Patients with structurally altered temporomandibular joints may present clinically with growth and development issues, Class II occlusions, anterior open bites, overjet bites, canted occlusal planes, irregular occlusal planes, overbites, facial asymmetries, compressed pharyngeal airway anatomy, or maxillary and mandibular retrognathia. Structural alterations in the TMJ typically begins at the soft tissue level, which is best assessed with MR and CBCT imaging offering visualization of the hard tissue.

Doctors who are new to TMJ imaging often say their patients won't agree to an MRI and a CBCT. This usually occurs because the patient does not have enough information to make a good decision about MRIs and CBCTs. The first step in helping patients understand why imaging is a good decision is to obtain an accurate history.

In previous Spear Digest articles, we discussed the importance of the history in the clinical exam. We discussed taking an accurate history of the joint, an accurate history of any injuries to the joints, an accurate history of previous treatment, and an accurate history of pain in the jaw joints – and the questions you should ask to ensure no element is missed.

After obtaining a complete history, the second step in the initial appointment is educating the patient. This step is important to the success of the new patient examination because it gives the patient the opportunity to learn just enough to make a good decision about accepting a recommendation of MR and CBCT imaging when this is appropriate for treatment planning.

There are six key clinical factors a patient must understand before confidently moving forward with TMJ imaging.

1. Understand the design of the system

The load is distributed most efficiently at the joint level through loading the soft tissue and hard tissue.
Figure 1: The muscles forces are distributed between the teeth and the jaw joints. Image source: Anomalous Medical

A load is being applied to the system by the jaw muscles. The muscles are positioned between the teeth and the jaw joints. The load applied by the muscles is distributed between the teeth and the jaw joints.

The load is distributed most efficiently at the tooth level though even intensity and simultaneous contact between the posterior and anterior teeth. The load is distributed most efficiently at the joint level through loading the soft tissue and hard tissue1.

2. Understanding the lateral and the medial pole

The disk is attached to the condyle with ligaments at the lateral and the medial pole.
Figure 2: Sagittal and corornal view of MRIs and CBCTs.

The condyle has a lateral pole and a medial pole (Fig. 2). The clinical significance relates to the anatomy of the joint socket. The anatomy at the medial aspect of the joint socket has dense bone that is ideal for load dissipation. The disk is attached to the condyle with ligaments at the lateral and the medial pole.2

3. The stages of joint changes

The disk covers the bone in the closed view and the open positions.
Figure 3: The disk covers the bone in the closed view and the open positions.

Normal -

The disk covers the bone in the closed view and the open positions (Fig. 3). The disk receives its nutrition from lubrication fluid being compressed into the during normal function. In this type of jaw joint, the soft tissue and hard tissue have normal size and contours.

The disk is herniated forward of the condyle in the closed position and the condyle moves under the herniated disk in the open position.
Figure 4: The disk is herniated forward of the condyle in the closed position and the condyle moves under the herniated disk in the open position.

Clicking -

The disk is herniated forward of the condyle in the closed position and the condyle moves under the herniated disk in the open position (Fig. 4). The disk is herniated forward of the condyle because the ligaments are torn at the lateral pole, the medial pole or both the lateral and medial pole.

These types of jaw joints are typically referred to as disk displacement with reduction. In this type of jaw joint, the soft tissue of the disk and the hard tissue of the condyle typically maintain normal size and contours.

The disk deforms due to a lack of nutrition and remains herniated forward of the condyle in both the closed and open position.
Figure 5: The disk deforms due to a lack of nutrition and remains herniated forward of the condyle in both the closed and open position.

Locking -

The disk deforms due to a lack of nutrition and remains herniated forward of the condyle in both the closed and open position (Fig. 5). These types of jaw joints are typically referred to as disk displacement without reduction. In this type of jaw joint, the soft tissue of the disk and the hard tissue of the condyle may have changes in both tissue contour and tissue size. In most cases, the size of the soft and hard tissue decreases.

The condyle moves though the soft tissue behind the herniated disk and is in direct bone to bone contact with the joint socket.
Figure 6: The condyle moves though the soft tissue behind the herniated disk and is in direct bone to bone contact with the joint socket.

Perforated -

The condyle moves though the soft tissue behind the herniated disk and is in direct bone to bone contact with the joint socket. In this type of jaw joint, the soft tissue of the disk and the hard tissue of the condyle most likely has changes in both tissue contour and tissue size.

In these cases, the size of the soft and hard tissue usually decreases. The changes in tissue shape and volume can be significant in these types of jaw joints.

