Topical Products Applied to the Nail
Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters in Cosmetic Formulation, 2019
UV-cured shellacs are nail cosmetics that offer better customer satisfaction, as they are known to dry rapidly. Shellacs are chip resistant and can be worn on natural nails comfortably for about 4–6 weeks after which they need to be soaked in acetone to facilitate removal. Shellacs have the same pigments used in the formulation of nail lacquers (Jefferson and Rich, 2012). Shellacs use a base that contains polymerization photoinitiator along with UV curable methacrylates or acrylate oligomers (Jefferson and Rich, 2012). The application of shellac involves six coating steps that includes two coats of the base polymer followed by two coats of pigmented polymers and finally two clear coats with intermittent UV curing after each application. They use methacrylate or acrylate oligomers and monomers in place of resins and standard solvents. However, great care needs to be taken to prevent sensitization of the skin as patients are likely to develop contact dermatitis to uncured excipients (Lawry and Rich, 1999; Vickery et al., 2010).
Injectable Scaffolds for Bone Tissue Repair and Augmentation
Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon in Tissue Engineering Strategies for Organ Regeneration, 2020
Another way to activate the hardening effect in the injectable paste at targeted site is use of ultraviolet (UV) light. Si doped HAp nanopowder incorporated photocurable aligate paste was prepared for orthopaedic application. Si doped HAp nanopowder incorporated alginate-based paste showed good injectability and hardened after UV exposure to generate a sparsely porous matrix (Gupta 2018). However, the chromosomal and genetic instability of exposed cells possess concern while using the UV lights for photo-polymerization (Dahle et al. 2005, Kappes et al. 2006). Care should also be taken with use of toxic photoinitiator or intense UV light irradiation along with these cell-encapsulated pastes as they can lead to cell damage.
Adjustable intraocular lenses: The light adjustable lens
Pablo Artal in Handbook of Visual Optics, 2017
The material and optical design of the LAL is based upon the principles of photochemistry and diffusion whereby photoreactive components incorporated in the cross-linked silicone lens matrix are photopolymerized upon exposure to UV light (365 nm) of a select spatial irradiance profile. Figure 14.1 displays a cartoon picture of the LAL and its major constituents. The first component of note is shown as the long green strands and corresponds to the polymer matrix, which acts to give the LAL its basic optical and mechanical properties. The polymer matrix is composed of a high-molecular-weight (>200 K) polysiloxane that also possesses a covalently bonded UV blocker (not shown). Due to its cross-link density and inherent low glass transition temperature (~–125°C), the LAL’s polymer matrix allows for relatively rapid diffusion throughout its polymer network. The second major constituent are the smaller, purple strands noted as macromer. The macromer is a low, relative to the matrix polymer, molecular weight polysiloxane. From a chemical standpoint, the majority of the macromer chain is the same as that of the polymer matrix, which allows for essentially infinite miscibility of the macromer within the polymer matrix. The fact that the macromer and polymer matrix are miscible with each other avoids the potential for phase separation and subsequent light scatter. The most unique aspect of the macromer molecule is the presence of symmetric, photopolymerizable methacrylate end groups at the end of each macromer chain. The final chemical moiety of note is listed as the photoinitiator, which acts to catalyze the photopolymerization reaction of the macromer end groups.
Influence of resin cement on color stability of ceramic veneers: in vitro study
Published in Biomaterial Investigations in Dentistry, 2021
Maryam Hoorizad, Sara Valizadeh, Haleh Heshmat, Seyedeh Farnaz Tabatabaei, Tahereh Shakeri
In resin cements, a low degree of conversion could explain discoloration [29]. Resin cement discoloration is influenced by some factors related to the material such as type of filler, resin matrix chemistry and photoinitiator. Variolink NLC contains a thiocarbamide photo-initiator derived from dibenzoyl germanium (Ivocerin). This is categorized as type II photoinitiator which is used to enhance the color stability of resin cements [30]. The current study showed greater color change for Variolink NLC. This result may be contributed to the chemical structure of cements including differences in content of fillers or monomer composition of cements. As there is no furthered information available regarding the composition of these two luting resin agents, future studies seems necessary to thoroughly investigate properties of the cements.
Monowave and polywave light-curing of bulk-fill resin composites: degree of conversion and marginal adaptation following thermomechanical aging
Published in Biomaterial Investigations in Dentistry, 2021
Sheila Celia Mondragón Contreras, Ana Luiza Barbosa Jurema, Evaniele Santos Claudino, Eduardo Bresciani, Taciana Marco Ferraz Caneppele
In some bulk-fill RCs, camphorquinone (CQ), which is the most common photoinitiator in conventional RCs, is also used [12]. First and second-generation light-emitting diode (LED) light-curing units (LCUs) show one emission peak (monowave, MW) that matches the absorption spectrum of CQ (430–500 nm) [16]. However, such LCUs may not provide adequate cure of RCs containing alternative initiators. Tetric N-Ceram Bulk Fill (TB) contains Ivocerin, a photoinitiator characterized by high quantum efficiency and high absorption capacity. This germanium-based initiator system has a greater photo-curing activity than CQ. The absorption peak of Ivocerin is set in the violet spectrum (380–420 nm) and slightly extends to the blue spectrum range (420–455 nm), where almost 50% of its peak absorbance occurs at 440 nm. Ivocerin is a photoinitiator with higher photopolymerization reactivity [17]. The third-generation LED LCUs are considered to be broad-spectrum devices. They have two or more emission peaks (polywave, PW) with narrower wavelengths; violet to activate alternative photoinitiators and blue to activate CQ [18].
Synthesis of high payload nanohydrogels for the ecapsulation of hydrophilic molecules via inverse miniemulsion polymerization: caffeine as a case study
Published in Drug Development and Industrial Pharmacy, 2019
Fiora Artusio, Ada Ferri, Valeria Gigante, Daniele Massella, Italo Mazzarino, Marco Sangermano, Antonello Barresi, Roberto Pisano
Concerning the differences in the plateau quantity of released caffeine, some considerations must be done. It is indeed well known that caffeine molecules undergo degradation under UV irradiation. Such an issue is quite common to several drug molecules and sometimes limits the shelf life of pharmaceutical formulations. Given the use of UV light in the synthesis of the nanocarriers, the potential degradation of the caffeine molecules had been initially assessed by spectrophotometry. After UV irradiation of a solution of caffeine, using the same operating conditions used for the encapsulation process, we observed a decrease of about 40% in the absorbance peak at 273 nm. Conversely, when photoinitiator was added to the solution according to the ratios used in the nanohydrogel synthesis, the decrease in caffeine absorbance turned out to be around 1%. Therefore, the photoinitiator had a vital role as concerns the protection of the active ingredient from UV degradation. These results suggest that our encapsulation process allows the protection of the drug molecule from external factors that could degrade it and is in agreement with the findings of Bazzano et al. [49] who successfully employed this approach to incorporate an even more UV-sensitive drug such as curcumin. Instead, the amount of drug released by the caffeine-loaded miniemulsion is lower and this is ascribed to the absence of the photoinitiator in the emulsion and therefore of UV protection.
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