PROMs Following Root Canal Treatment and Surgical Endodontic Treatment

The FDI is currently working on developing a tool to encompass patient-reported outcome measures (PROMs) within the overall assessment of outcomes of endodontic treatment. The outcome of endodontic treatment has traditionally been determined by various clinical and radiographic criteria. However, these parameters do not address the impact of treatment on a patient's oral health–related quality of life (OHRQoL). OHRQoL, a crucial PROM, can be used to understand treatment outcome from a patient-centred perspective, thus improving clinician–patient communication whilst guiding decision-making. This focussed review aims to recount the OHRQoL of patients following nonsurgical root canal treatment and surgical endodontic treatment, with a specific focus on the minimal important difference (MID; the minimum score changes of an outcome instrument for a patient to register a clinically significant change in their OHRQoL and/or oral condition) and the methods used to determine it. The current evidence indicates that the OHRQoL of patients requiring root canal treatment is poorer than those without such need. Accordingly, the literature suggests that OHRQoL improves following nonsurgical or surgical endodontic treatment. However, study methodologies vary widely, and conclusions cannot be drawn with high confidence, nor can MID recommendations be provided. Well-designed clinical studies with baseline measurements and appropriate follow-up time frames are therefore needed. Despite that the literature is rife with outcome studies, research on PROMs is an area that deserves greater attention, particularly in relation to the MID. Determining the MID will facilitate the understanding of changes in outcome scores from the patients’ perspective, thus allowing for more informed decision-making in clinical practice.


Introduction
Whilst the goal of root canal treatment is to eliminate infection, relieve pain, restore the health of the periapical tissues, and retain the functionality of the treated tooth, 1,2 treatment effectiveness and success have traditionally been measured using clinician-reported outcomes that rely on clinical and radiographic criteria. 1,3 Various criteria for successful root canal treatment have been proposed, most notably the "strict" 4 and "loose" 5,6 criteria, which are primarily categorised based on complete reversal of the periapical radiolucent area or its arrest. On the other hand, other terms such as favourable, uncertain, and unfavourable 1 as well as healed, healing, nonhealed, and functional 7 have also been proposed to describe endodontic treatment outcome. Dichotomisation of radiographic appearance as "success" or "failure" to convey prognosis may not be as relevant to patients, as they may have different goals, values, and/or treatment expectations than what the clinician may have in mind. 8 Evaluating the treatment effectiveness from the patients' perspective, that is, patient-centred outcomes, is of pivotal importance in the context of patient-centred care. 9 Patient-centred care has been associated with improvements in patient satisfaction and overall well-being. [10][11][12] In the context of endodontic therapy, patient-centred care emphasises the elimination of symptoms whilst prioritising functionality. 2 A recent white paper by the FDI affirms that these treatment philosophies are in line with the concept of "endodontic medicine," which suggests that endodontic diseases should be considered within a greater context, that is, the human body, as they not only affect the health of pulpal and periapical tissues but also impact general health. 2 Quality of life (QoL) is one of the key components of patient-centred outcomes that form the basis of the patient −dentist dialogue. 13 Whilst QoL indicators have been commonly employed throughout health care and general dentistry, [14][15][16] it has only recently emerged as a topic of interest in endodontics. Current evidence indicates that root canal treatment would positively influence oral health−related QoL (OHRQoL). [17][18][19] Despite such promising findings, a muchneeded critical appraisal into the potential applications of OHRQoL and different OHRQoL instruments in the field of endodontic research is lacking. Most notably, the minimal important difference (MID) largely remains to be described in detail from the context of root canal treatments. 19 The MID represents the smallest difference in a patient-reported outcome score that is considered clinically significant. 20 Thus, to understand whether a change in OHRQoL is meaningful to the patient, determining the MID for the given context is essential. Currently there is a paucity in the evidence pertaining to the MID for OHRQoL measures, demonstrating the need for research in this area. 21 Therefore, the aim of this review the current evidence to recount the OHRQoL of patients following nonsurgical root canal treatment and surgical endodontics, with a specific focus on MID.

Review
What is OHRQoL, why is it important, and how is it measured?
