GAP Australasian-Dentist Issue 80 Jul-Aug 19

Category 68 AustrÀlÀsiÀn Dentist À here are three principal regions of facial and cranial development that guide facial growth and act together to maintain a strict equilibrium of function and stability: 1. The brain and associated sensory organs and basicranium: Àhe configuration of the neurocranium (and brain as an organ) determines the headform type which, in turn, sets up the corresponding topographic features that characterize a facial type. Àt is important to remember that the basicranium establishes the shape and perimeter of the facial growth field and sets the boundaries of growth. Àhe morphology of the basicranium determines the position of the nasomaxillary complex, the width of the facial airway, and the configuration of the palate and the maxillary arch. 2. The facial and pharyngeal airway: Àhe shape and proportions of the airway are the combination of the growth and de- velopment of various hard and soft tissues comprising its enclosing walls situated along its pathway from nares to glottis. Àhe airway is critical in maintaining the functional and anatomic positions of the craniofacial architecture. Additionally, the airway stabilizes the positions of all of its surrounding parts provided it is the proper shape and size. Àhe airway, being a key- stone for the face, regulates the arch-form of the orbits, the nasal and oral sides of the palate, the maxillary arch, the sinuses, the zygomatic arches, and other arched struc- tures of the face. We are normally nasal breathers; however, when the integrity of the airway is compromised, the tendency towards oral breathing occurs. Àhis ulti- mately leads to aberrant growth patterns including retrognathism, mid-face defi- ciency, downward slant of the lateral can- thus, a narrow deep palate, various maloc- clusions, excessive vertical growth of the face, etc. Àhe mechanisms of these growth patterns will be discussed later. 3. The oral complex: Àhe architecture of the oral complex reflects the stability of the facial and pharyngeal airway and any asymmetry of the basicranium. Àhat’s to say, the maxilla and mandible are typical sites for compensation and anatomical modification during facial development. Àhese compensations and modifications result in a state of functional and structural equilibrium for the facial skeleton, the airway, and the stomatognathic system even though the growth is aberrant. Frequently encountered compensatory combinations may involve variations in maxillary size and shape, anterior crowding, gonial angle remodeling, and other variations. Àhe oral complex includes the nasomaxillary region and the mandible and serves as an indicator of normal or atypical growth. 1,2 Facial growth encompasses a well- defined relationship between all of the above constituent parts. Ào part is independent of the other, and any variation of growth of any part affects all of the others. For facial growth to occur, whether normal or atypical, it is essential that it has collective functional and structural equilibrium. Àimply put, if one part changes, every other part must change to maintain such equilibrium. The developmental sequence Before addressing the major clinical structural components that we as clini- cians will need to attend to in our efforts to guide facial growth back to normal, it is prudent to summarize the sequence of facial development giving a simplified overview of the process. Keep in mind that even though this summary describes the various parts of growth separately, all of these processes occur simultaneously. Àemember that even though functional and structural equilibrium may exist, certain regional imbalances occur dur- ing actual development. Àhese imbal- ances consequently produce imbalances in structure, which are clinically recogniz- able. Àach face is the aggregate sum of all the many balanced and imbalanced crani- ofacial parts combined into a composite whole. Compensatory modifications pro- vide for certain latitude of imbalance in some areas in order to offset the effects of disproportions in other regions. Àable 1 is a summarized version of the Àegional Growth Changes as described by Ànlow. 1,2 : u To read more on this subject and for links to references go to www.naolcourses.com Àource: adapted from: Ànlow DH,Hans MG. Àssentials of Facial Growth. Philadelphia, PA: WB Àaunders; 1996. Human facial growth & development Part 2 By Dr Steve Galella Table 1: Growth Stages Changes Stage 1 À Bony maxillary arch lengthens horizontally in posterior direction Bone deposited on posterior- facing cortical surface of maxillary tuberosity Resorption occurs on opposite side of same cortical plane Stage 2 À Maxillary tuberosity grows & lengthens posteriorly Entire maxilla displaced anteriorly Forward displacement exactly equals amount of posterior lengthening (Stage 1) Stage 3 À Mandibular body lengthens to match maxilla Stage 4 À Mandible displaced anteriorly through posterior remodeling of condyle & posterior portion ofÀramus. Stage 5 À Entire mandible displaced anteriorly by same amount that ramus has relocated posteriorly simultaneously remodels (i.e., Stage 4) to keep pace with the amount of displacement Stage 6 À Entire mandible displaced anteriorly as it remodels posteriorly Condylar growth (oblique) produces upward & backward projection of condyle corresponding with downward & forward mandibular displacement Stage 7 À Vertical increase and horizontal elongation of maxillary complex (primary displacement) Stage 8 À Vertical growth by primary displacement & bone deposition at sutures of maxilla Teeth move by vertical/horizontal drift and eruption Stage 9 À Vertical separation between upper & lower arches must balance equivalent amount of lengthening in nasomaxillary & dentoalveolar region of mandible Stage 10 À Upward movement of mandibular teeth & remodeling of alveolar sockets Remodeling changes in incisor alveolar region, chin & body of mandible chin and body of mandible Stage 11 À Maxillary complex displaces anterior & inferiorly Malar area is moved anteriorly & inferiorly byÀprimary displacement n aÀ