Asymmetries are found in every living being. A non-symmetrical structure is not necessarily pathological. Why then, is the diagnosis of asymmetry relevant for us as practitioners? In orthodontics, we can anticipate difficulties with treatment if we are well informed about the principles of symmetry and thoroughly familiar with craniofacial growth.

Severe mandibular asymmetry is relatively rare, appears early and becomes apparent at first sight to the practitioner. We find it associated with syndromes in patients for whom early multidisciplinary treatment is indicated.

Dyssymetry is a defect rather than an absence of symmetry. It is a mild form of asymmetry where the line between pathological and nonpathological is still unclear. The face can present different types of dyssymmetries including the whole gamut ranging from dental imbalance to imbalances of the jaws to cranial imbalances, each with its own signature that leaves its characteristic mark on the face. When dealing with mandibular laterodymorphias, the diagnosis must be made early in order to initiate an individualized treatment plan. We are providing some summary fact sheets that make it possible for the practitioner to clearly distinguish between the principal mandibular anomalies.

Describing an anatomical shape with a landmark points diagram allows the practitioner to use all the tools of geometric morphometry. Using a 14 point trigeminal for maxillofacial morphology, 10 points for basicranial morphology and 6 points for the orbital area, we have been able to identify the specific maxillofacial shapes associated with the major dysplasias (Class II or Class III ‘‘surgical limit’’) or simple malocclusions and to research the possible relationships between basicranial morphologies and maxillofacial morphologies. The asymmetries have thus been linked to other pathologies.

We have compared these results with those obtained by using a three-dimensional cephalometric analysis and with results obtained from the literature.

The conclusions on the epidemiology of the asymmetries are in agreement. Basically, the mandible with dominance of the right hemi-face was confirmed as the causative factor. The stability of the basicranial shape makes a solid case that it is not responsible for maxillofacial or occlusal pathologies.

Condylar hyperplasia is a rare pathology of the growth of the mandibular condylar cartilage leading to facial deformation. A bone scan demonstrates the active or inactive character of the condylar hyperplasia and helps guide therapeutic choices. There are two types of condylar hyperplasia, horizontal and vertical growth. Early condylectomy is the treatment of choice for active forms.

The presence of a chin is a specific and unique feature of the human face that is absent from the face of our hominid ancestors and all other primates. A number of anthropologists have studied this anthropomorphic characteristic and elaborated various theories concerning its genesis and anatomical usefulness. Recent research based on the analysis of stress using the finite element method (FEM) seems to establish that the presence of the chin is a biomechanical consequence of skeletal and muscular equilibrium peculiar to the human face. This data is an important addition to our matrix of thoughts that influences our attitude concerning the chin and orthognathic surgery. In particular, whether or not a genioplasty is necessary, and whether it should be performed separately from orthognathic surgery or at the same time.