4. The three types of jaw joints

Types of temporomandibular jaw joints including structurally intact, structurally altered at the lateral pole and structurally altered at the lateral and medial pole.
Figure 7: The Piper Classification System. Image source: Anomalous Medical

Structurally intact joints have the disk attached to the condyle at the lateral and medial pole.

These are usually stable joints with respect to bite stability and pain. These are typically referred to as Piper Stage 1 or 2 joints.

  • Piper Stage 1 joints have intact ligament attachments at the lateral and medial pole.
  • Piper Stage 2 joints have intact ligament attachments at the medial pole with beginning soft tissue changes in the ligament attaching the lateral pole to the condyle.

Structurally altered joints at the lateral pole have a torn ligament at the lateral pole attachment of the disk to the condyle. Structurally altered at the lateral pole joints have disk coverage at the medial pole and are usually stable joints with respect to bite stability and pain. These are typically referred to as Piper Stage 3A or 3B joints.

  • Piper Stage 3A joints have intact ligament attachments at the medial pole with a ligament tear at the lateral pole attachment. The condyle and disk have maintained normal shape and the condyle moves under the disk at the lateral pole in the open view. These joints will usually click.
  • Piper Stage 3B joints have intact ligament attachments at the medial pole with a ligament tear at the lateral pole attachment. The condyle and disk have changed shape and the condyle is unable to move under the disk at the lateral pole in the open view. These joints will usually not click.

Structurally altered joints at the lateral pole and the medial pole have a torn ligaments at the lateral and medial pole attachment of the disk to the condyle. Structurally altered joints at the lateral pole and the medial pole do not have disk coverage at the medial pole and while these joints can adapt, there is a higher incidence of pain and bite instability in these joints. These are typically referred to as Piper Stage 4A, 4B, 5A, and 5B joints.

  • Piper Stage 4A joints have a ligament tear at the medial pole attachment. The condyle and disk have maintained normal shape and the condyle moves under the disk at the medial pole in the open view. These joints will usually click.
  • Piper Stage 4B joints have a ligament tear at the medial pole attachment. The condyle and disk have changed shape and the condyle is unable to move under the disk at the medial pole in the open view. These joints will usually not click.
  • Piper Stage 5A joints are perforated with direct bone to bone contact between the condyle and the joint socket. These joints are typically painful.
  • Piper Stage 5B joints are perforated with direct bone to bone contact between the condyle and the joint socket. These joints are typically adapted.

Piper Stage 4A, 4B, 5A, and 5B joints do not have disk coverage at the medial pole. While these joints can adapt and be stable, there is an increased risk for bite instability and/or pain in the adult patients and incomplete growth in the growing patient.3

Piper Stage 4A, 4B, 5A, and 5B joints may present clinically with growth and development issues, Class II occlusions, anterior open bites, overjet bites, canted occlusal planes, irregular occlusal planes, overbites, facial asymmetries, compressed pharyngeal airway anatomy, maxillary and mandibular retrognathia. Recent literature has shown as malocclusion complexity increases, so do the odds of presenting with TMD.4

5. Understanding why patients may have pain

Digital mockup of jaw muscle, disk, bone, neck, and sympathetic system as part of the root causes of pain.
Figure 8: Pain can come from one or multiple sources. Image source: Anomalous Medical

The traditional approach to pain emphasized creating an even bite so the jaw muscles do not have to contract more than normal to function. Pain related to the occlusion and the jaw joints was assumed to be muscular in nature due to the lack of three-dimensional imaging.

When MRIs and CBCTs became available in the 1990s, it became apparent there were other sources of pain such as herniated disks, different bone conditions in the condyle, upper cervical misalignments, and influence from the central nervous system.

In terms of pain, it is important to understand that muscle contraction is a common pain source for many patients. While many factors increase muscle contraction, two of the main factors are how the teeth fit together and the influence of the central nervous system.

In terms of disk herniations, it is similar to herniations in other parts of the body. If the herniated tissue impinges on another structure or occupies a space another structure should occupy, it can increase the likelihood of pain.

There are three common bone issues -

  • The first bone issue is small bone.
    • Bone dimensions can be considered both in terms of condylar size and ramus length. Normal condylar size is approximately 8mm in an anterior-posterior dimension and 20mm in a medial-lateral dimension. Normal ramus length is approximately 60-70mm. Decreases in either condylar size or ramus length can occur in patients who injured their TMJ during the growing years. Decreases in bone size can lead to pain from loading on condyles with decreased surface areas compared to loading on condyles with normal surface area.
  • The second bone issue is eroded bone.
    • In the adult patient, if the outer shell of the condyle is eroded, there is an increased risk for both bite instability and pain. If the outer shell in intact, there is increased chance for stability. In the growing patient, if the outer shell in open, there is a chance for additional growth. If the outer shell is closed, there is a deceased chance for additional growth.
  • The third bone issue is any swelling in the marrow space of the condyle. There can also be swelling around a herniated disk. This type of swelling typically correlates with increased reports of pain.

