Fractured Cusp

Definition and Classification
Fractured cusp is one of the recognized types of longitudinal tooth fractures, predominantly affecting posterior teeth such as premolars and molars.

Nature and Characteristics

Origin and extension: The fracture begins at the crown of the tooth and extends subgingivally.
Orientation: It typically follows a mesiodistal or buccolingual direction.
Tissues involved: Unlike craze lines, which affect only the enamel, fractured cusps may involve both hard and soft dental tissues.

Etiology

Primary causes: Fractured cusps often occur in teeth with extensive caries or large restorations that weaken or destabilize the cuspal structure.
Mechanical forces: Normal functional stresses, such as mastication, can generate significant forces that lead to cusp fracture or, in severe cases, vertical root fracture (VRF).

Clinical Features and Diagnosis

Diagnosis of fractured cusp can be challenging, particularly in its early stages.

Patient history: Patients may report sharp pain upon application or release of pressure during biting.
Periodontal examination: If the fracture extends into the root structure, localized deep periodontal pockets may develop.
Biting test: Diagnostic tools such as the Tooth Slooth applied to a specific cusp can elicit sharp pain upon pressure or release, indicating a fractured cusp or cracked tooth.
Transillumination: Fiber-optic light can pass through enamel cracks; however, if the fracture extends into dentin, light transmission is blocked, indicating a deeper crack.
Staining techniques: Dyes such as methylene blue, iodine, or caries-detecting agents can highlight fracture lines and help determine their extent. Magnification with loupes or microscopes enhances visualization when combined with staining.

Management and Treatment Considerations

Treatment depends on the extent and depth of the fracture:

Complete fracture:

The fractured segment must be removed.
If pulp exposure occurs with signs of irreversible pulpitis, root canal therapy or vital pulp therapy is indicated.

Incomplete fracture:

The tooth should be restored.
Placement of a full cast crown is preferred to prevent progression of the fracture.

Key Restorative Considerations

Cuspal protection: In teeth that have undergone root canal therapy or are predisposed to fracture, protecting weakened cusps (e.g., with crowns) is essential to minimize flexure and prevent further fracture.
Treatment objective: The primary goal is to preserve tooth structure and prevent extension of the fracture.

Clinical Significance

Fractured cusp is more serious than craze lines due to its extension into dentin and potential pulpal involvement. Consequently, it requires active clinical intervention rather than mere observation.