QoL is "an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standard and concerns." 22 It is a multifaceted construct that incorporates physical, psychological, and social domains. It can be understood in terms of both positive-for example, having the ability to chew and function-and negative-for example, fatigue and pain-dimensions. 22 Oral health can have an impact on overall health and QoL by impacting an individual's ability to carry out certain functions, such as chewing, talking, and tasting. 23 Moreover, oral diseases can have psychological and social impacts that can affect an individual's well-being. 23,24 Specifically, OHRQoL refers to an individual's self-perceived "comfort when eating, sleeping and engaging in social interaction, their self-esteem and their satisfaction with respect to their oral health." 25 Attempts to conceptualise the complex notion of OHRQoL to provide a reference framework for researchers and health care professionals have demonstrated that no one unique dimension can represent OHRQoL (ie, multidimensional) as the different domains work in tandem (ie, integrative). 14,26,27 OHRQoL outcome measures are an essential component of patient-centred care since they allow clinicians to holistically evaluate the efficacy of different treatment options in light of the patient's needs and values. 13 This improves patient−clinician communication and facilitates the treatment decisionmaking process. 28 Furthermore, not all patients may have access to the "ideal" care because of social, cultural, and/or economic barriers; hence, patient-centred outcomes can facilitate the setting of individualised treatment goals. 28 Where treatments may not be able to eliminate the disease but rather provide palliative/supportive care, improving the QoL may become the primary goal of treatment. 29 In regards to public health, patient-centred outcomes may guide the development of health promotion programmes, allocate resources, and evaluate the efficacy of oral health care services. 13 Furthermore, QoL indicators can be employed in dental research to facilitate evidence-based dentistry, cost-utility analysis, and health service evaluation. 30 There are 3 main methods of evaluating OHRQoL: social indicators, global self-ratings, and multiple-item questionnaires. a) Social indicators describe community-level social costs of oral disease. Population surveys are carried out to understand the social impact of diminished oral health such as loss of working days, restricted activities, and absence from schools. 31 However, social indicators provide limited information about the impact of oral health on an individual's OHRQoL. 30 b) Global assessment ratings (global self-ratings or singleitem ratings) involve asking individuals one general question about their oral health status. 32 They can be used to determine the responsiveness of an instrument as well as the MID of patient-centred outcomes. 33 This method allows simple and general comparisons; however, it does not adequately reflect the various dimensions of OHRQoL. Therefore, global assessment ratings are often combined with multiple-item questionnaires. 34 c) Multiple-item questionnaires represent the instrument of choice 31 and can be categorised into generic-and diseaseor condition-specific instruments, such as the Oral Health Impact Profile (OHIP) 35 and Geriatric Oral Health Assessment Index, 36 respectively.
How has OHRQoL been measured in the endodontic literature?
A literature search was conducted to identify relevant studies using a search strategy that was developed based on previous reviews, [17][18][19] utilising keywords that related to endodontic treatment and OHRQoL (  37 conducted the first study investigating the OHRQoL of endodontic patients and, since then, the importance of PROMs has been thrust into the limelight, prompting a steady growth of OHRQoL studies in relation to endodontic disease and treatment. The ideal instrument for PROMs should be appropriate, reliable, valid, responsive, and interpretable. 9,31 However, as a "goldstandard" instrument for endodontic patients remains to be established, a myriad of measures has been employed to characterise the impact of root canal treatment on OHRQoL. 19 Currently, the most frequently utilised instrument in the endodontic literature is the OHIP, specifically the OHIP-14. The OHIP-14, which is a shortened version of the original OHIP-49, was developed based on Locker's conceptual model of oral health. 26 The questionnaire is subdivided into 7 domains: functional limitation, physical pain, psychological discomfort, physical disability, social disability, and handicap. The patient answers based on how often they have encountered each scenario within a specific time frame, usually 12 months, using a 5-point Likert scale. The scores are summated, with a higher total score indicating poorer levels of OHRQoL. 