Growth of the Craniofacial Skeleton

- Bone formation
- Growth mechanisms
- Growth-controlling factors
- Possibilities of influencing growth mechanisms.

Various aspects of the growth mechanisms are significant when assessing the etiology of malocclusions and the possible methods of treatment. The development of the craniofacial structures is not merely a symmetrical expansion of the outer bone contours (Fig. 3), but is based on three different growth mechanisms: Increase in size, bone remodeling, and bone displacement.

Fig. 3. Misconceptions about bone growth. Bone growth is not based on symmetrical enlargement of all structures and surfaces, i.e an adult’s mandible does not correspond to the photographic enlargement of a child’s mandible, as illustrated. Bone is subjected to a complex remodeling process which simultaneously takes place with increase in size and affects all sections of the structure (according to Ten Cate. 1980)

Unlike soft tissue, bone is a mineralized substance and cannot grow by means of interstitial enlargement but only by apposition of the outer, periosteal, and inner, endosteal surfaces.

Deposition and resorption take place simultaneously on the opposing bone surfaces, i.e. the outer and concurrently the inner cortical plates respectively. The deposition on the one side and the resorption of the other side not only causes an increase in proportions but also displaces the bone. New bone formation is closely associated with the bone remodeling process during the entire growth period.

The two mechanisms must be combined in order to ensure a well-balanced increase in dimensions of the bone structures whiles maintaining their shape and proportions. The third principle which applies to facial growth is bone displacement, and is based on the process by which adjacent bones move away from one another, where they are connected by articular joints (sutures, synchondroses, condyles), due to their increasing size.

The various growth mechanisms of the facial skeleton are governed and influenced by endogenous and exogenous factors, respectively, during the entire development period.

4. Various stages of mandibular growth superimposed on the condylar region. Radiograms of the mandibles of a newborn baby, a 5-year-old and an adult superimposed on one another. The anterior displacement of the mandible, which takes place during development, is quite apparent. The movement is directed simultaneously forward and downward.

5. Macerated mandibles of a neonate, a 5-year-old and an adult. Growth is considerably faster during the early postnatal period than during adolescence. The radiograms of the bones shown in this illustration are superimposed on one another in Figs. 4 and 6.

6. Various stages of mandibular growth superimposed on the gonial region. Due to the diverging growth direction of the two rami, most of the transverse development of the mandible takes place in a posterior direction. The increase in width anteriorly is minimal. Superimposing the different mandibles shows the regional remodeling processes which take place parallel to the increase in proportions.