Determining the Relationship Between Posture, Muscle Stiffness, Pain, and Jaw Functionality in Individuals With Bruxism (Bruxism)

Determining the Relationship Between Posture, Muscle Stiffness, Pain, and Jaw Functionality in Individuals With Bruxism: A Comparative Cross-Sectional Study

Bruxism is a repetitive jaw-muscle activity characterized by teeth clenching and/or grinding, often associated with temporomandibular joint dysfunction, pain, and impaired jaw function. This cross-sectional comparative study aims to investigate the relationship between jaw functionality, posture, muscle stiffness, pain, perceived stress, and sleep quality in young adults with bruxism. A total of 48 participants will be included: 24 individuals with clinically confirmed bruxism and 24 healthy controls.

Clinical and sociodemographic characteristics will be recorded using a Bruxism Assessment Form developed by dentists and physiotherapists. Posture will be assessed with the PostureScreen Mobile® application; pain intensity and thresholds will be measured using a digital algometer; masseter, temporalis, and trapezius muscle stiffness will be evaluated with a MyotonPro device. Perceived stress will be assessed using the Perceived Stress Scale-10, sleep quality with the Epworth Sleepiness Scale, and functional jaw limitation with the Jaw Functional Limitation Scale-20.

Statistical analysis will be performed using SPSS (Version 20.0). Between-group comparisons will be made using t-tests or Mann-Whitney U tests depending on distribution. Correlation analyses (Pearson or Spearman) will be used to evaluate associations among variables.

The primary outcome is to determine the relationship between jaw functionality, posture, muscle stiffness, and pain in individuals with bruxism. Secondary outcomes include the associations of sleep quality and perceived stress with these parameters. This study will provide novel insights into the multidimensional impact of bruxism and may guide future preventive and rehabilitative strategies.

Study Overview

• Status: Completed
• Conditions: Bruxism; Sleep Quality; Muscle Stiffness; Posture; Pain Assessment
• Intervention / Treatment: Other: Bruxism Assessment Form; Other: Clinical Examination; Other: Patient Evaluation Form; Other: Perceived Stress Scale-10; Other: Posture Assessment; Other: Muscle Stiffness Assessment; Other: The Epworth Sleepiness Scale (ESS); Other: Jaw Function Limitation Scale-20 (MFFS-20); Other: Pain threshold assessment

Detailed Description

Bruxism is a repetitive jaw-muscle activity, characterized by teeth clenching or grinding, that may occur during sleep or wakefulness. It is associated with temporomandibular disorders, increased muscle activity, pain, impaired jaw function, and reduced quality of life. Although bruxism has been linked to psychological factors such as stress and sleep disturbances, the relationship between jaw functionality, posture, muscle stiffness, and pain remains unclear.

This cross-sectional comparative study will include 48 young adults, consisting of 24 individuals with clinically confirmed bruxism and 24 age-matched healthy controls. Participants will undergo a comprehensive evaluation process. Bruxism will be confirmed by a dental specialist through clinical examination combined with a standardized Bruxism Assessment Questionnaire. Clinical and sociodemographic data will be collected with a patient assessment form.

Outcome measures will include:

Posture assessment: PostureScreen Mobile® application, using standardized digital imaging.

Pain assessment: Pain intensity and thresholds measured with a digital algometer on masseter, temporalis, trapezius muscles, and temporomandibular joint regions.

Muscle stiffness: Quantified with the MyotonPro device on jaw and neck muscles.

Perceived stress: Evaluated using the Perceived Stress Scale-10.

Sleep quality: Assessed with the Epworth Sleepiness Scale.

Jaw functionality: Evaluated with the Jaw Functional Limitation Scale-20.

Data will be analyzed with SPSS (Version 20.0). Normality will be tested with Shapiro-Wilk. Depending on distribution, parametric or non-parametric tests (Independent Samples t-test, Mann-Whitney U test) will be applied for between-group comparisons. Correlation analyses (Pearson or Spearman) will explore associations among variables. A significance level of p<0.05 will be adopted.

The primary objective is to determine the relationship between jaw functionality, posture, muscle stiffness, and pain in individuals with bruxism. The secondary objective is to examine the impact of perceived stress and sleep quality on these parameters and to compare findings with a healthy control group.

