**Core Concept**
In ideal occlusion, the facial cusps of maxillary posterior teeth oppose the lingual cusps of mandibular posterior teeth. This opposition is essential for proper mastication and distribution of occlusal forces. The concept of ideal occlusion is based on the principle of harmonious relationship between the maxillary and mandibular dental arches.

**Why the Correct Answer is Right**
The correct opposition of facial cusps of maxillary posterior teeth to lingual cusps of mandibular posterior teeth ensures that the occlusal forces are evenly distributed between the upper and lower teeth. This opposition prevents excessive wear on the dental surfaces and promotes proper mastication. The facial cusps of maxillary posterior teeth are designed to occlude with the lingual cusps of mandibular posterior teeth, allowing for efficient transfer of forces from the upper to the lower teeth.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the facial cusps of maxillary posterior teeth do not oppose the occlusal surfaces of mandibular posterior teeth in ideal occlusion.
**Option B:** This option is incorrect because the facial cusps of maxillary posterior teeth do not occlude with the buccal cusps of mandibular posterior teeth in ideal occlusion.
**Option C:** This option is incorrect because the facial cusps of maxillary posterior teeth do not oppose the incisal edges of mandibular anterior teeth in ideal occlusion.

**Clinical Pearl / High-Yield Fact**
In ideal occlusion, the maxillary and mandibular dental arches are in a harmonious relationship, allowing for proper distribution of occlusal forces and efficient mastication. This relationship is essential for maintaining the health and integrity of the dental tissues.

**Correct Answer:** D. Lingual cusps of mandibular posterior teeth