Association between bruxism severity and serum concentrations of 25‐hydroxyvitamin D levels

Abstract Objectives The aim of this study was to investigate the possible relationship between bruxism and blood levels of 25‐hydroxyvitamin D. Material and Methods One hundred male and female patients from Damascus joined the study. Their ages were in the range of 18–40 years. Two groups were considered in this study, the first group included patients who were already suffering from bruxism (76 patients) and the second group consisted of patients who were not suffering from any bruxism (24 patients). The analysis of the blood samples for 25‐hydroxyvitamin D levels of the two groups was carried out. Results The recorded results showed that there is a relationship between the levels of bruxism and 25‐hydroxyvitamin D concentration in the blood (p < .05), enhancing that the bruxism activity has been shown the associated deficiency in 25‐hydroxyvitamin D levels, which can be divided into five different categories. Conclusions Within the limitations of this study in spite of the number of patients (one hundred), according to the reported study, it appears that there is a significant relationship between bruxism and the level of 25‐hydroxyvitamin D in the blood.


| BACKGROUND
Bruxism is defined as a parafunctional activity of the masticatory muscles, which is characterized by the unconscious clenching and/or grinding of the teeth, and it may occur at any time of the day (Veiga et al., 2015). This activity has a multifactorial etiology associated with psychological factors, local factors, personal characteristics, and also disruption of sleep (Demjaha et al., 2019). Over the past two decades, several studies have highlighted the existence of a central administration in the mechanism of bruxism (Kato et al., 2003;Lavigne et al., 2007). On the other hand, this neurological mechanism is associated with sleep quality and the psychological state (depression, stress, and anxiety) of the individual (Herrero Babiloni & Lavigne 2018). Accordingly, bruxism as an oral condition has great importance to both researchers and doctors in the fields of dentistry, neurology, and sleep medicine (Lobbezoo et al., 2013) and it is not only limited to the state of clenching and grinding of the teeth.
The potential role of 25-hydroxyvitamin D (25(OH)D) levels, in a wide range of health outcomes has increased (Moon et al., 2017).
Vitamin D interferes with the neurological mechanism properties due to the spread of vitamin D receptors (VDR) in multiple areas of the central nervous system (Koundourakis et al., 2016) and also due to its potential role in the decline or improvement in mood and sleep stability of the individuals (Casseb et al., 2019;Gominak & Stumpf, 2012 Before participation subjects signed an informed consent form and were informed that they could refrain from the study at any time without any consequences.

| Participants, study design, and setting
One hundred persons participated in this present study. All participants were selected from our patients who were referred for general dental treatment in the dental school at Damascus University and they were asked to join this study voluntarily. They were divided into two groups depending on the bruxism status: bruxer individuals group (consisting of 58 females and 18 males) and nonbruxer group (including 8 females and 16 males) within the range age of 18-40 years (average age: 27 years). Both groups were referred to the laboratory for 25(OH)D levels analysis tests. The bruxism status of all participants was examined according to the recommendations of Pintado et al. (1997) (Table 1), and a 25item questionnaire (Bruxism severity classification questionnaire) (Molina et al., 2013) was answered by bruxer patients to determine the severity levels of bruxism (mild, moderate, severe, and extreme severe) 3-5, 6-10, 11-15, 16-25 signs and symptoms, respectively, side by side to the clinical examination ( Table 2). All examinations were performed in advance in the Oral Medicine department between 10:00 a.m. and 1:00 p.m. from the beginning of March until the end of November 2019.
The exclusion criteria for both groups were (Veiga et al., 2015): medication that could interfere with vitamin D metabolism (Demjaha et al., 2019), presence of fixed or removable prosthodontics for more than four units (Kato et al., 2003), presence of severe malocclusion (Lavigne et al., 2007) bruxism and electromyography for awake bruxism) side by side to clinical examination and self-reports (Lobbezoo et al., 2013). In our study, we did not determine the type of bruxism (sleep or awake) but we only used the questionnaire to measure the severity of bruxism after confirmation or denial.
Moreover, the limitation of the study sample was due to difficulties finding out volunteers and the limited available budget so that the number of sub-groups of bruxism severity levels was low.

| Laboratory procedure
In the laboratory, blood samples were taken from each patient's arm (the cephalic vein). 25(OH)D levels were analyzed with Roche Total 25-OH vitamin D kits (based on electro-chemiluminescence binding assay). According to the expected values of Elecsys ® 25-hydroxyvitamin D test characteristics, the normal range for 25(OH)D concentration in nanogram: <20 ng/ml was considered as deficient, between 21 and 29 ng/ml was considered as insufficient, between 30 and 150 ng/ml was considered as sufficient and finally the concentration of 25(OH)D is more than 150 ng/ml, which was considered as toxicity.

| Statistical analysis
The results were analyzed with SPSS (Statistical Package for the Social Science) and p values <.05 were considered statistically significant. Spearman's correlation coefficient analysis was used for the statistical analysis.

| DISCUSSION
Vitamin D is a prohormone that has a key role in calcium and phosphate balance and bone structure in the body (Autier et al., 2014). D intake from many resources, mainly through skin exposure to solar ultraviolet (UV) B radiation or from different nutrition resources (Zittermann, 2017 It should be noted that the above reasons may interfere with the toms as well as anxiety disorder (Han et al., 2018;Sherchand et al., 2018). Some studies, however, failed to find significant associations (Michaëlsson et al., 2018;Şahin Can et al., 2017).
In contrast, some researchers propose a hypothesis that sleep Our study relied on determining the possibility of bruxism through self-reports (questionnaire) and clinical examination only due to the lack of instrumental approaches at Damascus University.
Bruxism etiology is multifactorial; therefore, the psychoemotional is considered one of the most important etiological factors (Singh et al., 2015). Recently, Manfredini et al. (2015)  ALLAF AND ABDUL-HAK