Facial Types Facial Profi les Male and Female Faces Age Changes

Basic Concepts of Facial Growth Size Increases and Remodeling Displacement Process

Curve of Occlusion Mandibular Condyle and

Growth

Facial Growth and Development

Shingo Kuroda , Matthieu Schmittbuhl , and Antonio Nanci

C H A P T E R O U T L I N E

C H A P T E R

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328

Growth of the face is a gradual and diff erential matura-tional process taking many years and requiring a suc-

cession of changes in regional proportions and relationships of various parts ( Figure 14-1 ). An understanding of the mechanisms of growth and development of the face is per-tinent to dentistry, in general, and is essential for the practice of dentistry. Th e objective of this chapter is to present an overall view of events occurring during facial growth and development. *

FACIAL TYPES

Th ere are two general head types; the dolichocephalic head is relatively narrow and long, and the brachycephalic head wider and rounder. Each type gives rise to corresponding general facial types. Th ese are the long and narrow (leptopro-sopic) facial type, and the round and broad (euryprosopic)facial type.

Although many intermediate types of head forms and facial patterns exist in any general population, these two skull confi gurations ( Figure 14-2 ) tend to be associated with characteristic facial features. Th e narrow facial type tends to have a convex profi le with a prognathic maxilla and a retrog-nathic mandible. Th e forehead slopes because the forward growth of the upper part of the face carries the outer table of the frontal bone with it. A larger frontal sinus than is characteristic of the broad facial type because of the greater separation of inner and outer bony tables of the forehead, whereas the inner table remains fi xed to the dura of the frontal lobe of the cerebrum. Th e glabella and

supraorbital rims are prominent, and the nasal bridge is high. Th ere is a tendency toward an aquiline or Roman nose because the more prominent upper part of the nasal region induces a bending or curving of the nasal profi le. Because the face is relatively narrow, the eyes appear close set, and the nose is correspondingly thin. Th e nose also is typically prominent and quite long, and its point has a tendency to tip downward. Th e lower lip and mandible are oft en set in a somewhat recessive position because the long dimension of the nasal chambers leads to a downward and backward rotational placement of the lower jaw (the dolichocephalic head form also has a more open cranial base fl exure, which adds to the downward mandibular rotation). Th ese factors contribute to a downward inclination of the occlusal plane and a marked curve of occlusion.

Th e round, broad facial type is characterized by a more upright and bulbous forehead, with the upper nasal part of the face less prominent than in the dolichocephalic face. Th e nasal chambers are horizontally shorter but wider, in con-trast to the narrow but more prominent nasal region char-acterizing the dolichocephalic head form. Th e net capacity of the airway in both instances is thus equivalent. Th ere is less protrusion by the supraorbital ridges, the glabella is less prominent, and the frontal sinus is smaller. Th e nose is shorter vertically as well as horizontally and tends to be more puglike. Th e nasal bridge is lower, the nasal sides are broader, and the end of the nose oft en tips upward. Th e eyes appear widely set and the zygomatic bones seem prominent because the nose and forehead are less prominent. Th e face appears quite fl at and broad, in contrast to the more angular, narrow, deep, and topographically bold appearance of the dolichoce-phalic face. Th e cranial base angle of the brachycephalic skull tends to be more closed, and there is a greater tendency toward an orthognathic (straight-jawed) profi le.

* Th e reader is referred to the works of D. Enlow for a more com-prehensive treatise of facial growth and development.

CHAPTER 14 Facial Growth and Development 329

slope. In male faces that are long and narrow, however, the more marked extent of the upper nasal prominence is such that more of the nose sometimes lies forward of the vertical line.

People with a dolichocephalic head form (a characteristic feature of some white populations in northernmost and southernmost Europe, North Africa, and the Middle East) tend to have a retrognathic face. Th ose with a brachyce-phalic head form (a characteristic feature of Middle Europe and East Asia) have a greater tendency toward prognathism. Also, Asians commonly have a maxillary and mandibular alveolodental protrusion characterized by labial tipping of

FACIAL PROFILES

Th ere are three basic types of facial profi les ( Figure 14-3 ): (1) the straight-jawed, or orthognathic, type; (2) the retrog-nathic profi le, which has a retruding chin and is the most common profi le among white populations; and (3) the prog-nathic profi le, which is characterized by a bold lower jaw and chin.

