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Prosthodontics & Occlusion · single question

When instructing a laboratory on a custom impression tray for a final impression, which instruction is the EXCEPTION (NOT recommended)?

  1. Extend the tray flanges to the appropriate vestibular depth
  2. Provide 1 mm of relief (spacer) for impression material over the soft tissues
  3. Provide about 2 mm of relief for impression material
  4. Adapt the tray directly to the tissue with no space for impression material
Show answer and explanation

Correct answer: D. Adapt the tray directly to the tissue with no space for impression material

A custom tray needs a uniform spacer (about 1-2 mm) so impression material can flow without distortion; adapting it directly to tissue with zero relief produces a distorted, inaccurate impression, so that is the instruction NOT to give.Other options: Extending flanges and providing 1-2 mm of relief are correct custom-tray instructions.Key exam takeaway: Custom trays need uniform 1-2 mm relief and properly extended flanges; never zero-space the tray onto tissue.

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