Correlation and agreement among outcome measures in implant impression-making research: A validation study.

Objective To validate Root Mean Square (RMS) error calculation as an outcome measure of trueness by assessing its correlation and agreement with linear and angular outcome measures in implant impression-making research.Materials And Methods A maxillary implant cast with four parallel implants was scanned with a high-resolution desktop 3D scanner (Artec Micro II; Artec 3D; Senningerberg, Luxembourg) and scanned 100 times using an intraoral scanner (TRIOS 5; v 22.1.10; 3 Shape; Copenhagen, Denmark) under controlled conditions. Primary outcome measure was trueness, assessed by RMS error, linear and angular inter-implant deviations, and linear and angular intra-implant (platform-level) deviations. Secondary outcome measures included scanning time and number of photograms. Correlations among outcome measures were evaluated using Pearson's correlation coefficients with Bonferroni correction (α = 0.05), and agreement was assessed using Bland-Altman analysis for outcome measures that were directly comparable.Results Very large positive correlations were found between RMS error and both linear inter-implant deviation (r = 0.831, p = 0.001) and linear intra-implant deviation (r = 0.864, p = 0.001). Angular deviations were not correlated with other outcome measures except between themselves (r = 0.669, p = 0.001). Scanning time was moderately correlated with most deviation outcomes (RMS error: r = 0.478, p = 0.001; linear inter-implant: r = 0.318, p = 0.027; and linear intra-implant deviations: r = 0.319, p = 0.026). The number of photograms was correlated only with scanning time (r = 0.678, p = 0.001) and showed no correlation with deviation measures. RMS error and linear deviations showed partial agreement, whereas angular deviations showed acceptable agreement.Conclusions RMS error showed strong correlation and partial agreement with linear deviation measures, providing similar but not identical results due to the distinct physical aspects captured by each outcome.