Skin Imperfections Research Articles

Presented at the 16th DGK Symposium, March 2–4, 2005, Leipzig, Germany – Received the Award for the Best Poster Presentation 1 Influencing the equilibrium of the cutaneous ecosystem to improve the properties of skin prone to acne

The skin is colonized by a variety of microorganisms such as Propionibacterium acnes, Staphylococcus epidermidis and Malassezia furfur that are in a stable balance and form the resident skin flora. The homeostasis of this ecosystem is of fundamental importance as it plays a barrier role by limiting the invasion and growth of pathogenic bacteria on the skin surface. An internal or external change in the skin environment, a transitory lack of hygiene, a change in hormone status or hyperseborrhea can upset this balance at any time and enable the proliferation of saprophytic skin microorganisms or contamination by pathogens. Hyperseborrhea causes retention lesions such as open comedos and closed microcysts that can be transformed into papulae, pustules or nodules in the case of an inflammatory reaction caused by abnormal bacterial proliferation. These skin disorders are particularly pronounced between the ages of 12 and 25 but nonetheless affect all ages and cause oily skin accompanied by unsightly imperfections that are difficult to camouflage and live with. The skin combats microbial infections with its natural defense system. Keratinocytes produce and secrete a large number of peptides with direct and indirect antimicrobial activity (cathelicidins, β‐defensins). These natural antimicrobial peptides limit the proliferation of pathogenic bacteria and fungi such as Staphylococcus aureus or Candida albicans and can also induce an indirect immune response. They are indispensable for the homeostasis of the cutaneous ecosystem and are over‐expressed by keratinocytes in response to an inflammatory stimulus or an infection. When these natural defenses are disturbed or overwhelmed, they must be stimulated to limit the inflammatory reactions that result in the appearance of skin imperfections such as acne. To this end, we have developed an extract purified from Filipendula ulmaria (meadowsweet) that is rich in phenolic acids. Tested at 1% on human keratinocytes, the F. ulmaria extract stimulated the natural defense functions of the skin by boosting the synthesis of cathelicidins by 130%. In addition, when tested in vivo at 4%, the F. ulmaria extract significantly reduced the lipid index by 12% in 71% of volunteers after 28 days of twice‐daily treatment. The F. ulmaria extract stimulates the natural defense functions of the skin, preventing the proliferation of bacteria on the skin surface and thereby limiting complications from acne: The number of spots and their total occupied surface were significantly reduced by ‐10% and ‐12%, respectively. Finally, dermatological evaluation after 28 days of twice‐daily use showed the capacity of the F. ulmaria extract to significantly improve the quality of skin prone to acne: The homogeneity of skin grain was improved (+21%), the number of inflammatory lesions reduced (‐20%) and the infiltration of lesions decreased (‐22%).

Size Effect of Cohesive Delamination Fracture Triggered by Sandwich Skin Wrinkling

Because the observed size effect follows neither the strength theory nor the linear elastic fracture mechanics, the delamination fracture of laminate-foam sandwiches under uniform bending moment is treated by the cohesive crack model. Both two-dimensional geometrically nonlinear finite element analysis and one-dimensional representation of skin (or facesheet) as a beam on elastic-softening foundation are used. The use of the latter is made possible by realizing that the effective elastic foundation stiffness depends on the ratio of the critical wavelength of periodic skin wrinkles to the foam core thickness, and a simple description of the transition from shortwave to longwave wrinkling is obtained by asymptotic matching. Good agreement between both approaches is achieved. Skin imperfections (considered proportional to the the first eigenmode of wrinkling), are shown to lead to strong size dependence of the nominal strength. For large imperfections, the strength reduction due to size effect can reach 50%. Dents from impact, though not the same as imperfections, might be expected to cause as a similar size effect. Using proper dimensionless variables, numerical simulations of cohesive delamination fracture covering the entire practical range are performed. Their fitting, heeding the shortwave and longwave asymptotics, leads to an approximate imperfection-dependent size effect law of asymptotic matching type. Strong size effect on postpeak energy absorption, important for impact analysis, is also demonstrated. Finally, discrepancies among various existing formulas for critical stress at periodic elastic wrinkling are explained by their applicability to different special cases in the shortwave-longwave transition.

Unusual primary and secondary facial blast injuries

Purpose: To discuss unusual facial injuries resulting from a bomb blast. Materials and Methods: In March 1997, a bomb consisting of a bag of nails was detonated in a coffee shop in Tel Aviv. Two of the wounded were brought to our level 1 Trauma Center with unique facial injuries. Computed tomography (CT) scan and CT angiogram were performed. Results: The blast occurred to the immediate right of the victims who were sitting in an open cafe. Both had tympanic perforation. The first patient showed indirect damage to the facial nerve from a piece of shrapnel located anterior to the carotid artery and medial to the right mandibular angle. The second had a piece of shrapnel lodged in the parapharyngeal space that was initially missed and discovered only on reexamination 3 days later after the patient complained of pain in the temporomandibular joint; there was no facial nerve deficit. The port of entry was probably a small wound in the anterior wall of the external ear canal. Conclusions: The wounds are probably attributable to the spalling effect of the shrapnel passing through the parotid gland, which has mixed-density tissue. These cases show that nerves are susceptible to damage even in the absence of direct engagement and that the emergency room physician should be alert to even small skin imperfections in blast victims to avoid missing penetrating wounds. (Am J Otolaryngol 2003;24:75-77. Copyright 2003, Elsevier Science (USA). All rights reserved.)

Comparison of chemical peel and dermabrasion to carbon dioxide (CO 2) laser resufacing

Chemical peel and dermabrasion have been time-tested modalities for treating cutaneous imperfections. These techniques provide a reliable and effective means for treating superficial and deep skin imperfections associated with aging and long-term sun exposure. With significant experience, these procedures offer a predictable and uniform result. However, significant variability exists with each of these techniques and, in the hands of a less experienced and less skilled surgeon, procedural variability becomes a significant factor. The advent of new technologically advanced carbon dioxide (CO₂) lasers has provided a new means to exfoliate tissue. With computerized scanning devices, significant reduction of the inherent technique-dependent variability is possible. This provides a more controlled and uniform level of tissue exfoliation and potentially more reliable and improved results.