Endodontic Diagnosis

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Dentists are trained to thoroughly review medical and dental histories and perform comprehensive extra-oral and intraoral examinations. Yet, in spite of these efforts to optimally serve patients, the dominant clinical reality is that the vast majority of dentists do not know the status of the pulps within the teeth of the patients who visit them daily. If a complete endodontic examination is not conducted, then the pulpal status of any given tooth is unknown. The rationale for conducting a complete endodontic examination is similar to conducting a complete intraoral screening for soft tissue pathology; conducting a complete periodontal examination; or a physician conducting a complete physical examination on a seemingly healthy patient. Clinical judgment should be used to determine which patients, and which teeth, should receive an endodontic examination. Regretfully, a significant number of endodontically involved teeth are not diagnosed or treated. In fact, the vast majority of all endodontic procedures are performed secondarily to patients presenting with symptoms. It is critically important for dentists to accurately diagnose endodontic disease associated with both asymptomatic and symptomatic teeth.

THE REALITY

Figure 1. This human skull demonstrates several important anatomical relationships and serves to illustrate how a LEO can hide between intact cortical plates of bone.

It should be fully appreciated that pulpal health is not assured because a tooth is clinically asymptomatic or a well-angulated radiograph does not reveal a lesion of endodontic origin (LEO).1 Many pulpally involved teeth do not exhibit symptoms or demonstrate a LEO even though considerable breakdown and destruction may have already occurred in the less dense trabecular bone (Figure 1). Research has demonstrated that clinicians only see an “incipient” radiolucency when the more dense buccal or lingual cortical plates of bone have been invaded by a lesion.2 If a complete endodontic examination was conducted on each patient before commencing with any dental procedure, then a significant number of quiescent, pulpally involved teeth would be identified.3 Frequently, patients report they were comfortable before treatment, then following a so-called “routine” procedure developed a “toothache.” In summary, clinicians regularly treat the “toothache,” yet only sporadically find other “obvious” endodontic problems.

THE POSSIBILITY

Although it is impossible to quantify the magnitude of undiagnosed endodontically involved teeth, it is an unmistakable fact that a significant number of endodontic problems are not identified or treated.4 When a complete endodontic exam is performed, the results clearly communicated, and mutual trust has been established, then patients will generally schedule, as convenient, the appropriate treatment. Dentists have a professional responsibility to clearly communicate the risks versus benefits associated with the recommended treatment, alternatives to treatment, and the clinical ramifications of no treatment. Each clinician should carefully evaluate all the diagnostic information, consider the strategic nature of the tooth, and anticipate the treatment challenges. Additionally, each practitioner needs to evaluate their training and experience and decide if a referral would be in the patient’s best interest.5 Importantly, when a comprehensive endodontic examination is conducted, then virtually all of the “non-obvious” endodontically involved teeth can be identified. The endodontic examination serves to improve treatment planning, performance, and prognosis. Endodontic diagnosis and treatment represent important aspects of ideal oral health. In fact, oral infection has been identified as a risk factor for certain systemic diseases.6 The goal is to improve oral health by accurately diagnosing previously undiagnosed endodontically involved teeth.

ETIOLOGY OF PULPAL BREAKDOWN

Figure 2. A radiograph of a maxillary first bicuspid showing a gutta-percha point tracing a sinus tract and pointing to a lesion of endodontic origin.

The dental pulp is a dynamic tissue whose status at any given time can be assigned a position on a continuum that ranges from optimal pulpal health to pulpal necrosis. It is wise to appreciate that not all asymptomatic teeth that exhibit a normal response to pulp tests have the same degree of health or capacity to heal.7 The dental pulp has a restricted capacity to heal because it has a limited blood supply, is encased in unyielding dentinal walls, and represents terminal circulation. As such, the ultimate fate of the dental pulp is dependent on the magnitude and duration of an injury.8 The major threats to the pulp are caries, traumatic episodes, specific developmental anomalies, certain periodontal conditions and related treatment efforts, and extensive dental procedures.9 As an example, following many operative procedures, patients may report transient pain to a cold stimulus indicating a pulpal inflammatory response that is potentially reversible. In other instances, patients may report intense and lingering pain to a cold stimulus which generally infers an irreversible pulpitis.10 Obviously, recurrent caries, a leaking restorative, and repeated episodes of dentistry on the same tooth sharply escalate the potential for pulpal breakdown. Pulpal injuries frequently progress from reversible to irreversible inflammatory conditions and rapidly advance from ischemia, infarction, and partial necrosis to complete necrosis (Figure 2).11 The progressive cascade of histological events that occur within a degenerating pulp as it progresses along this continuum are well understood.7-11 Regretfully, clinicians who perform dental procedures without diagnostic pulp tests are unable to forecast the ultimate fate of the pulp.

