Light-cured cements

Preformed acrylic polymer facings (Fig. 13), cemented to fractured, deformed or discolored enamel surfaces by an ultraviolet light curing cement similar to the fissure sealant in composition, are currently in extensive use and seem to fill a cosmetic need. 

Another development has been the advent of the dual-cure resin cements. These are hybrids of glass polyalkenoate cements and methacrylates that set both by an add-base cementation reaction and by vinyl polymerization (which may be initiated by light-curing). In these materials, the solvent is not water but a mixture of water and hydroxyethylmethacrylate which is capable of taking dimethacrylates and poly(acrylic add)-containing vinyl groups into solution. In the absence of light these materials set slowly and... 

Minnesota Mining Manufacturing Company. (1989). Vitrabond Light Cure Glass Ionomer Cement Liner/Base. Report of Dental Products, 3M Health Care. 

Nicholson, J. W., Anstice, H. M. McLean, J. W. (1992). A preliminary report on the effect of storage in water on the properties of commercial light-cured glass-ionomer cements. British Dental Journal, 173, 98-101. 

Rice SL, Bailey WF, Wayne SF, Burns JA Comparative in vitro sliding-wear study of conventional, microfilled and light cured composite resin and glass ionomer cement. J Dent Res 1984 63 1173-1175. 

Kazemzadeh, A. (2012) Development of strong and bioactive calcium phosphate cement as a light-cure organic-inorganic hybrid. /. Mater Sci. Mater Med., 23 (7), 1569-1581. 

H.M. Anstice, J.W. Nicholson, Smdies on the structure of light-cured glass-ionomer cements, J. Mater. Sci. Mater. Med. 3 (1992) 447 51. 

For light-cured materials, the initiator system can be based on camphorquinone, so that cements can be cured with a conventional dental cure lamp emitting at a maximum wavelength around 470nm. Unlike formulations of composite resin, these materials cannot deploy amines as activators, because they would react with the carboxylic acid groups on the polymer, forming salts. Instead, a substance such as sodium p-toluene sulfinide is used as the activator. In addition, a photo-accelerator such as ethyl 4-NJ -dimethylamino benzoate is included [10]. 

Clinical use of resin-modified glass-ionomer cements (a) Light-cured RMGlCs... 

Apply first layer of cement to a maximum depth of 2 mm and light cure for 40 s. Apply next layers, curing each one for 40s. 

R.E. Kerby, J. Knobloch, A. Thakur, Strength properties of visible-light-cured resin-modified glass-ionomer cements, Oper. Dent. 22 (1997) 79-83. 

M. Raadal, A.B. Urldlen, O.L. Nilsen, Fissure seaUng with a light-cured resin-modified glass-ionomer cement (Vitrebond) compared with a resin sealant, Int. J. Paediatr. Dent. 

More recently, the question of the performance of light-cured resin-based calcinm hydroxide materials has been considered [41], In this study, the brand Biocal was compared with two self-cure calcium hydroxide chelate cements, Dycal and Hidro C. Two criteria were evaluated, namely water sorption and solubility, with pure water being the medinm in both cases. Results are shown in Tables 9.4 and 9.5. 

Calcium hydroxide can be used as a supersaturated solution, as chelate cements and as a light-cured resin (in UDMA systems). 

The predominant bonding mechanism is mechanical retention and the most common bonding systems are either a composite, generally light-cured, or polyalkenoate cements similar to those used in restorative dentistry (see Adhesion in dentistry restorative materiais). In a recent development to minimize operator errors, the bracket base is pre-coated with the adhesive so that there is no mixing, no contamination and there is a controlled amount of adhesive. The adhesive is typically a lightly filled combination of bisphenol A diglycidyl dimethacrylate and bisphenol A bis(2-hydroxyethyl ether)... 

An extension of the use of self or light curing fissure sealant compositions developed for enamel defects, is the application to cements for the attachment of orthodontic brackets to etched enamel (Fig. 12). This use has proven quite satisfactory. 

One of the most interesting recent developments has been the advent of the resin glass polyalkenoate cements (Antonucci, McKinney Stansbury, 1988 Mitra, 1989 Wilson, 1989, 1990 Mathis Ferracane, 1989 Minnesota Mining Manufacturing Company, 1989 Albers, 1990). They are dual-cure hybrids that set by a combination of acid-base and polymerization reactions, and there are several types. Polymerization is effected by either chemical or light initiation. 

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