The periodontist will also take a small measuring instrument called a probe and place it between the teeth and gums to determine the depth of those spaces, known as periodontal pockets; this helps the periodontist assess the health of the gums.
The ground substance of connective tissue is different from all of these fluids; it is the liquid medium through which these other fluid exchanges take place.
Ground substance is the background material within which all other connective tissue elements are embedded. In ordinary connective tissue, the ground substance consists mainly of water whose major role is to provide a route for communication and transport (by diffusion) between tissues.