Ultrasonography and magnetic resonance imaging (MRI) are used in researches to measure the thickness of masseter muscles and study the cross section and condition of masseter in recently. Ultrasonography helps diagnosing temporomandibular disorder (TMD) when inflammation occurs in masseter muscles.
In order to find out the relationship within factors that can associate TMD-related pains with masseter muscles through ultrasonography, this study analyzes whether the pain surrounding temporomandibular joint (TMJ) muscle is related to the increase in masseter thickness and analyzes the correlation within masseter thickness, pain score, maximum mouth opening, pain duration and TMJ sound to be of help in understanding the correlation between factors.
The subjects of this study were 37 patients with TMD who visited the department of oral and maxillofacial surgery of Mokdong Hospital of Ewha Womans University between June 1, 2017 and August 31, 2019 and measured masseter thickness through ultrasonic imaging.
After applying the selection and exclusion criteria among the 37 patients, total 26 patients selected. Among those were 6 patients with bilateral pain, 18 patients with unilateral pain and 2 painless patients.
The number of TMJ of the 26 patients was total 52 which were divided to 30 TMJs with pain and 22 TMJs without pain. The average masseter thickness of the group with pain was 13.04±2.47mm and that of the group without pain was 14.17±2.20mm. Among 18 patients with pain only in unilateral joint, the average masseter thickness of the group with pain was 13.83±2.63mm and that of the group without pain was 13.84± 2.0lmm. While the average masseter thickness was larger in the patients without pain, although the difference was statistically insignificant.
And the correlation coefficient between the masseter thickness and the Maximum mouth opening showed positive correlation with pain and painless groups. But this was statistically insignificant.
Furthermore, In the relationship between masseter thickness and pain score, except for the case where pain score was the group of patients without pain, at a severe level of pain score, the thickness of the masseter was high. At a level where the pain level was moderate, the thickness of the masseter showed a lowest level. This was not statistically significant.
Masseter thickness was higher in the case where the pain duration was longer than 6 months than in the case where the pain duration was less than 6 months, but the difference was statistically insignificant.
Masseter thickness was higher in the TMJs without TMJ sound compared to the TMJs with TMJ sound. And among the TMJs without TMJ sound, the masseter thickness was higher in the TMJs with pain compared to the TMJs without pain. Here, the results were statistically significant. That is, it was found that regarding the relationship with the TMJ sound which showed statistically significant difference, the condition in which there is pain but no TMJ sound was associated with the increase in masseter thickness.
Within the limitation of this study, the relation between the existence of pain in the muscles surrounding TMJ and masseter thickness was confirmed. Hopefully, such result will be of help in understanding the relevance of the factors that can be associated with masseter muscles in TMJ diagnosis using ultrasonic imaging and in setting up guidelines regarding the use of ultrasonic imaging for TMJ.