3D analysis of composite restoration at practical training using SS-OCT

Objectives:  Internal adaptation of restorations to the cavity wall is one of the important topics in clinic and necessary to be stressed at dental education. In this study, swept-source optical coherence tomography (SS-OCT) was used for detection of marginal and internal defects in the composite resin restorations as an educational device for undergraduate dental student.

Methods: An upper right melanin first molar tooth was used in the 4^th year practical examinations of 67 dental students. Class 1 and Class 2 composite restorations to the melanin tooth were assigned to the student and prepared at the skill test, where SS-OCT imaging was performed. Clearfil SE Bond (Kuraray Medical Inc.) as a surface treatment agent and Estelite Σ (Tokuyama Dental Co.) as a filling composite resin were used in this study. The 3D scan of each restoration was carried out from a direction that was almost perpendicular to the composite resin restoration using an SS-OCT imaging system (Prototype 2, Panasonic Health Care). Three Cross-sectional 2D tomographic images were obtained from the 3D scan to evaluate the internal adaptation of each restoration, including the presence or absence of large gaps and voids.

Results: SS-OCT could detect the internal gaps and voids within the restorations in a tomography image synthesized based on the backscatter signal. Large gaps voids were detected in 23 composite resin restorations. Of these, 14 contained bubbles, 16 contained gaps, and 7 contained both air bubbles and gaps.

Conclusions: The internal adaptation of composite resin restorations of melanin teeth using SS-OCT could be non-invasively evaluated on tomograms. Therefore, SS-OCT imaging system is highly useful as a device for visualizing the adaptive condition of composite resin restoration. Supported by Grant-in-Aid for Scientific Research (No. 23390432) from JSPS and Research Grant for Longevity Sciences (21A-8) from MHLW.