Root resorption is caused by osteoclast (bone destroying cells)  and pressure exerted by the erupting permanent tooth.X23704Around age 6-7, children begin the exciting stage of losing “baby” teeth to make room for the permanent dentition.  This photo is a great example of how the permanent tooth pushes right through the roots of the primary tooth that is in it’s way. This resorption is painless but sometimes the tissue will get sore from the top portion of the tooth wiggling around.