Evaluation of the accuracy of the soft tissue thickness measurements with three different methodologies: an in-vitro study

Abstract

Background Soft tissue thickness (STT) influences esthetics, peri-implant, and periodontal health. Non-invasive methods of STT evaluation include cone-beam computed tomography (CBCT) with Digital Imaging and Communications in Medicine (DICOM) files and registration of DICOM files with an intraoral scan or Standard Tessellation Language (STL) files. This study compares three methodologies: bone sounding, DICOM data alone, and DICOM and STL registration to absolute histomorphologic values. Materials and Methods Five human maxillas, including teeth #s 6-11, provided 90 sites for analysis. For standardization, reference grooves were placed at the cervical margin and the long axis of each tooth. Direct measurements with a no. 25 K-file were completed at the facial soft tissues at 3.00, 5.00, and 7.00 mm from the apical marginal reference. Indirect measures were performed with implant planning software. Histological measurements were rendered with imaging software. One-way analysis of variance (ANOVA) was used to compare the three techniques for the differences from histologic measurements (α = .05). Results Seventy-two sites were included for final analysis. The overall mean histological STT (mSTT) was 0.73 ± 0.31 mm. Bone sounding overestimated mSTT, 0.22 ± 0.20mm (p<.001); whereas, DICOM alone underestimated mSTT, -0.23 ± 0.19 mm (p<.001). DICOM and STL registration had non-statistically significant differences, -0.04 ± 0.21mm (p = .429). Intraclass correlation coefficient (ICC) of DICOM and STL registration achieved the highest agreement with histology (ICC: 0.74). Conclusions DICOM and STL file registration had the highest agreement with histological STT supporting the use of DICOM and STL registration for the evaluation of soft tissue thickness.