Fryback and Thornbury’s framework of the efficacy of diagnostic imaging
Nonendodontic Lesions Misdiagnosed as Apical Periodontitis
There are a number of nonendontic lesions, both benign and malign, mimicking apical periodontitis in the radiograph. These include fibroosseous lesions, ameloblastomas, nasopalatine duct cysts, keratocystic odontogenic tumor, metastatic injuries, and carcinomas [49, 50]. Some of these will present asymptomatic, whereas others will be present with both pain and swelling. Because the vast majority of all periapical bone lesions are indeed due to an infection of endodontic origin, there may be a risk of misdiagnosing those few who are not, as apical periodontitis. It is therefore emphasized that the clinical and radiologic examination as well as analysis of the patients’ medical history must be comprehensive. In root-filled teeth, the usually most valuable diagnostic tool, pulp vitality test, is not available. Therefore, the risk of a misdiagnosis may be more pronounced. If the medical history, clinical examination, and/or radiographic features result in a suspicion of a nonendodontic lesion, a biopsy and sequential histopathological analysis are mandatory.
5.3 An Everyday Practical Approach to Diagnosing Apical Periodontitis in Root-Filled Teeth
5.3.1 Diagnostic Strategy
The art and science of diagnosing apical periodontitis in root-filled teeth are hampered by several difficulties. Misdiagnosis can therefore not be completely avoided. A deliberate strategy may be a mean to steer away from unwanted mistakes or to guide to acceptable and calculated mistakes. If a clinician, in a given situation, wants to minimize the number of false-positive diagnoses, i.e., wants to minimize the number of healthy wrongly diagnosed as being ill, the requirements for a positive diagnosis should be kept strict, and a positive diagnosis should be reported only when absolutely certain. Adopting such a strategy, the patient or the tooth “benefits of the doubt.” If, on the other hand, the clinician wants to minimize the number of false-negative diagnoses, i.e., wants to minimize the number of sick registered as healthy, the requirements for a positive diagnosis should be more including, and a positive diagnosis should be reported whenever there is a suspicion of disease. Such a strategy in contrast to above could be characterized as “trap rather than free.” A reduction of false-positives diagnoses always brings an increase in the number of false-negative diagnoses and vice versa. Selection of strategy thus always has a desired and an undesired effect [33, 51].
It is likely that a more general use of CBCT would improve the diagnostic accuracy of apical periodontitis in root-filled teeth. In particular, the proportion of false-negative diagnoses could be reduced. But it cannot be ruled out that the risk of an increased amount of false-positive diagnoses could also be the result, in particular in the absence of symptoms and when then the preoperative appearance of the lesion is unknown. Also, because the dynamics of the healing process over time after root filling is undetermined, unrestrainedly use of CBCT would bring about risk of substantial overdiagnosis and as logical result also overtreatment (for further reading, see Chap. 6 “Decision Making”). As with any ionizing radiation exposure to patients, the potential benefits should outweigh the potential risks.
5.3.2 Arguments for “Benefit of the Doubt” Strategy
The high frequency of root-filled teeth with periapical bone destructions seems to persist despite the technical quality of root fillings has improved over time [52, 53].
Millions of teeth saved to survival and asymptomatic function are present in many countries all over the world. The risks of a systemic adverse effect on the health of untreated apical periodontitis may, on the basis of the evidence currently available, considered small for healthy patients (see Chap. 4 “Consequences”). Severe acute infectious condition resulting from apical periodontitis in root-filled teeth is also unusual and has been estimated to less than 5% over a period of 25 years . Unfortunately, there is no scientifically established method to distinguish between different severities of periapical disease. There is some evidence that there is a connection between the periapical size and the amount of involved microorganisms . Many different microorganisms, in most cases the bacteria but sometime fungi, have been found in the biofilms that persist in filled root canals. There are no accepted scientifically founded clinical methods to distinguish particularly “dangerous” or “harmless” biofilms from this perspective.
In many cases the root filling quality is poor, and an apical lesion is apparent to anyone who is observing the radiograph despite the fact the patient is free from symptoms. In such cases there is little or no doubt about the diagnosis; the tooth should be diagnosed with persistent apical periodontitis. In other situations, the periapical radiolucency is big and shows no signs of reduction in size despite adequate root canal treatment. It may be suspected that the periapical lesion represents a periradicular cyst without any further healing potential without further treatment [55, 56]. The next steps are to inform the patient and have a dialogue about how the situation should be managed. This process is reviewed in Chap. 6.
However, if the root filling quality is reasonable within acceptable standards, the clinician may remain ambiguous about the periapical diagnosis.
When uncertain about the diagnosis of apical periodontitis, it seems likely from the bulk of available information that most patients will “benefit from the doubt” when apical periodontitis in an asymptomatic and properly root-filled tooth is considered. In other words, false-positive diagnoses should be avoided. This means that the clinician deliberately should choose to refrain from diagnosing apical periodontitis in root-filled teeth when in doubt, rather than taking risk of diagnosing and hence treating teeth with healed or healing apical periodontitis.
5.3.3 Exceptions from the “Benefit from the Doubt” Strategy
A careful medical history is important for all patients under dental care. There are several medical conditions and medications that cause a deterioration of the immune system, by the lack of white blood cells or the inability of a patient to produce antibodies.