THE ENDODONTIC EXAMINATION

The comprehensive endodontic examination is a three-step diagnostic process comprised of the clinical examination, the radiographic examination, and vital pulp testing. This examination should be appropriately scheduled and performed on all new and existing patients regardless of whether they are asymptomatic or symptomatic. In the instance where there is a chief complaint, it is important to inquire as to the region, magnitude, and duration of the pain. Additionally, the dentist should ask if the sensitivity is diffuse or localized, intermittent or continuous, and if there is a specific stimulus that provokes the pain. It is important to listen, clarify, and then accurately record this information.12 The purpose of a full-mouth endodontic examination is to differentially diagnose between odontogenic versus nonodontogenic problems. Specifically, the endodontic examination serves to identify endodontically involved teeth and enables the clinician to classify any given tooth into one of four categories:

(1) Teeth that are asymptomatic and do not have a LEO.

(2) Teeth that are asymptomatic and have a LEO.

(3) Teeth that are symptomatic and do not have a LEO.

(4) Teeth that are symptomatic and have a LEO.

Clinical Examination

Figure 3a. A photograph reveals significant swelling secondary to a LEO that has broken through the buccal cortical plate of bone. Figure 3b. A photograph demonstrates a gutta-percha point tracing a sinus tract and a tattoo associated with an endodontically failing maxillary left central incisor.
Figure 4. A surgical photograph of an endodontically failing molar reveals a vertical root fracture possibly caused by the use of excessive force during obturation.

The purpose of the clinical examination is to thoroughly evaluate all aspects of the extraoral and intraoral tissues. The extraoral examination allows the dentist to observe a patient’s face and look for symmetry, color, and the overall complexion. Further, the examination reveals the presence of various diseases, traumatic injuries, and facial scars. Examining dentists should bilaterally palpate the submandibular nodes for lymphadenopathy as this is the site for regional drainage from the head and neck. The intraoral portion of the examination is directed towards inspecting all aspects of the soft and hard tissues. The soft tissue portion of the examination includes, but is not limited to, carefully evaluating the oral mucosa, oral pharynx, tongue, and floor of the mouth. Additionally, a thorough intraoral soft tissue exam reveals the color, texture, consistency, and contour of the soft tissues including the presence of a swelling, sinus tract, or tattoo (Figures 3a and 3b). The periodontal examination provides the opportunity to evaluate the mucogingival soft tissues, attachment apparatus, and probing pocket depths. Importantly, broad crater-shaped defects are more often associated with periodontal disease, whereas narrow vertical defects suggest either endodontic etiology or a radicular fracture (Figure 4).

Figure 5a.A photograph shows discoloration of the clinical crown of the mandibular left central incisor as a result of a traumatic accident. Figure 5b. A clinical photograph of the lingual surface of this maxillary incisor reveals a dens evaginatus and a sinus tract located high in the palatal vault.

The intraoral hard tissue exam reveals missing teeth, fractured teeth, discolored teeth, and developmental anomalies (Figures 5a and 5b). Further, all existing restorations are evaluated for marginal adaptation, contour, and aesthetics. The diagnostician looks for caries and recurrent caries, and inspects the cervical area of teeth for erosions, abrasions, and abfractions. The presence of inflammation or infection can contribute to the loss of attachment and excessive mobility of a tooth. Roots should be palpated laterally and apically, both on the facial and lingual aspects, as a lesion of endodontic origin can invade through the cortical plate. The percussion test is performed gently and conducted laterally, then vertically on the incisal edges of anterior teeth or on the buccal and lingual cusps of posterior teeth. A positive percussion test indicates an injury to the attachment apparatus, may cast suspicion regarding the status of the pulp, but, in and of itself, does not disclose information regarding the health of the pulp.

