Initial effect of dental loupe use on laminate veneer preparation accuracy: an in vitro 3D digital assessment

This study evaluated the initial effect of dental loupe use on the 3D accuracy of laminate veneer preparations performed by prosthodontic specialty residents under standardized in vitro conditions. Twenty-six residents completed two maxillary right central incisor (#11) typodont preparations using a within-participant fixed-order protocol (unaided vision followed by loupes). Prepared specimens were scanned, anonymized, and compared with a criterion reference preparation using Geomagic Control X–based 3D metrology analysis. The primary 3D accuracy outcome was root mean square (RMS) deviation across five regions of interest: the full prepared surface, cervical, middle, and incisal thirds, and a 0.5-mm marginal band. Average signed deviation (Avg) was used as a secondary descriptive measure to characterize the direction of preparation errors. No statistically significant differences were found between loupe-assisted and unaided preparations for RMS outcomes (all p > 0.05). Avg analysis showed a similar directional pattern under both conditions, with a tendency toward over-reduction in the cervical, middle, and marginal regions and under-reduction in the incisal region. Within the limitations of this in vitro study, immediate loupe introduction without an extended adaptation period did not significantly improve RMS-based laminate veneer preparation accuracy compared with unaided vision. In addition, Avg analysis showed no clear change in the directional pattern of preparation errors.