Pulp horn 6 within the solitary mesial pulp compartment maxillary and mandibular second premolars (Triadan 06). Scale bar: 5 mm. Maxillary 106, 9.5 years: Four pulp compartments are developed, with pulp horns 1, 3 and 6 derived from root canal I. Please note the furcation of root canal I into I1 and I2. Mandibular 306, 12.5 years: Two solitary pulp compartments are present. Pulp horn 6 is coalesced with distinct remnants of pulp horns 1, 3 and 4.