This study is expected to fill a gap in the literature by providing evidence on the multifactorial associations between bruxism, postural control, muscle characteristics, and psychosocial factors. Findings may contribute to the development of multidisciplinary preventive and therapeutic strategies in dentistry, physiotherapy, and rehabilitation.

• Study Type: Observational
• Enrollment (Actual): 50

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Istanbul, Turkey (Türkiye)
    • Istanbul Kent University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

In the literature, a moderate correlation has been found between the jaw functional limitation scale and pain level in temporomandibular joint dysfunction (r=0.3-0.4). Based on the results of the relevant study, G-power analysis was used to calculate the sample size. The expected effect size for our study was considered moderate at 80% power and an alpha value of 0.05 (effect size=0.4), and we planned to include 24 bruxism patients and 24 healthy individuals.

Description

Inclusion Criteria:

• Individuals diagnosed with bruxism following a physical examination and assessment questionnaire administered by a specialist dentist were included in the study.
• Being between the ages of 18 and 30
• Having jaw pain that has persisted for at least 3 months
• Patients who described pain in the face, temporal region, or ear, and who had pain detected in the masticatory muscles upon palpation.
• Volunteering to participate in the study
• Cooperative individuals with whom mutual communication is possible
• Literate

Exclusion Criteria:

• History of surgery or trauma to the maxillofacial region
• Active infection in the maxillofacial region
• Presence of cysts, tumors, or malignant pathologies affecting the TMJ region and muscles
• Presence of systemic rheumatic disease or musculoskeletal diseases affecting the bones
• Presence of any neurological problem that would preclude evaluations
• Diagnosis of any psychiatric disorder
• Receiving physiotherapy or other treatment methods for the TMJ or cervical spinal region within the last 6 months

