Relationship Between Wind Instrument Playing Habits and Symptoms of Temporomandibular Disorders in Non-Professional Musicians

Subjects and Data Collection

We recruited 72 wind instrumentalists (instrument group) who belonged to the orchestras of 3 universities in Tokyo, and 66 non-players (control group) who were similar to the instrument group in age and sex, enrolled at Tokyo Medical and Dental University, and had not played any musical instrument within 1 y.

This cross-sectional study was performed using an anonymous questionnaire with the approval (No. 997) of the ethics committee of the Tokyo Medical and Dental University, Japan. After the purpose and contents of the study questionnaire were explained before the study commenced, questionnaires were distributed to all subjects, and completed questionnaires were collected afterward. Written informed consent was not obtained because the identification of individuals was not required; answering the questionnaire was considered consent to participate.

Questionnaire

The administered questionnaire is shown in Table 1. Sex, age, and responses to items 1-10 were recorded. Items 1-4 are questions related to screening for TMD (screening questionnaire for TMD: SQ-TMD) that were developed by Sugisaki et al. [12]. The subjects rated the 4 screening items using a 5-point numeric rating scale (0 to 4).

The other 6 items were used to investigate factors related to playing wind instruments. Items 5-8 solicited information about habits while playing instruments, and the subjects were asked to rate these 4 question items using a 5-point numeric rating scale. Items 9 and 10 solicited information about years of experience and playing time per day.

Statistical Analysis

On the SQ-TMD, participants with a score ≥ 5.0 were assigned to the high risk of TMD (H-TMD) group, whereas those with a score ≤ 4.0 were assigned to the low risk of TMD (L-TMD) group.

The statistical analysis compared the instrument and control groups using Student’s t tests and chi-squared tests. Comparisons between the H-TMD group and L-TMD group were performed in the instrument group using Student’s t tests and chi-squared tests. For the item concerning habits while playing instruments, participants with a score ≤ 3 were assigned a value of “0 (low frequency),” whereas those with a score ≥ 4 were assigned a value of “1 (high frequency).”

In the instrument group, factors influencing the H-TMD were estimated using a logistic regression analysis with odds ratios (ORs) and 95% CIs as measures of association. The dependent variable was the result of the screening for TMD (L-TMD, 0; H-TMD, 1). Meanwhile, the independent variables were age, sex, years of experience, playing time per day, and various habits while playing instruments (low frequency, 0; high frequency, 1). The covariates were entered into the logistic regression analysis with a forward stepwise technique; P < 0.05 was considered statistically significant. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) (version 21.0, IBM, Tokyo, Japan).

Screening Questionnaire for TMD

The SQ-TMD used in this study was developed by Sugisaki et al. [12]. They extracted 4 items from a 20-item questionnaire administered to dental patients. When the cut-off value for the total score from these 4 items was 4.5, the sensitivity, specificity, and false-positive rate derived from the screening for TMD were 0.746, 0.811, and 0.189, respectively [12]. From these results, participants with a score ≥ 5.0 were assigned to the H-TMD group, whereas those with a score ≤ 4.0 were assigned to the L-TMD group. One item related to joint noise was omitted from the screening questionnaire, as an analysis using non-parametric item response theory (a Mokken analysis) showed that the validity of the 4 included items was higher than that of the 5 items. Nishiyama et al. [13] showed that the true-positive rate of detecting TMD (based on the Research Diagnostic Criteria for TMD: RDC/TMD) using the SQ-TMD was very high (81.6%), and the SQ-TMD could be used to screen for TMD in patients with moderate or severe pain and difficulty completing activities of daily living.

Comparison Between the Instrument and Control Groups

In this study, the prevalence of the H-TMD among all subjects was 25.4%. According to the SQ-TMD survey results of a working population of 2203 subjects, the prevalence of the H-TMD was 16.4% [9]. It was reported that TMD were a significant public health problem affecting approximately 5% to 12% of the population [2], and the prevalence among those younger than 30 years was higher than in those older than 30 years [14, 15]. Our result was consistent with the results of these studies. In this study, all participants were younger than 30 years of age. The ages of the participants were considered as one of the reasons for the high incidence of TMD.

The prevalence of the H-TMD in the instrument group (29.1%) was greater than that in the control group. Hada et al. [14] reported that the prevalence of TMD among wind instrumentalists was 31.5%. However, there was no statistically significant difference in our study. Few studies have investigated the relationship between playing wind instruments and TMD. Rampel et al. [16] reported that wind musicians showed a high incidence of developing TMD. On the other hand, Gotouda et al. [17] showed that the contractive load on jaw-closing muscles was small when playing both medium and high tones on a wind instrument, and playing an instrument for a long duration did not induce fatigue in the jaw-closing muscles.

Instrument Group

It is thought that trauma and habitual behaviors that burden the TMJ and masticatory muscles influence the development of TMD. Behavioral factors can include parafunctional habits, such as playing a musical instrument. Especially, wind instruments could overload the masticatory muscles and orofacial skeletal system, thereby possibly causing TMD or worsening existing TMD [10].

In the instrument group, the habit of strongly pressing the mouthpiece (or lead) to the lips was found to be a significant factor contributing to the manifestation of TMD. The mandible is pushed posteriorly by pressing the mouthpiece to the lip. It was considered that the duration of this pressure caused an overload of the TMJ or masticatory muscles. There is a report stating that the contractive load on jaw-closing muscles was small when playing a wind instrument [17]. However, participants in that study were professional musicians. Because participants in this study were students and non-professional musicians, it was considered that they had not been able to acquire the appropriate embouchure. It is possible that the embouchure during wind instrument playing is different between amateur musicians, professional musicians, and students who aim to become professionals. In many cases, because amateur musicians have not learned the correct embouchure, they may strongly press the mouthpiece (or lead) against their mouth or lip. According to research using a finite element method (FEM) in an anterior disc displacement model of the TMJ, a prolonged force equivalent to 20% of the maximum muscle contraction caused sustained displacement of the condyle, and large stresses were observed in the posterior part of the disc [18]. Because an extension in the duration that a mouthpiece (or lead) presses strongly on the mouth or lip increases the load on the TMJ while playing wind instruments, there is the possibility that it caused TMJ pain.

Limitations of the Study

In this study, a 7% difference in the prevalence of TMD was observed between the instrument and control groups; however, the difference was not significant. The reasons were some limitations of our study. First, this was a cross-sectional study, and the sample size was insufficient (n = 138). G*Power indicated that the ideal sample size would be 144 for an effect size of 0.3, an α-type error of 0.05, and a β-type error of 0.2. In the future, there is a need for further evaluation with improved statistical accuracy in a survey of a greater number of subjects. Second, this was not only a diagnosis made on a clinical and radiographic basis, but also based on the questionnaire analysis.