A Novel Digital Method for Evaluation of Mucosa Thickness Changes in Time: Changes Associated With a Removable Partial Denture

Abstract

The aim of the study was to propose a method for three-dimensional evaluation and visualisation of mucosa thickness and mucosa thickness changes and to validate it in four different software implementations. Cone-beam computed tomography (CBCT) and digitised mandibular impression, i.e., optical scan, of five patients treated with a mandibular distal extension removable partial denture were acquired at baseline (T0) and 1-year follow-up (T1). CBCT images were automatically segmented and then superimposed with a corresponding optical scan and within a patient. To obtain mucosa thickness changes in the T0-T1 interval, firstly, the distances between T0 and T1 models were computed for mucosa surface, representing surface changes (dSurface) and bone surface, representing bone changes (dBone). The distances were saved as scalar field values in the mesh model. Finally, the mucosa thickness changes (dMucosa) were calculated by subtracting the corresponding dBone from dSurface values. Distance computation algorithms in four different software were tested and compared. No differences were found between all four tested software (p0.001). Mean (and standard deviation) of median dSurface, dBone, and dMucosa of right and left residual ridge (n=10) was -0.47mm (0.43), -0.44mm (0.62), and 0.00mm (0.35), respectively. High local variability of dBone and dMucosa was found on the colour-coded maps. A novel method facilitates precise three-dimensional evaluation and visualisation of mucosa thickness and thickness changes, regardless of the software used.