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Bruxism; 24 patients diagnosed with bruxism will be included.	Other: Bruxism Assessment Form; To determine the presence of bruxism, the Bruxism Assessment Questionnaire, adapted from internationally accepted scales, will be administered. The questionnaire includes seven questions regarding both sleep and daytime bruxism. The questions were developed based on similar studies. Based on their responses, participants will be classified as having a low, moderate, or high risk of bruxism.; Other Names: Bruxism Assessment Questionnaire; Other: Clinical Examination; Participants will undergo a detailed clinical examination by a dentist to diagnose bruxism. The clinical evaluation will be based on the following parameters: a dental examination, a muscle examination, and a jaw joint examination. The dental examination will assess tooth wear, cervical wear, scalloping at the edge of the tongue, the presence of linea alba in the buccal mucosa, and palpation of the masseter, temporalis, and suprahyoid muscles. The jaw joint examination will assess the diagnosis and severity of bruxism by combining mouth opening, clicking or crepitation in the jaw joint, clinical examination findings, and questionnaire scores. Based on the questionnaire and clinical examination results, participants will be divided into three groups: "Probable no bruxism," "Possible bruxism," and "Definite bruxism." A healthy group (n=24) will be formed from the "Probable no bruxism" group, and a patient group (n=24) will be formed from the "Definite bruxism" group.; Other: Patient Evaluation Form; The patient evaluation form, developed by the researchers, will be evaluated in detail by the Specialist Dentist after the diagnosis is made. The patient will include the clinical characteristics of the disease, the patient's sociodemographic characteristics, the presence of a chronic or systemic disease, any medications used, the presence of deflection or deviation during mandibular depression, joint noise, the presence of trigger points in the masseter and temporal regions, jaw pain intensity using the Visual Analog Scale (upon waking, during eating, after eating, at bedtime, and temporal headache), and mandibular joint range of motion (painless, maximal, maximal assisted, right lateral and left lateral flexion, and protrusion) using a 10-cm ruler and digital calipers.; Other: Perceived Stress Scale-10; The Perceived Stress Scale-10 (PSS-10) questionnaire will be used to assess stress levels. The PSS-10 was developed by Cohen, Kamarck, and Mermelstein (1983). The PSS-10 is a 10-item self-report instrument designed to measure how unpredictable, uncontrollable, and stressful participants perceive their lives to be in the past month. Participants rate each item on a 5-point Likert-type scale ranging from "Never (0)" to "Very often (4)." Total scores range from 0 to 40, with higher scores indicating higher perceived stress levels. Items 6, 7, 9, and 10 are reverse-scored. Its validity and reliability in Turkish were conducted by Eskin et al.; Other Names: Perceived Stress Scale; Other: Posture Assessment; The PostureScreen Mobile® app will be used to assess posture in a standing position. This app is specifically designed for healthcare professionals who want to objectively assess patients' posture, movement, and body composition. The app calculates a total of thirty-nine variables using images taken from four different angles. It generates an output file containing the calculated values for posture variables and provides visuals showing the positions of the digitized points relative to normal posture. For the posture assessment, participants will be positioned at a designated marked point and asked to stand in a comfortable, neutral posture. Photographs of each participant will be taken from four different angles using the iPad camera. Researchers will take each photo from a distance of 8 feet (approximately 2.4 meters) from the participant. The camera height is not standardized and will be adjusted according to the participant's height.; Other Names: Posture; Other: Muscle Stiffness Assessment; Muscle stiffness will be assessed using the Myoton Digital Muscle Palpation Device in the masseter, upper trapezius, and temporalis muscles.; Other: The Epworth Sleepiness Scale (ESS); The Epworth Sleepiness Scale (ESS) was developed by Johns and will be used to assess sleepiness in patients. The ESS is a four-point Likert-type scale. It is scored as 0, 1, 2, or 3, with higher scores indicating increased sleepiness. A score of 0-5 indicates normal daytime sleepiness, 6-10 indicates normal but increased daytime sleepiness, 11-12 indicates increased but moderate daytime sleepiness, 13-15 indicates increased moderate daytime sleepiness, and 16-24 indicates increased severe daytime sleepiness. The ESS is a valid and reliable scale for assessing overall sleepiness levels and can be used in studies on sleep and sleep disorders in Turkey (Cronbach's alpha = 0.86).; Other Names: The Epworth Sleepiness Scale; Other: Jaw Function Limitation Scale-20 (MFFS-20); The MFFS-20 questionnaire will be used to measure jaw function and limitations during various activities. The scale includes 20 items in the areas of chewing, vertical jaw mobility, and verbal and emotional expression. Items 1-6 address chewing, items 7-10 address vertical jaw mobility, and items 11-20 address verbal and emotional expression of limitations. Patients will be assessed for their limitations on each item using a numerical rating scale of 0 to 10. "0" corresponds to no limitation, and "10" corresponds to severe limitation.; Other: Pain threshold assessment; Participants' pain sensitivity to pressure will be assessed using an algometer. A digital algometer (Commender Jtech Medical 801-478 USA) will be used for the assessment. The algometer will measure three times on the body of the masseter muscle, the anterior part of the temporalis muscle, the upper trapezius muscle, and the temporomandibular joint. The algometer will be placed perpendicular to these points, and participants will be asked to report the first time they experience pain. The average of the readings on the display will be read, and the pain threshold will be recorded in pounds (1kg = 2.2 pounds).
