Evaluation of Temporomandibular Disorders and Their Association With Tooth Wear Using Digital Methods

This analytical cross-sectional clinical study was conducted at the Department of Prosthodontics, Faculty of Dentistry, Necmettin Erbakan University between November 2024 and May 2025. The study aimed to investigate the relationship between tooth wear, occlusal contact area, and temporomandibular disorders (TMD) using validated diagnostic and digital tools. Ethical approval was granted by the Non-Invasive Clinical Research Ethics Committee of Necmettin Erbakan University (Approval No: 2024/520; Date: 26.12.2024; ID: 22023.R1). Written informed consent was obtained from all participants in accordance with the Declaration of Helsinki.

Sample size was determined using G*Power software (v3.1), with an effect size of f = 0.33, alpha = 0.05, and power = 0.90, indicating that a minimum of 40 participants per group was required. A total of 120 subjects were included.

TMD diagnosis was based on the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), following the 2014 Axis I protocol. Participants were classified into three groups:

None: No signs of TMD M: Muscular pain (myogenic) T: Joint-related pain (arthrogenic) The diagnostic process was based on clinical findings such as pain elicited by jaw movement, muscle palpation, or joint loading. Muscle-related pain was further subclassified according to whether the pain extended beyond anatomical boundaries (local muscle pain, myofascial pain, or referred pain). TMJ-originated pain was defined as pain induced by joint palpation or mandibular movements. TMJ-related headache diagnosis was based on pain elicited in the temporal area via palpation or functional movement.

Pain intensity and interference were assessed using the Graded Chronic Pain Scale Version 2.0 (GCPS v2.0). The Characteristic Pain Intensity (CPI) was calculated as the mean of items 2-4 multiplied by 10. The Interference Score was the mean of items 6-8, also multiplied by 10. Disability points were assigned based on the number of painful days in the past 30 days (item 5), resulting in a total pain grade from 0 (no pain) to 3 (severe pain).

Digital occlusal analysis was performed using the Medit i700 intraoral scanner (Medit Corp., Seoul, South Korea). All scans were taken once in the morning under maximum intercuspation. STL files were analyzed with the Medit Occlusal Analyzer plugin. Occlusal contact area percentages for premolars and molars were calculated, and non-contacting teeth were excluded. The average occlusal contact area per individual was used for statistical evaluation.

Tooth wear classification was performed using the Tooth Wear Evaluation System 2.0 (TWES 2.0) as proposed by Wetselaar et al. Occlusal/incisal and non-occlusal/non-incisal surfaces were graded on a 5-point ordinal scale.

For occlusal/incisal surfaces:

Grade 0: No visible wear Grade 1: Wear within enamel Grade 2: Dentin exposure with ≤1/3 crown height loss Grade 3: Crown height loss >1/3 but <2/3 Grade 4: Crown height loss ≥2/3

For non-occlusal surfaces (oral/vestibular):

Grade 0: No visible wear Grade 1: Wear within enamel Grade 2: Dentin exposure <50% of surface Grade 3: Dentin exposure ≥50% of surface Grade 4: Dentin exposure with total enamel/pulp loss Tooth wear grades were recorded separately for each tooth and surface. For statistical analysis, wear severity was simplified into three categories: no wear, enamel-level wear, and dentin-level wear.

Standardization and blinding were maintained by ensuring all scans and measurements were conducted by the same experienced prosthodontist using the same equipment in a controlled setting. TMD classification, wear evaluation, and pain assessment were carried out independently by different examiners.

Statistical analysis was performed using IBM SPSS Statistics 23. Shapiro-Wilk test assessed the normality of continuous variables. Non-parametric tests were used for non-normally distributed variables. Kruskal-Wallis test and Dwass-Steel-Critchlow-Fligner (DSCF) post hoc test with Bonferroni correction were used for group comparisons. Spearman's rho correlation was used to examine associations between variables. Multinomial logistic regression was applied to identify factors affecting TMD group classification. Ordinal logistic regression assessed the effects of pain level, wear severity, and occlusal contact. The interaction between pain and wear severity on TMD classification was analyzed using Generalized Linear Models (GLM). Statistical significance was set at p < 0.05.

Study limitations include its single-center design, limiting generalizability. Functional occlusal contacts during dynamic movements were not evaluated, and only static intercuspal position was analyzed. Additionally, due to insufficient data in pain Grade 4, this subgroup was excluded from analysis.