Root perforations: A review of diagnosis, prognosis and materials

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Introduction
Root perforation is characterized by a communication between the root canal system and the external tooth surface. 1 This issue can be caused by a pathological process (dental caries, root resorption) or an operative procedural accident.Pathological perforations are found in routine clinical exams, whereas iatrogenic root perforations may occur during access cavity opening, root canal preparation or during post preparation. 2,3,4,5,6,7,8,9,10,11Procedural operative errors may occur at any time in root canal treatment, and may cause the treatment to fail. 12me factors may predispose to operative procedural accident or errors. 12e presence of pulp stones, calcification, misplaced tooth (incorrect inclination in the arch, tipping or rotation), extensive caries, internal root resorption, misidentification of the root canal, an extra-coronal restoration or intracanal posts are factors that may make root canal access difficult, and predispose to root perforation. 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17 insufficient access cavity reduces the quality of root canal debridement and may affect the final root canal preparation shape.An exaggerated or misdirected access cavity is also conducive to root perforation, and makes the tooth susceptible to coronal/radicular fracture.
Root perforation, overfilling, endodontic and periodontal lesions, root fracture, periapical biofilm, traumatic dental injury, instrument fracture, apical periodontitis, and root resorption characterize the complex challenge facing the endodontist, and these may contribute (alone or in association) to a doubtful or poor prognosis. 12ring the operative procedures, the endodontist must avoid and prevent these nocuous events, since intraoperative accidents are risk factors that may result in failure of root canal treatment.Successful root canal treatment entails understanding the risk factors associated with root canal treatment failure. 12ot perforation may occur in different clinical conditions, which the patient should be immediately informed of, together with the procedures to be followed, the treatment options and the prognosis. 109][20] The consequences of root perforation may result in an inflammatory response associated with periodontal tissue and alveolar bone destruction.Depending on the severity of the injury, and possible chronic inflammatory reaction, it may cause the development of granulomatous tissue, proliferation of the epithelium, and, eventually, the development of a periodontal pocket. 9,19,21,22ck of understanding of root perforations and their consequences, to the extent that could delay diagnosis and treatment, may cause future problems leading to tooth loss.This review aimed to discuss contemporary therapeutic alternatives to treat root canal perforations.
Accordingly, the essential aspects for repairing this nocuous operative accident will be addressed, including its diagnosis, its prognosis, and a discussion about the materials used to seal root canal perforation.

Diagnosis and prognosis of root perforation
Several clinical findings may be determinant in diagnosing root perforations.The clinical and radiographical exams constitute the basis of root perforation diagnosis. 5,7,9,10,15,23,24,25,26During vital root canal preparation (pulp is emptied), the radicular pulp may be removed by pulpectomy (when the pulp is excised, or when root canals are narrow, removal is by fragmentation).After removal of pulp tissue, persistent bleeding during coronal access or root canal preparation may be a sign of perforation.A paper point with blood may also suggest perforation.
Systemic conditions, medications, teeth with an open apex and internal resorption and acute apical periodontitis may be associated excessive bleeding, and be confused with root perforation.Clinically, its diagnosis is a challenge ;10,12,14 however, the apex locator is a technological resource that may help in diagnosing root perforation. 27,28riapical radiography is the imaging method frequently indicated for endodontic diagnosis, treatment plan, and follow-up. 23,24radiolucency associated with a communication between the root canal walls and the periodontal space constitutes an important vestige of this procedural accident.][31][32][33][34][35][36][37][38][39] Shemesh et al. 38 compared ex vivo the sensitivity and specificity of CBCT scans and digital periapical radiographs (PR) in detecting strip and root perforations in 45 curved mesial roots of mandibular molars.The risk in misdiagnosing strip perforations was high with both methods, but CBCT scans showed a significantly higher sensitivity than PR.There was no significant difference between the methods for detection of root perforations.
An essential factor to consider is whether or not an endodontically treated tooth is associated with a root perforation.The diagnosis of root perforation in endodontically treated teeth may be complex.
Diagnostic errors occur and constitute a serious problem; errors are frequently detected in association with a metallic or solid structure of higher density, which produces an image artifact, lacking homogeneity and being defined by image contrasts.Misdiagnosis is a serious problem that has encouraged the search for alternatives to reduce the beam hardening effect during image acquisition and reconstruction. 40,41,42tallic artifacts associated with intracanal posts constitute potential risks for misdiagnosis, particularly when root perforation or bone destruction is suspected. 29,38,39map-reading strategy to diagnose root perforations near metallic intracanal posts using CBCT images was previously suggested by Bueno et al. 29 The strategy suggested minimizing metallic artifacts associated with that are difficult to detect in conventional periapical radiographies. 35,36,37e final diagnosis and choice of clinical therapeutics for these root perforations should always be made in conjunction with the clinical findings.The major potential of CBCT examinations is the possibility of viewing the different planes of all the surfaces and the location of the tooth, at the same time.29 After a root perforation is diagnosed, root canal treatment can be challenging.Root perforation could affect the prognosis of root canal treatment and retreatment.

