<prompt> Rate of primary dentin formation is4μmday5μmday6μmday7μmday  <response>: Secondary dentin forms at a slower rate 1μmday than primary dentin 4μmday and regularly but not uniformlymore formation is seen on the roof and floor of the pulp chamber. Hence this dentin is also known as regular secondary dentin. If the dentin forms as a reaction to an irritant trauma or dental caries to protect the pulp, it is called reparativereactivetertiaryirregular dentin 