Mobility assessment is the clinical evaluation of tooth movement within the alveolar socket when controlled force is applied, providing a direct measure of the integrity of the surrounding periodontal support structures. Unlike radiographic imaging, which captures static bone levels, mobility assessment offers a real-time, tactile indication of how securely a tooth remains anchored in place.
How It Works
The clinician applies firm, controlled pressure to the tooth crown using the handles of two instruments — or a finger opposing an instrument handle — then observes movement in horizontal (buccolingual and mesiodistal) and vertical directions. The most widely used grading scale classifies mobility into four levels:
- Grade 0: Physiologic mobility only — movement under 0.2 mm, considered normal for all teeth.
- Grade 1: Slight mobility — horizontal displacement up to 1 mm beyond physiologic range; clinically detectable but mild.
- Grade 2: Moderate mobility — horizontal movement between 1 and 2 mm; may begin affecting occlusal comfort.
- Grade 3: Severe mobility — horizontal displacement exceeding 2 mm or any detectable vertical (apical) movement.
Clinical Significance
Elevated tooth mobility rarely occurs in isolation — it reflects compromise of the supporting apparatus, most commonly the periodontal ligament and surrounding alveolar bone. As periodontitis drives progressive bone loss, the available bone-to-root surface area decreases, reducing resistance to lateral forces and causing measurable tooth movement. Other contributing factors include acute dental trauma, bruxism, periapical pathology, and occlusal overload from a high restoration or parafunctional habits.
Mobility findings are interpreted alongside radiographic bone levels, probing depths, and bleeding on probing to form a complete periodontal picture. A tooth with Grade 2 or 3 mobility paired with significant vertical bone loss carries a guarded-to-poor prognosis, directly influencing decisions about retention, extraction, and prosthetic planning. Serial mobility recordings across appointments allow clinicians to track disease progression or measure treatment response — decreasing mobility after scaling and root planing or surgical therapy is a favorable prognostic sign.
Documenting mobility at every comprehensive periodontal evaluation is a low-cost, high-yield step that enables early intervention before bone loss reaches a point of irreversible structural compromise.