38 Other variations of the OHIP have been found in the endodontic literature as well, such as the OHIP-17 37 and the OHIP-14_sev. 39 A key benefit of using the OHIP-14 in the context of endodontics is that it has been confirmed to be sensitive enough to detect changes in patients' OHRQoL following endodontic treatment. 40 It also has been translated and validated in multiple languages, [41][42][43] allowing adaptability for different cultural contexts. However, there exists much variation on how researchers interpreted the outcomes from OHIP-14. Some have dichotomised the results into "no impact" and "impact," 44 whilst others defined poor OHRQoL as scores that were amongst the upper quartile of the study group. 40 Furthermore, how studies deduced improvement in OHQRoL was not standardised in the endodontic literature, with some inferring it from changes in the total score whilst others based it on changes to the individual domains or even the individual item level. 19 It has been suggested that summed scores and domain-level analysis are favoured over itemlevel analysis. 45 Other OHRQoL instruments have made also appeared in the endodontic literature, such as the Patient Perception Questionnaire, [46][47][48][49][50][51][52][53] Health-related QoL Index, 54 Oral Impact on Daily Performance (OIDP), 55 General Oral Health Assessment Index, 56 OHRQoL instrument, 57 Post-operative QoL questionnaire, 58,59 OHRQoL research tool, 60 and the QoL Scale. 61 Although these instruments may provide an alternative means to measure PROMs, there are several factors that may hinder their widespread use in endodontic research. First, the responsiveness of most of these instruments have not been thoroughly investigated regarding OHRQoL changes associated with endodontic disease and treatment. Second, given their limited use throughout the endodontic literature, comparisons between studies may be challenging, which could prevent an accurate quantitative synthesis (ie, metaanalyses).
Health-related QoL measures, such as the General Health Questionnaire 62 and the EuroQoL-5D-5L instrument, 63 are sometimes utilised to provide an additional assessment of the patients' general QoL. These instruments may allow researchers to evaluate how endodontic treatment−related factors can affect a patients' self-perceived general health and overall well-being. However, the sensitivity of generic questionnaires is known to be inferior to disease-specific questionnaires. 64 Apart from the choice of instrument, a crucial element for consideration is the time period of assessment. Ideally, a baseline measurement of the patients' OHRQoL must be provided. Cross-sectional studies only capture the OHRQoL at a single time point, generally months to years posttreatment, which may result in susceptibility to recall bias. Prospective studies and randomised clinical trials thus possess a clear advantage. However, significant variation exists in regard to the evaluation periods. Whilst several studies have applied extended evaluation periods, for example, 1 year 54,65 to 2 years, 66,67 others reported postoperative assessments of only up to 7 days, sometimes without any preoperative baseline measurement. [46][47][48][49][50][51][52] It has been suggested that limited time frames, for example, 6 months or less, are insufficient to evaluate changes in OHRQoL as they are limited to describing the initial posttreatment recovery. Hence, follow-up periods of approximately 1 year may be more suitable. 18,45 On the other hand, further lengthening the period of evaluation may result OHRQoL fluctuations due to other oral diseases having emerged. 54 Table 1 -Search strategy used to identify articles in this narrative review.
Search Query #1 "Root canal treatment" OR "root canal therapy" OR "endodontic treatment" OR "endodontics" OR "root canal retreatment" OR "Endodontic retreatment" #2 "Apicoectomy" OR "apicectomy" OR "periradicular surgery" OR "Endodontic surgery" OR "apical surgery" OR "periapical surgery" OR "root-end surgery" OR "root-end resection" #3 "Patient-reported outcome measures" OR "healthrelated quality of life" OR "oral health-related quality of life" OR "Quality of life" OR "quality of life index" OR "patient satisfaction" OR "general quality of life" OR "WHOQoL" OR "QoL" OR "health utility index" OR "SF-36" OR "SF-12" OR "SF-9" OR "SF-6" OR "EUROQoL" OR "EQ-5D" #4 #1 OR #2 #5 #3 AND #4 The majority of patients did not experience any impact on OHRQoL (OHIP-14 score) after treatment. There was no significant difference of OHR-QoL between groups. OHRQoL was most impacted in the domains of "physical pain" and "psychological disability" in both groups. The endodontic group experienced significantly higher scores in the domains "psychological discomfort" and "psychological disability" compared to the implant group. Most participants expressed a desire to retain their natural dentition when possible. Yu et al 2012 55 Cross       OHRQoL associated with endodontic disease and treatment Endodontic diseases have been found to negatively impact OHRQoL 62,68 particularly in the domains of physical pain, psychological disability, and psychological discomfort. 