Three-dimensional analyses of aging-induced alterations in facial shape: a longitudinal study of 171 Japanese males

We sought to generate data to facilitate forensic facial comparisons. Specifically, we conducted a longitudinal study of alterations in face shape induced by aging. We obtained two three-dimensional facial shape measurements in 171 Japanese males at intervals of approximately 10 years. With this data, we created a homologous model consisting of 10,741 data points for each face based on 33 anatomical landmarks. We averaged the movements of corresponding data points between the two homologous models for each individual and used this data to predict up to 30 years of face aging in an average Japanese male. We clearly identified aging-induced shape changes, such as drooping and denting of the facial folds, drooping of the upper lip, and projection of the lower eyelid, in the virtually aged model. A quantitative comparison of aging-induced shape alterations among three age groups (individuals in their 20's, 30's, and 40-50's) showed that these alterations accelerated more quickly as age increased. Using our predictive model, we conducted a preliminary study focused on facial shape alterations induced by reductions in body weight. Our findings indicated that our proposed method would also be valid for this purpose.

The post-mortem resilience of facial creases and the possibility for use in identification of the dead

The post-mortem resilience of facial creases was studied using donated bodies in order to establish the efficacy of crease analysis for identification of the dead. Creases were studied on normal (pre-embalmed) and bloated (embalmed) cadavers at the Centre for Anatomy and Human Identification (CAHID) to establish whether facial bloating would affect facial crease visibility. Embalming was chosen to simulate the effects produced by post-mortem bloating. The results suggested that creases are resilient and changes were only detected for creases located on the periphery of the face, particularly at areas where the skin is thick, such as at the cheeks. Two new creases not previously classified were identified; these creases were called the vertical superciliary arch line and the lateral nose crease. This research suggests that facial creases may be resilient enough after death to be utilised for human identification.

Mechanical approach to aging and wrinkling of human facial skin based on the multistage buckling theory

A wrinkle formation mechanism with cutaneous aging is addressed through a mechanical calculation of linear buckling. Skin is divided into five mechanically distinct layers in this study. In general, the outer layer is stiffer than the inner layer, so buckling occurs in the outer layer against the uniform compression caused by muscle contraction. This buckling damages the skin and affects the formation of permanent wrinkles. We propose a multistage buckling theory for evaluation of the wrinkle property, namely, the specific wrinkle size and critical strain in three stages. The specific wrinkle size is derived as the wavelength of the minimum-buckling mode for infinite-length skin. A sensitivity analysis is carried out to investigate the effect of age-related changes of the mechanical parameters on the wrinkle property. We employ some aging hypotheses and prepare two sets of mechanical parameters, one for young and one for aged skin. The numerical results show that the buckling mode switch from Stage I to Stage II is the main reason why pronounced wrinkles suddenly appear in aged skin.