The psychological effects include aspects of knowledge, beliefs, attitudes, values, preferences, quality of life and satisfaction. Quality of life is concerned with the degree to which a person enjoys the important possibilities of life [27]. Surprisingly few studies have addressed these “patient-centred” outcomes of endodontic treatments [28]. Disease of pulpal origin negatively affects quality of life primarily through physical pain and psychological discomfort, and root canal treatment results in distinctive improvement [29].

The impact on daily life activities (eating, speaking, sleeping, contact with people, etc.) by painful exacerbations of persistent periapical lesions in root-filled teeth was reported in the previously mentioned study from Singapore [5]. Among the 127 patients with apical periodontitis in a root-filled tooth recruited for the study only 33 patients (38 teeth) had experienced some kind of impact over a period 38 years. But only five patients reported substantial impact.

The attitudes towards asymptomatic persistent lesions among patients affected have only met scarce attention. In two studies value judgements towards an asymptomatic root-filled tooth with a periapical lesion were investigated by methods used in the context of expected utility theory [30, 31]. In both studies elicited subjective values towards asymptomatic apical periodontitis and root-filled teeth showed great variation.

A great many teeth with pulpitis and apical periodontitis, even in countries with well-developed dental care, often do not come under dental treatment. They remain unrecognized, because they are asymptomatic or are considered among the ordinary discomforts of daily living. Or, the patient may be suffering from both pain and other symptoms for a prolonged period of time but because of economic limitations has not been able to seek dental care [32]. Cost is a significant barrier to receiving dental care and a very important factor in patients’ treatment choices. The “willingness to pay” for root canal treatment in order to save an asymptomatic nonvital lower first molar was studied in a population of 503 patients in England [33]. Only, 53% of the sample wished to save the tooth with a mean “willingness to pay” of £373. The variation in willingness to pay was found to be substantial and influenced by income. Initial cost may capture patients’ attention, but that is only the beginning. The original cost of tooth retention through root canal treatment and restoration is usually considered to be lower than tooth replacement using implants or fixed dental prostheses [34]. However, the lifetime cost model for different options should also include treatment failures. In a cost-effectiveness model from the United Kingdom, regarding a maxillary incisor, it was calculated that saving a tooth by root canal treatment, followed by non-surgical retreatment if indicated, was cost-effective. However, surgical retreatment was not found to be cost-effective [35]. On the other hand, an American cost-effectiveness modelling study, for a root-filled treated molar in need of re-intervention, ranked surgical retreatment, non-surgical retreatment, replacement using a fixed dental prosthesis and replacement using an implant, from the greatest to smallest cost-effectiveness [36]. There are several problems involved in using these data in a clinical situation for an individual patient’s point of view. First of all, the calculations are highly sensitive to different care providers’ fees for the interventions put into the algorithms. Secondly, it is possible that the benefits available under the prevailing dental care reimbursement system encourage one of the options at the expense of the other regardless of cost-effectiveness in the long term. Thirdly, cost-effectiveness analyses compare relative costs and outcomes but do not take into account individual patient values. One can, with good reason, assume that individuals who already paid for root canal treatment once are reluctant to pay for retreatment, in particular, if the tooth is asymptomatic. Data from the many epidemiological studies, showing that root-filled teeth with persistent apical periodontitis are very common, suggest that patients and their dentists, in many cases, assess the cost-benefit ratio to be too low to undertake any operation whatsoever.

When a patient presents with a root-filled tooth causing pain and swelling or chronic clinical findings in the form of redness, tenderness and fistulas, it is usually relatively straightforward to diagnose a persistent, recurrent or arising apical periodontitis. However, the most common situation is that the root-filled tooth is both subjective and clinically asymptomatic but an X-ray reveals that bone destruction remains. It is difficult to determine how long is the time that may be required for such a healing process in a particular case. The diagnosis of periapical tissues based on intra-oral radiographs has repeatedly unmasked considerable inter- and intra-observer variation. Besides the time aspect and observer variation, there is also a problem of determining what should be considered as a sufficient healing of bone destruction to constitute successful endodontic treatment. And as a consequence also what establishes a “failure” and hence an indication for retreatment is far from unambiguous.

According to the limited data available in the literature, claims concerning endodontics are common among dental professional liability cases [37, 38]. The high prevalence of root fillings of poor quality, as pointed out in numerous studies, makes this hardly surprising. However not all claims are justified. All healthcare, including endodontics, need to weigh the benefits of various measures against the risks. The goal of all dental care is of course that it will be of benefit to those who receive it. But sometimes the procedures per definition are resulting in injuries or damage. Some “damage” is planned, as when the affected tooth is opened by removal of hard tissue in order to get access to the root canal system. Unnecessary injuries may occur as a result of incompetence, negligence or by a single mistake. Even the most skilful, well-educated and experienced dentist can make mistakes sometimes. Some endodontic treatments can also be very complicated, with more built-in risk for complications than others. These injuries are regrettable but are an inherent risk of endodontic procedures that one can seek to reduce over time through improved treatments, better education and more hands-on instruction. But injuries that occur because of carelessness, incompetence or because the caregiver has not complied with in the scientific and technological developments in the profession are avoidable in a completely different way and cannot be viewed as acceptable. And as a result of quality deficiencies in the primary endodontic treatment, a suspicion or accusation of malpractice may emerge when a persistent apical periodontitis is diagnosed in a root-filled tooth.

When treating diseases of infectious and inflammatory disease emanating from the pulp, unsuccessful outcome may occur despite professional excellence in every detail. It is of paramount importance to inform about the possible risks of the treatment procedures and explain that treatment may not always lead to a successful result, even though it is performed in accordance with all the rules. This should be a part of the informed consent procedure. A malpractice claim might be perceived as a criticism of the dentist’s competence and skills but also as a sign of a downfall in communication with the patient.

If a root canal treatment “failure” is diagnosed despite a reasonable high-standard treatment procedure, and the patient understands and accepts the situation, there is also little to argue about. The problem is limited to a decision-making problem if and how the pathology should be treated.