Background:Occasional mouth breathing is one of the symptoms of temporomandibular disorder (TMD). Poor posture and temporomandibular joint pain is associated with dysfunctional breathing.

Objective:To evaluate respiratory functions, respiratory muscle strength, and postural abnormalities in patients with temporomandibular joint dysfunction in comparison with healthy controls, and to determine the relationship between these parameters.

Methods:23patients who met the inclusion criteria, and 23matched healthy individuals were included in the study. The primary outcome measures were pulmonary function tests and respiratory muscle strength [maximal inspiratory pressure(PImax) and maximal expiratory pressure(PEmax)].

Results:There was a statistically significant difference in PImax (p=0.028) and PEmax (p=0.001), however, no significant difference was found in pulmonay function tests between groups (p?0.05). A negative weak correlation was found between visual analog scale and FVC% in the TMD group (r=-0.423,p=0.049). There was no relationship between respiratory parameters with mandible movements and postural assessments (p?0.05), except for the positive weak correlation between both side chin-sternal-notch-distance and PEmax (r=0.413,p=0.050) (r=0.440,p=0.035). The respiratory muscle strength (?=5.666,p=0.035) was found positively and strongly related to TMD. But, there was no relation between TMD and pulmonary functions (?=0.720,p=0.128).

Conclusion: To our knowledge, current study is the first in the literature reported thatrespiratory muscle strengthmay be affected in patients with TMD.