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Anthropometry and Biomechanics
Published in Nancy J. Stone, Chaparro Alex, Joseph R. Keebler, Barbara S. Chaparro, Daniel S. McConnell, Introduction to Human Factors, 2017
Nancy J. Stone, Chaparro Alex, Joseph R. Keebler, Barbara S. Chaparro, Daniel S. McConnell
Kroemer (1987) identified other common terms including height, a straight vertical (i.e., inferior–superior) measurement; breadth, a straight horizontal (i.e., lateral–lateral) measurement across the body; depth, a straight, horizontal measurement from the front of the body to the back (i.e., anterior–posterior); and circumference, usually a closed, but noncircular measurement, whereas curvature is usually an open, noncircular measurement. Applying these terms, sitting height is measured from the seat to the top of the head (Pheasant, 1990), and shoulder breadth is measured between two shoulder landmarks. Similarly, sitting depth (or more specifically, the buttock–popliteal length) is measured from the chair back to the popliteal or the back of the knees (see Table 9.1). Another commonly used measure is stature, which is standing height from the floor to the top of one’s head (i.e., the vertex or crown) (Pheasant, 1990, 1996). For an in-depth look at various anthropometric measures and illustrations identifying what is measured, see Pheasant and Haslegrave (2006) or Roebuck (1995). Table 9.1 presents a list of common anthropometric measurements for US men and women 19–65 years of age.
Polymers-Based Devices for Dermal and Transdermal Delivery
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
Donatella Paolino, Margherita Vono, Felisa Cilurzo
Another alternative to conventional liposomes is represented by niosomes that are non-ionic surfactant vesicles formed through self-assembly in an aqueous media. In respect to liposomes, niosomes are characterized by low cost and great stability. Niosomes may be made up of a variety of amphiphiles bearing sugar, polyoxyethylene, polyglycerol, crown ether, and amino acid hydrophilic head groups; and these amphiphiles typically possess one to two hydrophobic alkyl, perfluoroalkyl, or steroidal groups (Manconi et al. 2003), and bolaform surfactants (Paolino et al. 2007, 2008). The topical application of niosomes can increase the residence time of the drug in the stratum corneum, allowing the epidermis to receive a local therapeutic effect, thus reducing the systemic absorption of the drug compound and consequently the appearance of side effects. Moreover, the topical application reduces transepidermal water loss and increases smoothness through the replenishment of lost skin lipids. The structure of non-ionic surfactant vesicles offers great opportunities for drug delivery because their size, shape, surface charge, and composition can be altered and adapted to the characteristics of the drug.
Core build-up resin composites: an in-vitro comparative study
Published in Biomaterial Investigations in Dentistry, 2020
L. Spinhayer, A.T.B. Bui, J.G. Leprince, C.M.F. Hardy
Strategies for restoring severely damaged teeth have changed considerably over the last few years with the advent of adhesive dentistry [1]. Dentistry is evolving to become less and less invasive, the preservation of dental tissues becoming a major concern for practitioners [2]. Indirect bonded restorations are therefore more and more common and reliable [3,4] Nevertheless, full crowns remain a valid option, with long survival rates [4], and are particularly indicated for specific indications, i.e. bridges, crown with precision attachment for removable prosthesis, crown replacement, or highly discolored teeth in need of coverage. In any case, the teeth requiring a full crown are often severely damaged, with large structural loss and, as a result, often root canal-treated. Whether the root canal treatment additionally weakens the tooth is debated [5,6], but most agree that the loss of tooth structure at the coronal level represents the major cause for increased risk of tooth fracture [7]. The low amount of remaining tooth tissue represents a major restorative challenge for the practitioner to ensure the best possible longevity of both the restoration and the tooth. The classical restorative strategy, supported by many clinical studies, consists of preparing a core build-up, with or without a root canal post, followed by the placement of a full crown.
Debonding mechanism of zirconia and lithium disilicate resin cemented to dentin
Published in Acta Biomaterialia Odontologica Scandinavica, 2019
Mina Aker Sagen, Ketil Kvam, Eystein Ivar Ruyter, Hans Jacob Rønold
Despite excellent mechanical properties of zirconia there are complications related to clinical use. Loss of retention of tooth supported crowns is reported as one of the most frequent technical complication. Many approaches have been studied with the aim to increase bond strength between resin cement and zirconia [5]. Tribochemical silica coating, plasma spraying, selective infiltration technique, hot etching and different lasers have been investigated [6]. The results varied when it came to both tensile and share bond strength in laboratory tests, and storage in water or thermocycling showed low predictability of a stable bond [7].