Manual Therapy in Vagus Nerve Neuromodulation for the Treatment of Bruxism

Efficacy of Manual Therapy in Indirect Non-Invasive Neuromodulation of the Vagus Nerve in the Treatment of Bruxism in Young Adult Population up to 40 Years Old

Introduction:

Sleep bruxism is defined as the repetitive activity of the masticatory muscles, characterized by clenching or grinding of the teeth. Studies confirm the association between sleep bruxism and episodes of masticatory muscle activity, with an increase in autonomic sympathetic activity observed during transient periods of sleep. This is associated with nocturnal awakenings, related to increased cardiac, cerebral (cortical arousal), respiratory, and muscular activity.

Objectives: The main objectives are "To study the mean power frequency (MPF) of the masticatory muscles measured by surface electromyography (sEMG) in the general population (with and without bruxism according to ICSD-3 and DC/TMD criteria)"; and "to assess the effectiveness of manual therapy applied to structures adjacent to the vagus nerve based on its impact on orofacial pain and symptomatology in patients with bruxism".

Material and Methods:

A cross-sectional observational study and a randomized controlled experimental study were designed. The first will analyze data collected by sEMG in the masticatory muscles, at rest and during maximum clenching, comparing results between bruxists and non-bruxists. The second will analyze, compared to the control group, data collected on signs (range of motion alteration, presence of sounds), symptomatology (pain, headaches, sensation of blockage, functional limitation) caused by bruxism, sleep quality (Pittsburgh Sleep Quality Index (PSQI)), oral health-related quality of life (OHIP-14), stress and anxiety status (Perceived Stress Scale and GAD-7 (Generalized Anxiety Disorder-7), respectively), and sympathetic-vagal balance (Heart Rate Variability in its frequency and time domains) before and after a manual therapy intervention on structures adjacent to the vagus nerve pathway (head, neck, thorax, diaphragm, abdomen). The collected data will be analyzed using IBM SPSS® version 25.0.0.

Inclusion Criteria:

1. Sleep bruxism diagnosed according to the ICSD-III (International Classification of Sleep Disorders, 3rd edition):

   • Regular or frequent tooth grinding sounds occurring during sleep and the presence of one or more of the following clinical signs and symptoms:

     1. Abnormal tooth wear consistent with reports of clenching/grinding the teeth during sleep
     2. Transient morning pain or fatigue in the jaw muscles; and/or temporal headaches; and/or jaw locking upon awakening, consistent with reports of clenching/grinding the teeth during sleep

2. Sleep bruxism diagnosed according to the RDC/TMD:

   • Interview: During the interview, subjects are asked about the following symptoms: reports of regular or frequent tooth grinding during sleep, muscle fatigue, temporal headache, transient morning muscle pain in the jaw, and jaw locking upon awakening.

   • Physical examination: Presence or signs suggesting abnormal dental wear, such as teeth with flattened cusps and/or loss of contour with dentin exposure.

     • Hypertrophy of the masticatory muscles
     • Dental impressions on the tongue
     • Linea alba on the cheeks along the bite line
     • Damage to dental tissue
     • Excessive dental wear

3. A minimum pain intensity score of 3 on the Visual Analogue Scale at the masseter and temporal algometry points.

4. EMGs with elevated mean power frequency for the masseter and temporalis muscles (to be defined in the first clinical phase-observational study).

5. Age between 18 and 40 years.

Exclusion Criteria:

1. Having suffered direct trauma, mandibular fractures, or surgeries in the orofacial region.
2. Loss of more than 2 teeth, except for the third molar.
3. Use of muscle relaxant medication or medications that may influence motor behavior.
4. Having received botulinum toxin treatment in the last 6 months.
5. Periodontal disorders or current orthodontic treatment or prosthesis.
6. Partial or total dentures.
7. History of medical disorders (severe psychiatric, physiological, or neurological conditions).