Recently, there has been increased interest and development in calcium phosphate-based remineralization technology (Reynolds and del Rio, 1984; Rosen et al., 1984). One of the newest modalities in preventive dentistry is the introduction of amorphous calcium phosphate (ACP) into methacrylate composites, gum, pastes, and other dental products. Casein is the predominant phosphoprotein in bovine milk and accounts for almost 80 percent of its total protein, primarily as calcium phosphate stabilized micellular complexes (Aimutis, 2004). Several laboratory and animal experiments have investigated the low cariogenic potential and the possible cario-static activity of dairy products (milk, casein, caseinates and cheeses). The use of casein as an anticariogenic additive to food, toothpaste or drinking water has not been implemented because of its adverse organoleptic properties and the large amount required for efficacy (Reynolds, 1998).

Casein phosphopeptide (CPP) contains the cluster sequence of -Ser (P)-Ser (P)-Ser (P)-Glu-Glu from casein (Iijima et al., 2004). CPP does not have the limitations of casein, has the potential for specific anticariogenic activity, and is at least 10 times greater on a weight basis than it is for casein (so not as much is needed for it to be effective). CPP can remarkably stabilize calcium phosphate (which usually is highly insoluble) in a state-forming CPP-amorphous calcium phosphate (ACP) complex. There is no conclusive evidence that ACP is an integral mineral component in hard tissues. Its advocates theorize that it likely plays a special role as a precursor to bioapatite and as a transient phase in biomineralization. In solutions, ACP is converted readily to stable crystalline phases such as octacalcium phosphate or apatitic products (Mathew and Takagi, 2001). Reynolds and colleagues have proposed that under acidic conditions, localized CPP-ACP buffers the free calcium and phosphate ions, substantially increasing the level of calcium phosphate in plaque and, therefore, maintaining a state of supersaturation that inhibits enamel demineralization and enhances remineralization (Reynolds et al., 1999). Rose conducted a laboratory experiment in which he showed that CPP-ACP binds well to dental plaque, providing a large calcium reservoir that may inhibit demineralization and assist in subsequent remineralization (Rose, 2000).

This technology has entered the orthodontic marketplace in two different forms: resin bracket bonding cement containing ACP and topical paste containing the CPP-ACP complex. Aegis-Ortho, an ACP-including resin bonding cement, has been marketed by Bosworth (Skokie, IL) as a substitute for ordinary bracket bonding cement, with the added benefit of caries prevention. The manufacturer claims that the acidic challenge (pH at or below 5.8) to the surrounding bracket area will trigger the release of calcium and phosphate from the cement, and a supersaturated calcium phosphate matrix will not only inhibit demineralization, but also remineralize the enamel. ACP-filled composite resins have been shown to recover 71 % of the lost mineral content of demineralized teeth (Skrtic et al., 1996).

A similar chemical process is manifested with MI paste (GC America, Alsip, IL). Instead of residing in the resin cement, the casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is applied topically in the mouth to affected areas. The manufacturer implicates this product not only lesion prevention (applied twice daily after brushing throughout orthodontic treatment), but also claims the patient can expect the complete reversal of such lesions after three months use post-debonding. Additionally, the manufacturer has recommended MI paste for dental patients with xerostomia, dental sensitivity, gastric reflux, fluorosis, exposed root surfaces, and as an adjunct to tooth bleaching.

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