A lower deciduous second molar usually has how many roots and cusps?

A lower deciduous second molar usually has how many roots and cusps?

• A. Three roots, six cusps
• B. Two roots, five cusps
• C. One root, four cusps
• D. Two roots, three cusps

Answer: (B)

Think about how deciduous lower molars are formed. For primary teeth, molars typically have two roots, not three, so the lower deciduous second molar usually has two roots. The crown is multi-cusped on the occlusal surface, typically with five cusps: mesiobuccal, mesiolingual, distobuccal, distolingual, and a distal cusp. That combination—two roots and five cusps—matches the usual anatomy of this tooth. The other options describe root or cusp counts that don’t align with its common structure.

Think about how deciduous lower molars are formed. For primary teeth, molars typically have two roots, not three, so the lower deciduous second molar usually has two roots. The crown is multi-cusped on the occlusal surface, typically with five cusps: mesiobuccal, mesiolingual, distobuccal, distolingual, and a distal cusp. That combination—two roots and five cusps—matches the usual anatomy of this tooth. The other options describe root or cusp counts that don’t align with its common structure.