In vitro degradation of polydimethylsiloxanes in breast implant applications.

BACKGROUND: The durability of breast implant material is associated with failure probability, increasing with time from implantation. The current study avoided the bias introduced by biological factors, to systematically investigate the degradation over time of shell materials. The same fundamental physical and chemical conditions were maintained (temperature and pH) throughout the study, to decouple biological aspects from the degradation process. METHODS: Six virgin implants of 2 brands were submitted to the in vitro degradation process, mechanical testing of shell materials, surface change analysis (via scanning electron microscopy [SEM]) and chemical composition analysis by Fourier transform infrared (FTIR) spectroscopy. RESULTS: FTIR results showed that the principal chemical bonds of the material remained intact after 12 weeks of degradation. Apparently the implants' shell structures remained unchanged. Despite this observation, there were statistically significant differences between strain at failure at different time points for the shells of both brands, translated into a stiffening of the material over time. CONCLUSIONS: Material stiffening is reported as an indicator of material degradation. This altered mechanical behavior, added to the mechanical friction from tissue-tissue and tissue-implant contact and to the external mechanical loading (physical activity), may alter the material performance in women's bodies. Ultimately these changes may affect the implants' durability. Further work is needed to understand the biological aspects of the degradation process and their impact on implant durability.

Biomechanical properties of breast tissue, a state-of-the-art review.

This paper reviews the existing literature on the tests used to determine the mechanical properties of women breast tissues (fat, glandular and tumour tissue) as well as the different values of these properties. The knowledge of the mechanical properties of breast tissue is important for cancer detection, study and planning of surgical procedures such as surgical breast reconstruction using pre-surgical methods and improving the interpretation of clinical tests. Based on the data collected from the analysed studies, some important conclusions were achieved: (1) the Young's modulus of breast tissues is highly dependent on the tissue preload compression level, and (2) the results of these studies clearly indicate a wide variation in moduli not only among different types of tissue but also within each type of tissue. These differences were most evident in normal fat and fibroglandular tissues.