In such situations, maybe that “trap rather than free” attitude by the clinician may be the best diagnostic strategy. However, it is unclear to what extent medically comprised patients benefit from diagnoses and in particular treatment of asymptomatic apical periodontitis in a situation of ongoing medications or disease that impede normal function of the immune defense system.
5.3.4 Some Common Situations and Guidelines for Determining Diagnosis
In the following we will give some typical examples where there may be an uncertainty regarding potential residual apical periodontitis in a root-filled tooth. We are also suggesting a concrete policy reaching a diagnosis in each one of the situations.
18.104.22.168 Pain from Root-Filled Tooth But No Sign of Apical Periodontitis on Intraoral Radiographs
The patient may experience soreness—pain or discomfort from a root-filled tooth. However, intraoral radiographs from one or two angulations show no apical radiolucency. The root filling exhibits good technical quality as can be judged from the radiographs.
Action: Suggest a CBCT scan.
If this shows that an apical radiolucency is present, there is indication for retreatment or in some cases extraction.
If no radiolucency, or other pathology, can be observed, one can suspect that the endodontic treatment caused a damage to sensory nerves involved. Or that pain is projected from a TMD disorder. There is no diagnosis of apical periodontitis and consequently no indication for retreatment or extraction. Instead extend the examination and consider other diagnoses that may mimic the symptoms of apical periodontitis in a root-filled tooth.
22.214.171.124 Asymptomatic Tooth But a Widened Periapical Contour
Another common situation is that the patient is asymptomatic; the root filling exhibits good technical quality. But, there is a widening of the periapical contour present.
Action: An expanded periodontal contour should not be considered pathological. The diagnosis shows great observer variations. Great uncertainty is present. The patient and tooth benefit from the doubt if no other findings suggestive of apical periodontitis are present.
126.96.36.199 Asymptomatic Tooth But Clinician Is Uncertain About a Possible Lesion
A similar common situation is that the patient is asymptomatic. The root canal exhibits good technical quality. However, the clinician is in doubt whether a periapical lesion is present or not.
Action: Consultation with a colleague on the radiograph. If the uncertainty persists, consult a radiologist who must decide.
188.8.131.52 Asymptomatic Tooth: A Lesion Is Present But Short Time Since Root Filling
In this scenario the patient is asymptomatic. However, there is an apical radiolucency evident in the intraoral radiograph. Root canal shows good technical quality. Relatively short time passed since the root canal treatment and root filling were performed (1–4 years).
Action: Good to fairly good healing potential remains. The closer to the point of root filling, the larger remaining of healing chances. Wait for periapical healing at least 4 years.
184.108.40.206 Asymptomatic Tooth: A Lesion Is Present Showing Reduced Size
Our last example is equally frequent. The patient is asymptomatic. Root filling shows good technical quality. More than 4 years have passed since root filling was performed. There is an apical radiolucency. However, compared with previous X-ray, it shows the radiolucency clearly and continuously reduced in size.
Action: Further healing potential may remain. Wait further healing and check again.
5.3.5 Patient Information and the Adoption of Measures
When the diagnosis of apical periodontitis is made, it is the dentist’s statutory obligation to inform about the diagnosis and demonstrate the potential of therapy. The dentist should also give suggestions on the treatment that he/she deems most appropriate. In addition, the dentist must inform if the treatment is requiring a referral to a specialist or not. It is the patient who must take the final decision to treat or not. This process will be further covered in Chap. 6.
When pain and/or swelling or a sinus tract from a root-filled tooth is present and at the same time an apical radiolucency can be observed on an intraoral radiograph, the diagnosis of apical periodontitis is evident.
When pain from a root-filled tooth registered without concomitant other clinical or radiographic signs of disease, a handful of other diagnoses should be considered, among them referred pain from TMD and neuropathic pain disorders.
When clear radiographic signs of apical periodontitis are present, the diagnosis is usually evident because of poor-quality root filling giving obvious space for microbial biofilm to persist.
When radiographic signs of apical periodontitis are uncertain, the diagnosis is surrounded by major uncertainties, especially if root filling quality is good. In such situations, we argue most patients will “benefit from doubt”—diagnostic strategy.
Brynolf I. Histological and roentgenological study of periapical region of human upper incisors. Odontologisk Revy. 1967;18(Suppl. 11). In this classical thesis, the author studied the periapical regions of root-filled teeth with histological as well as radiographic examinations. The studies provided data for the PAI score.
Reit C, Hollender L. Radiographic evaluation of endodontic therapy and the influence of observer variation. Scand J Dent Res. 1983;91:205–12. The authors clearly and elegantly demonstrated the intra- and interobserver variation problems involved in the diagnosis of periapical lesions in intraoral radiographs.
Reit C, Gröndahl HG. Application of statistical decision theory to radiographic diagnosis of endodontically treated teeth. Scand J Dent Res. 1983;91(3):213–8. The study explains why variations between the observers could be explained by their adoption of different criteria of periapical disease resulting in different positions on the ROC curve. It also explains why the best opportunities for revealing relative differences in disease prevalences are created when the examiner defines a strict criterion for disease and reported a positive finding only when absolutely certain.
Strindberg LZ. The dependence of the results of pulp therapy on certain factors. Acta Odontol Scand 1956;14(Suppl. 21). Classical study on outcome of root canal treatment clearly demonstrating that the number of healed cases will increase in the long term, also after such a long period as 4 years.