In my previous Spear Digest article, we discussed when we should think about obtaining TM joint imaging. Specifically, we reviewed two key questions to determine if we should consider TM joint imaging with MRI and CBCT.

  1. Does the patient have pain greater than five on a 1-10 scale?

  2. Are the teeth uncoupled greater than the thickness of the disk?

If either one or both questions are yes, it increases the likelihood one or both TM joints are structurally altered at the lateral and medial pole. Examining a clinical case can help to clarify the process.

Image depicting three TMJ classifications: 1a) structurally intact, 1b) structurally altered at the lateral pole, and 1c) structurally altered at both the lateral and medial poles.
Fig. 1: An image depicting three TMJ classifications including Fig. 1a: structurally intact, 1b: structurally altered at the lateral pole, and 1c: structurally altered at both the lateral and medial poles. Image source: Anomalous Medical

A TM Joint Clinical Case Study

A clinical case can help us understand the concepts outlined above. Below outlines the details of an 11-year-old patient referred by an orthodontist for a pre-ortho joint evaluation.

Details outlining an 11-year-old patient referred by an orthodontist for a pre-ortho joint evaluation
Fig. 2 Outlines details of an 11-year-old patient referred by an orthodontist for a pre-ortho joint evaluation.
Imaging and patient profile views from the case study referenced in Figure 2.
Fig. 3: Imaging and patient profile views from case study referenced in Fig. 2.
Imaging and patient profile views depicting Class II occlusions, anterior uncoupling, retrognathic maxilla, and retrognathic mandible
Fig. 4: Imaging and patient profile views showing Class II occlusions, anterior uncoupling, retrognathic maxilla, and retrognathic mandible.

If the orthodontist is referring the patient for a TM joint evaluation before beginning orthodontic treatment, there is an increased likelihood the patient has SA-LP/MP (structurally altered at the lateral pole and medial pole).

A clicking joint means there is a ligament tear in the TM joint. Once we know there is a ligament tear, the only thing we have to determine is if we think the ligament tear is at the lateral pole or the medial pole.

My clinical experience, along with peer reviewed literature, indicates there are significantly more structurally altered TM joints in growing patients than previously expected. In 2011, Sylvester wrote, “Out of the 38 patients who were excluded in our study, 28 were younger than 16 years old. This shows that internal derangement of the TMJ appears in young populations as well. patients are in their growing stages, and their articulations are supposed to tolerate stress due to their remodeling potential; however, they show chronic articular alteration, which may affect them for a lifetime.”

In 1993, Schellhas wrote about “the high percentage of evidence of TMJ abnormality from imaging studies could mean that the problem is more widespread than previously recognized. Since orthodontists do not routinely study the temporomandibular joint status of patients, the possibility exists that the specialty is not aware of the pervasiveness of the problem.”

The fact that there is pain on a regular basis along with 2- headaches per week increased the likelihood of SA-LP/MP TM joints. Growing patients should not have TM joint pain and if they do, it should warrant further investigation.

Clicking joint in growing patients increases the likelihood the disk is not covering the condyle in the growing years. In this scenario, there is an increased likelihood there will be decreased growth compared to normal growth. Nebbe wrote in 1997 about “the findings of the current study tend to support the argument that internal derangement may be associated with altered craniofacial morphology in an adolescent sample. This pilot study shows reductions in total posterior facial height development and ramus height and a compensatory adaptation in the maxillary dentoalveolar region with reduced vertical development of the maxillary first molar region.” The retrognathic mandible and maxilla increase the likelihood of having structurally altered TM joints at the lateral and medial pole.

The Class II occlusion in a growing patient increases the likelihood the disk is not covering the condyle. Many patients like this are sent to the orthodontist and they expect a perfect result. The Class II occlusion is usually due to a loss of joint dimension in the TM joint. The loss of TM joint dimension is almost universally due to the disk not covering the condyle.

Confirming the Diagnosis by MRI

Based on the information we learn at the initial consultation and at the clinical exam, we have to make a tentative TM joint diagnosis. After collecting the information in this case, it appears the tentative TM joint diagnosis is SA/LP/MP TM joints. These types of jaw joints have an increased likelihood to present with either pain, a Class II occlusion or, in this challenging case, both pain and malocclusion.

The MRI confirms the structurally altered TM joint at the medial pole.

MRI image confirming diagnosis, indicating decreased anterior posterior condylar volume, and showing 9:00 disk position
Fig. 5: MRI confirming diagnosis, showing decreased anterior posterior condylar volume, and 9:00 disk position.
MRI image confirming compressed joint space and decreased medial-lateral condylar volume
Fig. 6: MRI confirming compressed joint space and decreased medial-lateral condylar volume.

In examining this clinical case and reviewing imaging findings, several insights into TM joint health in growing patients emerge. The patient's presentation with Class II occlusions, anterior uncoupling, and retrognathic maxilla and mandible underscores the prevalence of TMJ structural issues in younger populations. Literature supports that such TMJ abnormalities are more common than previously recognized, potentially impacting craniofacial development. Diagnostic MRI confirmed decreased condylar volume and abnormal disk positioning, validating suspicions of structural TMJ alterations at the medial pole. These findings emphasize the critical role of thorough TM joint evaluation in orthodontic planning to optimize treatment outcomes and mitigate long-term joint complications in growing patients.

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

References:

  1. Sylvester, D. (2011). Association Between Disk Position and Degenerative Bone Changes of the Temporomandibular Joints: An Imaging Study in Subjects with TMD. The Journal of Craniomandibular Practice, 29(2), 117-126.

  2. Schellhas, K. (1993). Pediatric internal derangements of the temporomandibular joint: Effect of facial development. American Journal of Orthodontics and Dentofacial Orthopedics, 104, 51-59.

  3. Nebbe, B., Major, P., Prasad, N., & Kamelchuck, L. (1997). TMJ internal derangement and adolescent craniofacial morphology. Angle Orthodontist, 67(6), 407-414.

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