Tandem scanning reflected light microscopy: applications in clinical dental research.

The Tandem Scanning Reflected Light Microscope (TSRLM) enables the investigation of microscopic structures both at and deep to the surface of intact objects. The present paper reviews studies undertaken to determine whether the TSRLM would be usable and useful in the investigation of natural and restorative dental materials in vitro and in vivo. It was found that the TSRLM could be used to study normal and diseased dental tissues and the new materials which are used to replace lost substance. More importantly, it could be used to characterize the interface between tooth and optically translucent materials in bulk samples, giving high resolution information from not only a shallow depth of field, but at planes below cut surfaces. This makes it possible to study interfacial regions in three dimensions without the risk of delamination that must accompany the preparation of a microscopic section. The use of fluorescent markers enables more information to be derived from the tooth/adhesive interface. Studies to date indicate the need for the development of adhesion promoting agents which incorporate a fluorescent radical in their molecular structure. Preliminary work using the instrument for observation of cutting interactions between a high speed bur and a tooth indicates some useful potential in the study of cavity preparation techniques and tissue failure mechanisms. Recent developments of the TSRLM for three dimensional imaging in other dental applications are outlined. This microscope is an important advance in the microscopic assessment of adaptation of biomaterials to hard tissues.