Influence of Experimental Lighting Conditions on Digital Shade Matching and Intraoral Scanning Accuracy: A Clinical Study

OBJECTIVES: To evaluate the in vivo effect of varying experimental lighting conditions on the digital shade determination and scanning accuracy (trueness and precision) of two intraoral scanners (IOSs). MATERIAL AND METHODS: The maxillary arches of 10 volunteers were scanned using two IOSs (Trios 4 wireless, 3Shape A/S [TR]; and Primescan, Dentsply Sirona [PR]). Scans were performed under four illuminance levels (0, 500, 1000, and 2500 lx) with scanner-specific color temperature (TR: 5500 K; PR: 4100 K). Digital shade selection was performed at the middle third of the right central incisor against visual consensus by three experts for Vita toothguide Classical (VC) and Vita toothguide 3D-Master (VM) shade guides. Scanning accuracy was assessed by superimposing IOS scans onto reference datasets obtained by digitizing conventional stone models with a laboratory scanner (InEos X5; Dentsply Sirona). Shade matching capability (accuracy and reliability) was also evaluated. Data were statistically analyzed using one-way ANOVA (α = 0.05). RESULTS: Ambient lighting significantly influenced digital shade matching and scanning trueness (p < 0.05). For shade matching accuracy, TR demonstrated the highest values at 1000 lx/5500 K (VC: 93.33% ± 14.05%; VM: 76.67% ± 22.50%), while PR performed best at 2500 lx/4100 K (VC: 96.67% ± 10.54%; VM: 50.00% ± 28.33%). TR produced significantly lower reliability results at the "no-light" (0 lx) condition (p < 0.05), whereas PR displayed no significant difference among groups (p > 0.05). For scanning trueness, TR exhibited the lowest deviation at 1000 lx/5500 K (104.04 ± 20.88 μm), while PR performed best at 2500 lx/4100 K (100.78 ± 19.36 μm). CONCLUSIONS: Ambient lighting conditions significantly affected IOS performance in vivo. The optimal conditions were scanner-dependent: TR performed best under typical examination room lighting (1000 lx, 5500 K), while PR excelled under dental operatory lighting (2500 lx, 4100 K). CLINICAL SIGNIFICANCE: To optimize digital impressions and esthetic shade matching, clinicians should adjust ambient lighting according to the specific requirements of the intraoral scanner being used.