Cone Beam CT Evaluation of the Bony Changes in the Temporomandibular Joint and the Association with the Clinical Symptoms of Temporomandibular Joint Disorders

Introduction

The temporomandibular joint (TMJ) is a complex joint in the body, which plays a key role in speaking and mastication (1). Temporomandibular disorder (TMD) refers to the disorders that affect the masticatory system, including the muscles, TMJ, and tendons (1). TMD is the most common abnormality of the jaw, and the clinical symptoms are reported in 28-86% of adults and adolescents (2-6). TMD is classically characterized clinical symptoms such as joint noises, pain, and limited or deviated mouth opening (7-9).

Clinical examination alone cannot determine the cause of TMD. In most cases, the cause and a proper treatment plan are determined based on imaging modalities. Some of the imperative techniques for the diagnosis of TMD include a series of clinical examinations, using the Research Diagnostic Criteria for Temporomandibular Disorder (RDC/TMD), and TMJ imaging modalities (10).

Although several imaging techniques have been developed for the examination of TMJ bone changes, there is no general consensus on the best diagnostic imaging technique as a ‘gold standard’ for the tracking and identification of these lesions (11). The most common conventional imaging modalities in this regard are panoramic, submentovertex, transcranial, transpharyngeal, and lateral cephalometric techniques. However, their results often fail to match the clinical symptoms of the patients due to superimpositions and imaging limitations. New techniques, including computerized tomography (CT), magnetic resonance imaging (MRI), and cone beam computed tomography (CBCT) are increasingly used for the assessment of TMJ in order to eliminate the associated superimpositions and produce sectional images (9, 12).

CBCT scanners, which are designed for maxillofacial areas, could provide a spatial resolution of less than one millimeter within a shorter scanning time and low radiation dose compared to CT-scan. Therefore, they are applied in many dental clinics as an effective method for the diagnosis and evaluation of craniofacial problems (13). The application of CBCT has previously been investigated, and its diagnostic effects have also been confirmed for various dentistry purposes, such as endodontic therapy, oral and maxillofacial surgery (14), periodontology (15), restoration (16), and orthodontics.

Although the current literature is indicative of the efficiency of CBCT in evaluating the bone changes associated with TMJ (17), few studies have been focused on the use of this technique for the examination of TMD and its correlation with the bone changes caused by TMJ. The present study aimed to investigate the bone changes in sclerosis, osteophytes, and erosion in the patients with TMD symptoms using CBCT.

Materials and Methods

This retrospective, cross-sectional study was conducted on the patients visiting the Department of Prosthetics and Radiology (TMJ clinic) of the School of Dentistry at Hamadan University of Medical Sciences, Iran. The research protocol was approved by the Ethics Committee of the university (ethics code: IR.UMSHA.REC.1394.324).

The inclusion criteria was the presence of at least one of the symptoms of TMJ, including pain in the TMJ region, restricted mouth opening, joint noises, TMJ reciprocal clicking in vertical opening and closing occurring at a minimum of a five-millimeter distance from the inter-incisal space when opening the mouth (repeated in two of three consecutive tests) (18), clicking during lateral or forward movements (repeated in two of three consecutive tests), crepitus in the TMJ region, and jaw movement deviation (19).

The exclusion criteria of the study were as follows: 1) patients with congenital craniofacial disorders; 2) history of TMJ treatment (e.g., surgery, laser therapy, anti-inflammatory medication, and corticosteroid therapy); 3) history of orthodontic treatments, systemic disorders involving the TMJ (e.g., rheumatoid arthritis, multiple myeloma, scleroderma, and gout) and 4) history of pyogenic arthritis (20, 21).

Initially, the patients presenting with the TMD symptoms were examined by a dental prosthodontist, and the clinical symptoms were recorded in a TMJ checklist. In addition, CBCT imaging was performed on the patients if necessary.

