Background Leakage under dental restorations is problematic because it allows bacterial percolation and can cause a failure of dental restorations. Assessing microleakage and nanoleakage is one of the main topics of research regarding operative dentistry.

Objective This review compares the assessment methods of composite leakage using optical coherence tomography.
Results Optical coherence tomography (OCT) is useful in evaluating the internal adaptation of composite resin restoration and in quantifying resin–dentin interfacial gaps. The sealing performance of resin cementation before and after thermal cycling and monitoring of cariogenic demineralization at the enamel–composite interface was also attempted. OCT is still uncommon in developing countries. Saudi Arabia is the only Arab country that has conducted OCT-based studies.
Advances in Knowledge OCT (swept-source) is an excellent candidate for assessing adhesives, defects at the tooth/self-adhering flowable composite interface cavity, enamel cracks at the adhesive cavosurface margin, the microleakage of resin restorations, and cavity wall adaptation of composite restoration. The most promising area of research for OCT is the measurement of volumetric polymerization shrinkage in relation to internal adaptation in bulk-fill and conventional composites. The sealing performance of resin cement before and after thermal cycling, and monitoring of cariogenic demineralization at the enamel–composite interface was also attempted.