internal and external root resorption aetiology, diagnosis and treatment options

RestorativeDentistry

102 DentalUpdate March 2013

Internal and External Root Resorption: Aetiology, Diagnosis and Treatment OptionsAbstract: Root resorption is a pathological process that may occur after surgical, mechanical, chemical or thermal insult. Generally, it can be classified as internal and external root resorption. Depending on the diagnosis, an orthograde, surgical or a combined approach is used in management of these cases.Clinical Relevance: General dental practitioners can face difficulties in diagnosis and treatment planning for cases with root resorption. An understanding of the aetiology and pathogenesis of root resorption is critical for diagnosis, effective management and improves outcome.Dent Update 2013; 40: 102–112

Peter J Nixon

Zaid Al-Momani, BDS, MFDS RCSEd, MDentSci(Rest Dent), Specialist Registrar in Restorative Dentistry and Peter J Nixon, BChD(Hons), MFDS RCSEd, MDentSc, FDS(Rest Dent) RCSEd, Consultant in Restorative Dentistry, Restorative Department, Level 5, Leeds Dental Institute, Clarendon Way, Leeds LS2 9JT, UK.

Zaid Al-Momani

Root resorption is a pathological process that is not uncommon after injuries or irritation of periodontal ligament or pulp.1 Such injuries may result from surgical, physical, chemical or thermal insult. Resorption may also occur due to mechanical stimulation, infection or neoplastic disease.

PathogenesisThe result of this process is

loss of hard dental tissues (ie cementum and dentine) by dentinoclastic cell action. The function of dentinoclasts is controlled by various activating and preventing resorption factors. Activating factors include:

Osteoclast activating factor; Macrophage chemotactic factor; Prostaglandins, heparin and bacterial products.

Preventive factors acting on dentinoclasts include: anti-invasion factor and the intermediate cementum layer.2 Injuries and irritations may stimulate activating factors or reduce preventive factors, hence dentinoclasts may become activated and subsequent root resorption may occur.

Root resorption continues as long as the simulating factor is present. The stimulating factor could be mechanical stimulation, pressure, infection, neoplastic process or a combination of any of these factors.3,4 Once the stimulating factors are removed, root resorption may be arrested. Cementum and dentine may form again, depending on the severity of the damaged surface area.

ClassificationClassification of root resorption

has an important role in the process of diagnosis and treatment planning (Figure 1).

In addition to classifying the

type of resorption, the following issues need to be addressed to reach a treatment plan: Will the resorptive process be self limiting or does it require further intervention?; If the resorptive process is progressive (as observed from assessment over time), what treatment options can we provide?; If treated, what are the short- and long-term prognoses?; When is extraction and prosthetic therapy indicated?

The following section will discuss the signs and symptoms, clinical and radiographic presentations of each type of root resorption. This will be followed by clinical examples on the management of root resorption.

Internal resorptionThe process of internal

resorption occurs in chronic pulpal inflammation and less commonly after dental trauma or due to dystrophic idiopathic changes.5 In this process the pulp tissues coronal to the lesion become necrotic. In order for the internal resorption to progress, both dentinoclast-

March 2013 DentalUpdate 103


activating factors and the cells viable to keep the resorptive process going must be present. Hence, teeth that are actively continuing to resorb internally must be connected to the blood supply of the apical vital tissues.

Signs and symptomsIn most cases of internal root

resorption the tooth is asymptomatic, however, a history of pulpal symptoms may be a feature as the pulp is involved first. If the pulp succumbs completely and periradicular tissues become inflamed, symptoms of periapical periodontitis may be evident.5

Clinical presentationClinically, if the internal

resorption is in the cervical/coronal part of the tooth, it may present as a pinkish hue because of the prolific capillaries in the pulpal inflammatory tissue resorbing the coronal dentine and enamel.6 If internal resorption is in the mid/apical third of the root, it is for the most part clinically silent and would normally be diagnosed radiographically.7

Radiographic featuresRadiographs reveal the lesions

as radiolucent, round, oval or elongated within the root or crown and continuous with the image of the pulp chamber or canal. The outline is usually sharply defined and smooth or slightly scalloped

as a result of an irregular widening of the canal of the pulp8 (Figure 2).

External resorptionExternal inflammatory resorption

External inflammatory resorption usually occurs when infection is superimposed on a traumatic injury, however, it can also be induced in some cases of endodontic pathosis. Damage of the cementum layer will initiate this resorption, exposing the underlying dentine to the passage of bacteria or their metabolites to the external root surface. This activates the dentinoclast cells which results in resorption of both tooth and bone.

