Dental Resorption. From Diagnosis to Management: An Update for the GDP

External inflammatory resorption

External inflammatory resorption (EIR) occurs when there has been a loss of cementum of the root surface following trauma, alongside the root canal system becoming infected with bacteria.

The intracanal bacteria and their endotoxins are able to reach the periodontal ligament (PDL) more easily as a result of the loss of cementum, which can lead to EIR.⁶ Factors that may initiate EIR include replantation of avulsed teeth, intentional auto replantation and autogenous tooth transplantation.⁷ Radiographically, EIR is characterized by loss of tooth substance together with a radiolucency involving the adjacent PDL and bone. Clinically the tooth will not respond to pulp sensibility tests but there are usually no symptoms.⁶ EIR is a deteriorating lesion that, if not diagnosed and treated quickly and properly, could result in the gradual destruction of tooth structure and ultimately tooth loss.⁸ In cases where the resorptive process is established, the use of a corticosteroid–antibiotic intracanal medicament (e.g. Ledermix Dental Paste, Henry Schein, Kent) has been shown to be useful in the management of these lesions, followed by root canal therapy once it has been confirmed the resorptive process has ceased.⁶

An interesting cause of external inflammatory resorption was seen in a 20-year-old male patient who was part-way through fixed orthodontic treatment. During this treatment, he sustained trauma resulting in fractures to the left angle and right body of the mandible (Figure 1).

These fractures were fixed with metal plates (Figure 2) and the orthodontists were made aware of the injuries at his next appointment. He did not attend orthodontic appointments for over a year following this owing to leaving the country; however, when he returned, his GDP noted external resorption on the distal aspect of the LR4 as an incidental finding. The tooth was asymptomatic, percussion tests were normal and there was a negative response to vitality testing, all suggestive of external inflammatory resorption.

Radiographically, the lamina dura is not present on the distal aspect of the root of the LR4, and an unclear root outline is present, which is again suggestive of this type of resorption (Figures 3 and 4).¹⁷ Initially it was thought that the fracture fixation and screw positioning may have caused iatrogenic damage to the PDL; however, radiographic assessment showed the position of the screws were placed distant from the LR4 to avoid this. The most likely causative agent, therefore, is the fracture of the right body of the mandible, which disturbed the PDL.

External replacement resorption

External replacement resorption, a distinctive dental resorption form, involves the union of the tooth root with surrounding alveolar bone. It is often associated with factors such as trauma (particularly avulsion injuries) or infection during dental development. Ankylosis is the initial process and is defined as loss of the PDL, whereby there is effectively fusion of the alveolar bone and cementum. It is understood that ankylosis occurs when greater than 20% of the root surface is damaged.¹⁰ Fusion of the tooth to the alveolar bone prevents physiological tooth movement, resulting in functional and aesthetic concerns. Ankylosis is recognized radiographically by a lack of lamina dura and PDL. Clinically, these teeth will have a metallic or higher pitched sound on percussion.¹¹ Unlike other types of resorption, replacement resorption usually cannot be treated effectively, and often results in extraction of the tooth or burial of the root to support an overdenture.¹²

External cervical resorption

External cervical resorption is usually caused by trauma; however, factors such as orthodontic treatment and internal bleaching have also been discussed.¹³ It is one of the least understood types of external resorption and occurs most frequently in upper anterior teeth. It begins on the root surface immediately below the epithelial attachment and the coronal aspect of the alveolar process.¹⁴ Clinically, the lesion often begins asymptomatically and is usually discovered at clinical or radiographic check up. A pink spot may be observed in the cervical third of the tooth, which is pathognomonic of cervical resorption, owing to the high vascularity of the tissue seen through the enamel.¹⁵ In more advanced cases, patients may report symptoms similar to those of reversible or irreversible pulpitis, as the defects may be in close proximity to, or invade the pulp chamber. In the initial stages of the lesion where there is no involvement of the pulp, vitality tests are normal.¹⁶ Owing to this, the diagnosis can be difficult as caries can present similarly. In cases where the defect is supra-crestal and superficial, surgical repair without initiating root canal treatment is indicated. With regards to more extensive lesions involving the pulp, vital pulp therapy or root canal treatment may be indicated.¹⁴

A case of external cervical resorption with idiopathic origin was seen in a 30-year-old female attending an orthodontic consultation. The peri-apical taken (Figure 5) shows radiolucencies affecting the cervical root third of all lower anterior teeth. These teeth were asymptomatic, and this was noticed as an incidental finding. The patient reported no previous orthodontic treatment, no injuries to the teeth or mandible, and no use of tooth whitening agents.

Unfortunately, this shows a case of substantial external cervical resorption that had progressed to a point at which the teeth were unrestorable and so were due to be extracted and replaced with implants. A differential diagnosis for these lesions could be caries; however, the teeth appeared clinically sound. Given the pink hue at the cervical margin (Figure 6), these teeth can be confidently diagnosed as having external cervical resorption of idiopathic origin.

External surface resorption

External surface resorption involves only the outer surface of teeth and occurs as small areas of resorption on cementum that may occasionally progress into dentine.¹⁷ Surface resorption is selflimiting because there is no contamination by bacteria and thus, does not have a progressive stimulant. It is usually caused by an injury to the cementum or PDL. Clinically there are no symptoms or signs of surface resorption and radiographically, it is not usually seen, hence why is it unlikely to be diagnosed. There is no management for surface resorption owing to it being self limiting; however, if the root canal becomes infected during the injury, the resorption will progress to external inflammatory resorption and should then be treated as such.⁹

Internal inflammatory resorption

Internal inflammatory resorption is usually associated with chronic pulpal inflammation. It is initiated within the pulp space and involves loss of dentine. It is an asymptomatic process that is usually detected on routine radiographs as an oval-shaped increase in the size of the pulp chamber. It is important to note the presence or absence of the tramlines of the pulp chamber as this helps to differentiate internal resorption from external.¹⁸ If the lesion becomes more advanced, it may cause symptoms when it progresses to apical periodontitis. Vital pulp tissue is required for this process to occur, and so when the pulp is completely necrosed, the resorption defect will not worsen; however, apical periodontitis will develop.¹⁹ Root canal treatment must be initiated as soon as possible once these lesions are diagnosed to prevent further progression of the defect.¹⁸ If diagnosed and treated correctly, the management is fairly simple and has a reasonable prognosis.

Internal replacement resorption

Internal replacement resorption is rare and occurs when the pulp and dentine are replaced by bone. It is thought to occur following trauma or insult to the pulp, and many dentists may be unaware of this type of resorption. Clinically, these teeth may be discoloured or have a pink hue. The tooth is usually asymptomatic, and this type of resorption is often detected during routine radiographic examination.²⁰ It can occur anywhere within the root canal system and usually presents as an irregular radiolucency with a mottled or clouded appearance.²¹ Eventual extraction of these teeth is the most likely management, as usually diagnosis is not caught early enough for root canal treatment due to the lack of signs and symptoms.⁹