Spatial and temporal repair patterns of orthodontically induced surface resorption patches

Root resorption appears to be an inevitable sequel to orthodontic tooth movement, occurring either apically or along surfaces in and around the pressure zones. However, there is uncertainty as to the location of initial cementum repair in resorbed areas as well as the time of onset of repair. The aim of the present study was to map the spatial and temporal patterns of cementum repair in orthodontically induced areas of surface resorption following maxillary expansion. Two spatial patterns of repair of orthodontic surface resorption patches were observed with cementum deposition proceeding either from the periphery or starting somewhere in the center of the resorbing areas, although the deposition starting centrally was argued to be artifactual. Furthermore, onset of reparative cementum mineralization appeared to follow within 2 wk after release of the force, involving initially only acellular cementum formation. However, the pattern of formation changed gradually, favouring a slow deposition of cellular cementum at more advanced stages of healing.