Counselling treatment versus counselling associated with jaw exercises in patients with disc displacement with reduction—a single-blinded, randomized, controlled clinical trial

This study is a randomized single-blind clinical trial composed of two groups of 34 patients each, and it was conducted following the Consolidated Standards of Reporting Trials (CONSORT) [19]. This clinical trial was registered at Brazilian Clinical Trials Registry (http://​www.​ensaiosclinicos.​gov.​br/​rg/​RBR-7t6ycp/​) on 26/06/2020. The follow-up period was 30 days. This study was approved by the Research Ethics Committee of the Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), protocol #1.843.016, and conducted in accordance with the Helsinki declaration, revised in 2013.

Patients seeking for treatment at the Surgery and Periodontics Clinic of the UFVJM, with diagnosis of TMD, were recruited for the study. These patients were examined by a professional and those who met the inclusion criteria were invited to participate in the study, after signing a consent form. Those excluded patients were referred to appropriate treatment.

The inclusion criteria were patients aged 18 years or older, complaining of TMJ click (audible) during mouth opening/closing, followed or not by pain in the facial region, who never underwent any type of treatment for TMD’s. Exclusion criteria were: edentulous patients, patients who have already undergone any treatment for TMD’s; those patients with any systemic disease that could cause joint and/or muscle changes; and patients who were undergoing drug treatment for the condition.

This study was carried out at the Surgery and Periodontics Clinic of the UFVJM. A researcher (MAMS), properly calibrated and trained according to the video available on the RDC/TMD website (https://​ubwp.​buffalo.​edu/​rdc-tmdinternational​), was responsible for carrying out all evaluations. Each patient was evaluated in four appointments: baseline, 24 h, seven and 30 days after the interventions. Another researcher was responsible for teaching the participants the jaw exercises and for giving the instructions (counselling).

After the patients’ admissions to the study, a specific clinical form for TMD, the Research diagnostic criteria for TMDs (RDC/TMD) [20], was filled out. At this point, the presence of TMJ clicks was investigated through clinical examination. Pain was analyzed by palpation, and measured based on the RDC/TMD. The patients were asked if the click was causing discomfort. The Oral Health Impact Profile (OHIP-14) questionnaire was also applied [21].

The randomization process was previously conducted by an independent researcher who was blinded to the patients and interventions. Each intervention was written, drawn, and sealed in opaque envelopes before starting the study. The interventions were drawn as “A” for the test group, which received jaw exercises and counselling, and “B” for the control group, which received only counselling program. Only the researcher responsible for the interventions knew the envelope content. The numbers corresponding to the patients and the interventions (classified as “A” and “B”) were placed in opaque envelopes. Thus, each patient had their corresponding numbers placed on the envelopes along with the intervention, assigned by lottery. Each patient received the allocated intervention, which was taken from the envelope at the appointment time, and the clinician only knew the intervention to be applied at the time to execute it. The allocation remained hidden until the time of the intervention. The interventions were always executed by the same researcher, who did not participate in the evaluations.

The patients were divided into two groups: the test group received a counselling program (Table 1) [22] plus jaw exercises (Table 2) [23], and the control group received only counselling. All exercises were instructed to be performed in a total of 20 repetitions, thrice a day, with no pre-established time restriction for each repetition, every day until the end of the research. The instructions for the counselling program and jaw exercises were read and explained in a standardized way by the same researcher. In addition, the patients received all written instructions.

The RDC/TMD questionnaire for muscle and joint palpation at specific points, which uses a pain scale from zero to three (0: pressure only; 1: mild pain; 2: moderate pain; 3: severe pain), was applied in the baseline and 24 h, seven and 30 days after the interventions. At each evaluation, the patients were asked if the pain level was “better”, “worse” or “the same” in relation to the previous evaluation, and if the click was still making them uncomfortable.

The sample size calculation was based on the following parameters: the standard deviation obtained from pain intensity through the visual analogic scale (13.1 mm) [18]; the difference stipulated between groups, which was 9 mm; a significance level of 95%; and a power of 80%. Thus, it was required 34 participants per group in the study.

There are limitations to be considered in this study: the absence of a group treated only with exercises and a control group without any treatment. The latter would probably not be approved by the University Research Ethics Committee due to the presence of patients with pain. Therefore, it was decided for a group with orientations/ counselling.

The follow-up period may also be seen as a limitation, as some studies suggest a follow-up of more than 30 days to assess the therapies effectiveness [18, 26]. However, this randomized clinical trial showed significant results within 30-days.

Regarding pain, it is also important to consider that the clinical improvement of the DDWR can be attributed to the cyclical aspect of the dysfunction itself [34], or even an improvement due to the simple fact that the patient was included in a clinical trial, phenomenon known as the Hawthorne effect [35]. In other patients, the pain may have a reason other than DDWR.

This clinical trial has a high external validity because it evaluates therapeutic approaches easy to conduct and can be taught and monitored remotely [18, 36]. In the current global pandemic stage, with the restrictions of human proximity and mobility imposed by the consequences of the Sars-CoV-2, these treatment options become even more valid and useful [37]. Moreover, the low number of clinical trials comparing the two therapeutic approaches for DDWR, with high methodological rigor, make this study relevant [38]. The treatment evaluated herein demonstrated to be efficient, easy to understand, low cost, and it can be used by clinicians as a viable alternative therapy. Future research on this subject must focus on negative control group comparison and a long follow-up [39].