The early wear susceptibility of dentine following exposure to citric acid: In vitro study

Objective

This study investigated the effect of early erosion on the mechanical and structural properties of dentine, while comparing the influence of different citric acid pH and concentration levels.

Design

Twenty dentine specimens were randomly allocated into five groups, according to the citric acid (CA) solution: non-eroded; 1 % buffered CA (pH=3.8); 1 % unbuffered CA (pH=2.55); 6 % buffered CA (pH=3.8); and 6 % unbuffered CA (pH=2.06). Specimen numbers were determined from a sample size power calculation. Erosion groups were subjected to 6x cycles, each lasting 20 s, giving a total exposure of 2 min. Surface alterations were determined by atomic force microscopy (at nanoscale) after each cycle. Erosive changes were also assessed qualitatively/quantitatively with scanning electron microscopy and energy dispersive x-ray spectroscopy. Data were analysed by repeated measures ANOVA with Bonferroni correction.

Results

All erosion groups showed significant structural and mechanical changes after a 20 s exposure interval. Specimens exposed to 6 % unbuffered CA, revealed a significant reduction of modulus of elasticity (p < 0.01), and greater changes to topography and morphology, compared with other groups. The 1 % buffered group had the least erosive changes (p < 0.05). Dentine exposed to 1 % unbuffered CA had a comparably greater rate of erosion, compared with the 6 % buffered solution, as exposure times progressed.

Conclusions

Dentine was highly susceptible to early CA erosion, with significant changes occurring after 20 s, regardless of pH or concentration. Alterations to the pH and/or concentration significantly altered the rate and severity of erosion. Although, CA with a lower pH was the most critical factor for early dentine erosion.