Three clinical factors have been considered as relevant in
the prognosis and healing of root perforations: time (the time between the occurrence of the perforation and the appropriate filling); extent (a small perforation causes less tissue destruction and inflammatory response); location (perforations located apical to the critical zone, involving the level of the crestal bone and the epithelial attachment, are likely to have a good prognosis when the root canal is accessible and the treatment is appropriate). 7Thus, clinical parameters associated with the timeline (avoiding the onset of infection), with the severity of the tissue injury, and with its location in relation to the crestal bone, are factors essential to treatment prognosis. 7,8,9 has been suggested that perforations located apical or coronal to the crest bone and epithelial attachment have a good prognosis. 7,43,44The therapeutic factors associated In small furcal perforations, the prognosis is favorable. 7,9,11,20An important clinical feature is the thickness of the gingival and bone tissue, since a better prognosis occurs in patients with thick gingival and bone tissues. 46erall, the sealing of a root perforation has shown a high level of success; however, the impact of new therapeutic procedures on the prognosis of endodontic therapy should be carefully considered.Materials used to seal root perforations The endodontic literature published over the years presents reports on several intracanal medicaments that have been studied to treat infected root canals.
The material requirements of perforation repair materials vary depending on whether the perforation is located inside (intraradicular) or outside the root canal (extraradicular).
Additional requirements: • Ability to provide a bacteria-tight seal; • Unaffected by blood; Nowadays, the materials demonstrating antibacterial potential for infection control of the root canal system promote healing by mineralized tissue deposition and sealing ability.As such, they were selected to be the focus of attention of this review.  Accorly, three materials to seal root perforations were analyzed retrospectively, based on their biological, antimicrobial and physicochemical characteristics, namely calcium hydroxide, mineral trioxide aggregate and calcium silicate cements (bioceramics).

Mineral trioxide aggregate (MTA)
Mineral trioxide aggregate is still a widely accepted and commonly used repair material for perforations at bone level.MTA improves the prognosis of perforated teeth that would otherwise be classified as compromised.

Mode of action of MTA
The mode of action of MTA is based on the following mechanisms: • Formation of Ca(OH)2 and its release of calcium ions; • Alkaline pH of about 12.532; • Effects on cytokine production; • Promotes the differentiation and migration of cells involved in hard tissue formation; • Formation of hydroxyapatite on the surface of MTA.

Bioceramics
Bioceramics are non-metallic inorganic materials that were already well-known for their applications in the medical field (e.g. for joint replacement) before they were introduced in endodontics around 2008.They can be used as sealers as well as for orthograde and retrograde root canal filling, root perforation repair, pulp capping and apexification 76,77 .
Their enhanced biocompatibility gives new bioceramic materials an edge over conventional sealing materials 78 .
One in vitro study demonstrated the adhesion, proliferation and survival of human bone marrow mesenchymal stem cells, periodontal ligament cells, and dental pulp stem cells on the surface of a newly developed bioceramic material 79 .Another advantage is that, in contrast to MTA, bioceramics do not lead to coronal tooth discoloration 80

