When is MRI (Magnetic Resonance Imaging) used in dental diagnostics?

MRI in Dental Diagnostics: Clinical Applications

MRI is primarily indicated in dental diagnostics for temporomandibular joint (TMJ) disorders involving soft tissue pathology, head and neck cancer staging (particularly oral cavity tumors), and salivary gland disease evaluation.

Primary Indications for MRI in Dentistry

Temporomandibular Joint Disorders

MRI is the gold standard imaging modality for TMJ soft tissue evaluation, particularly for disc displacement and synovitis. 1, 2

• For TMJ ligament-capsule tissue disorders and disc pathology, MRI is the recommended imaging modality 1
• MRI excels at visualizing the articular disc position, morphology, and detecting joint effusion 3, 4
• The technique can distinguish between anterior disc displacement with reduction (ADDR) versus without reduction (ADDWR) by evaluating disc-condyle relationships at different mouth positions 4
• MRI detects early signs of TMJ synovitis, including inflammation of the synovial membrane, before structural bone changes occur 2, 3

Important caveat: For TMJ bone disease (condylar changes, erosions, or glenoid cavity pathology), CBCT or CT is preferred over MRI 1. Panoramic radiography provides insufficient information for TMJ diagnosis and should not be relied upon 1

Head and Neck Cancer Staging

MRI of the orbits, face, and neck (with and without IV contrast) is superior to CT for oral cavity tumor evaluation and surgical planning. 1

• MRI provides superior soft tissue resolution for delineating tumor extent, which is essential for T-staging and surgical planning 1
• MRI is less susceptible to metal artifact from dental implants, making it particularly valuable in the oral cavity where CT images may be degraded 1
• The modality excels at detecting perineural spread of disease, a critical prognostic factor 1
• MRI better delineates bone marrow involvement compared to CT, though CT remains superior for cortical bone erosion 1
• For oral tongue cancer, MRI achieves similar accuracy to CT in assessing depth of invasion 1

Combined pre- and post-contrast imaging is essential to properly identify and delineate primary tumors from surrounding normal tissues 1

Salivary Gland Pathology

• Salivary gland diseases are best investigated using ultrasound as the initial modality, but MRI provides superior soft tissue characterization when ultrasound is inconclusive 1
• MRI can detect salivary gland tumors, inflammatory conditions, and ductal abnormalities 5

Secondary and Emerging Applications

Chronic Non-Bacterial Osteitis (CNO)

• When CNO involves the mandible, MRI is the preferred imaging modality to detect bone marrow edema, an early and activity-related disease feature 1
• MRI helps exclude differential diagnoses and can detect soft tissue involvement 1

Facial Pain Evaluation

• MRI and CT are indicated in select conditions when evaluating chronic facial pain, particularly when structural pathology is suspected beyond routine dental causes 1
• The modality is not routinely indicated for acute dental pain or simple odontogenic infections 1

Maxillofacial Malformations

• MRI is not indicated as routine examination for cleft lip/palate or craniosynostosis, as these diagnoses are clinical 1
• MRI may be used selectively for treatment planning in complex craniofacial cases 1

Key Limitations and Practical Considerations

MRI has important disadvantages compared to CT:

• Decreased spatial resolution for fine bony detail 1
• Greater susceptibility to motion artifact due to longer scan times (typically >30 minutes vs. <5 minutes for CT) 1, 3
• Higher cost and less availability 1
• Contraindicated with certain implantable devices (pacemakers, neurostimulators) 1
• Patient tolerance issues due to scanner bore size and examination duration 1

Contrast administration: Intravenous gadolinium contrast should be used unless contraindicated by severe renal insufficiency (risk of nephrogenic systemic fibrosis) or allergy 1

When NOT to Use MRI

• Routine dental caries detection, periodontal disease, or periapical pathology - conventional radiography and CBCT are appropriate 1
• TMJ bone disease evaluation - CBCT or CT is preferred 1
• Acute dental infections with systemic symptoms - clinical diagnosis with conventional radiography is typically sufficient 1
• Orthodontic cephalometric analysis in moderate-light malocclusion - conventional radiography is adequate 1

Emerging Technology

Dental-dedicated MRI (ddMRI) systems are being developed with tailored field strength, dental radiofrequency surface coils, and optimized pulse sequences specifically for dentomaxillofacial imaging 6. These systems may eventually make MRI more accessible and cost-effective for routine dental practice, though further validation studies are needed 6.