanctimonious singularity. From this concept, a muscle hyperactivity is hypothesized and advanced as doctrine for the world of dentistry to accept. Unfortunately, those who would dare to read the works of Phanachet, Murray, Uchida, Ruangsri and Santosa regarding the heterogeneous response properties of the superior and inferior head of the lateral pterygoid complex would realize this is not a likely scenario.

In closing, for now, I had been a practicing centric relation dentist for 25 years and a rather staunch supporter of this approach. The inconsistencies lead me to research the underlying principles which govern this system. Unfortunately, I believe we have made a great mistake.
All challenges and questions are welcome.... on any level!

Posted @ Tuesday, December 13, 2011 2:06 PM by Larry Gottesman, DDS

Larry, I've been in private practice and education for over 3 decades and I have no idea of what you are saying or advocating.......................

Posted @ Tuesday, December 13, 2011 5:28 PM by Lane Ochi

Lane, that's just the point. Lot's of dentists talk about the joints,position of the joints, and treatment of TMD associated symptoms without very much educational background from allied scientific research. The really important articles are either ignored or simply, no one knows about them. I have heard these type of comments time and again from well-trained dentists who feel they have a good handle on this system and yet they have never heard of the concepts I discuss....you are not alone. If you really wnat to learn more about this system and expand your horizons,I would be happy to help. Post your email address and I will be happy to arrange a time when we can talk at length and share this body of information with you. I recently lectured on Saturda, November 26th at the GNYDM. I do not advocate an alternative position, but put into perspective why we see what we do and how the interpretation of this information has been misperceived. I look forward to speaking with you. Thanks, Lane

Posted @ Wednesday, December 14, 2011 7:42 AM by Larry Gottesman

Larry/Lane - I'll send you each the other's emails so you don't have to post them on this public blog. Doug

Posted @ Wednesday, December 14, 2011 11:11 AM by Doug Brown

Hi Doug and Lane:

Doug: Since you have requested that Lane and I keep you abreast of our conversational progress, I wanted to post my personal response to Lane;.

Lane:

It is my pleasure to meet you. Permit me to introduce myself. I am Larry Gottesman. You were nice enough to take the time to respond to my comments on Bite FX blog. I have taken a brief look at your long service to dentistry and I am quite sure that you are very well trained and an advocate for excellence in dentistry.

My goal is to reach dentists, like you, who have been exposed to occlusal concepts, gnathologic principles and have made a strong commitment to providing exceptional care on behalf of their patients. I embrace the same values.

I have spent the majority of my last 35 years as a practicing “Centric Relation” dentist. During the past 5 years, I have made a concentrated effort to unify the concepts which govern restorative options, joint treatment and position. What I found was a significant body of literature that captured my interest. The orthopedic paradigm which I learned from neuromuscular research (not NMD) explained the connection between proprioception and neuromuscular control in joint stability. From that time forward, I have devoted much of my spare time to developing a lecture syllabus that explains these principles to dentists, so they can understand how our system functions on a higher level. The story is compelling and enlightening.

I have been able to go deep inside the sensorimotor control system and pull out the salient components which govern the biomechanical principles of our dynamic system. Of course, you have never heard of any of these phenomenons and neither did I until 5 years ago: it has now become my passion. I have met many dentists who, like you, had never been introduced to any of these topics: they have become intrigued by the global perspective I bring to dentistry. I am the only one in mainstream dentistry, to my knowledge that has dovetailed the elements of the neurosciences with neuromuscular research and inserted it into a dental template.

This is not a body of work that comes with a cookbook or cookie-cutter approach to restorative care. Rather, it helps the dentist to grasp the concepts at work and use them to advantage treatment choices from a risk assessment perspective as never seen before.
For any fellow professionals who may be reading this blog, I offer explanations that go far beyond the conventional jargon. It would be my pleasure to help anyone who would want to learn more.

Larry

Posted @ Wednesday, December 14, 2011 7:15 PM by larry Gottesman

Buenos días Dr. Larry.
Me gusta su visión "INTEGRAL" respecto de el control Neuromuscular y su función integral .
Si lo desa puede conversar tranquilamente conmigo.

Saludos, afectuosos
Dr.Antonio Rey Gil
Valladolid-España

Posted @ Friday, December 23, 2011 7:59 AM by Dr.Antonio Rey Gil

Buenos Dias Dr. Antonio:

I am sorry that I don't speak Spanish. I will try to have your comment translated so I can respond to your comment.

Best,

Larry

Posted @ Friday, December 23, 2011 8:28 AM by Dr. Larry Gottesman

Dear Antonio:

Thank you for your kind thoughts. I would be happy to talk with you about this at any time. My son, Eric translated your comment for me.

Happy holidays.

Best,

Larry

Posted @ Saturday, December 24, 2011 10:59 AM by Larry Gottesman

Buenos días Dr.Larry, muchas gracias por su felicitación en esta Navidad.
Estoy encantado de saber de sus apreciaciaciones y su trabajo.
Dejo mi email para una mayor fluidez en nuestra conversación.
doctorrey@telefonica.net
Espero atentamente sus apreciaciones.
Yo tambien quiero felicitarles a usted y su hijo Eric, vea por favor esta felicitación aquí:
http://antonioreygil.wordpress.com/2011/12/16/feliz-navidad-familia-amigos-pacientes-y-colegas/

Posted @ Tuesday, December 27, 2011 7:37 AM by Dr.Antonio Rey Gil

Antonio -

Feliz Navidad a usted. Sería provechoso si usted podría utilizar una herramienta como Babelfish (http://babelfish.yahoo.com/translate_txt) para traducir su texto de modo que veamos el texto español e inglés junto.

