What causes a scalloped edge appearance on the tongue?

Scalloped Tongue: Causes and Clinical Significance

A scalloped edge appearance on the tongue is most commonly caused by chronic pressure from the tongue pressing against the teeth, typically resulting from tongue enlargement (macroglossia), tongue thrust habits, or anatomical constraints within the oral cavity.

Primary Mechanisms

The scalloped or "crenated" tongue edge develops when the lateral borders of the tongue are chronically pressed against the lingual surfaces of the teeth, creating indentations that mirror the tooth contours. This occurs through several mechanisms:

Tongue Enlargement (Macroglossia)

• True macroglossia causes the enlarged tongue to press continuously against the dentition, creating the characteristic scalloped pattern 1
• The tongue occupies more space than the oral cavity can accommodate, leading to persistent lateral pressure against teeth

Tongue Thrust and Abnormal Resting Posture

• Tongue thrust involves abnormal tongue positioning where the tongue rests forward and laterally against teeth rather than in the palate 2, 3
• This "mild but continuous lingual pressure factor" during rest creates sustained contact with the lateral dentition 3
• The resting tongue position can be classified as abnormal when it chronically presses against teeth, particularly in patients with malocclusion or after tooth loss 4
• Tongue posture changes are often adaptive responses to skeletal abnormalities like open bite, where the tongue positions itself between teeth during swallowing 5

Anatomical and Functional Factors

• Mandibular size and position affect available tongue space—a small or retruded mandible provides less room for the tongue, forcing lateral expansion against teeth 5
• Edentulous patients show higher incidence of abnormal tongue positioning as functional and anatomical changes from tooth loss alter the oral environment 4

Clinical Pitfalls and Differential Considerations

Important caveat: While scalloped tongue is usually benign and related to mechanical pressure, clinicians must not overlook serious underlying conditions:

• Hypothyroidism can cause true macroglossia with resultant scalloping
• Amyloidosis may present with tongue enlargement
• Temporomandibular disorders can alter jaw position and tongue space
• Sleep-disordered breathing may be associated with tongue thrust and abnormal posture

The scalloped appearance itself is not pathognomonic for any single condition—it is a physical sign reflecting chronic tongue-tooth contact from various etiologies.

Clinical Assessment Algorithm

When evaluating scalloped tongue:

1. Document the pattern: Bilateral scalloping suggests generalized macroglossia or tongue thrust; unilateral suggests asymmetric pressure or space constraints
2. Assess tongue size: Determine if true enlargement exists or if normal-sized tongue is compressed in inadequate space
3. Evaluate occlusion and jaw relationship: Look for open bite, Class II malocclusion, or mandibular retrusion that might force abnormal tongue posture 2, 5
4. Check for systemic signs: Thyroid dysfunction, fatigue, or other symptoms suggesting metabolic causes 1
5. Assess functional habits: Observe swallowing pattern and resting tongue position 3, 4

Management Approach

Treatment depends entirely on the underlying cause:

• If due to tongue thrust habit: Myofunctional therapy to retrain tongue posture and swallowing patterns may be beneficial, though evidence is limited 2, 3
• If due to skeletal malocclusion: Orthodontic or surgical correction of the jaw relationship can normalize tongue space and posture 5
• If due to systemic disease: Treat the underlying condition (e.g., thyroid replacement for hypothyroidism)
• If asymptomatic and benign: Reassurance that scalloping itself requires no treatment 1

The scalloped tongue appearance is a sign, not a diagnosis—the clinical priority is identifying whether it represents a benign anatomical variant or signals an underlying condition requiring intervention.