The relationship between obstructive sleep apnea (OSA), sleep bruxism, and temporomandibular disorders is becoming clearer, but data on how upper airway volume affects bruxism due to OSA is limited. Recent studies have shown that Cone-Beam Computed Tomography (CBCT) accurately images the upper airway, enabling analysis of its volume and its potential impact on bruxism. CBCT uses low radiation doses, significantly lower than harmful levels, making it a safe method for such assessments. Understanding these relationships can inform clinical practices for managing sleep bruxism, which affects 21% of the global population. The study aims to explore how upper airway volume influences the intensity of sleep bruxism related to OSA.

The main objective of the study is to assess the relationship between upper airway volume and sleep bruxism and obstructive sleep apnea. The following null hypothesis was adopted: upper airway volume influences the intensity of sleep bruxism induced by obstructive sleep apnea.

The relationship between obstructive sleep apnea and bruxism during sleep (behavior involving increased activity of the masticatory muscles during sleep) and temporomandibular disorders (a group of diseases and disorders related to the morphology and function of the masticatory system (mainly the temporomandibular joints and masticatory muscles) is becoming increasingly well understood. However, there is a lack of data on the relationship between the three-dimensional volume of the upper airways and sleep bruxism induced by sleep apnea. Recent scientific publications have demonstrated the ability of CBCT (Cone-Beam Computed Tomography) to image the upper airway very accurately in order to examine the minimum cross-section and total volume of the upper airway in three dimensions. 3D imaging using CBCT is a simple, effective, and safe method for accurate analysis of the upper airway, which will help determine the relationship between upper airway volume and bruxism induced by obstructive sleep apnea (OSA). Modern cone beam tomography is characterized by significantly lower doses of electromagnetic radiation, averaging between 0.05 and 0.6 mSv (50-600 µSv). It is estimated that, on average, each person receives a dose of radiation from natural sources of approximately 2.4 mSv (2,400 µSv) per year. Radiation doses in diagnostic imaging, therefore, represent only a fraction of these values. It is important to be aware of what dose of radiation is harmful. It is estimated that negative health effects may occur at doses of around 200 mSv (200,000 µSv), which is significantly higher than that received during modern imaging examinations.

Materials and Methods:

A total of 80 adult volunteers will be recruited for the research project, divided into two groups of 40 each, comprising both sexes, who will give their voluntary and informed consent to participate in the study. The study group will consist of patients with sleep bruxism and obstructive sleep apnoea. The control group will consist of patients with sleep bruxism without obstructive sleep apnoea. First, each potential participant in the project will undergo a clinical and physical examination of the stomatognathic system in accordance with the international DC/TMD guidelines (Diagnostic Criteria for Temporomandibular Disorders) and in accordance with the current international consensus on bruxism at the Temporomandibular Disorders Clinic of the University Dental Centre in Wrocław. The patient will undergo a clinical examination during which systemic diseases and medications taken will be recorded.

The study will also include a range of validated questionnaires assessing psycho-emotional well-being and selected aspects related to the functioning of the stomatognathic system, including the PHQ-9 (Patient Health Questionnaire 9), PSS-10 (Perceived Stress Scale 10), GAD-7 (Generalised Anxiety Disorder 7), SWLS (Satisfaction with Life Scale), SSS-8 (Somatic Symptom Scale 8), MIDAS (The Migraine Disability Assessment Test), JFLS-8 (Jaw Functional Limitation Scale - 8), TMD Pain Screener (Temporomandibular Disorders Pain Screener) and DC/TMD Symptom Questionnaire (Diagnostic Criteria for Temporomandibular Disorders Symptom Questionnaire). In addition, the following validated sleep questionnaires will be used: EPWORTH (Epworth Sleepiness Scale), PSQI (Pittsburgh Sleep Quality Index) and STOP-Bang Questionnaire. The next step will be to refer the patient for CBCT imaging, including measurements of the minimum cross-sectional area and 3D volume of the upper airways. Upper airway measurements will be performed in accordance with the protocol by Fonseca et al. (Fonseca C, Cavadas F, Fonseca P. Upper Airway Assessment in Cone-Beam Computed Tomography for Screening of Obstructive Sleep Apnoea Syndrome: Development of an Evaluation Protocol in Dentistry. JMIR Res Protoc. 2023;12:e41049. doi: 10.2196/41049). The CBCT scan will take place at the University Dental Centre in Wrocław. The patient will then be referred to the Department and Clinic of Diabetology, Hypertension and Internal Medicine at the University Hospital, 213 Borowska Street, Wrocław, for a polysomnography examination. Polysomnography (PSG) is a non-invasive test comprising an EEG (electroencephalogram), ECG (electrocardiogram), EOG (electrooculogram), EMG (electromyogram), assessment of chest and abdominal movements, and measurement of blood oxygen saturation. It is used as the gold standard for diagnosing the severity of sleep apnoea by determining the AHI (Apnoea-Hypopnoea Index) and sleep bruxism by determining the BEI (Bruxism Episode Index). The polysomnography will be performed in accordance with the current guidelines of the American Academy of Sleep Medicine. During PSG, numerous other parameters relating to bodily functions during sleep are also collected. The aforementioned medical facilities possess the necessary equipment, scientific and clinical knowledge and experience to carry out the aforementioned examinations (CBCT: Planmeca Viso G7 CT scanner, Helsinki, Finland; PSG: NOX A1 sleep recorder, Iceland). The collected data will undergo thorough and specialist statistical analysis.

Anticipation Results:

By analyzing the results collected during the study and establishing probable correlations or their absence, it will be possible to understand the relationship between specific disorders and behaviors, and then counteract their development in everyday clinical work with patients with sleep bruxism around the world. According to the latest meta-analysis, this is 21% of the global population (Zieliński G et al. Global Prevalence of Sleep Bruxism and Awake Bruxism in Pediatric and Adult Populations: A Systematic Review and Meta-Analysis. J Clin Med. 22 July 2024;13(14):4259. doi: 10.3390/jcm13144259).

Inclusion Criteria:

• age equal to/greater than 18 years
• moderate or high risk of sleep apnea according to the STOP-Bang questionnaire
• presence of bruxism symptoms in the oral cavity according to the current international consensus on bruxism
• positive history of bruxism during sleep

Exclusion Criteria:

• refusal to participate in the study
• pregnancy
• breastfeeding
• presence of severe mental illness
• alcohol and/or drug addiction
• taking medications that affect the neuromuscular and/or respiratory systems
• severe systemic diseases such as cancer
• severe neurological and autoimmune diseases
• multiple missing teeth
• edentulism in the upper and/or lower jaw

A total of 80 adult volunteers will be recruited for the research project, divided into two groups of 40 each, comprising both sexes, who will give their voluntary and informed consent to participate in the study. The study group will consist of patients with sleep bruxism and obstructive sleep apnoea. The control group will consist of patients with sleep bruxism without obstructive sleep apnoea. Participants are arbitrarily selected from a population.