The patients were divided into two groups of normal and restricted based on the pain caused by TMJ, including pain upon touching, using the TMJ, and maximum mouth opening (35-50 mm) (22). Another factor based on which the patients were classified into the mentioned groups was joint noises, including short singular clicking and repetitive rough noises (e.g., crepitus), which were recorded in the checklist of the clinical symptoms (23).

CBCT was performed using a Promax device (PLANMECA, Helsinki, Finland) with the following parameters: KVP=84, general filtration=2.5 millimeters of aluminum, FOV=8×8 cm², matrix size=512×512 pix, scan time=25 seconds, exposure time=12 seconds, and slice thickness=0.5 millimeter. A thyroid shield and a lead apron were used for protection against the radiation of the scanning procedures. The obtained images were reconstructed in the ROMEXIS format and stored in the DICOM format.

The images were initially examined in the sagittal, coronal, and axial planes by two radiologists. The sagittal images of the TMJ portions (condyle, joint cavity, and joint prominence) were assessed in terms of the bone changes caused by the disorder, such as sclerosis, flattening, erosion, and osteophytes. Conventionally, for the mentioned cases to be considered as a change, they have to be observed in at least two consecutive cuts. Bone changes in joints include:

1. Flattening (F), which is the loss of the uniform convexity or concavity of the joint surfaces;

2. Sclerosis (SC), which is the thickening of the cortical bone on the joint surface;

3. Osteophytes (OS), which is the localized bone prominence from the mineralized joint surface;

4. Erosion (E), which is the localized cortical bone rarefaction from the joint surface;

5. Concavity (Con), which is defined as the concavity of the bone contour with a dent;

6.Subcortical cyst (Cyst), which is the round radiolucent area located either underneath the cortical bone or deeper into the bone in the trabeculae (24).

Data analysis was performed in SPSS version 21 (Microsoft, IL, USA) using Chi-square and logistic regression analysis at the significance level of 0.05.

Results

In total, 160 TMJ images obtained from 12 male patients (15%) and 68 female patients (85%) were investigated. The mean age of the patients was 33.38±8.05 years. The majority of the patients were within the age range of 26-35 years (41.3%). Table I shows the frequency of the bone changes in the subjects, including flattening, sclerosis, osteophytes, and erosion. The results of Chi-square regarding the association between the bone-joint changes in the TMJ and pain indicated that the sensation of pain had significant correlations with flattening (P=0.032), sclerosis (P=0.001), and osteophytes (P=0.007).

Contrary to the association between TMJ pain and the mentioned parameters, the correlation between pain and erosion was not considered significant based on the Chi-square test. In addition, the results of Chi-square showed no significant association between the restricted movement of the TMJ and its bone changes (flattening, sclerosis, osteophytes, and erosion) (P>0.05) (Table II).

Logistic regression analysis was used to examine the simultaneous effects of the variables on each other. According to the obtained results, sclerosis was the only variable that could affect TMJ pain with a statistically significant difference (P=0.004) (Table III). Based on the regression model, the following equation could be used to predict the possibility of the occurrence of pain:

It could be stated that the possibility of pain in the patients with a history of sclerosis was 0.266 compared to someone who has no sclerosis.

According to the results of Chi-square, the only significant association was observed between flattening and clicking (P=0.023), and the three other variables had no correlations with clicking (P>0.05) (Table IV). Moreover, our findings indicated that crepitation had significant associations with sclerosis (P=0.001), osteophytes (P=0.009), and erosion (P<0.000). However, no significant correlation was denoted between crepitation and flattening (P>0.005) (Table IV).

Table I. Frequency of Various Bone Changes Observed in Patients

Table II. Contingency Tables Regarding Associations between Pain and Restricted Movement with Bone Changes (Flattening, Sclerosis, Osteophytes, and Erosion)

Table III. Estimation of Parameters in Logistic Regression Model

Table IV. Contingency Tables Regarding Associations between Clicking and Crepitus with Bone Changes (Flattening, Sclerosis, Osteophytes, and Erosion)