How many roots and pulp horns does this tooth typically have?

The maxillary first premolar most commonly has TWO roots (buccal and palatal, ~60–70% of cases) and TWO pulp horns corresponding to the buccal and lingual (palatal) cusps. The crown morphology dictates the pulp horn count: the premolar has two cusps, so two pulp horns. Be careful — the maxillary second premolar is usually single-rooted, and the mandibular first premolar is typically single-rooted with one major pulp horn.