37,39,44,68,69 Studies have reported OHRQoL improvement after primary 37,40,57,66 and secondary 67 nonsurgical root canal treatment as well as surgical endodontic treatment. 52 Conversely, studies have also reported no significant difference in OHRQoL after nonsurgical treatment. 60,63 These contrasting findings may be explained by the heterogeneity of endodontic patients in the disease-(ie, preoperative symptoms), treatment-(ie, complications), and patient-related factors (ie, experience of the treatment, psychosocial factors, and patient values). Furthermore, some endodontic diseases may manifest as "painless" ailments 70 resulting in minimal perceived impact on OHRQoL. 44,68 Therefore, it is likely that the extent of impact also depends on the severity of the symptoms, functional limitation, and psychosocial impairment. Nevertheless, based on the available literature, it may be considered that endodontic treatment generally improves the OHRQoL. [17][18][19] When root canal treatment was compared with other dental services such as extraction, restoration, prosthodontic, periodontal, and preventative treatment, there were no differences when compared to individual treatment groups. 66 Similarly, no significant difference was found in the OHRQoL between patients who had received root canal treatment vs extraction, although those in the extraction group expressed higher levels of embarrassment. 57 It has also been reported that a consistent theme with most patients was the desire to keep their natural dentition. 69 Factors that may influence the OHRQoL of endodontic patients A large cross-sectional study identified 3 key factors that were associated with poorer OHRQoL: multiple teeth needing treatment, retreatment, and pain. 62 Both preoperative pain 44,62 and persistent pain following treatment 55,71 were found to negatively impact PROMs. The association between OHRQoL and different sociodemographic factors such as gender, age, socioeconomic status, and marital status and has been demonstrated in some studies 39,44,52 and refuted in others. 68,72 Similarly, studies on the impact of operator experience have reported conflicting findings, although patient satisfaction was consistently higher when treated by specialists. 37,68 Multiple clinical studies have investigated how various procedural aspects of root canal treatment may impact OHR-QoL. This includes local infiltration of corticosteroids, 59 different instrumentation protocols, 58,65,73,74 obturation techniques, 65 and extent of foraminal enlargement. 61 In terms of surgical endodontics, the use of microsurgical protocols, 53 peizosurgery instruments, 46 papilla-based flap designs, 48 low-level laser therapy, 56 and autologous platelet concentrates have also been evaluated in the context of PROMs. Except for the study by Diniz-de-Figueiredo et al, 65 the period of evaluation was relatively short, spanning 2 weeks at most. Again, short evaluation times may be insufficient to thoroughly assess OHRQoL beyond patients' initial recovery. 45 Although it is entirely conceivable that different procedural aspects can impact the immediate postoperative experience of the patient, the influence of these factors on the long-term transformation of OHRQoL remains questionable.
A potential relationship between OHRQoL and clinical outcome has been implicated but not well substantiated in several studies. 37,40 One study found an association between poorer OHRQoL and patients who had an endodontically treated tooth with persistent disease. 37 The authors, however, encouraged caution in the interpretation of these results as radiographic outcomes given that this was a cross-sectional survey. 37 Another study reported that all domains of OHIP-14 were significantly associated with self-perceived improvement in oral health, whilst some domains changed with respect to improvement in radiographic outcome. 40 In general, clinical and radiographic parameters of success do not always reflect the changes in OHRQoL, whilst subjective measures such as self-perceived oral health appear to show a stronger correlation/association. 40,75,76 MID: a critical element for future research The extent of benefit gained from any treatment is important for all stakeholders (eg, clinicians, patients, policymakers) to make changes in treatment philosophies. From the context of PROMs, the magnitude of change is a crucial element that represents the benefit gained from treatment. Statistical methods such as calculating the effect size and half of the standard deviation have also been utilised to indicate the magnitude of change. 40,57,65 Global statements of change are widely used to assess the patients' self-perceived change in oral health status. 40,57,66 These methods can also be used to infer the responsiveness of the OHRQoL instrument.
