Objective: The growth and development of the mandible strongly depends on modelling changes occurring at its ramus. Here, the covariance patterns between morphology of the ramus and rest of the face were investigated.
Methods: Lateral cephalograms of 159 adults (55 males and 104 females) with no previous orthodontic treatment were collected. Geometric morphometrics with sliding semilandmarks were used. The covariance between the ramus and face was investigated with two-block partial least squares analysis. Sexual dimorphism and allometry were additionally assessed.
Results: Differences in the divergence of the face and anteroposterior relationship of the jaws accounted for 24.1% and 21.6% of the shape variation in the sample, respectively. Shape variation was greater in the sagittal plane for males than females (30.7% vs. 17.4%), whereas variation in the vertical plane was approximately similar for the sexes (23.7% for males and 25.4% for females). Size relating allometric differences between sexes accounted for variation in shape to a maximum of 6% regarding the face. With respect to the covariation between the shapes of the ramus and rest of the face, it seems that wider and shorter rami are related to a decreased lower anterior facial height as well as prognathic mandible and maxilla (PLS 1, 45.5% of the covariance). Additionally, more posteriorly inclined rami at their lower region corelated with a Class II pattern and a flat mandibular plane.
Conclusions: The width, height, and inclination of the ramus correlate with facial shape changes both in vertical and sagittal planes.

Keywords: mandibular ramus, face, morphometrics, covariance