title: Interaction of zinc with dental mineral.
abstract: As some currently available toothpastes contain zinc compounds, the reaction of zinc with dental mineral and its effect on crystal growth rates were studied using three synthetic calcium-deficient hydroxyapatites (HAP) as being representative of dental mineral. Zinc was readily acquired by all HAP samples in the absence of added calcium, the amount adsorbed being proportional to the HAP surface area; about 9 mumol Zn/m2 was adsorbed at high zinc concentrations. As zinc was acquired, calcium was released, consistent with 1:1 Ca:Zn exchange. Soluble calcium reduced zinc uptake and similarly, calcium post-treatment released zinc. Pretreatment of HAP with 0.5 mM zinc reduced its subsequent ability to undergo seeded crystal growth, as did extracts of a toothpaste containing 0.5% zinc citrate, even in the presence of saliva. The reverse reaction, i.e. displacement of adsorbed zinc by salivary levels of calcium, however, indicates the mechanism by which zinc can reduce calculus formation in vivo by inhibiting plaque mineralisation without adversely affecting the anti-caries effects of fluoride.
authors.affiliation: Unilever Dental Research, Port Sunlight Laboratory, Bebington, UK.
authors.forename: G S
authors.initials: GS
authors.lastname: Ingram
authors.forename: C P
authors.initials: CP
authors.lastname: Horay
authors.forename: W J
authors.initials: WJ
authors.lastname: Stead
mesh_terms: D000085:Acetates / Q000737:chemistry; D019342:Acetic Acid; D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry; D002951:Citrates / Q000737:chemistry; D019343:Citric Acid; D003460:Crystallization; D011756:Diphosphates / Q000737:chemistry; D017886:Durapatite; D005459:Fluorides / Q000737:chemistry; D006801:Humans; D006882:Hydroxyapatites / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D012463:Saliva / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012969:Sodium Fluoride / Q000737:chemistry; D013499:Surface Properties; D014100:Toothpastes; D015032:Zinc / Q000737:chemistry*
chemical_list: D000085:Acetates; D002130:Calcium Phosphates; D002951:Citrates; D011756:Diphosphates; D006882:Hydroxyapatites; D010710:Phosphates; D014100:Toothpastes; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C012980:fluorophosphate; D019343:Citric Acid; C485838:calcium phosphate, monobasic, anhydrous; D012822:Silicon Dioxide; D012969:Sodium Fluoride; D017886:Durapatite; C020243:calcium phosphate; D015032:Zinc; C485829:calcium phosphate, dibasic, anhydrous; D000537:Aluminum Oxide; D019342:Acetic Acid; D005459:Fluorides; D002118:Calcium