There are five types of resorption that effect teeth:
External, internal, replacement resorption (ankylosis), peripheral inflammatory root resorption (PIRR) and external-internal progressive.
The X-ray below is an example of the external-internal progressive type. The lesion begins externally, laterally and extends internally, often surrounding the pulp. When opening the access there is copious bleeding and granulation-like tissue is removed. The bleeding is managed with calcium hydroxide dressings. Once the dry chamber is achieved, the lesion needs to be sealed at the external defect
The x-ray below on the left shows the fill in an upper central incisor exhibiting internal resorption. The internal defect can only be filled with a warmed gutta percha compaction technique. Notice the lateral canal in this case. The second x-ray below on the right shows an advanced internal resorption defect in an upper left lateral incisor and then apically filled with MTA and back-filled with warmed gutta percha.
The next case is also of the external-internal progressive (central incisor) and internal resorption (lateral incisor). Both also unfortunately are ankylosed. This was clinically diagnosied by the "metallic" sound when percussing the teeth. The x-ray on the right shows an advanced replacement resorption with ankylosis on an upper central incisor. The tooth will be extracted in the near future. (please see blog in the proendo forum)
External root resorption is usually diagnosed with apical blunting or fore-shortening of the root length (as compared with adjacent root lengths). The active resorptive process must first be halted and osteoblastic (bone laying) cells promoted to provide healing. The cause for the resorption must be removed (for example, external resorption may present while the patient has active orthodontics. The force of the orthodontic braces might be too strong).
The treatment usually involves calcium hydroxide dressings over a number of appointments. The apical foramen must be guaged for size. The apical foramen is often larger and obturation is trickier due to the loss of apical "capture".
The example of an upper molar tooth below, presents with blunting of the buccal roots. The apexes were sealed with MTA and then backfilled with gutta percha. This case may be diagnosed of external root resorption due to a chronic infection.