To identify a person ’ s profi le type, imagine a line project-ing horizontally from the orbit. Drop a perpendicular line from this just brushing the surface of the upper lip. If the chin touches this vertical line, the profi le is orthognathic; if it falls behind or ahead, the profi le is retrognathic or prog-nathic. For a female face, the vertical line generally passes through the nose at a point about halfway along its upper

FIGURE 14-1 Changes in craniofacial proportions between an infant (2 months) and an adult. The skull at about birth has been enlarged to match the adult skull to illustrate the differences in form and proportions of craniofacial complex components. Note that the neurocranium in the infant is prominent whereas the face predomi-nates in the adult and represents a large part of the whole skull.

FIGURE 14-2 A, Dolichocephalic head form. B, Brachycephalic head form.

B

A

FIGURE 14-3 In A, an orthognathic profi le, the chin touches a vertical line along the upper lip perpendicular to the neutral orbital axis. In B, a slightly retrognathic profi le, the chin tip falls several millimeters behind this line . In C, a severely retrognathic face, the chin is well behind the vertical line . The lower lip also is much less prominent. In D, a prognathic profi le, the chin tip lies well forward of this vertical line .

A B C D

330 Ten Cate’s Oral Histology

the maxillary incisors that results from a protrusive mandibular dentition. Th us there are more malocclusions involving protruding maxillary teeth in some Caucasian populations and more malocclusions involving protruding mandibular teeth with alveolodental protrusion in Asian populations.

An important intrinsic developmental process of com-pensation functions to off set and reduce the anatomic eff ects of built-in tendencies toward malocclusions. A genetically determined retrognathic mandibular placement caused, for example, by some rotational factor in the cranial base can be compensated by the development of a broader mandibular ramus. Th us the whole mandible becomes longer and reduces the amount of retrognathism. Because latitude exists for compensatory adjustments, only a relatively slight degree of retrognathism, or some other anatomic imbalance, occurs in most persons ( Figure 14-4 ). For narrow-faced individuals, 3 to 4 mm of mandibular retrognathism (a mild malocclu-sion with some crowding of the incisors) is typical. A perfect occlusion is hardly to be considered normal because rela-tively minor dental arch or facial skeleton irregularities are almost universal. Only when the compensatory process fails do severe malocclusions occur.

MALE AND FEMALE FACES

Until about 12 years of age, boys ’ and girls ’ faces are essen-tially comparable. Shortly aft er puberty, the female face has attained most of its size and structural maturity, and growth ceases. Growth and development of the male facial complex, however, continue into the early 20s, bringing about noticeable diff erences between male and female faces ( Figure 14-5 ).

Male and female faces, whether of the narrow or broad type, have a composite of key topographic characteristics. On a scale from extreme masculine to extreme feminine, most individuals usually have intermediate features. In general, however, the male face tends to be noticeably more protuberant and more knobby, bulky, or coarse. Female faces tend to be fl atter, more delicate, and less bumpy.

Th e characteristically larger nose of the male face creates several related facial diff erences. Th e whole nasal region is larger because of the requirement for a greater airway capacity. Th us the relatively wide and long male nose con-trasts with the thinner and less prominent female nose. Th e hard palate forms the fl oor of the nasal cavity and the roof of the oral cavity. When the upper skeletal part of the nasal region becomes markedly prominent, a constraint is imposed on the lower part of the nasal skeleton by the palate and maxillary arch; that is, the upper part of the nose can become so prominent that the nasal profi le necessarily bends to give a resultant aquiline or Roman nose confi gu-ration. Alternatively, upper nasal prominence can produce a rotation of the whole nasal profi le into a distinctively more vertical alignment. In this classic male Greek nasal confi guration, the nasal profi le drops nearly straight down

FIGURE 14-4 Mandibular compensation. (A) represents the normal mandible; the cranial base is open-angled (BaSNa), (B) has the anatomic effect of placing the mandible in a retrognathic posi-tion. Because the whole mandible is in a backward and downward position, the occlusal plane has a slight downward inclination. The retruding tendency of the mandible is often compensated during facial growth by the development of a wider ramus, (C) , thus placing the mandibular arch in a more forward position.