The bite test is useful to identify teeth with incomplete or complete dentinal fractures and is best performed with a cotton roll, q-stick, or the Tooth Slooth (Sullivan-Schein Dental). These devices are placed interocclusally, and patients are instructed to initially bite gently and, if possible, to then bite firmly. Additionally, patients should demonstrate that they can move their mandibles into working and balancing excursions. A fiber-optic wand can be used to transilluminate the clinical crowns of teeth without extensive, full restorative coverage. When a natural crown is transilluminated facial to lingual, light will pass uniformly through tooth structure if there is no fracture. On the contrary, when a tooth exhibits a coronal fracture, then light will not uniformly pass through the clinical crown, and the fracture breaks the beam of light.

The clinical examination focuses on the masticatory system including the jaws, temporomandibular joint, and muscles of mastication. The occlusion is carefully checked by having the patient move into various lateral and protrusive excursions. Marking paper can be used to identify and address prematurities that can contribute to harmful wear facets, increased mobility, and thermal sensitivity. Habitual grinding is a behavior that promotes malocclusion and is frequently associated with fractured teeth. In summary, the clinical examination reveals valuable information regarding a patient’s dental history, and can serve as an indicator of their motivation to pursue oral health.

Radiographic Examination

The radiographic examination is generally performed following the clinical examination. In fact, the clinical portion of the diagnostic work-up often serves to identify the specific location(s) where the radiographic exam should be focused. The endodontic radiographic examination is optimized when three different, well-angulated, and high-quality images are obtained.13 A straight-on diagnostic film should be taken such that the x-ray cone is aimed perpendicular to both the facial aspect and long axis of the tooth. A second, mesially angulated film is attained by horizontally aiming the x-ray cone up to 30° mesial to the straight-on angle and perpendicular to the long axis of the tooth. A third, distally angulated film is obtained by horizontally aiming the x-ray cone up to 30° distal to the straight-on angle and perpendicular to the long axis of the tooth.

It is reasonable to inquire about the need for three pre-operative radiographs when a single film, in conjunction with the results from a vital pulp test and the clinical examination, will generally confirm a definitive diagnosis. The response is that a single film is a two-dimensional image of a three-dimensional object. A single film, along with the other diagnostic information, may endodontically condemn a tooth; however, a single radiographic image will not adequately prepare the clinician for optimal treatment planning and patient communication.

The diagnostic quality of a radiographic image is definitely enhanced using film holding and aiming devices and adhering to well-recognized and successful darkroom protocols. Digital radiography is improving the field of dental radiology as it provides several advantages over film-based radiography.14 Digital radiography reduces radiation, eliminates chemicals and film processing, and provides nearly instant, high-quality images that patients can clearly see. Centralized storage and retrieval allows clinicians to send, receive, and print images. Software tools afford several features that can be utilized to enhance images, such as zoom, measurements, adjustable contrast, image colorization, black/white reversal, and density measurement and comparison. Perhaps the greatest advantage of digital radiography is the potential to more effectively communicate with patients by allowing them to participate in discovery, diagnosis, and treatment planning.

Figure 6. A radiograph suggests the anterior bridge abutment is endodontically involved. Note the crown/root orientation and inclination of the canal coronally. Figure 7. A radiograph suggests this maxillary right central incisor has a dens in dente, internal resorption, a large asymmetrical lesion, and multiple canals.

When performing the radiographic examination, the clinician will observe that different angulated images enhance detecting the location and extent of caries or recurrent caries. A restoration should be evaluated radiographically regarding marginal adaptation, contour, relative depth, and relationship to the pulp chamber. At times, a bite-wing film is useful as it can provide additional information about splinted teeth and the presence of pins and buildup materials. Radiographic images frequently allow the clinician to determine the size of the pulp chamber as compared with adjacent teeth, the presence of stones, and if calcific material projects into the coronal aspect of a canal (Figure 2). Clinicians can visualize a radiograph to appreciate the crown/root ratio and orientation, and the angle of the coronal aspect of a canal relative to the long axis of the root (Figure 6). Different, horizontally angled films disclose information regarding the length and curvature of a root and, when present, the depth of an external concavity. High- quality radiographic images can be studied to better appreciate the root canal system and, at times, disclose canals that merge, curve, recurve, dilacerate, or divide. The astute clinician will identify atypical tooth morphology including the presence of a C-shaped molar, taurodontism, or dens invaginatus (Figure 7).15

Figure 8. A radiograph of a maxillary central incisor reveals a horizontal root fracture with displacement and a previously accessed lateral incisor.
Figure 9a. A radiograph of a mandibular left lateral incisor shows evidence of internal resorption and an apical lesion of endodontic origin. Figure 9b. This radiograph reveals massive root resorption associated with the maxillary incisors possibly caused by the erupting and mesially inclined canine.