Clinical overview
The life of an endodontically treated tooth is associated with correct diagnosis and treatment planning, root canal shaping, sanitization, sealing, and, lastly, tooth rehabilitation. 25The successful treatment of a root perforation depends on certain factors, like sealing material, perforation extent and location, time between diagnosis and treatment, presence of contamination and related operator experience, presence of preoperative lesions, communication of the perforation with the oral environment, and type and quality of the final restoration. 7,130,138e material recommended for treatment of root canal perforations should have good physicochemical and biological properties, proper sealing capacity, antimicrobial activity and osteogenic potential. 45A has been the most widely indicated material to seal root perforations. 9,10,11,22,45,70,71,72,82-104Histological studies have shown lateral and furcal perforations that have been repaired with MTA, and that have been found to have mineralized tissue over the material. 22,89inical studies have shown that MTA appears to provide a biocompatible and long-term effective seal for root perforation, with a higher success rate. 111,112,138,146ntius et al. 146 analyzed retrospectively the clinical outcome of 70 perforation repairs performed by 6 endodontic specialists, using a nonsurgical or combined nonsurgical/surgical approach.The success rate for repair of the root perforation was 90%.
intracanal post and endodontic material by making sequential axial slices of each root with an image navigation protocol from the coronal to the apical direction (or apical to coronal), and with axial slices of 0.1 mm/ 0.1 mm.This directional orientation provides precious information concerning the exact localization of vestiges that suggest points of communication between the root canals and the periodontal space, associated with radiolucent areas, suggesting root perforation.The dynamic navigation of CBCT images has made it a distinct tool by revealing what was once static.In the slices located near the post apex, the beam hardening effect is reduced, because CBCT allows us to capture a lesser amount of metal on the images. 29A new software program able to reduce metallic artifacts in future reconstructions of CBCT images has been tested (e.g., e-Vol DX, CDT, Bauru, SP, Brazil).The appropriate management of CBCT images could reveal abnormalities with the clinical protocols used during root canal treatment, and the systemic conditions associated with the periapical healing process of endodontically treated teeth, were recently discussed by Holland et al.45The repair process of endodontically treated teeth depends not only on the adoption of correct clinical approaches to promote better root canal treatment, but also on patient-related factors (such as chronic disease, hormones and age), and those that can change the host's immune defenses and interfere in the treatment outcomes and healing process.Thus, the risk factors of root canal treatment failures (such as systemic disease and periodontal status) must be addressed correctly during the treatment plan.Treatment success is influenced by the preoperative status of the dental pulp, associated with the presence or absence of a preoperative periapical lesion.The diagnosis of dental pulp and/ or periapical tissue previous to root perforation is an important predictor of prognosis (including such issues as clinically healthy pulp, inflamed or infected pulp, and primary or secondary infection).25Each clinical case must be analyzed carefully and individually, in order to determine the presence or absence of infection, the extent of perforation, the time elapsed before sealing, and the periodontal risk to the patient, to see whether or not the disease could interfere directly in the prognosis.The ability to access the perforation area and promote an appropriate sealing, and the pathological conditions, are clinical determinants of success or failure.In root perforation due to over-instrumentation, resulting in over-enlargement of the apical foramen, the treatment consists of determining a new working length, 1-2 mm short of the root apex, in which the main cone will fit tightly.An apical plug with calcium hydroxide should be maintained in the apex, and the remainder of the root canal should be filled.Clinical and radiographic follow-up should be conducted to determine success or failure.A surgical procedure (periapical surgery) is still an option if failure occurs.Root perforation near the apex presents a good prognosis, and those that are smaller in extent are easier to seal.The survival of an endodontically treated tooth, especially one with a history of root perforation, depends on understanding the biological and mechanical outcomes as multifactorial events over the individual's life span.10,12,25Tooth type, strategic position of the tooth (or surface of the tooth) and the level of the perforation influence the complexity of treatment.In lateral perforations, the relation of the crestal bone to the perforation may favor a good prognosis and sealing.In furcal perforations in molars, the major issue is the degree of tissue damage and the possibility of communication with the gingival sulcus.The probable extrusion of adhesive materials to seal large perforations constitutes a common occurrence.

• 23 Amalgam 20 ;
It should be possible to prevent extrusion of the material into the surrounding tissues 21,Cavit 21 ; Composite; Dentine chips; Foils (Teflon and indium foil, etc.); resin-modified glassionomercement (compomer) especially developed for the repair of severe cervical defects based on its good adhesion to dentine; Glass ionomer cement (GIC); Hydroxyapatite (HA); Zinc oxide-eugenol (ZOE) cement reinforced with plastic additives ;Calcium hydroxide; Freeze-dried bone; Mineral trioxide aggregate (MTA) with collagen; Plaster of Paris (calcium sulfate/burnt gypsum); Tricalcium phosphate have been tested as perforation repair material Calcium hydroxide has been extensively evaluated, andshows well-documented results. Howevr, new materials for sealing root perforations of iatrogenic and pathological origin have been made available for endodontics.
Miller DA, Kariyawasam SP.Histologic assessment of mineral trioxide aggregate as root end filling in monkeys.J Endod.1997 Apr;23(4):225-8.93.Torabinejad M, Ford TR, Abedi HR, Kariyawasam SP, Tang HM.Tissue reaction to implanted root-end filling materials in the tibia and mandible of guinea pigs.Duarte MA, Aguiar KA, Zeferino MA, Vivan RR, Ordinola-Zapata R, Tanomaru-Filho M et al.Evaluation of the propylene glycol association on some physical and chemical properties of mineral trioxide aggregate.Int