Background
Involvement of the temporomandibular joint (TMJ) is a common finding in patients with juvenile idiopathic arthritis (JIA) [
1,
2]. Long-term arthritis of the TMJ may lead to growth dependent deformation of the joint components and reduced joint mobility, which in turn, may lead to secondary compromise of TMJ function and related muscular structures [
3‐
7]. Arthritis-induced orofacial signs and symptoms are common entities in JIA, and are associated with young age at onset, long disease duration, involvement of upper extremities, and polyarticular and systemic JIA subtypes [
3,
8,
9]. Across the literature, the reported prevalence of orofacial symptoms in JIA varies greatly, possibly due to the differences in the included cohort characteristics, retrospective character of most studies, and the type of questions asked [
7].
Generally, there is a lack of knowledge of the long-term chronicity of orofacial symptoms in JIA. Although follow-up studies exist, the current knowledge of JIA-induced orofacial symptoms mainly originates from cross-sectional studies [
4]. Long-term observational studies by Bakke et al. (15 year follow-up) and Engstrom et al. (25 year follow-up) have outlined a high prevalence of patients with persistent JIA-induced orofacial signs and symptoms [
10,
11]. However, these studies represent JIA cohorts from the pre-biologic era, which are incomparable to the contemporary JIA cohorts receiving targeted therapy [
12]. A small prevalence of patients with persistent orofacial symptoms were described in a 5-year follow-up study by Twilt et al. in 2008 [
13]. In support of that, a longitudinal study by Zwir et al. from 2015 found a baseline prevalence of orofacial symptoms of 29%, with a reduction to 12% at 1 year follow-up [
14]. Therefore, only limited knowledge is available on the long-term nature of orofacial symptoms in contemporary JIA patients. Additionally, little knowledge is available of the impact of JIA-induced orofacial symptoms on quality of life specifically related to the orofacial area. Previous cross-sectional studies by Leksell et al. and Frid et al. have focused on the association between arthritis-induced orofacial symptoms and general health-related quality of life using the Childhood Health Assessment Questionnaire (CHAQ) and the Child Health Questionnaires (CHQ) [
9,
15,
16]. These questionnaires assess general impact of arthritis and are not tools specifically designed to assess the impact of orofacial dysfunction on parameters related to oral health.
The purpose of this prospective observational cohort-study was: 1) To study the long-term changes in self-reported orofacial symptoms, 2) To study the impact of orofacial symptoms on oral health-related quality of life (OHRQOL). We hypothesized that the presence of orofacial symptoms would have a significant impact on the OHRQOL.
Discussion
To our knowledge, this is the most comprehensive longitudinal study examining orofacial symptoms in JIA. The objective of this study was to study the long-term changes in self-reported orofacial symptoms and to study the impact of orofacial symptoms on OHRQOL. The findings of this study demonstrate: Orofacial symptoms are common findings in patients with JIA, and they tend to persist with time. Furthermore, the intensity, frequency and the characteristics of orofacial symptoms do not change significantly over time. The TMJ and masseter regions are the most frequent orofacial areas affected, however, multiregional orofacial pain was seen in a substantial number of patients with persistent symptoms. Orofacial pain is associated with functional disability in the majority of patients, and it is rare to see functional disability in the absence of orofacial pain. We found that the pain index composite variable (pain frequency x pain intensity) is an acceptable measure of patient global pain perception. Patients with orofacial symptoms reported a significantly higher negative impact of orofacial conditions on general quality of life compared to asymptomatic patients. Finally, patients with orofacial symptoms reported a significant negative impact on emotional and social well-being.
This study found a high prevalence (55%) of JIA patients with orofacial pain and dysfunction. This is in contrast to a previous 5-year follow-up study by Twilt et al., who reported a smaller prevalence of orofacial pain (13%) and limited mandibular function (10%) [
13]. In our study, 97% (60/62) of symptomatic patients at T0 experienced orofacial pain and 77% (46/60) of these patients still reported pain after 2 years (T1). This finding is in contrast with Engstrom et al. who reported a higher prevalence of orofacial symptoms over time in their 15 year follow-up study [
11]. In agreement with Frid et al. we found an increased prevalence of orofacial symptoms in patients with a polyarticular disease course [
9].
