Abstract
Background: There is limited knowledge of the possible side-effects of clear aligners on jaw function.Objectives: 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 different levels of self-reported oral parafunction.Materials and Methods: Participants were screened for oral parafunctional behaviours using the oral behavioural checklist. Respondents in <= 85th and >= 15th percentiles were invited to participate and allocated to a high (HPF: N = 15) or low (lower parafunction [LPF]: N = 16) parafunction group. Participants underwent a TMD clinical examination; somatisation and somatosensory amplification were assessed by questionnaires; OD and stress were assessed by visual analogue scales. While wearing PCAs, awake-time MMA was assessed three times over 9 days using a wearable electromyography device, along with OD, stress and TMD symptoms.Results: The wearing of PCAs was associated with a significant decrease in mean contraction episode amplitude in both groups (p = 0.003). OD levels increased and remained raised in all participants after insertion of the PCAs (p < 0.001), more so in the HPF group (p = 0.048). The HPF group had higher somatisation scores (p = 0.006) and reported more TMD symptoms at all time points (p <= 0.004). No significant changes in stress or TMD symptoms were found in either group during the study period.Conclusions: PCAs were associated with a decrease in MMA in all participants. HPF individuals had greater somatisation and reported greater discomfort when wearing PCAs than LPF individuals.