Theories of Craniofacial Growth

Theories of Craniofacial Growth
Presentation by:Mark H. Taylor, D.D.S., F.A.C.D.

What are the Causes
Theories of Craniofacial Growth

* Sicher's Theory
* Scott's Theory
* Moss' Theory
* Van Limborg's Compromise

Sicher's Theory

* Sutural dominance theory
* States that all skull tissue is controlled largely by its own intrinsic genetic information
* States that all bone forming elements are growth centers as opposed to growth sites
* This theory fails
* Examples:
* Microcephaly/Hydrocephaly
* Enucleation of the eye
* Damaged suture

Damaged Suture
Site of damage
Shift of sagittal suture
Normal rat skull
Experimental
rat skull

Scott's Theory

* Cartilagenous dominance theory
* States that cartilage and periosteum are growth centers and sutures are passive; this is largely not true
* Contribution was that Scott correlated sutural adaptation with growth of other tissues, such as synchondrosis growth

Synchondrosis Growth
Occipital
Sphenoid
Ethmoid
Frontal
Posterior cranial base
Anterior cranial base
Spheno-occipital
synchondrosis

Moss' Theory

* Moss denies any intrinsic regulatory control in the growing bony tissues
* Good theory, except for no intrinsic regulatory control
* Examples:
* rapid palatal expansion
* functional jaw orthopedics
* tongue volume vs. lower dental arch sizes (Tamari, et al, Am J Orthod Dentofac Orthop 1991; 100:453-8)

Van Limborg's Compromise
* Chondrocranial growth is controlled by intrinsic genetic factors
* Growth of the desmocranium (calvarium) is mainly controlled by many epigenetic factors (genetically determined influences originating from adjacent structures and spaces, such as brain, eyes, etc.)
* Growth of the desmocranium (calvarium) is influenced by local environmental factors (external environment such as local external pressure, muscle forces, etc.)
* Fails to classify the controlling factors for the mandible

A Modern Compromise

* Chondrocranium is the dominant factor in craniofacial growth
* Postnatal cartilage remnants - spheno-occipital synchondrosis (SOS) and nasal cartilage act as growth centers and are largely influenced by intrinsic genetic factors
* SOS exerts a direct action on the desmocranium, which is also dominated by brain expansion; sutures are growth sites or growth adjusters
* Nasal cartilage displaces maxilla downward and forward; functional matrix may also influence maxilla; orbits are dominated by functional matrix
* Mandible is dominated by local epigenetic and environmental factors (ex. 02 supply)
* cranial base growth alters position of glenoid fossa and therefore the position of the mandible
* nasal cartilage displaces the maxilla; therefore mandible is displaced

Theories of Craniofacial Growth.ppt