The Importance of Masticatory Muscle Function in Dentofacial Growth

Masticatory muscle function and its influence on craniofacial growth have been investigated in animal experiments and clinical studies. These investigations commonly show that the elevator muscles of the mandible influence transverse and vertical facial dimensions. Increased loading of the jaws associated with masticatory muscle function increases sutural growth and stimulates bone apposition, resulting in greater transverse growth of the maxilla and broader bone bases for the dental arches. Furthermore, an increase in masticatory muscle function is often associated with an anterior growth-rotation pattern and well-developed angular, coronoid, and condylar processes in the mandible. One interesting point that has not been thoroughly discussed is that individuals with strong masticatory muscles have a more homogeneous facial morphology, in contrast to individuals with weak masticatory muscles who show great interindividual variation in their vertical facial dimensions. Thus, individuals with strong masticatory muscles usually have a hypodivergent facial type, although not all individuals with hypodivergent facial form have strong masticatory muscles. The literature supports the hypothesis that a certain level of masticatory muscle strength may be sufficient for normal vertical craniofacial growth, though it is not a prerequisite.