Impact of different lighting conditions on the tooth-shade selection using intra-oral scanners: An in-vitro study

To evaluate the accuracy in tooth shade selection under various lighting conditions using different devices, including a color spectrophotometer (CSP) and two intra-oral scanners (IOS: IOS-1 and IOS-2).

Tooth shade measurements were performed on a standardized shade guide (16 shades, A1-D4) using CSP, IOS-1 and IOS-2. These evaluations were carried out under three lighting conditions: (1) DL - device light source only, (2) RL - DL plus room light, and (3) CL - RL plus dental-chair light. Each shade was measured ten times per lighting condition with each device by a single investigator. Shade detection accuracy was defined as the percentage of matches to the known shade. Logistic regression models were used for statistical analyses (α = 0.05).

A total of 1440 measurements were conducted. Lighting conditions of increasing intensity significantly decreased the shade detection accuracy of the devices (CSP: RLvsDL, p > 0.9999, Odds Ratio (OR) = 1; CLvsDL, p = 0.0726, OR = 0.6053, IOS-1: RLvsDL, p < 0.0001, OR = 0.2862; CLvsDL, p < 0.0001, OR = 0.05239 and IOS-2: RLvsDL, p = 0.0002, OR = 0.376; CLvsDL, p < 0.0001, OR = 0.1908). CSP, IOS-1, and IOS-2 had shade detection accuracies of 43.75 %, 74.38 %, and 59.38 % respectively under DL. In RL, IOS-1 and IOS-2 dropped to 50.63 % and 40.63 %, respectively; CSP remained unchanged. Under CL, the accuracy dropped for all devices (CSP: 35.63 %, IOS-1: 20.63 %, IOS-2: 28.75 %). Additionally, the devices demonstrated higher accuracy when measuring shade A compared to shades B, C, and D.

The findings of this in vitro study concluded that the accuracy of tooth shade detection was more reliable, particularly for individuals with shade A, when spectrophotometers and intraoral scanners were used with only their built-in light source. Further purpose-built clinical studies are required to confirm these findings in a clinical context.