On the SAME side as the working (laterotrusive) movement, an excursive interference occurs between which two cusps?

Correct answer: B. Lingual cusp of the lower and buccal cusp of the upper

• A. Buccal-to-buccal contact alone is incomplete; working-side excursive contacts involve paired inclines, and in crossbite the pairing inverts.
• B. Correct per the recall key. In a NORMAL (non-crossbite) relationship the working-side contacts that are adjusted follow the BULL rule — Buccal Upper, Lingual Lower — i.e. the inner incline of the maxillary buccal cusp against the outer incline of the mandibular buccal cusp, and the maxillary lingual against the mandibular lingual. Because these teeth are in CROSSBITE, the buccolingual relationship is reversed and the mnemonic must be re-derived from the actual anatomy rather than applied by rote.
• C. Lingual-to-lingual contact alone is incomplete for the same reason.
• D. This describes the classic NON-WORKING (mediotrusive/balancing) interference in a normal occlusion — maxillary lingual cusp against mandibular buccal cusp. It is not the working-side answer given by the source.

Note: ⚠️ CONTESTED / HIGH-DIFFICULTY. The recaller explicitly said they were unsure of this set. Study the underlying anatomy rather than the mnemonic: BULL (Buccal Upper, Lingual Lower) identifies the cusps adjusted for WORKING interferences and MUDL / lingual-upper-buccal-lower identifies NON-WORKING interferences — but at a crossbitten tooth the buccolingual relationship is reversed, so the standard mnemonics invert. Work it out from the picture on exam day.