Different, well-angulated films allow clinicians to observe the result of a traumatic episode such as a coronal fracture, horizontal root fracture (Figure 8), and at times, a vertical root fracture. The clinician needs to carefully observe films for the possible sequelae to traumatic events, such as internal and external resorptions (Figures 9a and 9b). High-quality images clarify root end proximity to normal anatomical structures such as the maxillary sinus, mental foramen, or mandibular canal. In fact, at times clinicians should expose a contralateral film to rule out a normal radiolucent anatomical landmark versus an abnormal radiolucent lesion. At times, additional films may be prescribed to augment an examination, including a panograph, lateral jaw, or occlusal radiograph. Diagnosticians should recognize that regardless of the various radiographic options, in the final analysis, interpreting a radiographic image is subjective and is a learned skill.16

Various horizontally angulated radiographs also provide critical information as to the etiology of endodontically failing teeth.17 Many endodontic failures can be attributable to coronal leakage resulting from failed restorations. Radiographs can clarify if the obturation material was gutta-percha, a silver point, carrier-based obturator, or paste filler. Additionally, radiographs reveal if a particular canal was well-shaped, and the vertical extent of obturation. Dentists who expend a considerable amount of their clinical time performing re-treatment appreciate that a short fill could suggest a blocked canal.

Off-angled films enhance the diagnostic assessment of root canals that exhibit a ledge, transportation, or perforation. A radiograph will generally reveal the presence of a post and additionally provide information as to its length, diameter, and orientation relative to the long axis of the root. Off-angled images can demonstrate the presence and position of a broken instrument or a missed canal. At times, a patient will be asymptomatic and demonstrate a radiographic radiolucency associated with a root apex. If there was a history of endodontic surgery, then the differential diagnosis should include the possibility of a surgical scar. However, discounting radicular fractures and hopelessly involved periodontal teeth, virtually all other endodontic surgical failures should be attributed to microleakage and bacterial invasion.

Figure 10a. A radiograph of an endodontically involved mandibular first molar showing a gutta-percha point passing through the buccal sulcus to a furcal lesion.
Figure 10b. A radiograph of an endodontically involved maxillary first bicuspid reveals a distocrestal lesion that is threatening the sulcus. Figure 10c. A radiograph shows a mandibular first molar with a poor fitting crown, incomplete endodontic therapy and a LEO associated with the mesial root.

The radiographic examination also provides information regarding the periodontal supporting structures. Certain probing defects masquerade as periodontal lesions when, in fact, the etiology may be attributable to  lateral canals disseminating pulpal irritants.18 Clearly, pulp testing schemes must be conducted to corroborate this suspicion allowing the clinician to differentially diagnose the presence or absence of a LEO. Over time it is becoming well understood that LEOs occur in the furcations of multi-rooted teeth (Figure 10a). Additionally, a LEO may be positioned crestally, laterally along a root surface, or symmetrically or asymmetrically around the apex of a root (Figures 10b and 10c). It must be understood that radiographic radiolucencies or radiopacities could represent a normal anatomical landmark, a nonodontogenic lesion, or a LEO, and the differential diagnosis is made by performing vital pulp tests.19

Vital Pulp Testing

The clinical and radiographic steps of the examination oftentimes cast suspicion of endodontic involvement of a specific tooth. Vital pulp tests (VPT) are essential components of the endodontic examination and serve to disclose the status of the dental pulp.12 Frequently, patients present reporting pain to a thermal stimulus in a specific quadrant. In these instances, vital pulp testing schemes should be performed first on presumably “pain-free” teeth, away from the area of the chief complaint. Specifically, the preferred sequence is to test contralateral teeth first, opposing teeth second, then presumably healthy teeth within the thermally painful quadrant, and finally, the most suspicious tooth last. This strategy of sequencing the vital pulp tests allows both the dentist and the patient to appreciate the range of “normal” pulpal responses exhibited by asymptomatic teeth. Importantly, performing repetitive pulp tests, as described, will tend to relax the patient, build confidence, and reduce the probability of a false positive or false negative report.

