Endodontic flare-ups: A review

Introduction

An inter-appointment flare-up is characterized by the development of pain, swelling or both, which commences within few hours or days after the initiation or even completion of root canal treatment1, which requires an unscheduled visit and active treatment. It is an undesirable event to both the clinician and the patient.

An endodontic flare up is defined asan acute exacerbation of an asymptomatic pulpal and /or periradicularpathoses, after initiation or continuation of root canal treatment².

Interappointment pain is almost exclusively due to the development of acute inflammation at the periradicular tissues in response to an increase in the intensity of injury coming from the root canal system³. The patient experiences varying degrees of pain, which is residual or even exaggerated during and following endodontic treatment⁴. It is of much concern when the patient was previously asymptomatic. Fortunately, the occurrence of flare-ups has no effect on the prognosis of the treatment.

The patients may underestimate the clinician’s skills and such an episode also, undermine the patient’s confidence in their dentists or patient satisfaction with the treatment⁶. Hence it is desirable to know about the various reasons for an endodontic flare up and also prevent and manage this complication.

Incidence

The incidence of endodontic flare-ups varies according to various studies. It varies from 1.4% to 1.6%^3,7 and upto 50%^7-9 in some researches. The occurrence of flare-ups depends on the preoperative pulpal and periapical diagnosis, the presence of pre-operative pain and swelling, medications taken, type of instrumentation technique and the number of visits taken to complete a root canal treatment. Its incidence has a direct relationship with the patient’s preoperative pathogenesis and signs/symptoms. Lowest frequency is found in patients with vital pulp without periapical pathogenesis and highest frequency among the patients with necrotic pulp and acute apical periodontitis¹⁰.

In a study conducted by Pamboo J et. al in 2014 the following inferences were observed. This study showed a low incidence of flare-ups of 2.35%. Age has no influence on the occurrence of flareups¹¹. Women experienced more pain compared to men and also had low pain threshold levels. Endodontic flare-ups are more prevalent in females under age of 20 years usually in maxillary lateral incisors, mandibular molars with large periapical lesion and retreatment of previous root canal treatment¹². Posterior teeth in the mandibular arch experienced more pain because of the presence of more number of canals and bifurcated root canals. The pre-operative pain has a direct influence on the incidence of flare-ups. The incidence of flare ups is more with a necrotic pulp than a vital pulp. Most of the post-operative pain can be controlled by the usage of anti-inflammatory drugs and the judicious use of antibiotics. There was no difference in the incidence of flare ups between single and multiple visits. Most of the studies have found that single visit treatment resulted in less pain compared to multiple visits. The crown down technique with rotary action combined with copious and frequent irrigation resulted in decreased incidence of flare-ups. Intra canal medication is a preventive measure to reduce the incidence of flare-ups¹¹.

Aetiology and related factors

Mechanical, chemical and/or microbial injury to the pulp and/or peri-radicular tissues are considered to be the main causative factors of flare-ups^13,14. It is otherwise called as an Endodontic Inter-Appointment Emergency.The etiological factors can be divided into three main areas. 1) Treatment procedures under the control of the operator, 2) microbial factors related to the contents of the root canal and 3) host factors such as patient demographics, local tissue changes, immunologic changes and psychological factors¹⁵.

Microbial causes

Generally there is balance between the bacterial aggression and the host defence mechanisms. In some situations during endodontic treatment this balance is disrupted, which favours the microbial aggression causing an acute periradicular inflammation. These situations could be when there is an apical extrusion of infected debris, changes in the root canal microflora and environmental conditions caused by incomplete chemo-mechanical preparation, secondary intraradicular infections and an increase in the oxidation- reduction potential within the root canal, all of which favours the growth of facultative bacteria. Specific pathogenic strains, virulent clonal types, the number of cells and microbial interactions are the factors which influence the development of pain associated with endodontic infections¹.

It has been suggested in some reports that the presence of certain bacterial species areassociated more with particular peri-radicular diseases. Symptomatic peri-radicular lesions including teeth with abscess are associated more with Porphyromonas species^16-19. Acute clinical symptomsare associated with Prevotella and Peptostreptococcus species²⁰. Percussion pain frequently exhibited Peptostreptococcus, Eubacterium, Porphyromonasendodontalis, P.gingivalis and Prevotella species²¹. All these reports is suggestive that Gram- negative anaerobic bacteria are closely associated with the occurrence of symptomatic endodontic infections including acute abscess^16-21.

