Digital Impression Accuracy Calculator

Intraoral scanner accuracy is usually reported as two separate numbers: trueness (how close the digital model is to the real tooth geometry -- systematic error) and precision (how repeatable the scan is between attempts -- random error). Both are typically expressed in micrometers, with published ranges of roughly 10-30 um trueness for a single prepared tooth, 20-50 um for a quadrant, and 30-100 um for a full arch, where trueness tends to worsen with scan extent because stitching together more overlapping images accumulates error. This calculator starts from those baseline ranges for the selected scan extent and then applies multiplying and additive adjustments for the clinical conditions most often cited as accuracy factors: moisture control (saliva, blood, or sulcular fluid degrade the optical capture), subgingival margin depth (each additional millimeter below the gumline adds measurable error because the scanner cannot directly "see" tissue it cannot optically reach), scanner generation, operator experience, the number of prepared teeth captured in one scan (more teeth mean more stitching), and ambient lighting.

The estimated marginal gap shown is a rule-of-thumb multiple (roughly 2-3x) of LOCAL trueness at the prepared tooth's own site, not the overall arch-level trueness figure above -- a single crown's margin depends on scan accuracy right at that prep, not on the cumulative stitching drift that accumulates across a whole full-arch scan, so a full-arch scan extent alone should not by itself make a single crown's estimated fit look worse. It is referenced against the commonly cited clinical thresholds of under 120 um as an acceptable crown margin and under 60 um as an ideal one, with implant frameworks needing tighter passive fit, often cited around 50 um or less -- implant fit stays tied to the overall arch-level trueness figure, since an implant framework spans more of the arch than a single crown margin does. These are estimates from published ranges and general accuracy literature, not a substitute for validating a specific scanner's real-world performance in your own hands.