1. Anti-Calculus-Benefit

Anti-Calculus-Benefit

Dental calculus forms through the mineralization of dental plaque, resulting in a variety of different crystalline forms (Sidaway 1978). First, new crystals form, that are composed of calcium and phosphate, which then grow and harden into calculus (Figures 18-19). The mineral content for supragingival and subgingival calculus is on average 37% and 58% by volume, respectively (Friskopp & Isacsson 1984). Supragingival calculus also contains bacterial debris and toxins as well as viable aerobic and anaerobic bacteria (Tan et al. 2004a; Tan et al. 2004b; White et al. 1997). This is of clinical significance as it can be a reservoir of pathogenic bacterialspecies (Tan et al. 2004b). Dental calculus is common in adults, and less common in children (Anerud et al. 1991).

Formation of dental calculus

Figure 18. Formation of dental calculus

In the 2-step and smooth texture formulas, the positively charged zinc ion (Zn2+) inhibits crystal growth by substituting for calcium in the crystal lattice of calcium phosphate (Figure 22). This interferes with the crystal formation and slows crystal growth (Segreto et al. 1991). Stannous fluoride also inhibits plaque formation, which is the structure on which calcium and phosphate precipitate.

Supragingival calculus

Figure 19. Supragingival calculus

Mechanism of action

Pyrophosphate helps to reduce dental calculus through a mineral chelating effect that inhibits plaque mineralization. It has a natural binding affinity for calcium ions. The anticalculus effect is due to adsorption and binding of the pyrophosphate to the tooth surface and to forming crystals of calcium phosphate in plaque, helping to inhibit the growth and maturation of calculus (White & Gerlach 2000; Rykke & Rolla 1990; Rolla et al. 1988). Sodium hexametaphosphate (Figure 20) is a longer-chain form of pyrophosphate, with more binding sites. It has a greater affinity for hydroxyapatite surfaces, and binds strongly to the tooth surface and the surface of developing calculus in plaque. (Figure 21 White & Gerlach 2000; Baig et al. 2002, Busscher et al. 2002)

Hexametaphosphate molecule

Figure 20. Hexametaphosphate molecule

Mechanism of action of sodium hexametaphosphate

Figure 21. Mechanism of action of sodium hexametaphosphate

In the 2-step and smooth texture formulas, the positively charged zinc ion (Zn2+) inhibits crystal growth by substituting for calcium in the crystal lattice of calcium phosphate (Figure 22). This interferes with the crystal formation and slows crystal growth (Segreto et al. 1991). Stannous fluoride also inhibits plaque formation, which is the structure on which calcium and phosphate precipitate.

Mechanism of action of zinc

Figure 22. Mechanism of action of zinc

Sodium hexametaphosphate and zinc inhibit calculus
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