The number of participants included in the study was determined as 98 for effect size = 0.67, α = 0.05 and power (1-β) = 0.95, 49 from FM and 49 from control group (Albertsen Malt et al. 2000). A total of 113 volunteers, 63 FM patients older than 18 years old who applied to the Physical Medicine and Rehabilitation outpatient clinic between May 2021 and August 2021 and were diagnosed with FM according to American College of Rheumatology (ACR) 2010 criteria and 50 sex- and age-matched non-FM volunteers, participated in the study. The exclusion criteria were determined as not having written consent, being younger than 18 years old, having been diagnosed with another chronic systemic disease that may affect mental health, and having cognitive dysfunction that would prevent them from completing the questionnaires. The study protocol was approved by the Ondokuz Mayıs University Clinical Researches Ethics Committee (No. 2021/148), and written informed consents were obtained from all participants.
The ACR 2010 fibromyalgia diagnostic criteria is consisting of two scales, the Widespread Pain Index (WPI) and the Symptom Severity (SS) Scale. The Widespread Pain Index questions the presence of pain in 19 different body regions, and each region receives 1 point and a maximum of 19 points can be obtained. On the SS scale, the severity of symptoms including fatigue, waking unrefreshed, and cognitive dysfunction, which are the symptoms accompanying FM, and the amount of accompanying somatic symptoms are scored between 0 and 3, with a maximum score of 12. Patients are diagnosed with FM when WPI ≥ 7 and SS ≥ 5 or WPI = 3–6 and SS ≥ 9 (Wolfe et al. 2010). The ACR 2010 fibromyalgia diagnostic criteria were found to be valid and reliable in the Turkish population (Atik 2014).
Age, gender, occupation, education, duration of complaint, oral diseases, dental experience, temporomandibular joint pain, xerostomia, glossodynia, dysgeusia were recorded. All participants were asked to answer the Modified dental anxiety scale (MDAS) and the Hospital Anxiety and Depression Scale (HAD anxiety and HAD depression, respectively). Also, Fibromyalgia impact questionnaire (FIQ) was administered to FM patients.
Dental anxiety was evaluated with the MDAS, which consists of 5 questions scored between 1 and 5. Its Turkish validity and reliability has been proven, and patients with an MDAS score of ≥ 16 indicates anxiety, while patients with a score of ≥ 19 are considered dental phobic (Tunc et al. 2005; Ilgüy et al. 2005).
Anxiety and depression were evaluated with HAD. The Turkish validity and reliability of this scale, which consists of 14 questions scored between 0 and 3, seven of which assess anxiety and seven that assess depression, has been proven (Aydemir et al. 1997). In our study, they were reported as HAD anxiety and HAD depression scores.
The FM disease severity was assessed with the FIQ. In this scale, where a maximum of 80 points can be obtained, a high score indicates high disease severity (Bennett 2005). The Turkish validity and reliability of this scale has been proven (Sarmer et al. 2000).
SPSS version 22 was used for statistical analysis (SPSS Inc., IBM Co., and Chicago, IL, USA). Descriptive statistics were performed for all data. Normal distribution was evaluated with the Kolmogorov–Smirnov test. Values which are normally distributed were given as mean ± standard deviation, and values which are non-normally distributed were given as median (minimum–maximum). In terms of the frequencies of demographic and clinical data, difference between the groups were assessed by the chi-square test. Whether there was a difference between the groups in terms of the scores of the scales evaluating anxiety and depression was evaluated with the Mann–Whitney U test. Correlation between variables was analyzed with Spearman's test. Significance level was accepted as p < 0.05.