Signs and symptoms - DI is often asymptomatic with minimal external deformity - Abnormal tooth shape, such as being wider mesio-distally or bucco-lingually, may be reported - Increased risk of caries and periradicular pathology - Infolding enamel can easily chip off, leading to abscess formation and displacement of dental structures - Incisal notching or pronounced talon cusp on lateral incisors may indicate DI and should be investigated with radiographs

Cause - Unclear cause, but several theories exist: - Infection - Trauma - Growth pressure of dental arches during odontogenesis - Rapid proliferation of internal enamel epithelium invading dental papilla

Diagnosis - Clinical examination may reveal abnormally shaped tooth - Radiographic examination is necessary for confirmation - Periapical radiograph shows invagination lesion as a radiolucent pocket beneath cingulum or incisal edge - Larger lesions can appear as fissures with radio-opaque structures - Cone beam computed tomography (CBCT) provides detailed 3D image for diagnosis and treatment planning

Oehlers classification - Class I: Partial invagination limited to crown, without involvement of pulp or periodontal ligament (PDL) - Class II: Partial invagination extending beyond crown and CEJ, with possible pulp involvement but no communication with PDL - Class IIIa: Complete invagination extending through root and communicating with PDL, usually without pulp involvement - Class IIIb: Complete invagination extending through root and communicating with PDL through apical foramen, with potential disruption to dental anatomy

Management - Preventative treatment, such as oral hygiene instructions and fissure sealant, is important - Intentional replantation may be considered - Root canal treatment with mineral trioxide aggregate can be performed - Periapical surgery with retrograde filling is an option - Extraction may be necessary in severe cases