Integration of optical coherence tomography and intraoral scanning for enhanced subgingival finish line trueness: A comparative analysis

Statement of problem

Intraoral scanning of subgingival finish lines without gingival displacement cords may compromise the accuracy of fixed dental prostheses. The integration of optical coherence tomography (OCT) may overcome this limitation, but further research is required.

Purpose

The purpose of this in vitro study was to compare the trueness of scan data obtained from an intraoral OCT system and an IOS for tooth preparations with subgingival finish lines.

Material and methods

A maxillary left central incisor was extracted and prepared for a zirconia crown. The prepared tooth was embedded in an artificial gingival model composed of silicone, with a refractive index similar to that of gingival tissue. The subgingival depth of the finish line was standardized between 0.50 and 0.70 mm. Scanning was performed using 4 methods: a CAD reference model (CRM) obtained using a laboratory scanner without gingiva, an IOS (i700; MEDIT) without gingiva (IOSO group), an IOS with artificial gingiva in place (IOSG group), and a dataset integrating OCT scans of the subgingival finish line with IOSG data (OCT group). Each group consisted of 15 specimens (n=15). The CRM dataset was used as the reference, and the best-fit alignment was performed for the IOSO, IOSG, and OCT datasets. The trueness of the finish line was assessed by measuring deviations at predefined points on virtual planes established relative to the CRM data. Additionally, 3-dimensional (3D) trueness was evaluated by calculating deviations across the entire point cloud of the CRM dataset. Statistical analysis was conducted using the Kruskal–Wallis test (α=.05).

Results

The IOSO group (median: 12.5 µm; interquartile range [IQR]: 10.5) and the OCT group (median: 17.3 µm; IQR: 16.7) exhibited significantly lower deviations compared with the IOSG group (median: 109.4 µm; IQR: 235.1) (P<.05). For 3D trueness, no significant difference was observed between the IOSO and IOSG groups (P>.05), while the IOSG group exhibited the highest deviation at the finish line (P<.05).

Conclusions

The integration of an intraoral OCT system improved the trueness of subgingival finish line scans compared with conventional intraoral scanning with gingival interference.