VPT procedures are initially performed to establish a normal “baseline” for any given tooth on any single patient. Once a baseline has been established then, and only then, should the appropriate VPT be performed in the quadrant where the patient is experiencing symptoms. Performing VPT on asymptomatic teeth establishes the baseline for testing and comparing an “abnormal” response in a symptomatic tooth. In fact, when VPT schemes are conducted in this manner, patients will frequently question why another tooth is either overreactive or nonreactive to the specific test. In these instances, additional diagnostic evaluation may be required to clarify the endodontic status of any given tooth.

Figure 11. This radiograph suggests the mandibular first bicuspid has a carious pulp exposure and reveals a LEO associated with the mesial root of the molar.

When pulpal inflammation is confined to the root canal space, diagnosticians should be skeptical when patients attempt to identify a specific tooth they perceive as the source of their pain. This doubt is justified because the dental pulp does not have proprioceptive nerve fibers.20 On the contrary, the attachment apparatus has proprioceptive nerve fibers that allow a patient to identify a tooth that is sensitive to biting pressure. As such, inflammatory conditions involving the dental pulp are diagnosed by reproducing the patient’s chief complaint. Thermal pain is pulpal in origin, whereas biting or chewing pain is related to injuries involving the periodontal attachment apparatus. The origins of attachment apparatus injuries are multifactorial and, as examples, could be periodontal or endodontic in etiology or attributed to a recently placed restoration in hyperocclusion. In summary, it is wise to appreciate that a symptomatic patient can present with two separate, distinct, and unrelated problems and, as an example, the tooth that is symptomatic to biting pressure may not be the tooth that is symptomatic to a thermal stimulus (Figure 11).

There are four methods that may be employed to determine the vitality of the dental pulp: cold, hot, electric, and cavity tests. Selection of the cold test or the hot test is based on the patient’s chief complaint. If a patient does not report any history of thermal pain then, for ease, the cold test is selected. However, it should be recognized that once the pulp is stimulated with cold, there is a refractory period of several minutes before a second cold or hot test can be accurately conducted. The electric pulp test is more technique sensitive, requires a dry field, and is oftentimes impractical to utilize in teeth with full restorative coverage. The cavity test is rarely used, and only considered when the clinical and radiographic information and pulp test results prove inconclusive. In these instances and when the patient situation supports intervention, then the cavity test could be considered as a last resort. If employed, the cavity test is initiated on a suspicious tooth, without anesthetic, and involves drilling a small window through either enamel or a restoration to dentin. The cavity test will stimulate a vital pulp and provoke a painful response when dentin is invaded. In the event of a vital response, a simple restoration is placed. On the contrary, the cavity test will not stimulate a partially necrotic pulp to the same extent as a vital pulp. In this situation, the dentist initiates the access cavity, invades progressively deeper into dentin, and often reaches the pulp chamber without exceeding the patient’s comfort level.

Thermal tests should be conducted on the cervical aspect of a tooth, and as close as possible to the free gingival margin. This location represents the thinnest aspect of enamel or a restoration and, importantly, the shortest distance to the pulp chamber. When performing a thermal test, the clinician is evaluating the immediacy, the intensity, and the duration of the response. The immediacy and intensity of a response to thermal testing can vary significantly depending on, as examples, the depth of a carious lesion, the placement of a new restoration, or recent periodontal surgery. It is useful to have the patient subjectively rate the intensity of a response utilizing a zero to ten scale where zero is a no response and ten represents maximum pain. Regardless of the immediacy and intensity, if the response rapidly dissipates upon removing the thermal stimulus, then although the pulp may have tested inflamed, this may be a reversible condition. Importantly, it is the duration of the response, compared with the baseline that was established by testing other teeth, that is most diagnostic.

In certain instances, a tooth tested with a thermal stimulus may elicit a “no response” which could infer the pulp is necrotic. It should be recognized that a patient may not respond to a thermal test if the pulp chamber has significantly calcified or receded apical to the crest of bone. Further, the absence of a response to a thermal test could imply a tooth has been involved in a recent episode of trauma, has an immature apex, or may be related to the use of analgesic medication. Additionally, a patient will not generally respond to a thermal stimulus on a tooth that has had root canal treatment. However, an endodontically failing tooth with a missed canal will, at times, illicit a painful response when tested with a hot stimulus.<