S

Ba

Na

S

Ba

Na

A

B

C

from the prominent forehead. Th ere is a great deal of ethnic variation in nasal shapes; in some population groups an aquiline confi guration, for example, is as common among females as males. Generally, however, the smaller, thinner female nose tends to have a concave-to-straight profi le

CHAPTER 14 Facial Growth and Development 331

greater nasal prominence, is carried forward. Th e result is a sloping forehead with large frontal sinuses and a supraorbital and glabellar overhang. Because of the more massive extent of both nasal and supraorbital skeleton in males, the zygo-matic bones appear less prominent, as does the whole upper jaw. Despite such basic sex diff erences in the face, recall that there are also similar facial diff erences between long and broad head form types as well.

AGE CHANGES

An infant ’ s face is round and wide because lateral facial growth occurs earlier and to a greater extent than vertical growth. With increasing age and body size, however, vertical facial enlargement exceeds lateral facial growth as the nasal chambers progressively expand inferiorly to provide an increased airway for the enlarging lungs. A baby ’ s face also appears rather fl at because the nose is small relative to the broad but short face. Because forward growth of the face has not yet occurred, the forehead is upright and bulbous. Buccal and labial fat pads give a full appearance to the cheeks. Brachycephalic adults usually have a rather juvenile facial character compared to the relatively angular and topographi-cally bolder adult dolichocephalic face. If an adult “ round face ” tends toward obesity, thus presenting a fat-padded face, the youthful parallel is augmented. Subcutaneous adipose tissue also tends to smooth out any age wrinkles, which further adds to the illusion of youth. Any marked loss of facial adiposity exaggerates an aged appearance because of consequent skin wrinkling.

Th e fi rm, turgid, velvety skin of youth becomes progres-sively more open pored, leathery, spotted, crinkled, and fl abby with advancing age. Overexposure to the sun greatly hastens some of these changes. In middle age the skin begins to sag and droop noticeably because the hypodermis becomes less fi rmly anchored to the underlying facial muscles and bone. Th is sag may be the result of weight loss, but biochemi-cal and physical alterations in the connective tissue of the dermis and hypodermis also exert an eff ect. Th ere is a dimin-ished fl exibility of component fi bers with a marked decrease in the content of water-bound proteoglycans. Th e latter results in a widespread subcutaneous dehydration, contrib-uting signifi cantly to a shrunken facial volume and conse-quent skin surplus. Th ese factors, in turn, lead to the onset of facial lines and wrinkles, sunken eyes, drooping bags, and suborbital creases.

Facial lines and furrows appear in characteristic locations. One of the fi rst to appear, which is associated with middle age, is the nasolabial furrow (extending down along the sides of the nasal alae lateral to the corners of the mouth) called a smile line . Th is is seen at any age when a face grins, but it becomes a permanent integumental mark during the late 30s or early 40s. In happy individuals who look younger than their years, the onset of these and other telltale lines may be delayed or are at least less noticeable. Other permanent lines that appear with advancing age include forehead furrows,

whereas the male nose has a tendency toward a straight-to-convex profi le.

A major diff erence exists between the sexes in the fore-head. In females the supraorbital ridges lie on or very near to the same vertical plane as the inferior orbital rims and cheekbones. Th ere are usually no more than a few millime-ters of supraorbital overhang in the female face. Th e female cheekbones therefore tend to appear more prominent, which is especially noticeable in a 45-degree view of the face (see Figure 14-5 ). Th e entire midfacial region, including the upper jaw, also seems more prominent in female faces. Th e outer bony plate of the forehead in males, because of the

FIGURE 14-5 Comparison of male and female craniofacial fea-tures. Relative to female crania, male crania are generally charac-terized by greater robusticity: massive glabellar prominence that form a rounded and well-developed projection frequently associ-ated with prominent supraorbital ridges; and a larger mastoid process that projects downward. The male mandible also generally exhibits a massive mental eminence and a relative fl exure of the posterior border of the ramus.

Glabella

Mastoidprocess

Mentaleminence

Masculinefeatures

Femininefeatures

Ramus flexure

FemaleMale

332 Ten Cate’s Oral Histology

on its outer surface and endosteal resorption on its inner surface. Beginning students oft en assume (incorrectly) that the bone of growing cortex must necessarily be produced by the periosteum. Actually, half or more of the compact bone tissue of the face and cranium is laid down by endosteum, the inner membrane lining the medullary cavity, and about half the periosteal surfaces of most bones in the face and neurocranium are resorptive (with about half depository) ( Figure 14-7 ). Th e reason is that remodeling is required to increase the size of any given bone.

