Effect of Dental Water Jet on Softened Enamel and Its Efficacy in Biofilm Removal

Objectives: 1. To determine the effect of dental water jet on the surface loss of acid-induced softened human enamel.
2. To evaluate the effect of dental water jet on removal of laboratory cultivated biofilm
Methods: Sixty enamel specimens were prepared, exposing 2 x 4 mm² window. After polishing (baseline), specimens were subjected to acid challenge (citric acid for 30 min) and divided into four groups (n=15 per group); (1) control (immersed in de-ionised water for 3 days), (2) 1-Day Biofilm, (3) 2-Day Biofilm, (4) 3-Day Biofilm. Specimens from group 2, 3 and 4 were inoculated with early laboratory cultivated biofilm for 1, 2 and 3 days, respectively. Specimens from group 1 were not inoculated with biofilm. All specimens from all groups were then subjected to water jet (WJ) for 20 seconds. Swept Source OCT (SS-OCT) was used to scan the specimens at baseline (t₁), post-erosion (t₂), with biofilm (t₃) and post-WJ (t₄) time points. Surface Microhardness (SMH) was measured at all time points except at t3. Enamel thickness and Supra-surface integrated reflectivity (IR_biofilm) values, derived from the OCT A-scans were used for evaluation.Repeated measures ANOVA was used to analyse the changes in surface microhardness (SMH) and enamel thickness (D), and, paired t-test were used to analyse the changes before and after WJ application.
Results: Results showed that there was a statistically significant reduction in SMH (p<0.05) after acid exposure compared to baseline, however, the mean enamel thickness (D) reduction was not significant (p>0.05). After application of WJ, no significant difference in SMH and D (p>0.05) were observed. Furthermore, paired t-test revealed that the IR_biofilm mean values showed no significant different after WJ application (p > 0.05) in all the groups.
Conclusions: The results suggested that a single application of WJ did not cause surface loss to acid-induced softened enamel, and was not significantly remove the laboratory cultivated biofilm.