Healthy; 24 healthy individuals will be included	Other: Bruxism Assessment Form; To determine the presence of bruxism, the Bruxism Assessment Questionnaire, adapted from internationally accepted scales, will be administered. The questionnaire includes seven questions regarding both sleep and daytime bruxism. The questions were developed based on similar studies. Based on their responses, participants will be classified as having a low, moderate, or high risk of bruxism.; Other Names: Bruxism Assessment Questionnaire; Other: Clinical Examination; Participants will undergo a detailed clinical examination by a dentist to diagnose bruxism. The clinical evaluation will be based on the following parameters: a dental examination, a muscle examination, and a jaw joint examination. The dental examination will assess tooth wear, cervical wear, scalloping at the edge of the tongue, the presence of linea alba in the buccal mucosa, and palpation of the masseter, temporalis, and suprahyoid muscles. The jaw joint examination will assess the diagnosis and severity of bruxism by combining mouth opening, clicking or crepitation in the jaw joint, clinical examination findings, and questionnaire scores. Based on the questionnaire and clinical examination results, participants will be divided into three groups: "Probable no bruxism," "Possible bruxism," and "Definite bruxism." A healthy group (n=24) will be formed from the "Probable no bruxism" group, and a patient group (n=24) will be formed from the "Definite bruxism" group.; Other: Patient Evaluation Form; The patient evaluation form, developed by the researchers, will be evaluated in detail by the Specialist Dentist after the diagnosis is made. The patient will include the clinical characteristics of the disease, the patient's sociodemographic characteristics, the presence of a chronic or systemic disease, any medications used, the presence of deflection or deviation during mandibular depression, joint noise, the presence of trigger points in the masseter and temporal regions, jaw pain intensity using the Visual Analog Scale (upon waking, during eating, after eating, at bedtime, and temporal headache), and mandibular joint range of motion (painless, maximal, maximal assisted, right lateral and left lateral flexion, and protrusion) using a 10-cm ruler and digital calipers.; Other: Perceived Stress Scale-10; The Perceived Stress Scale-10 (PSS-10) questionnaire will be used to assess stress levels. The PSS-10 was developed by Cohen, Kamarck, and Mermelstein (1983). The PSS-10 is a 10-item self-report instrument designed to measure how unpredictable, uncontrollable, and stressful participants perceive their lives to be in the past month. Participants rate each item on a 5-point Likert-type scale ranging from "Never (0)" to "Very often (4)." Total scores range from 0 to 40, with higher scores indicating higher perceived stress levels. Items 6, 7, 9, and 10 are reverse-scored. Its validity and reliability in Turkish were conducted by Eskin et al.; Other Names: Perceived Stress Scale; Other: Posture Assessment; The PostureScreen Mobile® app will be used to assess posture in a standing position. This app is specifically designed for healthcare professionals who want to objectively assess patients' posture, movement, and body composition. The app calculates a total of thirty-nine variables using images taken from four different angles. It generates an output file containing the calculated values for posture variables and provides visuals showing the positions of the digitized points relative to normal posture. For the posture assessment, participants will be positioned at a designated marked point and asked to stand in a comfortable, neutral posture. Photographs of each participant will be taken from four different angles using the iPad camera. Researchers will take each photo from a distance of 8 feet (approximately 2.4 meters) from the participant. The camera height is not standardized and will be adjusted according to the participant's height.; Other Names: Posture; Other: Muscle Stiffness Assessment; Muscle stiffness will be assessed using the Myoton Digital Muscle Palpation Device in the masseter, upper trapezius, and temporalis muscles.; Other: The Epworth Sleepiness Scale (ESS); The Epworth Sleepiness Scale (ESS) was developed by Johns and will be used to assess sleepiness in patients. The ESS is a four-point Likert-type scale. It is scored as 0, 1, 2, or 3, with higher scores indicating increased sleepiness. A score of 0-5 indicates normal daytime sleepiness, 6-10 indicates normal but increased daytime sleepiness, 11-12 indicates increased but moderate daytime sleepiness, 13-15 indicates increased moderate daytime sleepiness, and 16-24 indicates increased severe daytime sleepiness. The ESS is a valid and reliable scale for assessing overall sleepiness levels and can be used in studies on sleep and sleep disorders in Turkey (Cronbach's alpha = 0.86).; Other Names: The Epworth Sleepiness Scale; Other: Jaw Function Limitation Scale-20 (MFFS-20); The MFFS-20 questionnaire will be used to measure jaw function and limitations during various activities. The scale includes 20 items in the areas of chewing, vertical jaw mobility, and verbal and emotional expression. Items 1-6 address chewing, items 7-10 address vertical jaw mobility, and items 11-20 address verbal and emotional expression of limitations. Patients will be assessed for their limitations on each item using a numerical rating scale of 0 to 10. "0" corresponds to no limitation, and "10" corresponds to severe limitation.; Other: Pain threshold assessment; Participants' pain sensitivity to pressure will be assessed using an algometer. A digital algometer (Commender Jtech Medical 801-478 USA) will be used for the assessment. The algometer will measure three times on the body of the masseter muscle, the anterior part of the temporalis muscle, the upper trapezius muscle, and the temporomandibular joint. The algometer will be placed perpendicular to these points, and participants will be asked to report the first time they experience pain. The average of the readings on the display will be read, and the pain threshold will be recorded in pounds (1kg = 2.2 pounds).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Jaw Functional Limitation Total Score Assessed Using the 20-Item Jaw Functional Limitation Scale (JFLS-20)	Jaw functional limitation will be assessed using the 20-Item Jaw Functional Limitation Scale (JFLS-20). The outcome measure will be the total JFLS-20 score, ranging from 0 to 10 (mean global score; 0 = no limitation, 10 = severe limitation). Higher scores indicate greater jaw functional limitation (worse outcome).	At baseline (study enrollment)
Pain Intensity and Pain Threshold	Pain intensity will be assessed using the Visual Analog Scale (VAS), recorded as a score on a 0-10 cm (veya 0-100 mm, hangisini kullanıyorsanız) scale, with higher scores indicating greater pain intensity.Pressure pain threshold will be assessed using a digital algometer and recorded as pressure values (kg/cm², N/cm², ya da kullandığınız birim ne ise onu yazın), with higher values indicating higher pain threshold.	At baseline
Postural Alignment Parameters Assessed Using the PostureScreen Mobile® Application	Postural alignment parameters, including head position, shoulder alignment, spinal posture, and pelvic alignment (uygun olanları siz düzenleyin), will be quantitatively assessed using the PostureScreen Mobile® application.	At baseline
Muscle Stiffness (N/m) of the Masseter, Temporalis, and Trapezius Muscles Assessed Using the MyotonPRO Device	Muscle stiffness will be quantitatively assessed in the masseter, temporalis, and trapezius muscles using the MyotonPRO handheld myotonometer. Stiffness will be recorded in Newtons per meter (N/m) as the primary biomechanical parameter used for evaluation.	At baseline

