Neither author has a financial or proprietary interest in any material or method mentioned.

Biomechanics is often defined as ‘mechanics applied to biology’. Due to the variety and complexity of the behaviour of biological structures and materials, biomechanics is better defined as the development, extension and application of mechanics for a better understanding of physiology and physiopathology and consequently for a better diagnosis and treatment of disease and injury. Different methods for the characterisation of corneal biomechanics are reviewed in detail, including those that are currently commercially available (Ocular Response Analyzer and CorVis ST). The clinical applicability of the parameters provided by these devices are discussed, especially in the fields of glaucoma, detection of ectatic disorders and orthokeratology. Likewise, other methods are also reviewed, such as Brillouin microscopy or dynamic optical coherence tomography and others with potential application to clinical practice but not validated for in vivo measurements, such as ultrasonic elastography. Advantages and disadvantages of all these techniques are described. Finally, the concept of biomechanical modelling is revised as well as the requirements for developing biomechanical models, with special emphasis on finite element modelling.

Translucency is one of the most important parameters to be considered by digital systems when predicting the matching appearance and hence the quality of prosthodontic restoration work. Our objective has been to improve the effectiveness of the algorithmic decision systems employed by these devices by (a) determining whether Kubelka-Munk theory can be used as an algorithm for predicting restoration suitability, and (b) evaluating the correlation between the visual evaluation of prosthodontic materials and the predicted translucency based on the use of the ΔE*, OP, CR, and K/S algorithms. In this regard, three zirconia systems and one lithium disilicate have been spectrophotometrically and visually characterized. Based on the results of this study, it has been proven that zirconia systems and lithium disilicate systems exhibit different optical behaviors. The psychophysical experience suggests that none of the existing mathematical methods can adequately estimate translucency, spectrophotometric, and colorimetric techniques, and that which is perceived by an experienced observer. However, translucency evaluation through the K/S algorithmic decision system should not be disregarded. New methods to measure translucency should be developed to improve digital systems for prosthodontic applications.

We present a comparison between the methods used by two regulatory standards to estimate the luminance decay time for photoluminescent safety signs and safety way guidance systems (SWGS). One of these standards is the international ISO 16069. The other is the Spanish regulatory standard UNE 23035-1. Both standards define the luminance decay time as the time for the luminance emitted by the photoluminescent sample to reach 0.3 mcd/m 2 after the excitation light over the sample is removed. Due to the fact that decay time can be really long, they propose methods to estimate it by extrapolation. The points suggested by each standard to adjust the luminance decay time curve are quite different and so are the results obtained with them. To compare both methods, four different photoluminescent safety signs were tested using the methods provided by these two regulatory standards. The samples were illuminated for 5 min with a xenon-arc source of light; luminance measurements after illumination were made with a B-510 LMT photometer, for an interval of time according to methods explained by the standards. The results were compared with real measurements of luminance decay time for each sample, allowing the luminance value to reach 0.3 mcd/m 2 . Results obtained from the extrapolating methods provided by each standard showed that standard ISO 16069 was much more accurate than UNE 23035-1, which showed important deviations from real decay time values.