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I can't get the diffrence between "Centric Relation" & "Centric Occlusion"

Discussion in 'Dental' started by SHO4, Mar 2, 2012.

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  1. SHO4

    SHO4

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    Hello ladies and gentlemen! :)

    I've been trying to get the difference between "Centric Relation" & "Centric Occlusion" but I can't , please help?
    it would be helpful if you post some photos :luck:
  2. Sublimazing

    Sublimazing Nasal Intubator

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    Centric occlusion is the position and contact of the teeth when the jaw is in centric relation

    An edentulous patient can be in centric relation, not centric occlusion
  3. Dr. Dai Phan

    Dr. Dai Phan Senior Member Moderator Lifetime Donor SDN Advisor

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    When you think of CO/CR, think of the condylar head in the fossa and its relative position. CO or habitual position is position of the condylar head in the fossa when the teeth come together. This is often dictated by habit and the teeth that gives you the "feel right" feeling when you bite down. In this postion, the condylar head can be ANYWHERE within the fossa. CR is when the condylar head is in its most ANTERIOR and SUPERIOR position and in this position, most often the teeth don't come together normally. If you put yourself in CR and close down, you will feel the bite is off. So, the teeth,habit dictate CO position while condylar head/fossa dictate CR position.

    If a person does not have any teeth at all, then the condylar head/fossa relationship will be determined by:

    1. Habitual position.
    2. CO when dentures are in place. Yes, edentulous patients can have CO too.
    3. CR if you put patient in this position or the dentures are made in a way that upon closing down, the condylar head is in SUPERIOR/ANTERIOR position.

    Is that clear at all? DP
  4. djeffreyt

    djeffreyt Senior Member

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    Dr. Phan is correct in his more detailed response. The response quoted above is only correct if the teeth contact in maximum intercuspation perfectly with CR. Usually CR and CO do not coincide perfectly.
  5. Firm

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    Dr. Dai Phan does it again! What's up chump? :D How have you been Dr. Phan?
  6. Prince Kay

    Prince Kay

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    I think I've noticed something little in Dr Phan's contribution. From my understanding and references, when in centric relation (CR), the head of the condylar is in the most POSTERIOR and SUPERIOR position rather than ANTERIOR and SUPERIOR. Centric occlusion is the HABITUAL occlusion. In this case, the head of the condyle is not necessarily in the most posterior position, but may assume a central position. Thus, for most dentate people, CR and CO do not coincide but have a difference of up to 2mm.
    Edentulous patients do not have a CO on their own, but have a CR. Complete dentures are fabricated in CR because this is the only form of reproducible occlusion in edentulous patients. So with the complete dentures (teeth) in place, CR=CO for edentulous patients.
  7. Dr. Dai Phan

    Dr. Dai Phan Senior Member Moderator Lifetime Donor SDN Advisor

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    Regarding the position of the condylar head in CR, unless it is changed again in the past 10 years, it should be anterior/superior position. For edentulous patients, they have CO because not all cases are restored in CR position. Even without teeth, patient will have a habitual closing position (very rarely in CR position) and with dentures in place, patient will attempt to occlude to where the bite "feels right". If the registration is done in CR and IF the patient can occlude in this position and ADAPTS to it, then CR=CO. If the registration is done in habitual position, then denture patients will have CO which is not in CR. Therefore the statement that denture patient only has CR is incorrect.

    If you take random 100 complete denture patients and look at their condylar heads/fossa relationships upon closing, you will find out that most are not in CR when the teeth come together. This is because getting CR in denture patients is not easy due to instability of the denture bases. Second, denture patients have harder time getting into CR if their occlusion has been in CO for many years from the previous dentures. And third, again due to instability of the bases, effects of aging, condition of the plastic teeth occlusal surfaces, CR position is unlikely so what do we have now? CO or habitual position is the only logical and possible answer.

    So what is the moral of this? You obtain the registration in its repeatable position and restore the case regardless if it is in CR or not. CR is the operator induced position. It is the position that we think it gives the best chance of success but it is NOT the only position that we live by or consider it as the absolute. DP
  8. Dr. Dai Phan

    Dr. Dai Phan Senior Member Moderator Lifetime Donor SDN Advisor

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    Greetings,

    Edentulous patients have CO due to the habits aquirred from their previous dentures or simply from habitual arc of closure. Complete dentures are fabricated in CR because in some cases, it is the only way to get reproducible position. If you have a repeatable position and you do not restore patient at this position and insist on CR, very likely you will never get the occlusion correct at the try ins. Remember occlusion (O) can come from natural tooth, prosthetic tooth or from habits. DP
  9. Sublimazing

    Sublimazing Nasal Intubator

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    You obviously know more about this than me...but that just doesn't sound right at all. Occlusion is a term for contact between teeth (or prostheses)...but you don't have occlusion if you're edentulous. Denture/prostheses wearers may be able to come to the same position without dentures...but you can't call that "occlusion".

