The Outcome of Endodontic Treatment

Signs of favorable outcome
Subjective symptoms
Asymptomatic, comfortable, and functional
Good-quality restoration with no signs of caries
Pulp sensitivity
Normal positive response to thermal or electric pulp testing
Periradicular tissues
No signs of swelling, redness, or sinus tract
Periradicular tissues
No signs of periradicular bone destruction


Complete removal of the pulp and placement of a root filling is the most extreme treatment approach when a pulp has been exposed. The scientific literature on pulpectomy is limited, and in particular there are no studies of direct comparison between the results of pulp preservation therapies with pulpectomies. Furthermore, many follow-up studies have not been able to make a clear distinction between teeth with vital but inflamed pulps and necrotic ones. In a randomized controlled study [18], the outcome of pulpectomy in one or two treatment sessions was assessed by a single dentist specialized in endodontics who carried out the treatments. A majority of the teeth in the study were affected by caries and had symptoms because of pulpitis. In both treatment groups, teeth were asymptomatic and without clinical and radiological signs of periapical infection or inflammation in 93 % of the cases, with a follow-up time up to 3 years.
In another clinical study [19], where supervised dental students carried out the pulpectomies and root fillings, it was found that after an observation period of 3.5–4 years, teeth with positive bacterial samples at the time of root filling had a poorer outcome than that of teeth with negative samples. Also, significantly more unfavorable outcomes were noted after 3.5–4 years than after 1 year of observation. The findings are in concordance with the results of a review on the outcome of primary root canal treatments (including pulpectomies) in which four conditions were found to improve the outcome of primary root canal treatment significantly [4]. One of these factors, the absence of periapical radiolucency, indicates that a noninfected root canal is a prognostic factor favoring an outcome where no signs of apical periodontitis will develop. Consequently, holding on to a strict protocol for asepsis seems to be of importance when carrying out a pulpectomy.

8.5.4 Symptomatic Pulpitis

Many endodontic procedures begin in an emergency situation. Symptoms from an inflamed dental pulp vary from only enhanced sensitivity to thermal, osmotic, and tactile stimuli to conditions of severe lingering and tearing pain. Patients with pain may require pulpectomy in the long term, but in an emergency situation pulpotomy has a good effect. If pulpotomy can be applied with good results on longer term is not well known [13]. A recent published study seems to indicate that pulpotomy in molars performed with biocompatible materials may be as successful as pulpectomy in achieving favorable clinical results when performed by general dental practitioners [20].

8.6 Treatment of Pulp Necrosis and Apical Periodontitis

8.6.1 Pulp Necrosis and Asymptomatic Apical Periodontitis

Injury to the pulp may eventually lead to a complete breakdown of the tissue. The nonvital or necrotic pulp is defenseless against microbial invasion and will sooner or later be infected by indigenous microorganisms. No established methods exist to allow for debridement and antimicrobial combat and a subsequent reestablishment of a vital adult pulp. However, ongoing research within this area may change the treatment options in the future [21]. For the time being, the only established treatment modality in teeth with completed root formation is root canal treatment. The root canal is cleaned in order to remove microbes and their substrates. In addition to irrigants, antimicrobial substances are used as dressings to enhance the antibacterial effect. A root canal treatment is finished as the tooth receives a permanent root filling. Postoperative discomfort sometimes follows, but after a short period most teeth become asymptomatic. Normally, the tooth is restored with a filling or crown immediately or a short while after completion.

8.6.2 Symptomatic Apical Periodontitis

Most teeth with pulp necrosis and apical periodontitis prevail without acute signs of inflammation. Nevertheless, symptoms may develop spontaneously or be initiated in conjunction with root canal treatment. The symptoms may vary from relatively mild pain to life-threatening situations with abscesses or cellulites. In an acute situation, the clinician needs to deliberate on the seriousness and deploy adequate measures. These can range from simple root canal instrumentation to incision of an abscess with or without prescription of analgesics and antibiotics. The appropriateness of different measures depends on the risk of the spread of infection and the patient’s general health. When the acute phase has subsided, the affected tooth needs root canal treatment, which is performed in the same manner as for asymptomatic cases. There is no evidence that shows that teeth that have gone through a phase of symptomatic apical periodontitis have a worse prognosis than those that have not.

