Does occlusal performance have a significant influence on physiological cervical spine mobility in TMD patients and a control group?

The influence of occlusal forces on cervical spine (CS) muscle activation was determined with the aid of electromyography (EMG). For the first time in this pilot study, the hypothesis was tested that maximal and submaximal bite forces have a significant influence on all physiological CS movements in temporomandibular dysfunction (TMD) patients and a control group. Twenty female subjects were divided into a TMD group (n = 10) and a control group (n = 10) on the basis of a validated questionnaire. The range of motion (ROM) of the CS (flexion/extension/rotation/lateral flexion) was measured using the WinSpine system. The biteFork system was used to evaluate occlusal forces by recording the forces acting on the molars 15/16 and 25/26. The CS mobility measurements were made at occlusal force percentages of 0%, 25%, and 30%. Evaluation was based on the differences in the ROM with and without biting movements. This was followed by a temporomandibular joint (TMJ) examination, including evaluation of the mandibular movement range. A significant difference was observed in the control group between rotation to the left at occlusal force percentages of 0% and 25% (P 0.05). In the TMD group, the difference between flexion at occlusal force percentages of 0% and 25% (P 0.05), extension at occlusal force percentages of 25% and 100% (P 0.05), and rotation to the left at occlusal force percentages of 25% and 100% (P 0.05) were found to be significant. On comparing the data between the groups, a significant difference was observed between flexion at occlusal force percentages of 0% and 25% (P 0.05), and rotation to the left at occlusal force percentages of 25% and 100% (P 0.05). The initial hypothesis that the bite force has a significant influence on all six CS movements cannot be confirmed, since only 1 in 12 movements under loading in the control group, and 5 in 12 movements in the TMD group showed significant differences compared to the healthy control group. Nevertheless, the results indicate a connection between the temporomandibular and the craniocervical systems on a neuromuscular level. Larger sample sizes, more homogeneous samples, and the use of additional measuring instruments would be beneficial for further studies. Keywords: temporomandibular dysfunction (TMD), cervical spine (CS), range of motion (ROM), submaximal occlusal force, maximal occlusal force