[Advances in application of tissue clearing technique in hard tissues]

Tissue clearing is a novel technique developed within recent years, which could make the tissue optical transparency using physical or chemical methods by refractive index matching. Combined with fluorescence imaging and three-dimensional reconstruction technology, it could achieve three-dimensional observing and analyze the tissue structure at the cellular resolution. The tissue clearing technique is mainly applied to soft tissues, as less to hard tissues. In recent years, many researchers have modified tissue clearing methods and made them suitable for hard tissues, such as bone and teeth. The present paper reviews the recent application of tissue clearing techniques in hard tissues.