Signs and symptomsTeeth could be asymptomatic

or have signs of irreversible pulpitis or necrotic pulp.9

Clinical featuresClinical findings may include

tooth discoloration, tenderness to percussion, tooth mobility or periodontal defects. Careful evaluation of the periodontal condition is recommended because inflammatory resorption can be sustained by bacterial infection involving gingival tissues.10

Radiographic featuresRadiographically, this type

of resorption appears as an irregular

area of resorption involving loss of both tooth structure and adjacent alveolar bone (Figure 3). The irregular area may appear superimposed over the root canal and could be

Figure 1. Classification of root resorption.

Figure 2. Internal resorption on UL1.

Figure 3. External cervical root resorption: irregular area of resorption involving loss of tooth structure on UL2.



misdiagnosed as internal resorption. The main radiographic feature to differentiate between these two entities is that the outline and the integrity of the canal space remain uninterrupted in external resorption.11

External surface resorptionExternal surface resorption is

a shallow resorption of cementum, often with involvement of a small amount of underlying dentine. This type of resorption is self limiting and transient and can follow some traumatic injuries or orthodontic treatment. In the absence of superimposed infection surface, resorption heals by forming reparative cementum.

Signs and symptomsTeeth are asymptomatic and

the pulp is usually vital. The tooth in question is frequently firm and immobile but not ankylosed in the dental arch.12

Radiographic featuresThe apical and cervical

regions are common sites for this type of resorption. When the lesion begins at the apex, it generally causes smooth resorption of the tooth structure, resulting in blunting of the root apex. The bone and the lamina dura follow the resorbing root and present with a normal appearance around the shortened root.8

External replacement resorptionExternal replacement

resorption follows the death of viable periodontal ligament cells due to factors

such as compression or drying of the ligament cells in the case of delayed re-implantation of an avulsed tooth.13 This process involves the progressive replacement of tooth structure by alveolar bone and may (in severe cases) lead ultimately to tooth loss. External replacement resorption is commonly seen during and after orthodontic treatment. An incidence of 1.5% of external replacement resorption has been reported for the maxillary central incisors and 2.2% for lateral incisors.14

What has an effect on the progression of external root resorption to either external surface resorption or external replacement resorption is the severity of injury and the amount of damaged surface. If the injury is minimal and the damaged surface does not cover a large surface area, the tissues will heal by forming reparative cementum and external surface resorption will occur. On the other hand, if the injury is severe and the damaged area is large, bone cells will be able to attach to the root surface before the cementum-producing cells; external replacement resorption and ankylosis are the result of this process.12

Signs and symptomsInitially, teeth may appear

healthy but, as the tooth loses its vitality, signs and symptoms of necrotic pulp will be noted.

Clinical featuresClinically, teeth suffering

from replacement resorption have metallic sound upon percussion and lack of mobility; these are signs of ankylosis. In addition, they may have other clinical problems, such as infra occlusion, incomplete alveolar process development (if the patient was young when the trauma occurred), and prevention of normal mesial drift.10

Radiographic featuresRadiographically, replacement

resorption appears as total loss of periodontal ligament space followed by evidence of the progressive replacement of tooth structure by bone and, in time, radiographically the outline of the tooth

root is lost (Figure 4).13

Tables 1 and 2 summarize the aetiological factors and key features of root resorption, respectively.

TreatmentOnce a diagnosis has been

reached there is a need to assess: If endodontic intervention (orthograde/surgical) will stabilize the root resorption or not; and If the remaining tooth structure is restorable.

The exact treatment plan required is specific to each case, depending on patient factors, clinical and radiographic findings.

If the tooth is deemed to be unrestorable, the tooth has to be extracted and the treatment plan should be focused on replacing the tooth with an appropriate fixed/removable

Figure 4. External replacement resorption: loss of tooth structure followed by the progressive replacement of tooth structure by bone.

External resorption

Replantation of teeth Orthodontic forces Eruption of adjacent teeth Root fracture Trauma Necrotic pulp Root planing Pathology - Cysts - Ameloblastoma - Giant cell tumours - Fibro-osseous lesions Heredity Bleaching Surgery - Dento-alveolar - Orthognathic Mandibulectomy/Maxillectomy

Internal resorption Chronic pulp inflammation Trauma Pulpotomy Restorative procedures Cracked tooth Invaginated cingulum Orthodontic tooth movement

Table 1. Aetiological factors for root resorption.



prosthesis. However, if the tooth is restorable, endodontic intervention with either orthograde or surgical endodontics, or both, may be feasible to preserve the tooth.

The aim of orthograde root canal treatment is to stabilize the root resorption process and to achieve hermetic seal. Alteration in the anatomy of root canal systems due to root resorption may make this more challenging to achieve.

If root resorption has resulted in an open apex, then it may be necessary to create an apical barrier prior to the obturation stage. Mineral Trioxide Aggregate (MTA) can be placed from an orthograde approach (Case 1) to create this apical barrier.

