The effect of dental water jet application on softened human enamel surfaces: A preliminary in vitro study using swept-source optical coherence tomography

Objectives: To evaluate the surface loss of enamel, following water jet application, on acid-induced softened human enamel surfaces. Methods: Ninety enamel windows of 2x4 mm(2) were prepared on 45 extracted human premolar teeth. The specimens were divided into 2 groups: Group 1 (n=45) exposed to distilled water; Group 2 (n=45) exposed to citric acid (pH 3.2) for 30 minutes. All specimens were then subjected to a water jet for 20 seconds. Surface microhardness (SMH) and enamel thickness measurements were taken at baseline (t(1)), post-distilled water/post-erosion (t(2)) and post-water jet (t(3)). Enamel thickness measurements were derived from the depth-resolved intensity profile (A-scans) of swept-source optical coherence tomography (SS-OCT) and SMH was used as a measurement of the state of mineralization. Repeated measures ANOVA was used to analyze the changes in SMH and enamel thickness (D) (alpha=0.05). Results: For Group 2, at t(2), there was a 54.28% and 14.14% reduction in SMH and D, respectively. Repeated measures ANOVA showed that the aforementioned mean reduction in SMH and D were statistically significant (P<0.05) at t(2) compared to t(1) for Group 2. However, at t(3), no significant difference (P>0.05) was observed in both measurements, compared to t(2) for both groups. Conclusion: Within the limitations of the study, the application of a water jet may not affect the thickness of enamel softened by acidic conditions.