When preparing a custom tray for a final impression, which of the following is an EXCEPTION (not recommended)?

Correct answer: D. Adapt material directly to the gingiva without space for impression material

• A. Extending flanges to proper vestibular depth is correct custom tray design.
• B. Leaving ~1 mm of relief space for impression material is an acceptable/recommended spacing.
• C. Leaving ~2 mm of relief space is also an acceptable spacing range (1-2mm) for impression material.
• D. Correct (the exception/incorrect technique). Adapting the tray material directly onto tissue without any relief space prevents adequate flow/thickness of impression material, leading to distortion and inaccurate impressions.

Note: There must be 1-2 mm of space for impression material to flow without distortion, and flanges must cover the entire vestibular area.