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2009 Annual Meeting Abstracts


Aging of the Mandible and its Aesthetic Implications: A Three Dimensional CT Study
Robert B. Shaw, Jr., MD1, Evan Katzel, BA1, Peter Koltz, MD1, David M. Kahn, MD2, John A. Girotto, MD1, Howard N. Langstein, MD1.
1University of Rochester, Rochester, NY, USA, 2Stanford University, Stanford, CA, USA.

Purpose: Facial aging is a dynamic process involving the aging of soft tissue and bony structures. The skin undergoes atrophy with a loss of tone and elasticity. Subcutaneous fat atrophies with a decreased adherence to underlying layers leading to gravitational descent. The aging process also affects the facial bones. Multiple studies support the theory that bony aging of the orbit and midface is a process primarily of contraction and morphologic change. In regards to aging of the mandible, however, recent studies analyzing cephalograms have stated that the mandible continually enlarges throughout life. In this study, we will evaluate how specific bony aspects of the mandible change with age in both men and women and what implications these structural changes may have on the techniques used in facial cosmetic surgery.
Methods: Facial bone computed tomography (CT) scans were obtained from 120 Caucasian patients, (60 female, 60 male). There were twenty male and twenty female patients in each of three age categories (20-40, 41-64, and 65+). Each CT scan underwent 3-D reconstruction with volume rendering. Edentulous patients were excluded from this study. The following measurements were then obtained from each scan: bigonial width, ramus breadth, ramus height, mandibular body height, mandibular body length and mandibular angle. The data was then analyzed with one-way Anova, and results were considered significant at a p-value less than .05.
Results: There was no significant change in regards to bigonial width or ramus breadth across ages for either gender. Ramus height significantly decreased from the middle to old age groups for both genders. The mandibular body height decreased significantly from the young to middle age groups in our male population and between the middle and old age groups for our female population. Mandibular body length decreased significantly between the young and middle age groups for both genders. The mandibular angle increased significantly between all age groups for our female population and between the young and middle age groups for our male population.

Mean Mandible Measurements by Age and Gender
Young (20-39)Middle (40-64)Old (65+)
Mandibular Body Length
Male (mm)(SD)
Mandibular Body Length
Female (mm)(SD)
90.3 (5.4)
86.9 (3.2)
83.1 (2.9)*
80.9 (3.5)*
82.1 (6.3)
80.7 (4.0)
Mandibular Body Height
Male (mm)(SD)
Mandibular Body Height
Female (mm)(SD)
35.4 (2.9)
31.5 (3.5)
32.9 (1.8)*
30.5 (2.9)
32.3 (1.6)
27.7 (3.9)**
Mandibular Angle
Male (degrees)(SD)
Mandibular Angle
Female (degrees)(SD)
112.3 (6.9)
119.9 (5.3)
123.9 (3.7)*
125.8 (5.1)*
125.9 (5.8)
132.0 (4.9)**
Ramus Breadth
Male (mm)(SD)
Ramus Breadth
Female (mm)(SD)
34.4 (4.0)
31.5 (2.7)
31.9 (2.2)
30.3 (2.8)
31.9 (3.8)
30.5 (2.9)
Ramus Height
Male (mm)(SD)
Ramus Height
Female (mm)(SD)
62.9 (4.2)
54.3 (2.0)
60.8 (3.4)
53.3 (2.7)
55.1 (4.5)**
49.1 (8.2)**
Bigonial Width
Male (mm)(SD)
Bigonial Width
Female (mm)(SD)
100.9 (9.5)
91.7 (6.1)
101.1 (3.2)
94.7 (4.9)
100.2 (6.3)
94.1 (5.4)
*p <.05 young vs middle
**p<.05 middle vs old

Conclusions: Mandibular length and height both significantly decreased for each gender. These bony changes may result in the appearance of decreased lower face projection and height that is found with increased age. The mandibular angle increased with age, which resulted in blunting or the loss of definition of the lower border of the face. The overall loss of mandibular volume may also contribute to decreased support of the buccal fat pad allowing its descent and the appearance of jowling. Mandibular volume loss also affects the aging of the neck as it may contribute to the increased laxity of the platysma and soft tissues of the neck. These results suggest that the mandible changes dramatically with age and that facial bone aging is overall a process of bony volume loss and remodeling. Thus, we feel a balanced approach to facial rejuvenation should include volume augmentation and soft tissue envelope.

 

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