Determining abrasion rates with microtribological tests
The researchers at the IWM have chosen an alternative method to this radiotracer system. "Our new approach enables us to determine realistic abrasion rates and characterize the interaction between brush, enamel and toothpaste. What’s more, our tests are less laborious than the time-intensive radiotracer procedures carried out by only a handful of laboratories worldwide," says Dr. Andreas Kiesow, team leader at the IWM. The scientist and his team have successfully managed to determine the abrasion of various toothpastes on a microscopic scale and to measure the friction values using microtribological experiments. "Until now, tribological values such as friction coefficient, did not exist" says Kiesow.
The researchers use human teeth as well as different toothpastes made by industrial partners for their experiments. These toothpastes were diluted with water and saliva in order to create a solution whose consistency corresponds to the mixture of toothpaste and saliva that is present when people brush their teeth. The friction and wear tests were each carried out with a single bristle — referred to as a monofilament. This is mounted in specialized tribological instruments, a microtribometer and a nanoindenter, and moved over the sample in both straight and circular motions, in the latter case up to 8000 times. Highly sensitive instruments then measure the depth of the resultant marks left on the surface of the tooth.
"Our findings reveal that the RDA value of toothpastes correlates with the depth of abrasion; the higher the value, the greater the abrasion. By analyzing the friction value we also identified a clear relationship between the friction behaviors of the bristle on the dental enamel and the abrasiveness of the toothpaste," sums up Kiesow. The new process allows the researchers to not only characterize the abrasion more quickly and simply, but also to describe how different geometries of toothbrush filaments act upon the surface of the tooth and how the bristle shape should ideally be designed. The experts at IWM can use their know how to support manufacturers of dental hygiene with product development. At the end of the day it is the consumer who benefits most.