Call for improved research efforts on clinical procedures in endodontics

Careful analysis of the scientific basis for the methods that we apply in endodontics has demonstrated extensive shortcomings. For example, the Swedish Council on Health Technology Assessment (SBU), which is a national governmental agency that assesses healthcare technologies, conducted recently a thorough review of the methods that we use to diagnose, prevent and treat inflammation and infection of the dental pulp and the periapical tissue (Swedish Council on Health Technology Assessment 2010). It reported that Certainly, many clinical investigations have confirmed that an inflamed pulp can be successfully treated with a conservative procedure. Yet, to date, there is no analysis available of the presenting clinical conditions as to which cases are likely to respond well and which treatment measures will render teeth functional and asymptomatic. Many follow-up studies have also demonstrated that teeth with necrotic and infected pulps can be treated endodontically to achieve a healthy outcome that can last many years. Yet, there is a lack of scientific evidence to show which treatment protocols are the most effective and result in root-filled teeth with minimal risk of recurrent symptoms, periapical inflammation or fracture. Hence, without doubt, there are significant knowledge gaps in our clinical field of dentistry. Critical assessment of our research in endodontics not only challenges our discipline but prompts us to conduct a thorough analysis of what we can do to improve our clinical knowledge base. SBU proposed that the lack of good research in our field demands well planned and carefully conducted clinical studies. Randomized, controlled, blinded trials (RCTs) are the standard of excellence for comparisons of treatment effects over time. However, improved rates of randomized controlled clinical studies may not necessarily be the solution to all our clinical questions. While RCTs are useful to observe a given treatment method or procedure when all other variables are maintained the same, such studies may not show superiority when considering the large number of clinical variables that may affect the outcome. More reasonable is prospective cohort studies. The SBU report found very few published such studies that could be used for its assessment and proposed that substantially more effort should be given to conduct studies, which focus on key clinical issues. Because of their selection and training, dentists in general and scholars in particular tend to prefer the kind of precise measurements the physical and biological sciences provide and they avoid or discount others, especially for research. Yet, relief of symptoms and promoting satisfaction with a feeling of well-being are among the most important outcomes of dental care and are central to the concerns of patients and dentists. To guide clinical decisions, clinical research must include such basic measurements and deliberations. In the SBU report, a number of areas that ought to be addressed were highlighted. For the first, it was stated that there is a great need for clinically applicable methods, which can accurately determine the status of the pulp in teeth affected by deep caries, trauma or other injuries (Mejàre et al. 2012). The information is important to assess the prognosis of a treatment that is intended to preserve some or all of the pulp through pulp capping or pulpotomy. It would certainly be desirable to have access to specific markers, which can determine the severity of a pulpal condition. Yet, it seems unlikely that such methodology will become available in the near future. However, the interpretation of prevalent clinical signs and symptoms can be better investigated. They include symptoms of pain of varying intensity and duration and the character of the bleeding from an exposed pulp. RCTs in which the validity of these signs are investigated may be tested in standardized clinical exposures of the pulp. Digital volume tomography (CBCT) is very likely to assume increasing importance in the diagnosis of periapical bone changes and to monitor the status of root canal treated teeth. To date, the diagnostic accuracy of this methodology has not been adequately investigated, and there is a need for studies comparing CBCT with conventional intra-oral radiography (Petersson et al. 2012). Indeed, such studies are limited by the difficulty of obtaining adequate reference tests. It is thus important to evaluate the construct validity of the method. Construct validity is present to the extent that the measurement is consistent with other measurements of the same phenomenon. Consequently, construct validity of CBCT is present to the extent that the CBCT evaluations are consistent with other essential manifestations of apical periodontitis. A possible solution to this problem is the analysis of biopsies, taken in conjunction with apical surgery, where cases with negative and positive signs of apical periodontitis are compared. At least equally important is the investigation of any possible link between the appearances of apical periodontitis on CBCT scans and clinical parameters such as increasing size of the periapical bone destruction, root resorption, pain or risk of local or systemic spread of disease. A critical question in endodontics is how teeth with deep caries should be best treated. A primary question here is whether a treatment intended to preserve the pulp or a treatment aimed to remove it and replace it with a root filling is optimal. The question is highly relevant from a health economic aspect, because root filling and subsequent restoration of such teeth are expensive both for the individual patient and society. A disadvantage of conservative treatment including direct or indirect pulp capping is that failure may result in severe pain and suffering. In many cases, identifying the offending tooth may also be a challenge. RCTs employing well defined and sufficiently large samples of patients are therefore urgently needed. Valid results, however, require follow-up periods of five years or more, so that the frequency of late failures becomes recognized. Treatment of teeth with clinical and radiographic signs of apical periodontitis remains a most critical issue. While we now are about to receive more scientific data on the frequency and character of biofilms in endodontic infections, few reports exist to show the importance of separate interventions and treatment steps for disinfection and root filling of teeth with pulpal necrosis. This means that there is still uncertainty over which treatment methods are the most effective for relief of symptoms and prevention of recurrent infection. Although in many cases root fillings have functioned well, the methods in use today rely on inadequate scientific data and hardly any RCTs or prospective cohort studies with reasonably large patient samples can be identified. Results of clinical studies must be judged in relation to two broad questions. Can the diagnostic method or treatment work under ideal circumstances? Does it work in ordinary settings? The words efficacy and effectiveness have been applied to these concepts. Even with improved knowledge of the outcome of various methods in endodontics, there are important practical parameters, which are not easily controlled for. These include the operator's (dentist's) experience, ability, attention to detail and skill. Yet, it is seldom possible to determine how such factors affect the outcome in treatment studies. It is nevertheless reasonable to assume that in a clinical discipline such as endodontics, these factors are of great importance. Such factors probably also contribute to the great variation in endodontic treatment outcomes in cross-sectional studies. For obvious reasons, so far most clinical studies in endodontics have been conducted in academic or specialist settings (efficacy). Devices that substantially facilitate the technical procedures ought to be researched to determine whether or not the application of modern devices and equipment affects treatment outcomes. It is of utmost importance that such clinical research is conducted in general practice settings, where the majority of endodontic procedures are performed (effectiveness). In epidemiological cross-sectional studies, the frequency of periapical bone destruction, as an indication of apical periodontitis, may be as high as 50%. If such a bone lesion is regarded as an indication for further endodontic treatment, there will be a substantial number of teeth that are candidates for retreatment. It may be calculated that in Europe alone, many millions of teeth may be affected. Yet, investigation into practice routines implies that teeth with asymptomatic inflammatory processes are often left without intervention. Whether this can be carried out without risk of acute flare-up or adverse systemic effects has yet to be confirmed. The scientific evidence describing the natural course of events and prognosis for root-filled teeth is inadequate and needs further documentation. Important areas deserving investigation include: These questions are probably best addressed by large prospective cohort studies and will require cooperation between academic institutions and dental health organizations. The results of such investigations should provide valuable data for a critical review of the indications for endodontic retreatment. There is also a need for more knowledge on endodontic retreatment methods (orthograde or retrograde or both), as to whether they are effective and result in long-term tooth survival. In this context, it is also important to evaluate the alternatives to retreatment, extraction and replacement by a tooth-supporting bridge or an implant from the perspective of quality of life and cost effectiveness.