Gracias,

Doug

Others: Here are (Babelfish) translations of Antonio's comments (not 100% but probably sufficient for reasonable understanding).

From 12/23:

Good morning Dr. Larry. I like his vision " INTEGRAL" with respect to the Neuromuscular control and its integral function. If desa can talk calmly with me.

From 12/27:

Good morning Dr.Larry, thank you very much by its congratulation in this Christmas. I am enchanted of knowing of its apreciaciaciones and their work. I leave my email for a greater fluidity in our conversation. doctorrey@telefonica.net I wait for its appreciations kindly. I also want to congratulate you to them and his son Eric, sees this congratulation please here:

<<link to Dr. Rey's Christmas greeting video>>

Posted @ Tuesday, December 27, 2011 5:26 PM by Doug Brown

Larry - A couple of questions on your first post:

1. You say the deep massetor, along with some other muscles, is likely to pull the jaw down and back. As, to my understanding, all the muscles mentioned pull in the upward direction it is difficult to see how they produce a downward motion. How does that work?

2. Gravity is a pretty weak force compared to the capabilities of the muscles so I'd only think it plays a significant role if the upward-pulling muscles are relaxed. In what way do you see it as being a significant force?

Thanks,

Doug

Posted @ Tuesday, December 27, 2011 5:35 PM by Doug Brown

Hi Doug:

Thanks for your question. Take a look at the works of Blanksma and van Eijden regarding the heterogeneity of the Masseter and temporalis muscles. There is considerable diversity in their isoforms and fiber-type composition as well as histochemical differences. Also, Weijs in 1999 discusses the specialized role of the posterior deep masseter. All of the muscles of mastication, as in many of the other muscles of the body are functionally partitioned. In other words, they have regional variation and specialization. If you want to take a look at the lateral pterygoids, you should review the works of Phanachet, Murray, Uchida, Santosa and Ruangsri. It will open your eyes dramatically because the hyperactivity model does not exist as being causally related to a prematurity to CR which is considered to create a slide resulting in increased EMG in the lateral pterygoids and disk displacement. You should also take note of the timing and amplitude of different muscle regions during various excursions and movements which is called "task-dependent."

I'm sorry to say, that the story both you and I learned is no more than made up. Though well told and compelling, common sense always works best in the presence of ignorance.
These studies I suggest you read have been around for quite some time, Starting with Thornbell and Erikson in 1983 and continuing with a grouping of landmark article by McMillan and Hannam starting in 1992. Unfortunately, nobody has taken the time or impetus to carefully analyze the system from a scientific approach and put it into perspective.

Take a look at Posselt's envelope of motion. The diagram tells us that RCP + HMIP or CO are located below CR. The only time the joint is relatively unloaded is by the teeth at CO. Otherwise, as soon as your teeth separate, you are on the border path and your condyle-disk-fossa assembly is articulated and loaded. This tells us that the condyles are not the posterior determinants of occlusion-- the teeth are the posterior determinants of occlusion. The condyles become the static and dynamic stabilizers of load on the path.

As for gravity, the sensitivity to gravity is inherent in the sensorimotor system of all nature's creatures. While you may think it small, it is quite effective. Under circumstances of microgravity, take a look at the NASA website related to the adverse biological events which occur during space travel. Furthermore, the posterior and middle temporalis would likely assist in the downward and backward movements of the condyles not to mention the cnanges in intra-articular pressure.

Doug, there is no substitute for study in this area. This whole story regarding the hinge axis position and CR is made to accomodate gnathological principles developed from treatment of edentulous states (when there were no posterior determinants of occlusion). The buck stops here. I have close to 5,000 articles across all scientific borders to deal with the fallacies which have been generated related to this concept.

Most of the dentists involved in CR dentistry are great people who want to embrace the concepts which will benefit their patients and give them predictable results. I applaud all of them. However, a discrepancy between CO and CR is present 100% of the time because it is supposed to be like that! That's what the envelope of motion tells us. It is about time somebody stood up and said this is wrong!

If you want to set up a debate regarding this issue, I will be happy to stand alone with whatever panel you would set up and defend this position.

Thanks,

Larry

Posted @ Tuesday, December 27, 2011 7:05 PM by Dr. Larry Gottesman

Doug:

You should also take a look at the configuration of the deep masseter and deep posterior and middle fibers of the temporalis. Most standard texts on occlusion leave the deep masseter out of the picture. Get a good pictorial atlas so you can see it clearly. If you send me your email address, I will send a few pictures of the muscles in pdf.

However, the origin within the zygoma of the deep masseter and its insertion on the various parts of the ramus and coronoid process set up pivoting actions between the various muscle partitions to pull it back and down.

Thanks,

Larry

Posted @ Tuesday, December 27, 2011 7:15 PM by Dr. Larry Gottesman

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Do You Measure Where the Condyle Goes from Centric Relation?

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