In vitro investigations in dental research are important as they allow for conditions such as tooth erosion to be extensively studied in controlled environments for product development and testing. The studies in this thesis investigate citric, phosphoric and hydrochloric acids under varying conditions of concentrations and immersion times in erosion and erosionabrasion models and use non-contact profilometry and Knoop microhardness to measure the change in the surface of enamel. The effects of different experimental protocols on profilometry and Knoop microhardness were investigated. Using the results from these preliminary studies, a modified erosion model was developed to investigate the effects of low concentration fluorides and time of application. The role of fluoride experiment was furthered by investigating a dose response effect using sodium and stannous fluoride at concentrations normally found in mouth rinses and toothpastes.
Citric and phosphoric acid were more erosive than hydrochloric acid at pH 3.2. The effect of increasing the immersion time and concentration increased the amount of erosion. The addition of abrasion produced a non-linear response, suggesting a more complex mechanism was operating rather than the simple eroded surface being more susceptible to abrasion. Profilometry and to a lesser extent Knoop microhardness were effective measurements to quantify the amount of erosion. Tooth surface/type, ultrasonication, storage, agitation and speed, rinsing, volume and position of sample all influenced the mean step height and Knoop microhardness change. Stannous fluoride (225ppm) produced significantly lower (p<0.001) mean step height and higher Knoop microhardness change than sodium fluoride. The application before an erosive challenge produced a significantly lower mean step height (p<0.04) for stannous fluoride compared to the application after. A dose response effect was observed between the different fluorides. Both fluorides produced significantly lower mean step height (p<0.001) and Knoop microhardness (p<0.001) change compared to the control. Sodium fluoride provided less protection (significantly higher mean step height) (p<0.05) compared to stannous fluoride. These studies show that the different experimental protocols can influence the measured outcome and that further work is needed to fully understand the effects of all the experimental protocols and abrasion. Greater standardisation and detailed reporting in method sections need to be promoted in in vitro dental research.
|Date of Award||2016|
|Supervisor||Rebecca Moazzez (Supervisor) & David Bartlett (Supervisor)|