Real-time Tomographic Monitoring of Composite Restoration Placement Using SS-OCT

Objectives: The aim of this study was to use swept-source optical coherence tomography (SS-OCT) for real-time tomographic assessment of tooth/restoration complex during placement of resin composite. Methods: An SS-OCT system with a laser center wavelength of 1310nm was used to record tomographic images and videos during bulk placement and light-polymerization of four combinations of composite/adhesive materials; two low-shrinkage composites (Filtek Silorane/Adhesive and Kalore/SE Bond), and one conventional hybrid composite with either a two-step self etch or an all-in-one adhesive system (APX/SE Bond and APX/S3 Bond). The composites were bulk filled into 1.7-mm-deep standard class I dentin cavities. The movies were used to monitor the placement and polymerization procedures up to 2min after photo-activation. Single fine shots were analyzed to quantify the interfacial gap resulting from polymerization shrinkage, dimensional contraction, and structural voids in a central cross section of the restored cavity. The specimens were then sectioned and analyzed using a confocal laser scanning microscope (CLSM) to confirm the SS-OCT findings. Results: Gaps due to the polymerization shrinkage were detected in APX/S3 Bond group, but APX/SE Bond showed no gap formation. APX resulted in the largest dimensional changes. Low-shrinkage composites showed minimal dimensional changes during polymerization; however, Silorane had a thicker consistency resulting in more voids and a relatively poor adaptation to the cavity walls. The optical contrast between the material and air helped in detection of interfacial gaps. CLSM confirmed that SS-OCT was capable of detecting interfacial gaps and structural voids on a submicron scale. Conclusions: Adhesive system, polymerization shrinkage and consistency of composite were the factors that affected the outcome of bulk-filled composite restoration. SS-OCT is capable of providing simultaneous high-speed high-resolution images for non-destructive assessment and monitoring of tooth restoratives and the surrounding biological tissues, a viable tool for dental materials research. Supported by GCOE program at TMDU.