The concept of responsiveness was first introduced by Guyatt et al 77 and was used to describe the ability of an instrument measuring patient-centred outcomes to detect a clinically important change. Subsequently, Jaeschke et al 78 suggested the term minimal clinical important difference to denote the smallest difference in score which patients perceive as being beneficial. Since then, a myriad of terms have been introduced to represent similar concepts, for example, MID, 20 minimally important change, 79 subjectively significant difference, 80 and clinical important difference. 81 Despite the many variations in terminology, it has been suggested that MID is the term that is generally used in the literature. 82 Ascertaining the MID of PROMs provides multiple benefits. 19 Interpreting the changes in the outcome scores remains unintuitive to both the clinicians and the researchers because statistical significant differences do not reflect the inherent value of the change in score to the patient. Thus, determining the MID allows health care professionals and researchers to interpret the significance of the changes in outcome score. 21 Furthermore, improvement or deterioration in clinical measurements does not always align or adequately represent the changes from the patient's perspective. Therefore, the MID facilitates better understanding of a patient's self-perceived changes in oral health status and OHRQoL. 33 There are 2 main methods used to determine the MID: anchor-based methods and distribution-based methods. Anchor-based methods use an external marker of change, proms in endodontics that is, the anchor, to identify whether the difference in outcome score is of clinical significance. 82,83 The anchor can be objective or subjective; however, the latter is more widely used and is often operationalised in the form of a global statement of change. 82,84 Distribution-based methods make inferences from the data collected from the patient-reported outcome instrument whilst using the distribution of the scores to calculate the MID value. 83 These statistical approaches most commonly include the calculation of effect size, standard error of measurement, and ratios of standard deviation. 85 The major benefit of using distribution-based methods is that no additional data are required. 82 However, many argue that the MID of PROMs can only truly be assessed through an understanding of the patient's subjective experience. Hence, it has been suggested that different approaches should be combined to determine MID values, with distribution-based methods providing a supporting role whilst anchor-based methods provide primary evidence. 84,86,87 MID has been thoroughly investigated in regards to various medical conditions and treatments. 77,[88][89][90][91][92] On the other hand, its appearance in OHRQoL research has been lacking. 21 The majority of studies have solely used distributional methods. [93][94][95] One of the first studies to use an anchor-based approach reported that the MID for OHIP-14 was 5 scale points for an elderly dental population. 32 When applied to a group of periodontal patients, the MID was around 5 scale points for the OIDP index. 96 A recent study investigating OHR-QoL after oral rehabilitative treatment reported a range of values for variants of the OHIP, including 14 scale points for the OHIP-49 and 3 scale points for the OHIP-14. 97 Only one study has investigated the MID of OHRQoL for endodontic patients; however, only distribution-based approaches were utilised. 65 To the best of our knowledge, there are no studies evaluating MID of OHRQoL for endodontic patients using anchor-based methods. It has been emphasised that specific MID values should be interpreted within the context of a given application, with special attention paid to the OHRQoL instrument used and the characteristics of the study group. 86 Given that the FDI is currently working on the development of an oral health measurement tool, which incoprorates patient-centred outcomes as a measure in the assessment of oral health outcomes, 2 research on MID may signifcantly improve the clinical usefulness of such tools.

Conclusions
A combination of PROMs with clinical and radiographic outcome measures can result in a more comprehensive understanding of the impact of endodontic treatment and the value of different treatment modalities. The evidence supports that endodontic diseases can have a negative impact on OHRQoL, and whilst endodontic treatment has been shown to enhance patients' OHRQoL, the extent of improvements vary. To strengthen the current evidence, well-designed large-scale clinical studies are needed to determine the effect of root canal treatment on OHRQoL in comparison with alternative modes of treatment, such as extraction and/or implants. These studies should include a baseline measurement of OHRQoL, a suitable time period of assessment, and an appropriate choice of instrument. In addition, there is a need to develop endodontic-specific OHRQoL instruments to be used in tandem with generic OHRQoL instruments in future research. Last, investigating the MID is elemental for a thorough interpretation of OHRQoL measures. Understanding the MID gives insight into both the magnitude and value of change after an intervention from the patient's perspective and hence should be a prime focus of future studies.