Ultraviolet light dental applications

Since most of the dental applications employ a photoinitiated process (visible or ultraviolet light), the rate of initiation may be expressed as [92]... 

Heavy metals such as mercury, lead, nickel copper and cadmium have been proven to cause serious health effects on human [1], Mercury had been widely used in many fields, such as medical, scientific research applications, and in amalgam material for dental restoration. It is used in lighting electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce, making visible light. 

DPC is an adaptation of DSC which involves the use of an ultraviolet or visible light source to study the behaviour or photoreactive systems and has specific application to light curable coatings, films, inks, adhesives and dental materials. In particular, it can be used to study the effect of different initiator systems on the cure behaviour of these products, and to investigate the influence that parameters such as the other additives in the products and the cure conditions have on the cure rate etc. The technique is therefore particularly useful for studying the curing behaviour of coatings and inks. 

Dental composite resins (DCRs) based on bisphenol A and (meth)acrylates, e.g. BIS-GMA, have been used since 1962 (Bowen 1962). In addition to acrylics, DCRs contain additives that trigger polymerisation at an appropriate time. These additives include initiators, e.g. benzoyl peroxide, activators, e.g. tertiary aromatic amine, and inhibitors, e.g. hydroquinone they are aU sensitizers (Kanerva et al. 1989). Sensitisation from epoxy acrylates has been reported in dental personnel (Kanerva et al. 1989) and in the ultraviolet (UV) or light-printing industry (Nethercott et al. 1983 Bjorkner 1984). Acrylated urethanes are allergens. They are used in dental composite and sealant applications and have the same role as BIS-GMA (Nethercott et al. 1983 Bjorkner 1984). 

We learned in Section 12.2 that polymers can be characterized by their physical properties. Elastomers are used as biomaterials in flexible tubing over leads for implanted heart pacemakers and as catheters (tubes implanted into the body to administer a drug or to drain fluids). Thermoplastics, such as polyethylene or polyesters, are employed as membranes in blood dialysis machines and as replacements for blood vessels. Thermoset plastics find limited but important uses. Because they are hard, inflexible, and somewhat brittle, they are most often used in dental devices or in orthopedic applications, such as in joint replacements. To fill a cavity, for example, the dentist may pack some material into the cavity, then shine an ultraviolet lamp on it. The light initiates a photochemical reaction that forms a hard, highly cross-linked thermoset polymer. 

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