Enamel matrix derivative Enamel matrix derivative In dentistry, enamel matrix derivative (EMD) is an extract of porcine fetal tooth material used to biomimetically stimulate the soft and hard tissues surrounding teeth to regrow (in a process known as regeneration) following tissue destruction. There are three hard tissues that comprise human teeth: enamel, dentin and cementum. The majority of the tooth structure is formed from dentin, and the enamel serves as the superficial layer of the crown while the cementum serves to cover the root. In the mid-1990s, however, it was discovered that a very thin layer of enamel actually exists between the dentin
Active layer in permafrost regions due to the low rate of weathering in the very cold climate. The slow rate of decomposition of organic material means gelisols (permafrost soils) are very important as a sink for carbon dioxide. This carbon dioxide and other greenhouse gases (chiefly methane) forms from the very slow decomposition of the excess organic matter that remains in most gelisols and is mixed down into the pereletok layer during relatively hot summers and below that layer during warmer periods about 5000 to 6000 years ago. This storage of carbon means thawing of permafrost may accelerate global warming - some