    Like I said...I guess I wouldnt know this stuff, but that sounds contradictory to common sense :)
  10. mike3kgt

    mike3kgt Hopefully scuba diving

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    From Glossary of Prosthodontic Terms:

    occlusion \a-kloo#shun\ n (1645) 1: the act or process of closure or of
    being closed or shut off 2: the static relationship between the incising
    or masticating surfaces of the maxillary or mandibular teeth or
    tooth analogues
    —see CENTRIC O., COMPONENTS OF O.,
    ECCENTRIC O., LINE OF O., LINEAR O., MONOPLANE
    O., PATHOGENIC O., SPHERICAL FORM OF O. —comp
    ARTICULATION

    centric relation \se˘n#trı˘k rı˘-la#shun\ 1: the maxillomandibular
    relationship in which the condyles articulate with the thinnest
    avascular portion of their respective disks with the complex in the
    anterior-superior position against the shapes of the articular eminencies.
    This position is independent of tooth contact. This position
    is clinically discernible when the mandible is directed
    superior and anteriorly. It is restricted to a purely rotary movement
    about the transverse horizontal axis (GPT-5)
    2: the most
    retruded physiologic relation of the mandible to the maxillae to
    and from which the individual can make lateral movements. It
    is a condition that can exist at various degrees of jaw separation.
    It occurs around the terminal hinge axis (GPT-3) 3: the most retruded
    relation of the mandible to the maxillae when the condyles
    are in the most posterior unstrained position in the glenoid fossae
    from which lateral movement can be made at any given degree of
    jaw separation (GPT-1) 4: The most posterior relation of the
    lower to the upper jaw from which lateral movements can be
    made at a given vertical dimension (Boucher) 5: a maxilla to mandible
    relationship in which the condyles and disks are thought to
    be in the midmost, uppermost position. The position has been
    difficult to define anatomically but is determined clinically by
    assessing when the jaw can hinge on a fixed terminal axis (up
    to 25 mm). It is a clinically determined relationship of the mandible
    to the maxilla when the condyle disk assemblies are positioned
    in their most superior position in the mandibular fossae
    and against the distal slope of the articular eminence (Ash) 6:
    the relation of the mandible to the maxillae when the condyles
    are in the uppermost and rearmost position in the glenoid fossae.
    This position may not be able to be recorded in the presence of
    dysfunction of the masticatory system 7: a clinically determined
    position of the mandible placing both condyles into their anterior
    uppermost position. This can be determined in patients without
    pain or derangement in the TMJ (Ramsfjord)
    Boucher CO. Occlusion in prosthodontics. J PROSTHET DENT 1953;
    3:633-56. Ash MM. Personal communication, July 1993.
    Lang BR, Kelsey CC. International prosthodontic workshop on complete
    denture occlusion. Ann Arbor: The University of Michigan School of
    Dentistry, 1973.
    Ramsfjord SP. Personal communication, July 1993.
  11. Sublimazing

    Sublimazing Nasal Intubator

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    So the way I interpret this is that I was correct. Occlusion is the static relationship between teeth or tooth analogues...with nothing in the mouth no relationship is formed. Therefore an edentulous patient without analogues in has no CO. He may be able to close into the same jaw relationship as he would with analogues in place... But there's no static surfaced to form that static relationship
  12. Dr. Dai Phan

    Dr. Dai Phan Senior Member Moderator Lifetime Donor SDN Advisor

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    When I talk about CO in edentulous patients, I am talking about patients with prosthetic teeth in place that provide occlusal contacts. If the patient is not restored with prosthetic teeth, then there is no need to discuss about CR, CO, MI and the point is mute. In short, this is how I would approach in fabrication of complete dentures. If patient has NO other repeatable positions other than CR, then the dentures will be set in CR and hope that patient will learn to occlude in this position. However, if patient has a repeatable habitual position that is learned from an old set of dentures or from past habit, then restore at that position even it is not CR. There is no need to have patient reconditioned to a new position that may be not be adaptable to him. I have learned this from thousands of dentures that I have made in my career and counting... DP
    Last edited: Mar 7, 2012
  13. mike3kgt

    mike3kgt Hopefully scuba diving

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    Dentures are static and are considered tooth analogs. That being said, however, the term "centric relation" is often not correct for denture patients, it's safer the say "centric". You can still say "centric relation" when it comes to dentures because if you look at the defined term it applies. Denture patients are often put into a posterior rather than anterior position because of chin-point guidance techniques. Some clinicians will bi-manually manipulate their denture patients though.

    The "superior-posterior" position is considered not correct today and the GPT will give all of the previous definitions underneath the current one.

