After the age of 6 years, where does the greatest increase in the size of the mandible occur?

The greatest increase in the size of the mandible after the age of 6 years occurs distal to the first molar. During this period of dental development, significant changes in the jaw's growth and configuration take place, particularly as permanent teeth begin to erupt and the occlusion matures.

The area distal to the first molar is particularly important because it accommodates the growing second molars, which become important in establishing the posterior occlusion and functional dynamics of the mandible. As the child's face and jaw continue to grow, this area sees considerable bone remodeling and expansion to provide sufficient space for the eruption of these teeth and to support the overall aesthetic and functional proportions of the face.

The symphysis, while it does experience growth, does not show as pronounced an increase as seen in the area distal to the molars. Similarly, the regions between the canines and in the central incisor area undergo growth but are primarily involved in accommodating the respective teeth rather than experiencing the greatest overall increase in size. Hence, the most significant growth of the mandible is observed at the location distal to the first molar.