Th ree essential processes bring about the growth and development of various cranial and facial bones: size increase, remodeling, and displacement. Th e fi rst two are closely related and are produced simultaneously by a combination of bony resorption and deposition. Th e third (displacement) is a movement of all the bones away from each other at their articular junctions as each undergoes size increases. In clinical procedures, to control properly and thereby make use of the complex processes of growth, the following concepts must be fully and thoroughly understood.

SIZE INCREASES AND REMODELING

As a bone enlarges and remodels there is addition of new bone on one side and removal of old bone from the opposite side, leading to an overall repositioning of the bone in the direction of deposition. Th e composite of repositioning changes throughout the bone brings about its overall enlargement.

Th e term growth site is oft en used to designate some area or part that plays a noteworthy role in the growth process (e.g., the mandibular condyle). All parts and areas of a bone and their covering membranes, however, participate directly

suborbital creases, crow ’ s feet at the lateral corners of the eyes, vertical corrugations over the glabella and on the upper lip, lines extending down from the corners of the mouth on both sides of the chin, bags below the cheekbones, and jowls along the sides of the mandible. In advanced old age, the face can become an expansive carpet of “ noble ripples ” and may also be characterized by a decrease in the vertical dimension resulting from loss of teeth.

BASIC CONCEPTS OF FACIAL GROWTH

Two common but incorrect assumptions must be discarded before an understanding of facial growth is possible. Th e fi rst is that various individual bones (e.g., mandible, maxilla, ethmoid, and sphenoid) enlarge simply by a symmetric expansion of the outer contours ( Figure 14-6 ). Th e second is that a bone grows by a combination of periosteal deposition

FIGURE 14-6 Erroneous schema of bone growth. Bone does not simply “ grow ” by symmetric expansion. Rather, it undergoes a complex remodeling process throughout all its regions and parts. Compare with Figure 14-7 .

FIGURE 14-7 Growth and remodeling fi elds. The entire facial and neurocranial skeleton is covered, inside and out, by a characteristic spread of regional growth and remodeling fi elds. Resorptive fi elds are shaded . Depository fi elds are free of shading.

CHAPTER 14 Facial Growth and Development 333

Th us, as already stated, the mandible is continuously dis-placed in an anteroinferior direction but enlarges by equal amounts posteriorly and superiorly ( Figure 14-10 ). All the various bones of the nasomaxillary complex also become separated from each other at their various sutural junctions by displacement, and the sutural membranes (comparable to periosteal membranes) deposit bone in an amount equal to that lost by the displacement separation.

CURVE OF OCCLUSION

Because of the notably long vertical human face, there is a tendency for the mandible and occlusal plane to have a downward- and backward-rotated position. Th is rotational alignment would produce an anterior open bite but for a compensatory action on the part of the dentition ( Figures 14-11 to 14-13 ). Th e mandibular incisors and their alveolar sockets undergo additional upward drift , which closes the occlusion in the incisor region. Th e occlusal plane has a characteristic curve as a result that tends to be more or less marked according to the downward rotation of the mandible produced by vertical growth of the nasomaxillary region. As the mandibular anterior teeth undergo this vertical drift ing process, their axial inclinations shift to a more upright align-ment, which continues until they come into occlusion with the upright-oriented maxillary teeth. Incisor alignment con-trasts with alignment of the mandibular posterior teeth,

FIGURE 14-8 Growth of the hard palate, illustrating the process of relocation and remodeling. In the infant (2 months old), the level of the hard palate is just slightly inferior to the level of the inferior orbital rim (left). As the nasal cavities expand, the bony palate becomes relocated downward.

FIGURE 14-9 Downward remodeling of the palate. A, This is pro-duced by deposition on the inferior-facing (oral) side and resorption from the superior-facing (nasal) side, thus bringing about a pro-gressive and continuous inferior relocation of the whole palate and maxillary arch. B, The maxillary teeth are moved downward at the same time by a process of vertical drift associated with remodeling (resorption and deposition) of alveolar bone. (From Proffi t WR, Fields HW Jr., Sarver DM: Contemporary orthodontics, ed 4, St. Louis, 2007, Mosby.)