MTA is considered to be an ideal material for use against bone, because it is the only material that is reported to allow apposition of cementum and the formation of bone consistently, and it may facilitate the regeneration of

the periodontal ligament. In addition, MTA has an antimicrobial effect, is highly biocompatible and possesses good sealing properties.15 These properties also mean that MTA is ideal for surgical repair of external resorption which is not supragingival. MTA cannot be used supragingivally as its slow set (4−24 hours) means that it may be washed away by saliva. For repairs that are partly supragingival, a material such as composite or glass-ionomer is required.

The use of gutta-percha (GP) cones and thermoplastic GP is generally the method of choice to achieve complete obturation of the canals. Thermoplastic GP is particularly useful to treat irregular canal anatomy such as that seen in internal root resorption.

If the tooth suffers from external root resorption, a surgical approach may be considered in the management of these cases. In these cases, a muco-periosteal flap could be

raised to identify the resorbed area. This may be followed by curettage and repair of the root surface area with appropriate sealing material. Prior to attempting any surgical repair, it is essential to locate the position of the resorption (buccal/lingual) and assess whether its size is likely to be amenable to repair. The location of root resorption could be located with the use of parallax technique, when obtaining radiographs, or with the use of Cone Beam Computerized Tomography (CBCT).

In cases of complex external and internal root resorption, both of the previously mentioned techniques could be used in an attempt to arrest root resorption process. However, these cases should be appropriately selected and should be carried out by experienced clinicians.

The following section will explain cases in which orthograde, surgical and combined (orthograde and surgical) techniques were used in the management of root resorption.

Resorption Type Clinical Features Clinical Findings Location on Root Pulp Sensitivity Radiographic Root Canal (Thermal or Electric) Features

Internal resorption Pink spot on crown May have Anywhere May be positive Symmetrical Canals expand into in cervical 1/3. tenderness over oval-shaped lesions Mostly has no apex enlargement of clinical symptoms root canal in mid/apical 1/3

External Tooth No symptoms, or Anywhere Negative Irregular Intactinflammatory discoloration, signs of irreversible radiolucent resorption tenderness to pulpitis or necrotic lesion of root and percussion, tooth pulp adjacent bone mobility and periodontal defects

External surface Healthy None Usually apical as Positive Smooth resorption Intactresorption a result of trauma resulting in or orthodontic blunting of root treatment apex and shortened root

External Metallic sound on No symptoms, Anywhere May be positive Asymmetrical Intactreplacement percussion, lack of initially signs replacement ofresorption mobility of necrotic pulp as root structure with tooth loses vitality bone. Loss of periodontal ligament space

Table 2. Key features of root resorption.



Cases 1 and 2: orthograde technique

Case 1A 24-year-old lady had her LR5

transplanted to replace the UR1 when she was 11 years of age. She was referred to the restorative department regarding the

unsatisfactory appearance of the crown on the UR1 due to gingival recession. This was improved by adding a small amount of composite filling cervically. Figure 5 shows the initially transplanted LR5 in the position of the UR1. The LR5

was extirpated and a radiograph was obtained with a file in situ showing that the root resorption originates from the mesial aspect of the apical third of the root (Figure 6). After root canal preparation, an MTA plug was placed at the level where the external root resorption is communicating with the root canal to achieve appropriate apical seal (Figure 7). The remainder of root canal space was filled with thermoplastized gutta-percha (Obtura II, Spartan, US). After 18 months of carrying out the treatment, the patient was still symptom-free. Clinically, the tissues were healthy and no tenderness was noted. Radiographic examination revealed full bony infill and apical healing with the root-treated tooth (Figure 8).

Case 2A 66-year-old patient was

referred from his GDP regarding persistent infection related to his UL1. Upon clinical examination, the UL1 was not tender to percussion. No mobility or pocketing was noted. Radiographic examination revealed a well-defined, round-oval radiolucency on the cervical and mid apical third (Figure 2). The diagnosis was internal resorption. The treatment of choice in this case was an orthograde approach by chemo-mechanical debridement of the canal using conventional hand instruments and filling the apical two-thirds with GP (Figure 9), as opposed to MTA in the previous case, and to backfill the remainder of the canal with thermoplastized gutta-percha (Obtura II, Spartan, US). The patient was reviewed 6 months later, and there were no signs of infection, clinically or radiographically (Figure 10).

Case 3: surgical techniqueAn 18-year-old patient was seen

in the restorative department regarding the pink appearance of the UL2. The patient reported a history of extensive orthodontic treatment. On clinical examination, the UL2 had external cervical resorption, along with gingival overgrowth covering part of the lesion (Figure 11). The sensibility tests for the UL2 were positive. The treatment of choice in this case was to use the surgical approach to gain access to the cervical root resorption and to repair

Figure 5. Initial transplanted LR5.Figure 6. External root resorption is on the mesial aspect of apical third of the root.

