In Vitro Investigation of Erosive Changes on Dentine by Evaluating Surface Loss

Abstract

Introduction: Dental erosion is a chemical process of mineralised tissue loss from enamel or dentine due to acid exposure. Sodium fluoride may have a protective effect on both pre- and post-dietary acidic challenges with or without abrasion. The aim of this work was to investigate the effect on human dentine of acid erosion alone or with abrasion under the influence of 1,450 ppm and 5,000 ppm sodium fluoride (NaF). Materials and methods: Dentine specimens were sectioned from the coronal aspect of previously extracted human molars and polished using previously published protocols. With acid erosion alone, the dentine samples were eroded with pH 2.6 of 0.3% citric acid at 10, 15, 20 and 25 min. For acid erosion and erosion/abrasion, the dentine samples were pre-treated by immersion into either 1,450 ppm NaF solution (F1450), 5,000 ppm NaF solution (F5000) or water (0 ppm) for 3 mins and then placed in artificial saliva for 30 mins. Following that, each group was fully immersed in 0.3% citric acid at pH 2.6. Then, samples with erosion/abrasion were exposed to 240 strokes. Samples were analysed using profilometry and digital microscopy for mean step height and SEM for a qualitative assessment of change. Results: The mean and standard error (SE) step height of the dentine samples with acid erosion alone with the 0.3% citric acid at pH 2.6 was at 10 mins 1.82 (±0.4 μm) which increased to 9.37 (±0.9 μm) at 25 mins. A statistically significant difference (p<0.05) was noticed 3 between all groups at different acid immersion times. The mean (SE) step height change with 0, 1,450 or 5,000 ppm of NaF were for 0 ppm 4.4 (± 0.6 μm) at 10 mins and 9.0 (± 0.7 μm) at 25 min acid immersion, for F1450 fluoride groups 4.97 (± 0.57 μm) and 8.74 (± 0.58 μm) and for F5000 groups 3.47 (± 0.77 μm) and 7.01 (± 0.56 μm), respectively. There were statistically significant differences (p<0.05) in the step height between 0 ppm and F5000 with erosion, however, there were no statistically significant differences with F1450. The mean (SD) in step height with 0, 1,450 or 5,000 ppm of NaF with 0.3% citric acid at pH 2.6 for 25 min which were subjected to 240 brushing strokes were for 0 ppm 12.24 (± 0.43 μm), for F1450 groups 11.35 (± 0.76 μm) and for F5000 10.53 (± 0.77 μm). There were statistically significant differences (p<0.05) in the step height between 0 ppm and F5000 with erosion/abrasion. However, there were no statistically significant differences with F1450 with erosion/abrasion. There were no statistically significant differences in the step height between profilometry and digital microscopy in an erosion/abrasion model. Conclusions: Step height increased with increasing the time of exposure to citric acid. Sodium fluoride had statistically significantly less step height only for F5000 and this was repeated when abrasion was included. For erosive tooth wear on dentine in this laboratory study, 5,000 ppm of sodium fluoride had a protective effect against acid challenges. The digital microscope is an alternative approach for measurement of dentine step height under the conditions performed in this thesis.