In addition to pain from joint tissue, pain can also occur from misalignments in the upper cervical spine. CBCTs may offer an opportunity to visualize upper cervical anatomy.

The influence of the sympathetic nervous system can increase our sensitivity to pain. Two things that can influence the sympathetic nervous system is the anatomy of the jaw joint and the airway anatomy.

Injured tissue in the jaw joints, poor breathing due to deviated nasal septums, or compressed airways can increase the influence of the sympathetic nervous system resulting in increased pain.5

Today, we know due to three-dimensional imaging with MRI and CBCT, we have a better idea how to assess treatment options if we can visualize the soft tissue with MRI and the hard tissue with CBCT.

6. Understanding your bite

Inside of mouth to illustrate how at the tooth level, the upper and lower teeth fit against each other which stabilizes the occlusion.
Figure 9: Clinical photograph.
Occlusion to illustrate how changes at the joint level can result in malocclusions at the tooth level.
Figure 10: Clinical example of an anterior open bite due to lack of mandibular growth.

If we look at the design of the system, we can understand our bites. At the tooth level, the upper and lower teeth fit against each other which stabilizes the occlusion at the tooth level. At the joint level, the condyle and disk fits together which stabilizes the occlusion at the joint level.

If the disk at the medial pole becomes herniated, the soft tissue and the hard tissue may not remain the same size and shape. If there are changes at the joint level, these can result in malocclusions at the tooth level.6

In the case illustrated, the anterior open bite in this 17-year-old female was originally diagnosed as a tongue thrust. Upon closer evaluation of the imaging, however, it becomes obvious the anterior open bite is due to the short rami lengths which resulted due to a joint injury before growth was complete.

Coming Soon – The Examination

I hope this article will help you provide your patients with the information they need to make good decisions about diagnostic records.

The third step in the process, after obtaining an accurate history and educating the patient, is the clinical exam. Introducing these six clinical concepts before doing the clinical exam allows you to refer back to many of the issues you discussed during this presentation. Stay tuned for upcoming articles discussing the exam.


Jim McKee, D.D.S., is a member of Spear Resident Faculty.

References

  1. Choukas N, Sicher H, et al. The structure of the temporomandibular joint. Oral Surgery, Oral Med Oral Pathol [Internet]. 1960;156(10):555–65.
  2. Piper, DMD MD, Mark. "Temporomandibular Joint Imaging." Handbook of Research on Clinical Applications of Computerized Occlusal Analysis in Dental Medicine. IGI Global, 2020. 582-697.
  3. Piper, DMD MD, Mark. "Temporomandibular Joint Imaging." Handbook of Research on Clinical Applications of Computerized Occlusal Analysis in Dental Medicine. IGI Global, 2020. 582-697.
  4. Zúñiga-Herrera ID, Herrera-Atoche JR, Escoffié-Ramírez M, Casanova-Rosado JF, Alonzo-Echeverría ML, Aguilar-Pérez FJ. Malocclusion complexity as an associated factor for temporomandibular disorders. A case-control study. Cranio - J Craniomandib Pract [Internet]. 2021;00(00):1–6. Available from: https://doi.org/10.1080/08869634.2020.1868907
  5. Piper, DMD MD, Mark. "Temporomandibular Joint Imaging." Handbook of Research on Clinical Applications of Computerized Occlusal Analysis in Dental Medicine. IGI Global, 2020. 582-697.
  6. Laskin, DM. Etiology of the pain-dysfunction syndrome, JADA 1969;79:147-153
  7. Larheim, T. TM joint disk displacement: Comparison in asymptomatic... Radiology, 2001:218(2), 428–432.
  8. Sano, T. Osseous abnormalities related to the TM joint. Sem in Ultrasound, CT and MRI, 2007: 28(3), 213–221.
  9. Braun BL. A cross-sectional study of TM joint dysfunction in post-cervical. J Cranio Disord Fac Oral Pain, 1992;6:24-21
  10. Fechir, M. Evolving understandings about complex regional pain syndrome...Curr Pain Headache Reports. 2008;12(3):186-191.

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