Apical extrusion of debris

The apical extrusion of infected debris into the peri-radicular tissues is one of the principal causes of post-operative pain^13,22,23. In asymptomatic cases, there is a balance between the bacterial aggression and the host defence. During the chemo-mechanical preparation, when the infected debris is extruded, this balance is disrupted, for which the host mobilizes an acute inflammation in order to re-establish the equilibrium¹. Overinstrumentation promotes the apical foramen enlargement, which permits the influx of exudates and blood into the root canal, enhancing the nutrient supply to the remaining bacteria within the root canal, which proliferates causing an acute exacerbation of a chronic peri-apical lesion²⁴. Crown- down technique with rotary motion and frequent irrigation usually extrude less infected debris into the periapical area1.

Changes in the endodontic microflora and / of environmental conditions

Normally the root canal bacteria exist in harmony and equilibrium with their environment. Endodontic procedures cause a change in the root canal environment. When the microorganisms are not completely eliminated from the root canal, environmental changes occur, causing the previously inhibited species to overgrow and turn virulent. This damages the peri-radicular tissues leading to an acute exacerbation. When the environmental changes cause a turn on of the virulent genes, previously asymptomatic tooth turns symptomatic. When environmental changes induce a turn-off of the virulent genes, remission of symptoms of the previously symptomatic cases could occur. In order to avoid this, a complete chemo-mechanical preparation should be completed within the same visit whenever possible and intra canal medicament should be placed in cases of multiple visit procedure¹.

Secondary intra-radicular infections

They are caused by microorganisms which were not present in the primary infection. They penetrate the root canal during the treatment, between the appointments or after the completion of the endodontic treatment1. The main source of recontamination could be the remnant plaque, calculus or caries; leakage from rubber dam; contamination of endodontic instruments or irrigating solutions²⁵; leakage through breakdown of temporary restoration; fracture of tooth²⁶ and when the tooth is left open for drainage²⁷. Regardless of the time of introduction of microbes, a secondary infection can cause a flare-up,  if the microbes are virulent and they multiply to reach a sufficient number to cause an acute inflammation of the peri-apical tissues¹.

Increase in oxidation-reduction potential

When the tooth is opened, the oxygen penetrates the root canal, changing the microbial growth pattern from anaerobic to aerobic. The energy yield is more marked in the presence of oxygen, and there is a faster growth rate causing an acute peri-apical inflammation²⁸.

Prevention of the microbial causes of flare-ups

Selection of an instrument technique which extrudes less amount of debris apically, completion of the chemo-mechanical preparation in a single visit, placement of an intra canal medicament between multiple visits in cases of infected tooth, not leaving the tooth open for drainage and maintaining an aseptic chain during the endodontic procedures prevent the microbial causes of flare-ups¹.

Patient-related factors

The patient presenting factors associated with an increased risk of developing an endodontic flareup could be patient demographic(age and gender), systemic conditions, pulpal and periapical diagnosis and pre-operative signs and symptoms¹⁰. Various studies have shown that female gender, necrotic pulp, acute apical abscess, acute apical periodontitis, large periapical radiolucency and pre-operative pain and swelling have an increased risk of developing an endodontic flare-up¹¹. A vital pulp, sinus tract and obturated tooth have reduced chances of developing flare-ups¹⁰.

Treatment factors

These include the factors which are under the control of the dentist. They are the treatment plan and specific treatment approaches that are adopted by the clinician.