Figure 8. Radiograph 18 months post-operatively. Figure 7. The MTA plug on the level of external root resorption.



Figure 9. Radiograph with master cone to fill apical two-thirds with GP. Figure 10. Radiograph 6 months post-operatively.

Figure 11. Ginigival margin overgrowth covering the cervical root resorption on UL2.

Figure 12. A mucoperiosteal flap raised from UL1–3.

Figure 13. Cervical root resorption was restored with composite.

Figure 14. Flap repositioned and the gingival margin contoured.

with composite. A mucoperiosteal flap with a distal vertical releasing incision was raised to expose the lesion (Figure 12). The cervical root resorption was restored with composite (Figure 13), the

flap was repositioned and the gingival margin was contoured with inverse bevel gingivectomy (Figure 14). The patient was reviewed and the site of surgery healed well. Composite was used in this case as

the restoration was partly supragingival.

Case 4: surgical and orthograde approachA 44-year-old patient was

referred regarding persistent infection

Figure 15. Pre-operative clinical view of external cervical root resorption on UL2.

Figure 16. A mucoperiosteal flap raised to identify the extent of resorbed area on UL2.

Figure 17. The enamel and dentine on UL2 was minimally prepared.

Figure 18. The resorbed area on UL2 was restored with composite.



related to UL2. Clinical examination revealed a cavity which was probed on the labial aspect of the tooth (Figure 15). Radiographic examination revealed an appearance of external cervical root resorption and a short single point root filling (Figure 3). In this case, the plan was to replace the root canal treatment, this to be followed up by a surgical procedure to restore the resorption area.

After the root canal retreatment, a mucoperiosteal flap was raised to identify the extent of the resorbed area (Figure 16). The enamel and dentine were minimally prepared (Figure 17). The cavity was restored with composite (Figure 18) and the flap repositioned. On a 1-year review, the patient was still asymptomatic and the gingivae had healed well (Figure 19). Radiographically, the repaired area was sound and the periapical area had healed well (Figure 20). As the periodontal ligament does not re-attach to composite, there is a periodontal pocket in the region of the repair. That is in contrast to MTA, to which soft tissues may attach.

DiscussionThe basis of this paper is

to provide clinicians with an overview on root resorption with a view to increasing their understanding of this topic and to assist them in reaching a diagnosis. In addition, it explains methods of root resorption management. Decisions on management are made on a case by case basis. Orthograde endodontics, surgical endodontics and, on occasion, a combination of the two may be able to stop further resorption successfully and preserve the affected tooth.

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3. Barclay CW. Root resorption: aetiology, classification and clinical management. Dent Update 1993; 20: 248−250.

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6. Heithersay G. Clinical endodontic and surgical management of tooth associated bone resorption. Int Endod J 1985; 18: 72−92.

7. Gulabivala K, Searson L. Clinical diagnosis of internal resorption: an exception to the rule. Int Endod J 1995; 28: 255−260.

8. White S, Pharoah M. Oral Radiology: Principles and Interpretations 5th edn. St Louis, Mo: Mosby, 2004: pp357−358.

9. Andreason JO. External root resorption: its implication in dental traumatology, paedodontics, periodontics, orthodontics and endodontics. Int Endod J 1985; 18: 109−118.

10. Bakland L. Root resorption. Dent Clin N Am 1992; 36: 491−525.

11. Frank A, Torabinejad M. Diagnosis and treatment of external invasive resorption. J Endod 1998; 94: 500−504.

12. Fuzz Z, Tsesis I, Lin S. Root resorption − diagnosis, classification and treatment choices based on stimulation factors. Dent Traumatol 2003; 19: 175−182.

13. Heithersay G. Management of tooth resorption. Aust Dent J 2007; 52

(Suppl 1): S105−S121.14. Garber T, Eliades T, Athanasiou A.

Risk Management in Orthodontics: Experts’ Guide to Malpractice. London: Quintessence Publishing, 2004: p61.

15. Schwartz R, Mauger M, Clement D, Walker W. Mineral Trioxide Aggregate: a new material for endodontics. J Am Dent Assoc 1999; 130: 967−975.

Figure 19. One year post-operative clinical view of UL2.

Figure 20. One year post-operative radiographic view for UL2.

CPD AnswersJanuary/February 2013

1. A, B, D 6. D

2. A, D 7. C

3. A, B, C, D 8. C

4. B, D 9. B

5. A 10. D

internal and external root resorption aetiology, diagnosis and treatment options

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