Prenatal and Postnatal Growth and Development of Maxilla and Palate
The maxilla is the second largest bone of the facial skeleton, the first being the mandible. It is a pneumatic bone that is paired and forms the upper jaw. It is an irregularly shaped bone that contributes to the formation of the roof of the oral cavity, the orbit, the nasal cavity, the infratemporal fossa and the pterygomaxillary fossa. Growth and development of an individual can be divided into PRENATAL & POSTNATAL periods.
According to “TODD” “Growth is an increase in size” and “Development is progress towards maturity.” As described by Krogman, it involves “Increase in size, change in proportion & progressive complexity.”
Prenatal Development of Maxilla and Palate
The pre-natal period of development is a dynamic phase in the development of a human being. During this period, the height increases by almost 5000 times as compared to only a threefold increase during the post-natal period. Maxilla forms with in the maxillary prominences. Ossification of maxilla occurs slightly later than in the mandible, and the primary ossification centre appears in the 7th week. Secondary centers include the zygomatic, orbitonasal, and nasopalatine areas.
During prenatal development, the maxilla forms from the maxillary prominences. The palate develops from the maxillary processes and palatal shelves. The palatal shelves initially grow vertically but then reorient horizontally and fuse in the midline. Regarding associated structures, Meckel’s cartilage is derived from the first branchial arch around the 41st-45th day of intra-uterine life and provides a template for guiding the growth of the mandible.
Postnatal Growth Mechanisms
Postnatally, the maxilla grows through processes like displacement, growth at sutures, and surface remodeling. The growth of the nasomaxillary complex is produced by the following mechanisms:
- Displacement: Here the whole bone is carried by a mechanical force.
- Growth at sutures: The maxilla is connected to the cranium and cranial base by a number of sutures.
- Surface remodeling: A process of reshaping and resizing a growing bone as it is relocated to new levels.
| Mechanism | Description and Site |
|---|---|
| 1º Displacement | The physical carry takes place in conjunction with the bones own enlargement. |
| 2º Displacement | Movement of bone and soft tissues not directly related to its enlargement, such as growth of the middle cranial fossa. |
| Growth at Sutures | Includes fronto-nasal, fronto-maxillary, zygomatico-temporal, zygomatico-maxillary, and pterygo-palatine sutures. |
| Surface Remodelling | Carried out by the osteogenic membranes and other surrounding soft tissues through deposition and resorption. |
Skeletal Changes and Arch Lengthening
Remodeling at the maxillary tuberosity causes horizontal lengthening. It is a depository field, hence causes lengthening and widening of the arch and provides space for the eruption of molars. This allows the clinician to “expand the arch” by distalization of molars into an area of bone deposition. Massive bone remodelling by deposition and resorption occurs and brings about an increase in size, change in shape of bone, and change in functional relationship.
Alveolar Ridges and Palatal Remodelling
Growth at the alveolar ridges occurs by bone deposition at alveolar margins, which is termed as vertical drift. This increases the maxillary height and depth of palate. In palatal remodelling, the external labial side of the whole anterior part of the maxillary arch is resorptive with bone being added into the inside of the arch; the arch increases in width and the palate becomes wider (V Principle).
Nasal Cavity Development
The lining surface of the bony walls and floor of the nasal chambers are predominantly resorptive, which produces a lateral and anterior expansion of the nasal chambers. These changes contribute to the complex growth and development of the nasomaxillary complex.