Treatment plan

Factors related to the treatment plan include whether single or multiple visits are employed, conventional or retreatment procedures and whether partial or complete debridement is done. The goal is to minimize the post-operative pain whether it is done in a single or multiple visits. Some studies reveal it is better to complete the procedure in a single visit to minimize the postoperative pain. Obturation done in the same visit minimizes the incidence of flare-ups²⁹. However in cases of pulpal necrosis with apical periodontitis the incidence of flare ups is more, so multiple visits can be employed. The main goal of the endodontic treatment is to completely debride and disinfect the root canals to get rid of the microbes that cause persistent infection. Inadequate debridement could lead to acute exacerbation. Intra canal placement of steroids or NSAID’s could reduce the postoperative pain¹⁰. Other factors that have an influence on the incidence of flareups include over-instrumentation, incorrectly measured working length, periapical extrusion of infected debris, extruded irrigants, overfilling and  hyperocclusion³⁰.  Inadvertant extrusion of irrigants beyond the apical foramen will lead to violent reactions – pain, swelling, haematoma, burning sensation, ulceration, tissue necrosis. Also, excessive pressure during irrigation will cause large amounts of irrigant to come in contact with the periapical tissues³¹. Occlusal reduction as a prophylactic procedure is ineffective, but for teeth with  pain on mastication, occlusal reduction reduces the post-operative pain³².

Therapeutics

Many studies reveal that prophylactic antibiotics are unrelated to the incidence of flare-ups^33,34. But this depends on the pulpal and periapical diagnosis. Many studies show the pre-treatment administration of analgesics and anti-inflammatory drugs minimize the post-operative pain and reduce the incidence of flare-ups. A combination of the non-steroidal anti-inflammatory agents (NSAID’s) and an opiate are effective in reducing the incidence of flare-ups³⁵.

Treatment of flare-ups

The treatment of endodontic flare-ups includes local treatment measures, psychological management and usage of pharmacotherapeutics.

Localized treatment measures

These measures include re-instrumentation, relief of occlusion, placement of intra canal medicament and establishment of drainage.

Re-instrumentation

When the working length is short of the apex, it leads to incomplete debridement leaving remnant necrotic pulp tissues uncleaned in the apex which may lead to the development of flare-ups. If the working length is too far beyond the apex, there is extrusion of the infected debris, irrigants and medicaments  periapically causing an inflammatory response. Once the patient reports with a flare-up, correct working length is established, followed by complete debridement carefully with frequent and copious irrigation, placement of an intra canal medicament and a temporary restoration⁵. Radiographs should be taken at different angles to rule out the incidence of any missed canals³⁶.

Relief of occlusion

When an acute abscess develops post-operatively, the tooth gets extruded from the socket, resulting in tenderness on percussion and difficulty in biting. Such teeth should be relieved of occlusion judiciously especially the functional cusps⁵. However some authors suggest a prophylactic occlusal reduction in cases reporting with apical periodontitis³².

Establishment of drainage

Suppuration usually results in the presence of infections. In such a scenario, drainage of the exudate is the most effective method of reducing the pain and swelling. This is established by removing the temporary dressing from the root canal and the temporary filling of the access opening. In most cases, the accumulated exudates surge through the root canal. In some instances, when there is a blockage of the debris apically, drainage is difficult. In such instances an endodontic instrument is passed through the root canal to re-establish the patency. In exceptional cases, when this also does not provide relief, surgical intervention is necessary. A soft tissue incision or removal of the alveolar bone over the tooth apex to create an artificial sinus tract provides relief. Following the drainage, when the exudation has reduced, a temporary closed dressing can be given. However, some authors prefer to leave the canal open for drainage till the next visit. But this exposes the tooth to the oral microflora and the salivary products leading to an increase in the bacterial growth, introduces new microorganisms into the root canal thereby activating the complement system, leading to an acute exacerbation^5,37.

Intra-canal medicaments

Medicaments that have been claimed to provide relief during the acute exacerbation include anti-microbial agents, irrigating solutions, sulfa compounds and steroids.

Antimicrobial agents

Since the microbes are the major cause of exacerbations, intra canal placement of root canal antiseptics should indirectly reduce the post-operative pain³⁷. The anodyne properties of formocresol, eugenol, iodine-potassium iodide, cresatin and camphorated monochlorophenol have been studied^38,39.  None appeared to be effective in reducing the incidence of flare-ups⁴⁰.

Irrigating solutions

The type of irrigating solution used has a very little difference in the incidence of post-operative discomfort, provided the irrigating solutions were not forced beyond the apex³⁷. Harrison et. al found a higher incidence in post-operative pain in canals either not irrigated or irrigated with normal saline, compared with those irrigated with 5.25% sodium hypochlorite and 3% hydrogen peroxide⁴¹.

