Background: the decrease of facial movements in peripheral facial paralysis and the resulting aesthetical sequels may have important emotional repercussions as a consequence to the functional deficit, and depending on the intensity of the clinical condition. Orofacial rehabilitation has as a purpose to favor the recovery of orofacial movements and to adequate and/or adapt orofacial functions and facial mimic. However, quantifying therapeutic results in an attempt to measure the muscle tonus is a challenge. Generally, the used forms of measurement are general and subjective. Aim: to propose the labial commissure angle as an anthropometric marker and to evaluate its reliability as an objective tool to evaluate the modification of the facial muscle tonus after rehabilitation. Method: participants of the study were 20 patients presenting peripheral facial paralysis - level IV. The study was conducted using images from the photographical documentation taken fifteen days to one year post-onset of facial paralysis. The angle was measured by tracings determined by pre-established anthropometric facial points, such as the line between the glabella and the gnation and the crossing with the left and right chelion points determining an angle manually measured with a protractor on the photography. Results: The average Labial Commissure Angle before treatment was of 101.70 and after rehabilitation of 93.80 (standard deviation, SD = 4.3). The statistical analysis indicated a significant difference (p < 0.001). 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