Arm Description:

Participants will first receive digital intraoral scanning of their fully edentulous upper and/or lower jaw using the TRIOS 5 intraoral scanner (3Shape). The scanning process follows a structured sequence to capture the entire arch, including the palate and ridge slopes. Each arch will be scanned three times during the same visit to assess precision (consistency of repeated scans). Then the same participants will also undergo a conventional impression procedure using a custom tray and border molding technique.

Participants will first receive digital intraoral scanning of their fully edentulous upper and/or lower jaw using the TRIOS 5 intraoral scanner (3Shape). The scanning process follows a structured sequence to capture the entire arch, including the palate and ridge slopes. Each arch will be scanned three times during the same visit to assess precision (consistency of repeated scans). Then the same participants will also undergo a conventional impression procedure using a custom tray and border molding technique.

Trueness will be checked by looking at the Root Mean Square (RMS) deviation (mm) after superimposing the IOS Standard Tessellation Language (STL) over the conventional impression scan STL (reference) using Geomagic Control X. The primary metric is the participant-level mean RMS over the full arch surface (edentulous maxilla and mandible analyzed separately). Lower RMS indicates greater trueness (higher accuracy). Region-specific RMS (static vs. dynamic tissues) will be recorded as prespecified analyses (see secondary outcomes).

Alignment: Initial + best-fit alignment; conventional scan = reference file. Reporting (participant level): Mean RMS (mm) per arch. Reporting (study level): Mean [Standard Deviation (SD)], RMS per arch; 95% CI; distribution plots as applicable.

Unit of Measure: millimeters (mm), RMS deviation Regions analyzed: Static (palatal rugae, ridge slopes, crest) and dynamic (labial, buccal, lingual sulci, hamular notch, posterior palatal seal).

Precision will be quantified by pairwise deviation analysis between three repeated IOS scans per arch taken on the same day. STL files will be aligned (Initial + Best-Fit ICP) in Geomagic Control X. For each arch, the following pairs will be analyzed: (Scan1-Scan2), (Scan1-Scan3), and (Scan2-Scan3). Each pair will be aligned in both directions (each file alternately as reference), and all RMS values will be averaged to yield the participant-level mean pairwise RMS (mm) for that arch. Lower RMS indicates greater precision (repeatability).

Reporting (participant level): Mean of all pairwise RMS values per arch. Reporting (study level): Mean (SD) RMS per arch; 95% CI; distribution plots as applicable.

Unit of Measure: millimeters (mm), RMS deviation

Compute mean RMS trueness (mm) per arch (as defined in Primary Outcome 1). The between-arch difference will be calculated as maxilla minus mandible (mm). Positive values indicate higher RMS (worse trueness) in the maxilla.

Reporting (study level): Mean (SD) difference; 95% CI; paired analysis. Unit of Measure: millimeters (mm), RMS deviation

Using the precision pipeline (Primary Outcome 2), compute regional mean pairwise RMS (mm) for static and dynamic regions per arch and participant, then calculate Dynamic minus Static (mm). Positive values indicate higher RMS (worse precision) in mobile tissues.

Reporting (study level): Mean (SD) difference; 95% CI; by arch as applicable. Unit of Measure: millimeters (mm), RMS deviation