Sulfa-compounds

Sulfa compounds when placed inside the root canals, have been reported to reduce the incidence of pain postoperatively³⁷. Some studies show that sulphonamides are no better than placebos⁴².

Corticosteroids

The anti-inflammatory property of corticosteroids is its ability to retard the release of lysosomes from the cells and inhibit the liberation of free arachidonic acid from phospholipids of the cell membrane by phospholipases. Steroids not only prevent the formation of prostaglandins and thromboxanes but also leukotrienes and other oxygen derivatives. This hormone may cause a hyperpolarization of the nerves in the inflamed area leading to increase in cyclic AMP, which reduces the transmission of nerve impulses^43,-45. The disadvantage of the usage of steroids in endodontic therapy is that it interferes with phagocytosis and protein synthesis as a result of which the repair gets delayed⁴⁶.

Psychological management

The patient presents with fear, anxiety, doubt and often the patient assumes that the treatment has failed and extraction is needed. Hence Reassurance is a critical aspect of treatment. The patient must be explained that flare-ups do occur and are treatable and such instances do not affect the outcome of the treatment. Since fear and anxiety are directly related to the perception, the pain can be successfully managed if there is a reduction in the level of fear and anxiety. The problem must be addressed to the patient and explained about the possible reasons for the pain and swelling. The most important step is to break the pain cycle^5,10.

Pharmacotherapeutics

Local anaesthetics

Sensory nerve blockade is difficult with analgesics, thus demanding the use of long acting local anesthetics⁴⁷. Breaking the pain cycle is important psychologically and neurophysiologically⁴⁸.

Antibiotics

Antibiotics are widely used in endodontics, but their use is debatable in patients with pain and swelling. The systemic use of antibiotics should be restricted and prescribed only when there are systemic manifestations like cellulitis, fever, malaise and toxaemia^5,37. Antibiotics are effective when the cause of fare-ups is microbial. Penicillin is used for most of the dental infections. Because of the poly- microbial cause of dental infections, antibiotics to treat the anaerobic infections are also commonly prescribed³⁷.

Analgesics

Mild to moderate cases are treated with NSAID’s and severe cases or which are unresponsive to NSAID’s are treated with opioids and steroids⁵. NSAID’s have analgesic with little or no anti-inflammatory properties. Their analgesic and anti-inflammatory property is due to the inhibition of prostaglandin synthesis by cyclo-oxygenase enzyme⁴⁹. They also inhibit phosphodiesterase, leading to increased cyclic AMP production⁵⁰. Narcotic analgesics react with the neurons in the brainstem, spinalcord, thalamus and cerebral cortex⁵¹. Sharp, localized pain are poorly reliev0ed by opiates, whereas they relieve dull, chronic and less severe pain. However they are capable of increasing the pain threshold by causing relaxation and freedom from anxiety⁵².

Systemic corticosteroids have been successfully used to reduce the pain and swelling of dental origin^53-57. The incidence of post-op pain was less when steroids were administered pre-operatively.

Prevention

Certain guidelines should be followed by the clinician to prevent the occurrence of flare-ups. Access cavities should never be left open during the inter-appoinment period as there are chances for the development of secondary peri-radicular infections. Access cavities should never be dried with compressed air as there are chances for extrusion of debris. To avoid this cotton pellets can be used for this purpose. Instrumentation technique which causes less periapical debris extrusion should be selected. Cases reporting with pain on percussion in the first visit should be relieved occlusally. The entire treatment should be performed under aseptic conditions with frequent irrigation. Single visits are preferred in cases of vital teeth and multiple visits in cases with apical periodontitis. Mechanical debridement should be completed in the same visit. Interappointment dressing with medication is effective in eliminating the microflora³⁷.

Conclusion

Though the occurrence of endodontic flare-ups does not affect the treatment outcome, it is undesirable to both the patient and the clinician. So it is the responsibility of the clinician to follow proper guidelines and employ proper measures to prevent its occurrence and be able to treat it effectively if it occurs. Having knowledge of its etiopathogenesis, contributing factors and treatment modalities will help to manage the situation effectively.