The nature of the questionnaire used in this study allowed for a comprehensive analysis of changes in orofacial pain characteristics in JIA over time. In the group experiencing pain at both T0 and T1, we did not observe a specific pattern for changes in pain frequency or pain intensity over time. The current literature lacks information about orofacial pain frequency in JIA [
4]. This study therefore contributes valuable information by demonstrating that daily/weekly pain fluctuation is a characteristic finding in JIA patients who report orofacial symptoms. Many patients experienced orofacial symptoms during mastication and maximal mouth opening maneuvers. However, when asked about pain frequency, full-time symptoms were rarely reported, and the majority did not experience orofacial symptoms every day. From a clinical point of view, this is important because it conflicts with existing standardized guidelines on clinical orofacial assessment like the DC/TMD criteria, which was not exclusively developed for JIA [
20]. A critical tenet of the DC/TMD criteria is the notion that arthralgia, can only be established if pain on palpation is present during the clinical examination [
20]. Applied to a JIA population, this would mean an under reporting of orofacial pain, since many patients only experience pain in conjunction with functional demands like mastication. To capture the fluctuation of orofacial pain in JIA, we introduced the pain index variable (pain frequency x pain intensity). The acceptable agreement between the pain index variable and the patient global pain score of
r = 0.78 reveals that this may be a useful variable to address the fluctuation of orofacial pain in JIA. Interestingly, the reported T0 and T1 median pain index scores were surprisingly small considering the range 0–400 of the pain index outcome measure.
In the present study, patients reporting persistent T1 pain reported more widespread pain distribution as well as higher prevalence of multiregional pain compared to those reporting pain at T0 only. Notably, the locations of the affected pain regions and the characteristics of orofacial symptoms did not significantly change over time in patients with persistent orofacial symptoms.
In this study, the presence of orofacial pain and/or functional disability significantly impacted general health related quality of life. This is in agreement with a previous study by Leksell et al. and Frid et al. [
9,
15] but contrasts with findings of Twilt et al. [
13] who reported no significant impact on general quality of life between patients with and without TMJ involvement. However, an only moderate association (
r = 0.54) between the pain index variable and the impact of an orofacial condition on general quality of life demonstrates that a high level of orofacial pain may not negatively impact general quality of life and vice versa.
Patients with persistent orofacial symptoms experienced a greater impact on their general quality of life compared to patients with symptoms at T1 only. Although we do not have any information about pain related symptoms between those two observation points, this suggests that long-term symptoms impact general quality of life to a greater degree than short-term orofacial symptoms. Moreover, we also observed that patients who only had symptoms at T0 reported a significantly greater impact of orofacial conditions on general quality of life at T1 when compared to asymptomatic patients. This is an interesting finding, and may indicate that previous orofacial symptoms can impact general quality of life even after symptoms have resolved. However, the present study does not allow us to make firm conclusions in this regard. Future work with a larger patient cohort studied at more frequent time intervals could help to clarify some of these findings.
In the present study, we used a validated questionnaire to assess domains related to emotional and social well-being [
18]. This is the first study to assess oral health related quality of life in JIA. We found that emotional and social well-being were significantly reduced in patients with orofacial symptoms. Currently no validated OHRQOL questionnaire exists exclusively for use in JIA which constitutes a limitation to the present study. The questionnaire used, in the present study, has been validated in non-JIA children and adolescence with “orofacial conditions” (18). This warrants a future validation of OHRQOL questionnaires exclusively to the JIA population.
Our cohort consisted of consecutively enrolled JIA patients, from the entire JIA population in Denmark, thus decreasing the risk for selection bias at T0. Although the background cohort reflects the JIA population in Denmark, it should be noted that there were no patients with enthesitis-related arthritis and undifferentiated arthritis completing the questionnaires at both time-points in the present study. Furthermore, standardized questionnaires were used assessing orofacial symptoms and OHRQOL, thus minimizing the risk of information bias. There were however some limitations to this study. The current data does not contain information about presence/absence of TMJ inflammation at the time the questionnaires were completed; this would have been important information to collect. However, this is likely of minor significance since previous studies have revealed that the presence of orofacial pain is a weak predictor of TMJ arthritis [
4]. When interpreting symptoms, we typically attributed orofacial symptoms to previous TMJ arthritis leading to structural damage and impaired TMJ function. However, orofacial symptoms are also seen in non-inflammatory temporomandibular disorders, a common finding in the general population, and thus a potential confounder to the prevalence of symptoms reported in this study [
21]. Therefore, a general limitation to the present study is the lack of a non-JIA control group to reflect the frequency of orofacial symptoms and OHRQOL in the background population. At this point, no validated examination methods exist to differentiate between “general temporomandibular disorders” and JIA-induced orofacial conditions and that constitute a limitation to the present study.
In addition, the degree of fluctuation of orofacial symptoms during the 25-month observation period is unknown, since we only examined two time-points (T0 and T1). Therefore, the term “persistent symptoms” in patients with reports of orofacial symptoms at both time points is somewhat vague and does not accurately characterize the degree of fluctuation or persistence of symptoms between these time points.