8.6.3 Successful Outcome of Root Canal Treatment

The desirable and best possible long-term outcome of root canal treatment is a retained and functional asymptomatic tooth with no clinical or radiographic signs of apical periodontitis. Ng et al. [4] identified 63 studies published from 1922 to 2002, which fulfilled their inclusion criteria for a review. The reported mean rates of a “successful” outcome ranged from 31 to 100 %. This large variation could partly be the result of different radiographic criteria when evaluating the periradicular tissues on radiographs.
Despite the lack of high-quality scientific evidence, a meticulous analysis of the literature pointed out four circumstances that improve the possibility to maintain or reestablish healthy periradicular tissues in root-filled teeth: (i) preoperative absence of periapical radiolucency, (ii) root filling with no voids, (iii) root filling extending to 2 mm within the radiographic apex, and (iv) satisfactory coronal restoration [4], (Box 8.2). If these conditions are attainable, root canal therapy has been reported to be able to fulfill the requirements of “complete success” in 85–95 % of cases. Clinical experience and data from studies [4, 16, 18, 22, 23] have shown that root-filled teeth can be retained and stay healthy for many years.
Box 8.2. Prognostic Factors for Pulpectomy and Root Canal Treatment
Prognostic factors for pulpectomy and root canal treatment
Enough remaining tooth structure for a restoration that can avoid or counteract with adverse masticatory forces
Aseptic control and disinfection measures applied during treatment
A root-filling without voids in all main root canals
A root-filling extending to 2 mm within the radiographic apex
A good-quality coronal restoration

8.6.4 Unsuccessful Outcome of Root Canal Treatment

When root-filled teeth cause pain, it is usually a sign of infection. Especially so, if corresponding clinical findings in the form of swelling, tenderness, and fistulas at the same time are present. In situations like these, it is usually frank to diagnose a persistent, recurrent, or arising apical periodontitis. The treatment result is classified as a “failure.” There is an obvious indication for a new treatment intervention, retreatment, or extraction of the tooth (or sometimes only a root).

8.6.5 Asymptomatic and Functional but Persisting Radiological Signs of Apical Periodontitis

Nevertheless, a common situation is that the root-filled tooth is both subjective and clinically asymptomatic but an X-ray reveals that bone destruction has developed, or that the original bone destruction remains. In cases where no bony destruction was present when root canal treatment was completed, and in particular in cases of vital pulp therapy, it can be rationally assumed that microorganisms have entered in the root canal system. For teeth that showed clear bone destruction at the point of treatment, sufficient time must be allowed for healing and bone formation to occur.

8.6.6 Uncertainties in Classifying the Outcome into “Success” and “Failure”

The Time Factor

It is difficult to determine the amount of time that may be required for a periapical bone lesion to heal. A majority of root canal treated teeth with initial bone destruction show signs of healing within 1 year [24]. However, in individual cases, the healing process can take a long time [22]. In a study by Molven et al. [23], it was reported that some cases had required more than 25 years to completely heal. The finding that there is no absolute time limit for when healing may eventually be diagnosed can also be deduced from epidemiological studies [16].

The Reliability and Validity of Radiographic Evaluation

The diagnosis of periapical tissues based on intraoral radiographs is subject to considerable interobserver and intraobserver variations [12].
There are also uncertainties regarding the validity of the radiographic examination. Only a limited number of studies have compared the histological diagnosis in root-filled teeth to radiographic signs of pathology [12, 25]. In these studies, false-positive findings (i.e., radiographic findings that indicate apical periodontitis while histological examination does not) are rare. The number of false-negative findings (i.e., radiographic evaluation indicates no apical periodontitis while histological examination gives evidence for inflammatory lesions) varies between the studies. However, from experimental studies, it is well known that bone destruction and consequently apical periodontitis may be present without radiographic signs visible in intraoral radiographs.
The advent of cone beam computed tomography (CBCT) has attracted much attention in endodontics in recent years [12]. In vitro studies on skeletal material point to that the method has higher sensitivity and specificity than intraoral periapical radiography. The higher sensitivity of CBCT is confirmed in clinical studies. CBCT provides a three-dimensional image of the area of interest, an advantage when assessing the condition of multirooted teeth. As a result, the reliability of results of endodontic treatment in follow-up using conventional intraoral radiographic technique has been questioned [26]. It has been suggested that CBCT should be used in future clinical studies, because conventional radiography systematically underestimates the number of teeth with osteolytic lesions. In this respect, long-term studies are required to investigate if healing of periapical bone destruction may take longer than previously assumed. Also, there is not enough scientific evidence to tell whether lesions on CBCT images provide accurate clues as to the histological diagnosis present. So far, there are also disadvantages of CBCT, such as greater cost and a potentially higher radiation dose. Up to date, there is no evidence that suggests that individuals with subjectively and clinically asymptomatic root canal treated teeth with normal appearance of surrounding bony structures in an intraoral radiographic examination would benefit from further evaluation by a CBCT scan.

