Which muscle is MOST affected when the vertical dimension of occlusion is excessively INCREASED by a restoration or prosthesis?

Correct answer: D. The masseter

• A. The BUCCINATOR is a muscle of facial expression that positions the bolus between the teeth. It has no elevator function.
• B. The DIGASTRIC is a DEPRESSOR of the mandible. It is not stretched by an increased vertical dimension; if anything, it is shortened.
• C. The LATERAL PTERYGOID is a PROTRUDER and depressor and is implicated in disc displacement and deviation on opening, rather than in an increased vertical dimension.
• D. CORRECT. Increasing the vertical dimension stretches the ELEVATOR muscles beyond their comfortable resting length and eliminates the FREEWAY SPACE — the 2 to 4 mm interocclusal gap that normally exists at rest. The elevators are then held in continuous low-grade contraction rather than allowed to rest. The MASSETER, the most powerful and most superficial elevator, is the one that becomes fatigued and tender to palpation, along with the temporalis and medial pterygoid. Patients report a tired, aching jaw, teeth that click together during speech, and soreness that is worse at the end of the day.

Note: ⚠️ Worth confirming with the group — the source records no key. The reasoning is anatomical: an increased VDO overstretches the ELEVATORS (masseter, temporalis, medial pterygoid) and eliminates freeway space, so a mounted diagnostic assessment should always verify that at least 2 mm of freeway space remains before the restoration is finalised.