Surface Enamel Characterization by Gas Adsorption

Objective: The objective of this study was to quantitatively determine the porosity of non-decayed dental enamel before and after acid etching. Specifically, our goal was to characterize total surface area, pore size, pore volume and pore distribution of etched and unetched surface dental enamel.

Method: Surface area of enamel from 20 sound molars and premolars were analyzed by Multipoint Brunnauer, Emmett and Teller (BET) nitrogen adsorption. Pore size and pore volume were calculated using the Barrett-Joyner-Halenda (BJH) method. Scanning electron micrographs (SEM) were obtained from each specimen to evaluate pore distribution. All measurements were done on the same samples before and after 30 seconds of etching with 37% phosphoric acid. Two-tailed, paired t-test was used to evaluate the statistical significance of the changes of porosity and surface area after etching. Pearson's correlation coefficient was used to measure association between pore size, pore volume and surface area.

Result: Statistically significant differences were found in total surface area, pore size and pore volume between the etched and unetched samples. A significant correlation was found between surface area and porosity.

Conclusion: The significance of this research is that defining the porous enamel structure is central to improving acid-etching protocols. We anticipate that this research will lead to a better understanding of both dental enamel and the effects of acid etching.