A characteristic feature of lingual surface of the mandibular first premolar is:: (A) Rudimentary lingual cusp, (B) Mesial marginal ridge, (C) Mesiolingual developmental groove, (D) Lingual triangular ridge
Answer is C. A characteristic of the lingual surface of the mandibular first premolar is the mesiolingual developmental groove. This groove acts as a line of demarcation between the mesiobuccal lobe and the lingual lobe and extends into the mesial fossa of the occlusal surface.