Role of zinc in maintaining periodontal health
Zinc has a major influence on the oral mucosa, bone metabolism, and host response. Deficiency in zinc alters the thickness and keratinization of oral mucosa which becomes more susceptible to infections. It can also deepen the periodontal pockets and thicken the palatal tissues.
- Zinc deficiency affects the functioning of immune cells such as monocytes, natural killer cells, neutrophils, T‑cells, and lymphocytes.
- It also increases the secretion of pro‑inflammatory cytokines which is an integral component of antioxidant enzymes and its altered levels result in the generation of oxidative stress.
Zinc acts as an antioxidant to decrease oxidative stress. When the oxidative stress in the body is increased, the zinc starts to exhibit its antioxidant property and combat the oxidative stress. This leads to the depletion of zinc level in the body.3
Effect of zinc on oral microorganisms
There are many reports that zinc has several biologic effects in the oral cavity. Zinc has shown to exhibit anti-bacterial, anti-plaque, and anti-caries effects.4
- Zinc can displace cations which are essential for enzymatic processes of the bacteria.4
- Zinc inhibits the trypsin like protease activity of organisms such as Porphyromonas gingivalis as well as being an effective inhibitor of acid production by mutans streptococci.5
- Zinc may act indirectly by inhibiting protease induced adhesion thereby changing the structure of bacterial cell proteins. 4
- Zinc can bind to the surface of oral bacteria and alter their surface potential, and this may affect bacterial adhesion to teeth. 4
- Zinc inhibits the phosphotransferase transport system (PTS) and may reduce glucose uptake by inhibition of enzyme I in the PTS. 4
Effect of zinc when used in a toothpaste
Zinc is generally added to toothpaste as an anti-bacterial agent to help to control plaque, reduce oral malodour and calculus formation through crystal-growth modification/inhibition. To exert these effects, zinc must be present at the site of action at an effective concentration for a long duration of time. 1
After application of zinc, 15-40% of the concentration is retained in the mouth. Good oral substantivity was confirmed by several studies, which reported that when zinc when applied from a toothpaste, 30% of the concentration is retained in the mouth and only 5.7% was removed by rinsing three times. Zinc is generally cleared from saliva bi-modally, with relatively high post-application concentrations falling rapidly after 30-60 min, after which it will be present in low concentrations for many hours. This trend reflects rapid clearance of loosely bound zinc followed by slower clearance of more firmly bound zinc.1