Tray/material errors causing distortion (flexible tray, poor handling)
What it is
Making an impression (especially with elastomerics like VPS/PVS or polyether) using a tray or technique that allows distortion — most commonly: • using a flexible plastic stock tray (or a flexing dual-arch tray) • insufficient tray support/adhesion • non-uniform/too-thick material bulk that increases polymerization shrinkage effects and deformation Result: the impression rebounds/warps, and the cast/restoration is inaccurate.
Why it happens
• Tray not rigid enough: plastic stock trays and some dual-arch trays can flex during seating and/or while the patient occludes, which can distort the set impression • Poor tray selection/fit: tray contacts teeth/soft tissue, or is undersized → forces flexure and "spring back" distortion • No tray adhesive / inadequate adhesion: elastic recovery + removal forces can allow the impression to separate microscopically and distort • Inconsistent impression material thickness (too bulky in areas): thicker sections increase dimensional change risk; controlling space is one reason custom trays are used for precision • Handling/removal errors: rocking the tray on removal or removing before full set can permanently deform the impression
The full clinical mistake entry includes
- How to avoid it — the prevention protocol
- The clinical tip experienced clinicians use
- The documented reference behind the mistake
More clinical mistakes
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