Among women, the forehead is straighter (Fig. 2, Table 2), the glabella is more curved and less pronounced, and the supraorbital rim is less noticeable than in men.
The midface in women presents more subtle angles, whereas the midface in men presents more pronounced zygomatic bones (Fig. 3). In men the mandible is larger, stronger, and more faceted and has more clear-cut angles than in women. Also, the chin is larger, giving men a square-shaped face, whereas women tend to have a triangular or heart-shaped face.
The pyriform aperture becomes larger with aging, experiencing remodeling of lateral and inferior walls, whereas the upper and olfactory cavities remain intact, so that the nasal cavity presents a lateral and anterior expansion and the palatus is reallocated inferiorly. The maximum nasal aperture (the length of the base of the pyriform aperture) increases with age (Fig. 4).
With the process of aging, the floor of the orbit expands inferiorly and laterally, losing the round shape observed in younger skulls (Fig. 4). The lacrimal bone works as a pivot: its inferior portion rotates laterally, leading to an inferior slide of the maxilla. The maxilla is more anterior and more prominent in younger skulls, whereas in older skulls an anterior and inferior bone resorption takes place, giving the appearance of a retrusion of the face (Fig. 5). The zygoma presents an anterior resorption (Fig. 6), whereas the zygomatic arch suffers a posterior and anterior remodeling, increasing the temporal fossa. The MM/OM ratio increases from <20 years to 20–50 years and decreases in >50 years group (Table 3).
The mandible undergoes a posterior and superior bone formation, although it suffers an anterior and inferior resorption (Fig. 5). Without the presence of teeth, the mandible experiences further atrophy. The angle of the mandible increases with age (97 degrees in younger skulls to 135 degrees in older skulls), mainly due to resorption of the inferior border of the angle, next to body–ramus junction (Fig. 7). Also, the chin becomes more anterior, oblique, and shorter with age (Fig. 7).
Not all the bones in the skull suffer resorption. Although the midface recedes, the forehead suffers continuous expansion, due to bone deposition in the external wall of the frontal bone, especially in the supraorbital rim (Fig. 8).
The sexual dimorphism among human skulls is a well-established subject in anthropology. These differences have aided in the distinction of male and female skulls (Fig. 2). Nevertheless, it is the array (Table 2), and not single characteristic that allows gender determination of skulls.7,8
The correct knowledge of gender differences of the human skull is vital in the aesthetic approach to aging, because exaggerated filling of particular areas may render a masculine appearance to women, for example. A prominent supraorbital region is characteristic of men (Fig. 2), so that filling these areas in women must be careful and subtle, only to restore the retro-orbicular fat loss. On the other hand, when treating the aging midface, it is imperative to remember that a more curvilinear prominent cheekbone is peculiar to women, whereas men present a more angled face, due to strong muscle insertions.
Furthermore, deep knowledge of the anatomy of the aging face allows a better approach to the underlying cause of the fold, rendering better and more natural results than just simply filling up the fold. The maxillary retrusion, associated with the decrease in collagen content of the skin and loss of fat compartments, works as a true slide for soft-tissue descent (Figs. 5, 6).9 Because the zygoma works as a support of the soft tissue of the midface, restoring the volume of the zygomatic prominence would not only improve the local area, giving a youthful and more natural appearance, but would also improve10,11 and minimize the need to treat the nasolabial fold itself. The changes in MM/OM ratio observed in this study reflect the increase in orbit and pyriform aperture size, at the expense of the maxillary bone in the process of aging, corroborating the findings of previous authors.6,12,13 High G prime hyaluronic acid or poly-l-lactic acid injections deep in the supraperiosteal area and in the pyriform fossa help soften the lengthening of the nose, drooping of the nose tip, and enlargement of the nostrils.
The orbit does not age homogeneously. The superior-medial and inferior-lateral aspects of the orbit have the greatest tendency to resorb, which is associated with soft-tissue laxity that occurs with aging, leading to an increased prominence of the medial fat pad and lengthening of the lid–cheek junction, giving the patient a sad appearance.13–16
The facial remodeling depends entirely on growth, development, and overlying soft-tissue function. All bone volume or size changes throughout life occur in response to functional demand of the face.17,18 Indeed, loss of teeth, due to infection, trauma, or aging, increases local bone resorption and is listed among the major bone factors that impact aesthetic outcome.19,20 The decrease in mandible volume and shortening of the chin, due to decrease in bone support, lead to further soft-tissue excess and sagging (Fig. 7).21,22
The clinical approach to the aging face has changed in the past years.2 The knowledge of the anatomy of the aging face, taking into consideration all the layers (skin, fat pads, muscles and bones), as a whole, for the treatment of folds and shadows, is vital for a better and more natural final aesthetic outcome.
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Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of The American Society of Plastic Surgeons.
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