Remineralisation, the natural repair process.

It is well known that your enamel is acellular, and unlike bone, it cannot regenerate and remodel itself [1]. But did you know that the enamel can be restored by a reversible chemical reaction that takes place at the tooth surface?

During this reaction, mineral ions are converted to enamel crystallites, and enamel crystallites are simultaneously converted to calcium and phosphate mineral ions. The reincorporation of calcium and phosphate ions into the tooth is known as remineralisation and the migration of calcium and phosphate ions from the tooth is known as demineralisation [3]. If these reactions take place at the same rate, then no alterations are made to the enamel. However, if these reactions take place at different rates, then it does have the potential to alter the enamel. Under favourable conditions, remineralisation occurs at a greater rate and restores mineral ions to the enamel, it is therefore regarded as a natural repair process. Alternatively, when demineralisation occurs at a greater rate it results in a loss of enamel mineral ions, if this occurs continuously it can lead to dental caries or erosive tooth wear. This reversible chemical reaction is influenced by our lifestyle, let us look at the mechanisms that promote demineralisation and remineralisation, and how we can manipulate them to restrict demineralisation and promote remineralisation [4].

when remineralisation is favoured it is regarded as a natural repair process

Bernd Grohe and Silvia Mittler

Demineralisation

Demineralisation is initiated by acid exposure causing the pH of the mouth to fall below 5.5. This occurs when acidic food and drinks are consumed, or when sugars are fermented by microorganisms present in the mouth [5]. To prevent this from constantly occurring at a greater rate than remineralisation, it is preferable to lower the consumption of foods and drinks that are acidic or contain simple sugars. Tooth brushing is also incremental in reducing the rate of demineralisation. It mechanically removes plaque and reduces the number of acid-producing bacteria [6]. Additionally, brushing with a toothpaste that contains antimicrobial, or bacteriostatic ingredients (sodium fluoride, nano-hydroxyapatite, phytochemicals, zinc, and xylitol) may help to regulate the resident microbial community by preventing acid-producing bacteria from flourishing [6–8].

Remineralisation

For remineralisation to occur the pH should be raised above 5.5, and the saliva and plaque should be supersaturated with calcium and phosphate ions. Remineralisation can be boosted by utilising a toothpaste that contains a remineralising agent, which is a material that is capable of carrying calcium and phosphate ions to the demineralised enamel crystallites [9]. To date, fluoride compounds have been the primary agents for promoting remineralisation because they readily react with the demineralised enamel crystallites and calcium and phosphate ions present in the saliva [1]. However, there are a number of new remineralising agents under investigation, this largely includes calcium-phosphate solids. These compounds are either dissolved to provide calcium and phosphate ions for remineralisation, or they are directly absorbed and fused with the demineralised enamel crystallites [4]. Nano-hydroxyapatite is an example of one of the calcium-phosphate compounds that act as a remineralising agent. In recent studies, it has been reported that a toothpaste containing 10% nano-hydroxyapatite is as effective as a toothpaste with 950 ppm [10], 1000ppm [11] and 1450ppm [12] sodium fluoride. Based on these findings, EvaGlo utilises 10% w/w nano-hydroxyapatite as an effective alternative to fluoride in toothpaste.