Aims. The diagnosis of headache attributed to temporomandibular disorder (HATMD) was included in the international classification of headaches in 2004. Given the causal relationship between temporomandibular disorders (TMD) and HATMD, it is supposed that HATMD should respond to TMD treatment.
This study aimed to determine whether occlusion splints and/or incobotulinum toxin A injections can effectively treat HATMD.
Subjects and methods. The sample consisted of 126 consecutive adult patients referred for TMD to the Department of Dental Prosthetics (Division of Stomatology, University Medical Center Ljubljana) and were diagnosed with HATMD according the International Classification of Headache Disorders 3rd Edition (ICHD-III).
Patients with HATMD were randomly divided into four groups and received therapy. Therapeutic options included counselling for all, the first group received a Michigan splint and incobotulinum toxin A injections, the second group received a Michigan splint and placebo injections, the third group received a cognitive splint and incobotulinum toxin A injections, and the fourth group received a cognitive splint and placebo injections. Counselling included instructions on avoiding stressful situations, eating soft food, chewing on both sides, and light aerobic exercise (light running, walking, etc.). Thermoformed occlusal and placebo splints were fabricated using vacuum-formed foils. The placebo splint was made without raising the bite, the teeth were in contact, and the splint did not cover the occlusal surfaces. A qualified neurologist administered incobotulinum toxin A or placebo injections into the temporal and masseter muscles. The incobotulinum toxin A injection protocol in the temporalis muscle to treat TMM was 20 units symmetrically, and in the masseter muscle, 30 units symmetrically in each muscle. The effectiveness of HATMD treatment was evaluated by the patient's self-assessment of oral health-related quality of life, sleep quality, pain, depression, anxiety, somatization with Slovenian versions of questionnaires on the day of the first examination, on the day of the treatment, one month and three months after splint insertion and/or incobotulinum toxin A or placebo injection respectively. At the same time, TMD status was evaluated with the Axis I of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) protocol in the same periods after splint insertion and/or incobotulinum toxin A or placebo injection respectively.
The differences between the groups were checked with the Kruskal-Wallis test or, in the case of descriptive variables, with the chi-square test or the Fisher exact test. The correlation between the questionnaires’ scores and groups and treatment time was analysed with a linear mixed model, by which the patients were included as a random factor and time and group as a fixed factor. The confidence interval was set at 95%. The analysis was performed using software R 4.1.3 (R Foundation for Statistical Computing, Vienna, Austria).
Results. The study was completed by 122 patients (4.8 % dropout). Randomization into four groups was successful, as no statistically significant differences were detected between the groups in the demographic variables. After clinical examination according to the DC/TMD protocol, patients were diagnosed with: myalgia (100% of patients), TMM headache (100% of patients), myofascial pain (29% of patients), right TMJ arthralgia (28% of patients), left TMJ arthralgia (30% of patients). Based on clinical examination and magnetic resonance imaging of the jaw joints, we also made individual diagnoses of the jaw joints; the left (24% of patients) and right jaw joints (26% of patients) had disc displacement with reduction and degenerative changes in the jaw joints, more in the right (13% of patients) than in the left (9.8% of patients) jaw joints.
Pain on palpation at three sites on each masseter and three sites on each temporal muscle was statistically significantly lower in all groups at the third examination compared with the first examination, but the differences between the control and the remaining groups were not statistically significant.
Self-assessment of headache on a three-point scale showed improvement in all three groups in comparison with the control group, but no statistically significant differences were detected between the groups measured at different time intervals.
The results of psychometric tests were evaluated in four-time periods, and in all questionnaires used, there was a statistically significant improvement in the whole sample compared to the one-month assessment after therapy, as well as three months after therapy. Compared with the control group, sleep quality improved statistically significantly only in the Michigan splint group. Compared with the control group, oral health-related quality of life improved statistically significantly only in the Michigan splint group. For the other questionnaires’ scores, there were no statistically significant differences between the groups.
Conclusion. In the whole sample, there were statistically significant improvements in all constructs, i.e., oral health-related quality of life, sleep quality, chronic pain, depression, anxiety, and somatization, but we did not demonstrate a statistically significant difference between both treatment modalities.
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