Normal resorptive processes occur to allow the exfoliation of primary teeth in preparation for the eruption of the permanent teeth. However, there are other resorptive processes that can result in the destruction or removal of tooth structure including external resorption, which affects the outer surface of the tooth, and internal resorption, which affects the pulp chamber and canal(s) housed inside the tooth. Some cases may be referred to as idiopathic when no causal factor can be identified for the resorption.
A common entity, external resorption tends to be mild, affects one or more teeth, and usually is only discovered upon radiographic examination.7,9 It most commonly involves the dentin and cementum of the root surfaces of the teeth but the crown of an unerupted tooth (Figure 48) can be affected as well.9 In most situations, it does not present any substantial clinical problems. However, 10% of patients demonstrate significant external resorption.7 A number of factors are associated with this condition such as excessive mechanical forces, extreme occlusal forces, tooth reimplantation, dental trauma, as well as systemic conditions and pathologic entities.16 Root resorption may be an aftermath of orthodontic treatment when heavy forces are applied to the teeth, and significant tooth movement is required to correct malocclusion (Figure 49).7 A genetic component may be at play in situations in which the resorption is severe.7
While less common than external resorption, internal resorption can affect both the primary and permanent teeth.9 When internal resorption does occur, usually it is associated with trauma to the tooth and inflammation of the pulp tissues.7,9 The resorption involves the pulp chamber or pulp canal and the adjacent dentin, giving rise to an enlarged or expanded pulp structure (Figure 50).7,16 The permanent central incisors and the first and second molar teeth are most frequently involved.9 Typically asymptomatic, internal resorption can illicit pain if the resorption results in major pulpal inflammation. When the resorptive lesion affects the coronal pulp structure, a pink coloration known as the pink tooth of Mummery may be observed clinically.7 If the root and pulpal canal are involved and the integrity of the normal canal anatomy is breached, an oval or balloon-shaped radiolucent area of expansion may be visualized radiographically (Figure 51).7,16 In severe cases, perforation of the lateral root can occur. If the tooth remains sound, endodontic therapy can be rendered to stop the resorptive process, or in cases of root perforation, surgical endodontic retrofill procedures may be necessary.16 Ultimately, extraction may be required if the tooth is unrestorable.16