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sleep Quality	Daytime sleepiness will be assessed using the Epworth Sleepiness Scale (ESS). The outcome measure will be the total ESS score (range 0-24), with higher scores indicating greater daytime sleepiness.	At baseline
Perceived Stress	Perceived Stress Scale-10 (PSS-10) score	At baseline

Collaborators and Investigators

• Sponsor: Istanbul Kent University
• Investigators: Principal Investigator: Emine Nur Demircan, Asst. Prof., Istanbul Kent University; Study Director: Berfin Erdemli, Res. Asst., Istanbul Kent University; Study Director: Melis Usul, Res. Asst., Istanbul Kent University; Study Director: Ozge Okcu, Asst. Prof., Istanbul Kent University; Study Director: Fatma Yüce, Asst. Prof., Istanbul Kent University

Publications and helpful links

General Publications

• Izci B, Ardic S, Firat H, Sahin A, Altinors M, Karacan I. Reliability and validity studies of the Turkish version of the Epworth Sleepiness Scale. Sleep Breath. 2008 May;12(2):161-8. doi: 10.1007/s11325-007-0145-7.
• Szucs KA, Brown EVD. Rater reliability and construct validity of a mobile application for posture analysis. J Phys Ther Sci. 2018 Jan;30(1):31-36. doi: 10.1589/jpts.30.31. Epub 2018 Jan 27. PMID: 29410561; PMCID: PMC5788770.
• Xiong X, Xiao CQ, Yang YC, Li YJ, Cheng QY, Wang XY, Liu Y. Temporomandibular disorder patients with excessive daytime sleepiness present greater pain intensity and reduced jaw function. J Oral Rehabil. 2024 Apr;51(4):639-647. doi: 10.1111/joor.13639. Epub 2023 Dec 15.

Study record dates

Study Major Dates

• Study Start (Actual): October 15, 2025
• Primary Completion (Actual): November 30, 2025
• Study Completion (Actual): April 15, 2026

Study Registration Dates

• First Submitted: September 27, 2025
• First Submitted That Met QC Criteria: April 28, 2026
• First Posted (Actual): May 1, 2026

Study Record Updates

• Last Update Posted (Actual): May 1, 2026
• Last Update Submitted That Met QC Criteria: April 28, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Posture; Sleep Quality; Young Adults; Bruxism; Epworth Sleepiness Scale; Pain Threshold; Perceived Stress; Temporomandibular Joint Disorders; Muscle Stiffness; Algometry; MyotonPro; Jaw Function; Jaw Functional Limitation Scale (JFLS-20); PostureScreen Mobile; Comparative Cross-Sectional Study
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Stomatognathic Diseases; Nervous System Diseases; Muscular Diseases; Mental Disorders; Joint Diseases; Jaw Diseases; Tooth Diseases; Sleep Wake Disorders; Mandibular Diseases; Sleep Disorders, Intrinsic; Dyssomnias; Craniomandibular Disorders; Behavior; Habits; Bruxism; Sleep Initiation and Maintenance Disorders; Temporomandibular Joint Disorders; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena; Investigative Techniques; Therapeutics; Behavior Control; Immobilization; Restraint, Physical; Posture; Perceived Stress Scale
• Other Study ID Numbers: IstanbulKentU (Other Identifier: IstanbulKentU)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No