Comparing analog and 3D measurements of vertical dimension in edentulous subjects

Objective
This study aimed to explore the feasibility and reliability of measuring the vertical dimension of occlusion/rest (OVD/RVD) on 3D facial scans of edentulous patients.

Methods
Nineteen edentulous participants rehabilitated with complete removable dental prostheses (CDs) participated in this study. Analog measurements (control) were obtained directly on the face for each participant with the jaws positioned at the rest position (without CDs, RVD) and at centric occlusion (with dentures, OVD), between the facial landmarks: Glabella (G) and Soft Pogonion (SP), Pronasale (PN) and SP, and Subnasale (SN) and SP. Participants’ faces were scanned twice, using a face-scanner (Class 1 LASER, Obiscanner). Scans were imported into a mesh-processing software, and the OVD/RVD were measured digitally. Two investigators performed all the measurements and were blinded. Data analysis included intra-class correlation coefficient (ICC) and pairwise comparison tests (p < 0.05).

Results
Digital measurements were higher than analog measurements, and the mean paired difference ranged from -4.86±3.2 to 0.42±2.7 mm. All the differences were statistically significant, expect for SN-SP (p = 0.110). Magnitude of the differences for the RVD were large for G-SP and SN-SP (ES>0.80) and moderate for PN-SP (ES>0.50). There was a large effect for G-SP when measuring OVD (ES>0.50), and small effect for PN-SP and SN-SP (ES≤0.20).

Conclusion
Considering the limitations associated with the specific type of facial scanner used in this study, it can be concluded that registering the resting vertical dimension in edentulous patients through digital methods may not be currently recommended. This is due to the potential errors that may arise during the data acquisition process, which could compromise the accuracy and reliability of the measurements.