Controversies of “Success” and “Failures” of Root Canal Treatment

Besides the time aspect of periapical bone lesions, there is also a problem with determination of what should be considered healing sufficient to constitute a “successful” endodontic treatment. As a consequence, the question of what establishes a “failure” and hence an indication for retreatment is far from unmistakable. According to the system launched by Strindberg [22], the only satisfactory post-treatment situation, after a predetermined healing period, combines a symptom-free patient with a normal periradicular situation. Only cases fulfilling these criteria were classified as “success,” and all others as “failures.” In academic environments and in clinical research, this strict criteria set by Strindberg in 1956 [22] has had a strong position.
The periapical index (PAI) scoring system was presented by Ørstavik et al. [27]. The PAI provides an ordinal scale of five scores ranging from “healthy” to “severe periodontitis with exacerbating features” and is based on reference radiographs with verified histological diagnoses originally published by Brynolf [25]. The results from Brynolf’s work indicated that by using radiographs, it was possible to differentiate between normal states and inflammation of varying severity. However, the studies were based on a restricted biopsy material to upper anterior teeth. Among researchers, the PAI is well established, and it has been used in both clinical trials and epidemiological surveys. Researchers often transpose the PAI scoring system to the terms of Strindberg system by dichotomizing scores 1 and 2 to “success” and scores 3, 4, and 5 into “failure.” However, the “cutoff” line is arbitrary.
The Strindberg system, with its originally dichotomizing structure into “success” and “failure” has achieved status as a normative guide to action in clinical contexts. Consequently, when a new or persistent periapical lesion is diagnosed in a root-filled tooth, failure is at hand and retreatment (or extraction) is indicated.
However, as early as 1966, Bender and colleagues [28] suggested that arrested bone destruction in combination with an asymptomatic patient should be a sufficient condition for classifying a root canal treatment as an endodontic success. More recently, Friedman and Mor [29] as well as Wu et al. [30] have suggested similar less strict classifications of the outcome of root canal treatment.

Prevalence of “Failures”

The presence of subjective or clinical signs of failed root canal treatment is only occasionally reported in published follow-ups and epidemiological studies. The results are measured thus exclusively through an analysis of X-rays. In epidemiological cross-sectional studies, the frequency of periapical radiolucencies in root-filled teeth varies. In a systematic review of the matter, Pak et al. [31] included 33 studies from around the world with frequencies of failed cases varying from 12 to 72 %. The weighted average of periapical radiolucencies in the 28,881 endodontically treated teeth included was 36 %. The high frequency of root-filled teeth with periapical bone destructions seems to persist regardless of the fact that technical quality has improved over time [31]. Yet, cross-sectional studies cannot distinguish between cases that will finally heal and osteolytic lesions that will persist. On the other hand, longitudinal studies have shown that root-filled teeth without periapical radiolucent areas may develop visible lesions over time [16].

Consequences of “Endodontic Failures”

