Dental X-rays When do you need a TMJ exam

Many people believe that traditional dental X-rays are sufficient to diagnose all oral and jaw problems. However, in reality, some areas — especially the temporomandibular joint (TMJ) — require more precise imaging techniques.Among these advanced methods, Transcranial Projection stands out as one of the most effective techniques for examining the TMJ from the side, helping detect structural changes and potential joint disorders.

In this Daleely Medical article, we will cover:

What is Transcranial Projection?
How does it work?
Its uses in dentistry
Advantages and limitations
How it compares to other dental radiography techniques

What Is Transcranial Projection?

Transcranial Projection is a type of extraoral X-ray technique specifically used to image the temporomandibular joint (TMJ) from the side of the skull.

This method allows dentists to visualize the relationship between the bones that make up the joint, including:

Condyle (part of the lower jawbone)
Glenoid fossa (part of the temporal bone)
Articular disc (soft tissue inside the joint)

It provides insight into the joint's position during different mouth movements—like opening and closing.

How Does Transcranial Projection Work?

This technique is performed in a few precise steps:

1. Patient Positioning

The patient sits upright with their head stabilized.
The film or digital sensor is placed next to the ear, on the side of the head.

2. X-ray Beam Direction

The X-ray beam is directed from the opposite side of the head at an angle (usually around 25 degrees) so it passes through the skull and captures the TMJ area.

3. Taking Two Images

One image is taken with the mouth closed, and another with the mouth open.
These images are compared to assess joint movement and detect any abnormalities.

Why Use Transcranial Projection?

This technique is primarily used to diagnose:

Jaw joint pain
Clicking or popping sounds when moving the jaw
Difficulty opening or closing the mouth
TMJ disorders (TMD)
Degeneration or erosion of the joint
Injury assessment after trauma to the jaw

Advantages of Transcranial Projection

✅ 1. Precise View of the TMJ

Offers a clear lateral image of the joint, ideal for structural assessment.

✅ 2. Quick and Efficient

The scan takes just a few minutes and requires minimal preparation.

✅ 3. Cost-Effective

Less expensive than advanced imaging like CBCT or MRI, making it accessible in most clinics.

✅ 4. Widely Available

It can be performed using standard X-ray equipment with slight angle modifications.

Limitations of Transcranial Projection

❌ Cannot Visualize Soft Tissues

It does not capture soft structures like the articular disc, which may be key in certain TMJ disorders.

❌ Image Overlap

The image passes through the skull, so overlapping bones may affect clarity.

❌ Highly Sensitive to Positioning

Even slight movement of the head can compromise image quality.

Comparison with Other Imaging Techniques

Imaging Type	Bone Visibility	Soft Tissue	Accuracy	Cost	Use Case
Transcranial Projection	✅	❌	Moderate	Low	Initial TMJ evaluation
CBCT (Cone Beam CT)	✅✅	❌	High	High	Implant planning, bone evaluation
MRI (Magnetic Resonance)	✅	✅✅	Very High	Very High	Disc/joint soft tissue evaluation
Panoramic X-ray	✅	❌	Limited	Low	General jaw and dental overview

When Is Transcranial Projection Recommended?

Your dentist may recommend this X-ray if you're experiencing:

Pain while chewing or opening the mouth
Restricted jaw movement
Clicking or popping sounds in the jaw
Suspected joint dislocation or misalignment
Post-surgical follow-up of the TMJ

Tips Before Undergoing Transcranial Projection

Inform your dentist if you're pregnant
Remove all jewelry, glasses, or metal objects from the head and neck area
Keep your head still during the procedure for accurate imaging
Follow your dentist’s instructions carefully when asked to open or close your mouth

Frequently Asked Questions (FAQs)

❓ Is this X-ray harmful?

Not at all. It uses very low levels of radiation, well within medically safe limits.

❓ Can it fully diagnose TMJ disorders?

It’s ideal for mild to moderate cases. However, complex conditions may require further imaging like CBCT or MRI.

❓ Is the procedure painful?

Absolutely not. It is non-invasive and painless, with no anesthesia required.

❓ How long does it take?

Typically, 5 to 10 minutes from start to finish.

Conclusion

Transcranial Projection is a valuable and practical radiographic method that enables dentists to assess TMJ conditions effectively and affordably. While it may not capture soft tissues, it remains highly useful for tracking bone structure and joint movement.

In a time when dental diagnostics are advancing rapidly, this technique still plays a crucial role—especially when used accurately and as part of a comprehensive evaluation plan.

Daleely Medical Tip ????

If you're experiencing jaw pain, clicking sounds, or difficulty moving your jaw, ask your dentist whether Transcranial Projection is right for your case. It might be the first step toward effective and accurate treatment.