    You are a resident... in oral surgery maybe? We've seen that most oral surgery residents are still taught that centric relation is a superior-posterior position. This can work just fine in surgery... BSSO for example but in reality you are really pushing superiorly and seating the condylar head in that fashion. Posterior force is minimized because it's not easy to exert a posterior force when the anterior portion of the mandible is separated.
  14. Sublimazing

    Sublimazing Nasal Intubator

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    No, even worse, dental anesthesiology :D...like I said I'll defer to the experts. But I still say what i said was right...if I wasn't clear I understand dentures are tooth analogues, I was saying that without those tooth analogues physically in the mouth there cannot be centric occlusion until those dentures are placed back in :)

    it doesn't matter tho...the only impact I'll have on a patient's bite will be when I slam out their incisors with a laryngoscope (jk)
  15. mike3kgt

    mike3kgt Hopefully scuba diving

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    Well, to get picky, centric relation is independent of tooth/tooth contact or analog/analog contact. It is a skeletal position or "bone on bone" contact, but technically bone-disc-bone contact. Edentulous patients (without prostheses) do still have a centric relation position but do not have a centric occlusion position. They cannot occlude because they don't have teeth or analogs.

    From GPT:

    centric occlusion \se˘n#trı˘k a-kloo#zhen\: the occlusion of opposing
    teeth when the mandible is in centric relation. This may or may
    not coincide with the maximal intercuspal position—comp
    MAXIMAL INTERCUSPAL POSITION

    That being said, they sure can chew even though they can't occlude. I've had patients very proudly tell me they're great a "gummin'" a t-bone steak. :laugh:
  16. Dr. Dai Phan

    Dr. Dai Phan Senior Member Moderator Lifetime Donor SDN Advisor

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    The terminology of CR, CO, MI need to be updated to clarify confusion especially in undergrad studies and even among practicing dentists. CR is "bone-disc-bone" relationship while CO is "tooth-tooth contact". These are two seperate entities so they should not be used together while talking about dental occlusion. I would prefer to use CO and MI because these two terms involved tooth to tooth relationship. However, CO is considered a questionable term and should not be used that adds more to the confusion. DP
  17. DrJeff

    DrJeff Senior Member Moderator

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    Agree. I think, especially as the entire CR/CO/MI concept is trying to be taught in dental school, that much of the confusion can arise in the simple fact that for *most* patients with a "normal" dentition and occlussion, even though CR may not equal CO, the actual difference between the two is quite small, but there is a difference in most. This can be a confusing concept to grasp at first.

    Secondly, for most of my patients, CO is their "comfort" position, in a sense like that comfy old pair of slippers that just feels right to them. You can get them into CR in most circumstances without great issue, HOWEVER the patient wants to be in CO.

    Usually the types of patients where I see a significant difference between where CR and CO are located fall into 1 of 2 categories. #1, the patient with a significant skeletal relationship issue (i.e. the neck of the condyle is significantly longer on one side than the other, etc) or #2 the partially edentulous patient where they are missing all/almost all of their posterior teeth and have moved their CO generally anteriorly in an effort to increase their chewing ability.

    This second situation where the CR/CO difference tends to be a learned difference rather than an naturally happening difference, for me atleast tends to be the most difficult type of patient to restore. As usually in these patients you need to get them back further towards their CR position, and very often their muscles of mastication from a trained, comfort factor want to keep them in their CO position which often has some significant mechanical/physics issues that hinder the ability to restore them in a way that is both comfortable for them, and as functional as possible. What good is it to restore a patient to CR if from a comfort and functional standpoint they can't function in CR, but want to function in CO? This can lead to the "But Doc, they might look great, but these teeth just don't feel right" conversation where you can tell them until you're blue in the face "But Mrs. Smith I restored you back the ideal position that mother nature wants your jaw to be in" and all they know is that it just doesn't feel right to them :eek: Fortunately, this type of patient isn't the usual scenario, but they do occur. And I feel strongly that this is where sometimes one as a clinician needs to use their ability to think on their own rather than to just think like one was told they should to handle that type of case
  18. mike3kgt

    mike3kgt Hopefully scuba diving

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    Agree. The hard part is that when you talk with most GPs, they still know "CO". It's like saying "bridge" instead of "FPD" or "FDPD".

    The current GPT still has "centric occlusion" as a defined term but we should all get away from that and only use MIP/MICP and when you are in CR you are in "CR". If MIP = CR, it's still called "CR" and not "CO".

    :thumbup:
  19. Dr. Dai Phan

    Dr. Dai Phan Senior Member Moderator Lifetime Donor SDN Advisor

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    Man, this reminds me of weekly Friday AM classic literature review sessions when I was in pros school 15 years ago! DP
  20. mike3kgt

    mike3kgt Hopefully scuba diving

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    Haha, we have a prosthodontic swear jar. You get your name put in the jar every time you use dental potty language. :)
  21. DrJeff

    DrJeff Senior Member Moderator

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    I was thinking that it was starting to remind me of the 1st time I tried, without the assistance of the manufacturers rep, to order the proper impression and restorative components and drivers to restore an implant ;):eek::D
  22. SoulPower

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    The way this was explained in my dental anatomy class was that; Centric relation is a condylar position, more specifically the most superior anterior position of the condyle against the eminence. Centric occlusion is the occlusion a person has while in centric relation.

    For most people, I believe, maximum intercuspation or maximum closure or habitual occlusion, these are all synonyms, is not centric occlusion because most people do not bite down in centric relation, although it is possible.

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