Consumption of acidic foods and drinks and other factors that cause enamel wear are responsible for the daily enamel loss and degradation. Use of some toothpastes that have been showed to possess different properties of remineralisation and/or repair of the enamel surface may help to protect tooth enamel. The aim of this study was to evaluate whether the use of toothpaste containing Zn-carbonate hydroxyapatite (CHA) nanostructured microcrystals may exert remineralization/repair effects of the enamel surface. In conclusion, this study demonstrates that the toothpaste containing Zn-CHA nanostructured microcrystals, differently from nitrate potassium/sodium fluoride and non-specified fluoride toothpastes, may promote enamel superficial repair by means of the formation of a protective biomimetic CHA coating (1).

Several dentifrices have shown to be effective in reducing dentine hypersensitivity (DH), but more effective products are needed. The aim of the study was to evaluate the desensitizing efficacy of a new dentifrice based on zinc-carbonate hydroxyapatite (CHA) nanocrystals. This study documented that the new dentifrice containing zinc-CHA nanocrystals significantly reduced dentinal hypersensitivity after 4 and 8 weeks, supporting its utility in clinical practice (2).

This 12-week prospective, randomized, double-blind, two-center trial evaluated the impact of a microcrystalline zinc hydroxyapatite (mHA) dentifrice on plaque formation rate (PFR) in chronic periodontitis patients. We hypothesized that mHA precipitates cause delayed plaque development when compared to a fluoridated control (AmF/SnF2), and therefore would improve periodontal health. In patients with mild-to-moderate periodontitis, periodontal therapy and use of a mHA-or AmF/SnF2 dentifrice without instructions induced comparable improvements in periodontal health but did not significantly reduce the PFR (3).

Biodegradable zinc materials are promising candidates for the new generation of orthopedic implants. However, the slow degradation rates and unsatisfactory cytocompatibility of pure Zn in bone environments limit its future clinical applications. Generally, alloying is a common way to improve the performance of pure Zn. In this study, metal matrix composite was chosen as a novel strategy to solve the problems. Hydroxyapatite, as a bioactive component, was added into Zn matrix via spark plasma sintering. We find that Zn-HA composites exhibited adjustable degradation rates and improved biocompatibility both in vitro and in vivo. This study provides exhaustive and significant information including microstructure, mechanical performance, degradation behavior, biocompatibility, hemocompatibility and antibacterial property for the future Zn based implants design (4).

References________________________________________________________________________

(1) Marco Lelli, Angelo Putignano, Marco Marchetti, Ismaela Foltran, Francesco Mangani, Maurizio Procaccini, Norberto Roveri, Giovanna Orsini Remineralization and repair of enamel surface by biomimetic Zn-carbonate hydroxyapatite containing toothpaste: a comparative in vivo study  Front Physiol. 2014; 5: 333. Published online 2014 Sep 5. Prepublished online 2014 Jul 27. doi: 10.3389/fphys.2014.00333

(2) Orsini G, Procaccini M, Manzoli L, Giuliodori F, Lorenzini A, Putignano A  A double-blind randomized-controlled trial comparing the desensitizing efficacy of a new dentifrice containing carbonate/hydroxyapatite nanocrystals and a sodium fluoride/potassium nitrate dentifrice.  J Clin Periodontol. 2010 Jun;37(6):510-7. doi: 10.1111/j.1600-051X.2010.01558.x

(3) Harks I, Jockel-Schneider Y, Schlagenhauf U, May TW, Gravemeier M, Prior K, Petersilka G, Ehmke B. Impact of the Daily Use of a Microcrystal Hydroxyapatite Dentifrice on De Novo Plaque Formation and Clinical/Microbiological Parameters of Periodontal Health. A Randomized Trial.
Harks I, Jockel-Schneider Y, Schlagenhauf U, May TW, Gravemeier M, Prior K, Petersilka G, Ehmke B.
PLoS One. 2016 Jul 28;11(7):e0160142. doi: 10.1371/journal.pone.0160142. eCollection 2016.

(4) Yang H, Qu X, Lin W, Wang C, Zhu D, Dai K, Zheng Y. In vitro and in vivo studies on zinc-hydroxyapatite composites as novel biodegradable metal matrix composite for orthopedic applications. Acta Biomater. 2018 Apr 15;71:200-214. doi: 10.1016/j.actbio.2018.03.007. Epub 2018 Mar 9.

