The Effect of Asymmetrical Occlusion on Surface Electromyographic Activity in Subjects with a Chewing Side Preference: A Preliminary Study

The relationship between asymmetrical occlusion and surface electromyographic activity (sEMG) in people with different chewing preferences is not clear. In this study, the 5 s sEMG changes in the masseter muscle (MM), sternocleidomastoid (SCM), lateral (LGA), and medial (MGA) gastrocnemius muscles were recorded in controls, and subjects with chewing side preference (CSP) during clench with bilateral (BCR), left (LCR), and right (RCR) posterior teeth placement of cotton rolls. The images of the middle 3 s were selected and expressed as the root mean square (unit: μV/s). The EMG waves of bilateral muscles were compared by computing the percentage overlapping coefficient (POC). Only the POCMM of the CSP showed gender differences at BCR and RCR. Between the control group and the CSP group, there were significant differences in the POCMM and the POCLGA at BCR. In addition, there was a significant difference in POCMM and POCSCM between the two populations in different occlusal positions. The change in the POCSCM correlated with the change in the POCMM (r = 0.415, p = 0.018). The experiment-induced asymmetrical occlusion showed that the altered symmetry of the MM correlated with the altered symmetry of the SCM. Long-term asymmetrical occlusion (i.e., CSP) not only affects MM but also has potential effects on other superficial muscles (e.g., LGA).

Chewing side preference and laterality in patients treated with unilateral posterior implant-supported fixed partial prostheses

BACKGROUND

It is not clear to what extent chewing is improved by unilateral oral rehabilitation with implant-supported fixed partial prostheses (ISFPPs).

OBJECTIVES

This study aimed to investigate whether patients treated with unilateral ISFPPs in the maxilla use their prostheses during mastication to the same extent as they used their contralateral natural teeth. A further aim was to investigate whether there is a correlation between preferred chewing side and laterality.

METHODS

Chewing side preference was assessed in 15 participants treated with unilateral ISFPPs in the maxilla. The first, second, third, fifth and tenth chewing cycles were assessed, and the test was repeated 10 times. All participants also answered a questionnaire about their chewing side preference.

RESULTS

Most of the participants presented bilateral chewing, but two (13%) chewed only on the ISFPP. There was no statistically significant association between the objectively assessed chewing side and dental status (natural teeth or ISFPPs) during any of the recorded chewing cycles (p > .1). There were statistically significant correlations between both the subjectively reported usually preferred chewing side and the subjective chewing side preference during the test and the objectively assessed chewing side for the first three chewing cycles (p < .01). No correlation was found between handedness and the objectively assessed chewing side.

CONCLUSION

In the present study, most participants chewed bilaterally, and chewing was performed both on the ISFPP and on the natural teeth. No correlation was found between the preferred chewing side, objectively or subjectively determined and laterality.

Occlusal analysis of patients with chewing side preference and symptoms of temporomandibular disorders

OBJECTIVES

In this study, TeeTester digital occlusal analysis system was used to analyse the occlusal characteristics of chewing side preference (CSP) and non-CSP patients with TMD symptoms.

METHODS

According to the questionnaire and oral examination, 80 subjects were screened and divided into four groups: 20 CSP patients with TMD symptoms, 20 CSP patients without TMD symptoms, 20 non-CSP patients with TMD symptoms, 20 non-CSP patients without TMD symptoms. TeeTester digital occlusal system was applied to measure the occlusal characteristics in all four groups, including total contect area (TCA), total occlution force (TOF), distribution of occlusal force (DOF), asymmetric index of occlusal force (AOF), occlusal time (OT), disclusion time (DT) and center of occlusal force(COF). SPSS 25.0 was used to analyze the statistical data.

RESULTS

At intercuspal position, the data reveals significant differences in the maximum TOF and TCA among the four groups (P<0.05). There was significant difference in the distribution of occlusal force between the preferred side and the other side of CSP patients with or without TMD symptoms (P<0.05). Among the four groups, there were statistically significant difference in the position of the center point of occlusal force, the direction of the center point of occlusal force, and the vertical distance between the center point of occlusal force and the center line (P<0.05). The COF, maximum TOF and TCA of the preferred side of dentition were significantly positive correla⁃ted with CSP (P<0.05), according to Spearman correlation analysis. However, the maximum TOF and TCA of the both side of dentition were significantly negative correlated with TMD symptoms (P<0.05).

CONCLUSIONS

1) The occlusal characteristics of CSP patients and non-CSP patients with TMD symptoms are different. TeeTester digital occlusal analysis system provides objective parameters for the dynamic evaluation of occlusion. 2) Among all the occlusal cha⁃racteristics, maximum TOF, TCA and COF of the preferred side of dentition were positively correlated with CSP. The abnormal occlusal characteristics (maximum TOF and TCA of the whole dentition) caused by CSP are related to TMD symptoms.