Abstract
Aim: This study aimed to determine the short-term effect of passive clear aligners (PCAs) on masticatory muscle activity (MMA), occlusal discomfort (OD), and temporomandibular disorder (TMD) symptoms in adults with high or low levels of self-reported oral parafunction.
Methods: University students were screened for oral parafunctional behaviours using the oral behavioural checklist. Respondents in 85th and 15th percentiles were invited to participate. The final sample consisted of 31 individuals: 15 with high parafunction (HPF) and 16 with low parafunction (LPF). Selected participants underwent evaluation of their temporomandibular joints, vertical facial proportions, and hypervigilance. Digital intraoral scans were used to fabricate PCAs. MMA was assessed three times over nine days using a portable electromyography device connected wirelessly to a smartphone. A control recording without PCAs in situ was followed by recordings on Day 1 and Day 8 of PCA wear. Participants’ OD, free-way space (FWS), stress, and TMD symptoms were monitored. Results were analysed using descriptive statistics and linear mixed modelling.
Results: PCAs were associated with a significant decrease in mean contraction episode amplitude in both groups (p = 0.003). No significant changes in mean contraction episode duration or frequency were observed between the two groups over time. OD increased in all participants on insertion of the PCAs (p < 0.001), with a significant interaction between ‘group’ and ‘time’ (p = 0.048) indicating that the perceived discomfort while wearing the aligners over time was significantly greater in the HPF than the LPF group. The HPF group had higher reported TMD symptoms at baseline and on day 8 of aligner wear (p < 0.004), they also had higher somatisation questionnaire scores (p = 0.006). Lower anterior facial height was greater in the LPG group (p = 0.015). No significant changes in FWS, stress, or TMD symptoms were identified during the study period.
Conclusions: PCAs were associated with a decrease in MMA in all participants. People with high self-reported oral parafunction are more hypervigilant and reported greater discomfort when wearing PCAs than those with low self-reported oral parafunction.