A

B

in the growth sequence, whether or not they are specially designated. A mosaic of remodeling fi elds blankets all outside and inside surfaces of all individual bones (see Figure 14-7 ), and these growth fi elds produce the enlargement of each bone. Although some changes in a given bone shape may be involved, the essential function of remodeling is to move the various parts of a bone to successively new locations (reloca-tion) so that the whole bone can then enlarge ( Figures 14-8 and 14-9 ). Remodeling fi elds represent the morphogenetic activity of the enclosing periosteum, endosteum, and other soft tissues. Th us the entire bone is involved in the growth process, not just certain restricted growth sites or growth centers.

DISPLACEMENT PROCESS

As all the various muscles, epithelia, connective tissues, and other soft tissues of the head grow and expand, a separation eff ect occurs at the articular joints among the diff erent bones, which are physically carried away from each other by masses of enlarging soft tissue. Th is process is termed displacement, and the bone ’ s osteogenic membranes and cartilages are immediately triggered to respond by producing overall bone enlargement and remodeling. Th e displacement movements of the bones, in eff ect, create the space into which bones grow. Spaces as such never develop, of course, because dis-placement and subsequent bone growth are virtually simul-taneous. When a functional and biomechanical equilibrium is attained between the soft tissues and the bones, the stimu-lus for skeletal growth ceases.

334 Ten Cate’s Oral Histology

FIGURE 14-10 Superimposed growth stages of the mandible from a child (5 years old) compared to an adult. A , Remodeling of the infant mandible occurs by local combinations of resorption and deposition. This process relocates the ramus in posterior and superior direction and provides for a lengthening of the corpus. B, During the growth, the whole mandible undergoes an anterior and inferior displacement.

B

A

FIGURE 14-11 Perfectly balanced craniofacial composite. The occlusal plane is approximately perpendicular to the maxillary tuberosity. It is rotated neither upward nor downward to any marked extent and is approximately parallel to the neutral orbital axis. In most faces, some degree of occlusal plane rotation occurs.

CHAPTER 14 Facial Growth and Development 335

FIGURE 14-12 Lowered maxillary arch, resulting in a downward and backward alignment of the mandible. Note also the retrusion of the chin and lower incisors. This, in part, is the anatomic basis for a class II malocclusion among persons having a long, narrow head form. (An open cranial base angle has the same effect and adds to the extent of the mandibular retrognathism.)

FIGURE 14-13 Dental compensations precluding an anterior open bite as a consequence of the mandibular rotation seen in Figure 14-12 . The anterior mandibular teeth drift vertically in a superior direction, the anterior maxillary teeth drift inferiorly, and the result (frequently encountered) is the curve of occlusion.

336 Ten Cate’s Oral Histology

its condyle have the capacity to provide for this develop-mental adaptability, within normal latitude, by varying the amount and direction of their growth to accommodate what-ever nasomaxillary and dental height, length, and width exist during the changing course of growth. Similar variations occurring in the cranium are also accommodated.

Th e mandibular growth process involves a feedback mechanism. Continuously changing growth circumstances (e.g., physiologic changes, soft tissue increases, biomechani-cal forces, bioelectric alterations, neurologic changes, hor-mones, and possibly other factors) trigger the ramus and condyle to grow or stop growing, in more or less upward and backward directions. Th is is an exceedingly important and fundamental growth function, carried out by the condyle and the ramus as a whole.

A summary of the facial growth changes that have been discussed in this chapter appears in Figure 14-14 , which depicts the face and skull from 3 to 18 years of age.

which tend to be inclined slightly anterior because of the downward mandibular rotation.

MANDIBULAR CONDYLE AND GROWTH

In Chapter 13 , the condylar cartilage was described as having, along with the remainder of the ramus, a special developmental role to accomplish: an adaptive function involved in the continued placement of the mandibular arch in juxtaposition with the maxillary arch and cranial base as they all grow to become an interrelated whole. Because the mandible articulates with the cranial base at one end (at the temporomandibular joints) and with the maxilla through tooth contact in the occlusal plane, its growth must be adapt-able to the wide range of dimensional, anatomic, rotational, and developmental variations that occur in the nasomaxil-lary complex, dentition, and neurocranium. Th e ramus and

FIGURE 14-14 Summary of postnatal growth and development from 3 to 18 years of age. A is a lateral view, and B a frontal view. The location of the sella turcica is denoted by x .

BA

x

RECOMMENDED READING

Enlow DH , Hans MG : Essentials of facial growth , Philadelphia , 1996 , Saunders .