Persistent Pain
Surprisingly little is known about the frequency of pain from root-filled teeth. From the available data in follow-up studies from universities or specialist clinics, in a systematic review, the frequency of persistent pain >6 months after endodontic procedures was estimated to be 5 % [7].
Local Spread of Disease
A large majority of root-filled teeth with apical periodontitis remain asymptomatic. It is known that the inflammatory process occasionally turns acute with the development of local abscesses that have the potential for life-threatening spread to other parts of the body. Case reports in the literature describe the occurrence of more or less serious complications in the nearby organs (respiratory tract, brain), due to spread of bacterial infection from the root canals of teeth. However, the incidence and severity of exacerbation of apical periodontitis from root-filled teeth has met only scarce attention from researchers. A low risk of painful exacerbations (1–2 %) was reported from a cohort of 1032 root-filled teeth followed over time by Van Nieuwenhuysen et al. [32]. In a report from a university hospital clinic in Singapore where 127 patients with 185 nonhealed root-filled teeth were recruited [33]. Flare-ups occurred only in 5.8 % over a period of 20 years. Less severe pain was experienced by another 40 % over the same time period. The incidence of discomforting clinical events was significantly associated with female patients, treatments involving a mandibular molar or maxillary premolar, and preoperative pain.
Systemic Effects
Oral infections have been associated increasingly with severe systemic diseases, such as atherosclerosis, stroke, and even cancer. The potential of an association between chronic marginal periodontitis and cardiovascular disease is recognized in numerous reports. Indeed, the increasing numbers of reports of a relationship between atherosclerotic vascular diseases prompted a systematic review and American Heart Association Scientific Statement that examined possible correlations [34]. However, no clear answers to the questions about the possible causative relationship between atherosclerotic vascular disease and periodontal disease could be established.
Less attention has been given to a corresponding association with disease processes originating in the dental pulp. The scientific basis is insufficient to assess the association between infections of endodontic origin and disease conditions of other organs [9].

Disease Concepts

To retreat or not to retreat “an endodontic failure” is the issue. It has been argued that both modern medicine and dentistry face fundamental ethical problems if too rigorous and consistent concepts of disease prevail. The discussion about different concepts of disease goes back to ancient philosophy and has bewildered and occupied philosophers ever since. In this book about molar endodontics, we can only hint at the fundamental issues. For further reading, the interested reader should seek in books on philosophy of medicine [35].
Two fundamentally different concepts of disease can traditionally be recognized.

  • The naturalist theory defines disease in terms of biological processes. Disease is a value-free concept, existing independently of its social and cultural contexts. Disease is discovered, studied, and described by means of science.
  • The normativist theory, on the other hand, declares that there is no value-free concept of disease. Rather than discovered, the concept of disease is invented. It is contextual and given by convention.
These theories address different aspects and pose different challenges to medicine and dentistry as a whole and therefore also to endodontics. But the two predominant concepts have been challenged for several reasons. For example, they neither separately nor together fully acknowledge all important perspectives on human disorders. An alternative approach is to apply the “triad of disease, illness, and sickness” [36] (Box 8.3). Despite criticism, the triad is widely used and discussed. The definition of the triad’s different components is by no way clear-cut. The triad and its implications on dentistry were elaborated by Hofmann and Eriksen [37]. Kvist et al. [38] made cautious and initial attempts to apply the theory to the problem of asymptomatic root-filled teeth with radiographic signs of apical periodontitis.
Box 8.3. An Attempt to Apply the Triad of Disease, Illness, and Sickness to Root-Filled Teeth with Signs of Apical Periodontitis
Phenomena studied
Pathophysiological, histological, microbiological, and radiographic events
Pain, swelling, or other symptoms presented now or in the future
Criteria for classification and grading of disease
Purpose from the professions’ point of view
To study the medical facts of apical periodontitis in order to improve knowledge of how to prevent and cure
To identify and describe the incidence, frequency, and intensity for patient-related outcomes (pain, swelling, spread)
To decide upon common criteria for classification, define different severities of disease, and construct decision aids to guide clinical action
Purpose from patients’ point of view
To get an explanation of the situation
To value and accept or not accept the situation
To understand what is regarded “sick,” respectively “healthy,” and to be helped to make a clinical decision in his or her situation
  • Disease means the disorder in its physical form, the biological nature, the clinical, and paraclinical findings (histology, microbiology, radiography, etc.).
  • Illness is used to describe a person’s own experience of the disease, how it feels, and what sufferings it gives now or in the future. Illness also includes anxiety and anguish.
  • Sickness is the third label; it tries to capture the social role of a person who has illness or disease (or both) in a particular cultural context. What is eligible for being “sick” can consequently vary over time and between societies.
The three approaches to disease do not replace but complement each other. It is also the case that they are strongly intertwined. However, using the above matrix of “disease,” “illness,” and “sickness” makes it easier to understand the variation in clinical decision-making regarding root-filled teeth with persistent apical lesions, both when it is tested in different setups by researchers as well as in the clinical situation with an individual patient.
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Dec 30, 2016 | Posted by in Endodontics | Comments Off on The Outcome of Endodontic Treatment
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