This story originally appeared on Materials Today earlier this month
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A collaboration between dentists and engineers from University of Nottingham’s Malaysian Campus has shown that soft drinks cause physical and mechanical damage to your teeth.
Dentists have proclaimed the damaging effects of soft drinks for years, but a global study by Credit Suisse showed that in 2013, the average American drank more than 160 liters of them, almost half a liter every day. So a paper in the March issue of Materials Letters [DOI: 10.1016/j.matlet.2014.12.085] seems timely.
Led by Prof M Enamul Hoque, this work fabricated a series of disc-shaped dental porcelain samples, and soaked them in three different types of wet media (distilled water, soft drink (Cola) and rice vinegar). Previous work had demonstrated that soft drinks could cause orthodontic brackets to lose adhesion and sheer off the tooth surface. But this paper measured the physical and mechanical of these model teeth directly. The samples of dental porcelain were produced using artificial form of dentin – the material that makes up the bulk of a tooth’s mass. This was shaped into discs and fired at temperatures of up to 910°C, before being glazed. The samples were either left dry or soaked in distilled water, cola or rice vinegar for 1 – 4 weeks.
SEM analysis showed that samples soaked in distilled water showed no significant change in surface morphology throughout the soaking period. Images of the samples in Cola and rice vinegar showed that the longer the samples were soaked, the rougher their surfaces became, with those soaked in cola degrading more than those in vinegar. This increasing roughness of the porcelain is due to hydrolysis, where water molecules split into ionic pairs (H+ and OH-). While both acidic, cola’s pH of 2.44 is lower than that of rice vinegar (2.6–3.2). The team suggests that it is these pH values that explain the different rates of demineralization.
Similar results were seen in the team’s mechanical tests, with the dry control and distilled water samples maintaining their fracture strength of 52.13 MPa. However, there was a significant decrease in the fracture strength observed in the samples soaked in cola and rice vinegar. Over the course of four weeks, the fracture strength dropped to 17.24 MPa (cola) and 31.95 MPa (rice vinegar) respectively.
The team’s conclusions are clear – acidic soft drinks really are damaging your teeth!
Materials Letters (2015) DOI: 10.1016/j.matlet.2014.12.085