Zinc Hydroxyapatite  is an inorganic chemical compound obtained by neutralising an aqueous suspension of calcium carbonate, calcium hydroxide and zinc hydroxide with phosphoric acid.

The name defines the structure of the molecule:

• Zinc is a chemical element with the symbol Zn. In this compound, zinc ions replace some of the calcium ions in the hydroxyapatite structure.
• Hydroxyapatite refers to the mineral compound with formula Ca₅(PO₄)₃(OH), but is usually spelled Ca10(PO4)6(OH)2 to indicate that the crystalline cell comprises two entities.

The synthesis of zinc hydroxyapatite typically involves the precipitation method. Here is a simplified version of the process:

• Aqueous solutions of calcium nitrate [Ca(NO₃)₂], ammonium hydrogen phosphate [(NH₄)₂HPO₄] and zinc nitrate [Zn(NO₃)₂] are prepared. The molar ratio between calcium and phosphate is kept at 10:6, while the zinc concentration can be varied to achieve different levels of zinc substitution.
• The phosphate solution is slowly added to the calcium-zinc solution under constant stirring. The pH of the solution is carefully controlled during this process, usually by adding a base such as ammonium hydroxide (NH₄OH).
• The mixture is then aged, filtered and washed to remove unreacted ions.
• The resulting precipitate is dried and then heated (calcined) to produce zinc hydroxyapatite.

When we talk about Zinc Hydroxyapatite we refer to a chemical compound that is mainly used in the form of powder or microparticles. A thermal process called "spark plasma sintering" is generally used to combine Zinc and Hydroxyapatite.

What it is used for and where

Cosmetics

Oral care agent. This ingredient can be placed in the oral cavity to improve and/or maintain oral hygiene and health, to prevent or improve a disorder of the teeth, gums, mucous membrane. It provides cosmetic effects to the oral cavity as a protector, cleanser, deodorant.

Commercial applications

Oral Care Agent. Zinc Hydroxyapatite is used in toothpastes and other oral care products to remineralize tooth enamel and prevent cavities.

Abrasive Agent. Used in toothpastes to help remove plaque and food residue from teeth.

Anti-Caries Agent. Has demonstrated properties to combat cavities through the promotion of enamel remineralization.

Anti-Plaque Agent. Zinc Hydroxyapatite can help to prevent the formation of plaque on teeth.

Ingredient in Skin Care Products. Used in some skin care product formulations for its soothing and anti-inflammatory properties.

The most relevant studies on this chemical compound have been selected with a summary of their contents:

Zinc Hydroxyapatite, studies

See also  "Hydroxyapatite" 

Thanks to the physico-chemical properties of its particles, it adheres durably to bacterial surfaces. This can create various therapeutic options including the inhibition of dental biofilm development (1).

References_____________________________________________________________________

(1) Harks I, Jockel-Schneider Y, Schlagenhauf U, May TW, Gravemeier M, Prior K, Petersilka G, Ehmke B. Impact of the Daily Use of a Microcrystal Hydroxyapatite Dentifrice on De Novo Plaque Formation and Clinical/Microbiological Parameters of Periodontal Health. A Randomized Trial.-  PLoS One. 2016 Jul

Abstract.  Aim: This 12-week prospective, randomized, double-blind, two-center trial evaluated the impact of a microcrystalline zinc hydroxyapatite (mHA) dentifrice on plaque formation rate (PFR) in chronic periodontitis patients. We hypothesized that mHA precipitates cause delayed plaque development when compared to a fluoridated control (AmF/SnF2), and therefore would improve periodontal health. Material & methods: At baseline and after 4 and 12 weeks, PFR and other clinical and microbiological parameters were recorded. Seventy periodontitis patients received a mHA or AmF/SnF2 dentifrice as daily oral care without hygiene instructions. Four weeks after baseline, participants received full mouth debridement and continued using the dentifrices for another 8 weeks... Conclusion: In patients with mild-to-moderate periodontitis, periodontal therapy and use of a mHA-or AmF/SnF2 dentifrice without instructions induced comparable improvements in periodontal health but did not significantly reduce the PFR.