Evaluation of the Stomatognathic System before and after Osteopathic Manipulative Treatment in 120 Healthy People by Using Surface Electromyography

Participants

• Number: 120 people (73 female and 47 male, mean age 25.6 years)
• Criteria of inclusion: absence of the following conditions: orthodontic therapy, ongoing or during the previous year, temporomandibular disorders, pain of the oral cavity, ongoing or during the previous year, mobile prosthesis, bite, surgery or accidents during the previous 6 months; presence of at least 24 healthy teeth
• Groups of study: three groups obtained by randomization
  • Group 1: OMT, 40 people (28 female and 12 male)
  • Group 2: sham treatment, 40 people (23 female and 17 male)
  • Group 3: control, 40 people (22 female 18 male)

Interventions and evaluations

• At the beginning of the study, extraoral and intraoral assessment of the stomatognathic system to highlight asymmetries, malocclusions, bite alterations and other dysfunctions, in particular related to the movements of the mandible and of the temporomandibular articulation according to the criteria proposed by the Italian Association of Gnathology
• Evaluation of the masticatory muscles activity with sEMG before and after the intervention
  • at any evaluation the tests carried out were 4:
    1) sitting with eyes closed in maximum voluntary clenching on cotton rolls;
    2) sitting with eyes open in maximum voluntary clenching on cotton rolls;
    3) orthostatic position with eyes open in maximum voluntary clenching on cotton rolls;
    4) sitting with closed eyes in maximum voluntary clenching
• Each person underwent an osteopathic assessment to evaluate their posture in a static position
• Only 1 30-minutes single session of OMT, sham treatment or control
• OMT: treatment with three standardized techniques (techniques of direct inhibition of the masseter muscles, the temporal muscles and external and internal pterygoid muscles) and 3 techniques chosen by the operator on the basis of the characteristics of the person treated
• Sham treatment: fictitious treatment
• Control: no treatment (wait)

Results

• Primary outcomes: in the OMT group, 40% of people showed statistically significant changes. In particular, there was an improvement (greater symmetry) in the temporalis muscles activity in all positions and in the masseters in orthostatic position, as well as in the occlusal center of gravity and in the balance of muscle activity between temporalis and masseters.
  The sham treatment, on the other hand, seems to have induced statistically significant effects only in 7.5% of people with regard to the muscular effort, although remaining within the physiological range, and on the activity of the temporalis muscles, which, nevertheless, worsened. In the control group, despite remaining within the physiological ranges, statistically significant results emerged in 17.5% of people regarding muscle symmetry, balance between temporalis muscles and masseters, and occlusal center of gravity.
• Further analysis: the effect size (the relevance of the result obtained) was calculated between the various interventions and, consequently, the power of the study: the sham treatment had an effect size of 0.42 (power = 0.62) compared to the control, the OMT had an effect size of 0.19 (power = 0.18) compared to sham treatment and of 0.51 (power = 0.80) compared to the control.

Discussion

Compared to the sham treatment and to the control group, the OMT induced significant changes in muscle activity in a greater number of people, taking into account that all these changes were of a meliorative nature. On the contrary, in the other groups there were more worsenings than improvements in the muscular activity of the stomatognathic system.

The reason for these worsenings may lie in the psychological-emotional stress due to the tests carried out as well as in the wait for more of them to come. In fact, it is reported in the related literature that psychological factors, together with initial pain and diagnosis, are important prognostic factors for the treatment of temporomandibular disorders.

It is also interesting the result obtained in the group subjected to sham treatment, where the touch has not reported beneficial results in spite of its intrinsic placebo effect.

Given the results obtained, OMT can be considered a useful support in the treatment of temporomandibular disorders due to its ability to positively influence muscle activity. However, larger studies are needed, especially involving people with stomatognathic system disorders.